Birds placing sticks on train tracks?

Birds placing sticks on train tracks?

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I live in a semi-rural area in Germany, close to a park which trains go through every 20 minutes.

Today, I saw something that left me perplexed.

There is a large population of birds that look like crows or ravens, yet fatter. They seem to be quite social and move around in large groups. Today, I spotted one carefully laying sticks from a nearby tree on the train track while the others seemed to spectate.

What exactly was that bird doing? Is this common? Did it have a purpose, or was it just coincidental?

There is a large population of birds that look like crows or ravens, yet fatter. They seem to be quite social and move around in large groups.

First of all, this seems like a crow. Crows are very social birds, they live in flocks or murder.

Theory: It may be a Mating Ritual?

No! The have a very spectacular mating ritual!.

Theory: It's Making a nest

Obviously No! Crows nests are always way hidden at 18-60 feet above ground(mostly) in the tree trunk.

My Theory

Crows are very curious birds. What you saw, might be a new play the young crows found. It's common that crows will do unusual thing when spectated by the elders and siblings.

Crows have been known to use human actions in order to accomplish their own purposes: read this story about them using cars and waiting for the lights to change at a crossroads. Then of course, the question is whether they have a specific purpose in your case with these sticks, or whether it's just… for the fun of it?

The secret call of the wild: how animals teach each other to survive

S am Williams’ Macaw Recovery Network in Costa Rica rewilds captivity-hatched fledgling scarlet and great green macaws. But introducing young birds into a complex forest world – bereft of the cultural education normally provided by parents – is slow and risky.

For 30 years or so scientists have referred to the diversity of life on Earth as “biological diversity”, or just “biodiversity”. They usually define biodiversity as operating at three levels: the diversity of genes within any particular species the diversity of species in a given place and the diversity of habitat types such as forests, coral reefs, and so on. But does that cover it? Not really. A fourth level has been almost entirely overlooked: cultural diversity.

Culture is knowledge and skills that flow socially from individual to individual and generation to generation. It’s not in genes. Socially learned skills, traditions and dialects that answer the question of “how we live here” are crucial to helping many populations survive – or recover. Crucially, culturally learned skills vary from place to place. In the human family many cultures, underappreciated, have been lost. Culture in the other-than-human world has been almost entirely missed.

We are just recognising that in many species, survival skills must be learned from elders who learned from their elders. Until now, culture has remained a largely hidden, unrecognised layer of wild lives. Yet for many species culture is both crucial and fragile. Long before a population declines to numbers low enough to seem threatened with extinction, their special cultural knowledge, earned and passed down over long generations, begins disappearing. Recovery of lost populations then becomes much more difficult than bringing in a few individuals and turning them loose.

Ecologist and writer Carl Safina. Photograph: Ines Duran

Many young birds learn much by observing their parents, and parrots probably need to learn more than most. Survival of released individuals is severely undermined if there are no free-living elder role models. Trying to restore parrot populations by captive breeding is not as easy as training young or orphaned creatures to recognise what is food while they’re in the safety of a cage – then simply opening the door. “In a cage,” Williams says, “you can’t train them to know where, when and how to find that food, or about trees with good nest sites.” Parents would normally have done exactly that.

A generational break in cultural traditions hampered attempts to reintroduce thick-billed parrots to parts of south-west America, where they’d been wiped out. Conservation workers could not teach the captive-raised parrots to search for and find their traditional wild foods, skills they would have learned from parents.

Landscapes, always complex, are under accelerated change. Culture enables adaptation far faster than genes alone can navigate hairpin turns in time. In some places, pigeons and sparrows have learned to use motion-sensors to get inside enclosed shopping malls and forage for crumbs. Crows have in some locales learned to drop nuts on the road for cars to crack. In at least one area they do this at intersections, so they can safely walk out and collect their cracked prizes when the light turns red and the cars stop. They’ve developed answers to the new question: “How can we survive here, in this never-before world?”

Because the answers are local, and learned from elders, wild cultures can be lost faster than genetic diversity. When populations plummet, traditions that helped animals survive and adapt to a place begin to vanish.

In a scientific article on the vocabulary of larks living in north Africa and Spain titled, “Erosion of animal cultures in fragmented landscapes”, researchers reported that as human development shrinks habitats into patches, “isolation is associated with impoverishment”. They write: “Song repertoires pass through a cultural bottleneck and significantly decline in variety.”

Unfortunately, isolated larks are not an isolated case. Researchers studying South America’s orange-billed sparrow found that sparrow “song complexity” – the number of syllables per song and song length – deteriorated as humans continued whittling their forests into fragments. When a scientist replayed 24-year-old recordings of singing male white-crowned sparrows at the same location she’d recorded them, they elicited half the responses they had when first recorded. The birds’ responses show that changes in the dialect lead to changes in listener preference, a bit analogous to pop music. And as with humans, preferences can affect whether a particular bird will be accepted as a mate. White-crowned sparrows singing a local dialect become fathers of more offspring than do singers of unfamiliar dialects, indicating females prefer a familiar tune.

Study of the orange-billed sparrow (Arremon aurantiirostris), pictured, found that song complexity deteriorated with habitat loss. Photograph: Chris Rabe/Alamy

I’m not just talking about a few songs. Survival of numerous species depends on cultural adaptation. How many? We’re just beginning to ask such questions. But the preliminary answers indicate surprising and widespread ways that animals survive by cultural learning. Regionally different vocalisations are sometimes called “song traditions” but the more commonly used word is “dialects”. More than a hundred studies have been published on dialects in birds. And it’s not just birds but a wide array of animals Including some fish.

“Cod particularly,” said Steve Simpson of the University of Exeter, “have very elaborate calls compared with many fish.” You can easily hear differences in recorded calls of American and European Atlantic cod. “This species is highly vocal with traditional breeding grounds established over hundreds or even thousands of years.” Many fish follow elders to feeding, resting and breeding areas. In experiments, introduced outsiders who learned such preferred locales by following elders continued to use these traditional routes after all the original fish from whom they learned were gone.

Cultural survival skills erode as habitats shrink. Maintaining genetic diversity is not enough. We’ve become accustomed to a perilous satisfaction with precariously minimal populations that not only risk genetic viability of populations but almost guarantee losing local cultural knowledge by which populations have lived and survived.

A pair of African grey parrots exchanging tokens. Researchers have shown that the birds are willing to help others, including strangers, in need. Photograph: Anastasia Krasheninnikova/PA

In all free-living parrots that have been studied, nestlings develop individually unique calls, learned from their parents. Researchers have described this as “an intriguing parallel with human parents naming infants”. Indeed, these vocal identities help individuals distinguish neighbours, mates, sexes and individuals the same functions that human names serve.

Williams tells me that when he studied Amazon parrots, he could hear differences between them saying, essentially, “Let’s go”, “I’m here, where are you?” and “Darling, I just brought breakfast”. Researchers who develop really good ears for parrot vocalisation and use technology to study recordings show that parrot noise is more organised and meaningful than it sounds to beginners like me. In a study of budgerigars, for instance, birds who were unfamiliar with each other were placed together. Groups of unfamiliar females took a few weeks for their calls to converge and sound similar. Males copied the calls of females. Black-capped chickadees flock members’ calls converge, so they can distinguish members of their own flock from those of other flocks. The fact that this happens, and that it takes weeks, suggests that free-living groups must normally be stable, that groups have their own identity, and that the members identify with their group.

Group identity, we see repeatedly, is not exclusively human. Sperm whales learn and announce their group identity. Young fruit bats learn the dialects of the crowds they’re in. Ravens know who’s in, who’s out. Too many animals to list know what group, troop, family or pack they belong with. In Brazil, some dolphins drive fish toward fishermen’s nets for a share of the catch. Other dolphins don’t. The ones who do, sound different from the ones who don’t. Various dolphin groups who specialise in a food-getting technique won’t socialise with other groups who use different techniques. And orca whales, the most socially complex non-humans, have layered societies of pods, clans and communities, with community members all knowing the members of all their constituent pods, but each community scrupulously avoiding contact with members of another community. All this social organisation is learned from elders.

Sperm whales (Physeter macrocephalus), such as this group of adults and calves, learn and announce their group identity. Photograph: SeaTops/Alamy

Elders appear important for social learning of migratory routes. Various storks, vultures, eagles and hawks all depend on following the cues of elders to locate strategic migration flyways or important stopover sites. These could be called their migration cultures. Famously, conservationists have raised young cranes, geese and swans to follow microlight aircraft as a surrogate parent on first migrations. Without such enculturation, they would not have known where to go. The young birds absorbed knowledge of routes, then used them in later seasons on their own self-guided migrations. Four thousand species of birds migrate, so Andrew Whiten of the University of St Andrews in Scotland speculates that following experienced birds may be an underappreciated but “very significant realm of cultural transmission”.

When you look at free-living animals, you don’t usually see culture. Culture makes itself visible when it gets disrupted. Then we see that the road back to reestablishing cultures – the answers to the questions of “how we live in this place” – is difficult, often fatal.

Young mammals too – moose, bison, deer, antelope, wild sheep, ibex and many others – learn crucial migration routes and destinations from elder keepers of traditional knowledge. Conservationists have recently reintroduced large mammals in a few areas where they’ve been wiped out, but because animals released into unfamiliar landscapes don’t know where food is, where dangers lurk, or where to go in changing seasons, many translocations have failed.

Williams describes his procedure with the macaws as “very much a slow release”. First his team trains the birds to use a feeder. With that safety net, they can explore the forest, gain local knowledge, begin dispersing and using wild foods.

Some rescue programmes declare success if a released animal survives one year. “A year is meaningless for a bird like a macaw that doesn’t mature until it’s eight years old,” says Williams.

I ask what they’re doing for those eight long years.

“Social learning,” Williams replies immediately. “Working out who’s who, how to interact, like kids in school.”

Macaws do not mature until they are eight years old and spend their juvenile years learning social interaction. Photograph: Zoonar GmbH/Alamy

To gain access to the future, to mate and to raise young, the birds Williams is releasing must enter into the culture of their kind. But from whom will they learn, if no one is out there? At the very least they must be socially oriented to one another. Ex-pets are the worst candidates for release they don’t interact appropriately with other macaws, and they want to hang around near humans.

To assess the social abilities of 13 scarlet macaws who were scheduled for release, Williams and his crew documented how much time they spent close to another bird, how often they initiated aggression, things like that. When the bird scoring lowest for social skills was released, he flew out the door and was never seen again. The next-to-lowest didn’t adapt to the free-living life and had to be retrieved. The third-lowest social scorer remained at liberty but stayed alone a lot. The rest did well.

Becoming Wild by Carl Safina, UK edition. Photograph: Courtesy of Oneworld

All of the above adds up to this: a species isn’t just one big jar of jellybeans of the same colour. It’s different smaller jars with differing hues in different places. From region to region, genetics can vary. And cultural traditions can differ. Different populations might use different tools, different migration routes, different ways of calling, courting and being understood. All populations have their answers to the question of how to live where they live.

“Sometimes a group will be foraging in a tree,” Williams says. “A pair will fly overhead on a straight path. Someone will make a contact call, and the flying birds will loop around and land with the callers. They seem to have their friends.” Bottom line, said Williams, there is much going on in the social and cultural lives of his macaws and other species, much that they understand – but we don’t. We have a lot of questions. The answers must lurk, somewhere, in their minds.

As land, weather and climate change, some aspects of cultural knowledge will be the tickets necessary for boarding the future. Others will die out. Across the range of chimpanzees, cultures vary greatly, as do habitats. All populations but one use stick tools. Some use simple probes, others fashion multi-stick toolsets. Only one population makes pointed daggers for hunting small nocturnal primates called bush-babies hiding in tree holes. Only the westernmost chimpanzees crack nuts with stones.

As researchers have noted, distinctive tool-using traditions at particular sites are defining features of unique chimpanzee cultures. Whiten wrote: “Chimpanzee communities resemble human cultures in possessing suites of local traditions that uniquely identify them … A complex social inheritance system that complements the genetic picture.”

Some chimpanzee populations have learned to track the progress of dozens of specific trees ripening in their dense forests. Others live in open semi-savannah. Some are more aggressively male-dominated, some populations more egalitarian. Some almost never see people some live in sight of human settlements and have learned to crop-raid at night. For a long, long time chimpanzees have been works in progress. “We’ve learned,” writes Craig Stanford, “not to speak of ‘The Chimpanzee’.” Chimpanzees vary and chimpanzee culture is variable at every level.

A female Bonobo Chimpanzee (Pan paniscus) teaches a young male to balance. Chimpanzees vary and their culture is variable at every level. Photograph: Ger Bosma/Alamy

“It’s not just the loss of populations of chimps that worries me,” Cat Hobaiter emphasised when I spent several weeks with her studying chimpanzees in Uganda. “I find terrifying the possibility of losing each population’s unique culture. That’s permanent.”

Diversity in cultural pools – perhaps more crucially than in gene pools – will make species survival more likely. If pressures cause regional populations to blink out, a species’ odds of persisting dim.

Williams’ goal is to re-establish macaws where they range no longer, in hopes that they, and their forests, will recover. (Most of the central American forests that macaws need have been felled and burned, largely so fast-food burger chains can sell cheap beef.) It often takes a couple of generations for human immigrant families to learn how to function effectively in their new culture it may take two or three generations before an introduced population of macaws succeeds. In other words, macaws are born to be wild. But becoming wild requires an education.

So what’s at stake is not just numbers. What’s at stake is: ways of knowing how to be in the world. Culture isn’t just a boutique concern. Cultural knowledge is what allows many populations to survive. Keeping the knowledge of how to live in a habitat can be almost as important to the persistence of a species as keeping the habitat both are needed. Cultural diversity itself is a source of resilience and adaptability to change. And change is accelerating.

This is an edited extract from Becoming Wild: How Animals Learn to be Animals by Carl Safina, which published in the UK by Oneworld on 9 April and in the US by Henry Holt and Co on 14 April

Where did the phrase &lsquoTo bury your head in the sand&rsquo come from?

We might have Pliny the Elder (23-79AD) to thank for the myth.

A Roman scholar, Pliny was a curious man, working tirelessly throughout his life to understand the world around him. He had such a passionately curious soul that he died attempting to &ldquounderstand&rdquo the eruption of Mt. Vesuvius, as it erupted.

However, before he died, he wrote one of the first Natural History encyclopedias, a 37-book attempt to catalogue the entirety of Roman knowledge. In Book 10, Chapter 1, he mentions the ostrich&rsquos head-in-the-sand habits. He wrote, &ldquo&hellipthey imagine, when they have thrust their head and neck into a bush, that the whole of their body is concealed&rdquo.

Then again, Pliny also thought that swallows (a species of bird) went underground when they migrated away every winter. I wonder why the idea that birds could simply fly away never struck Pliny as obvious!



When a track is made, the heel slides into the ground, registers and pulls out. No track will register straight down. There is always some angled component (looking at the track cross-section) either from the foot entering or the foot leaving.

The softer the soil, the greater the slope of the wall creating a larger distortion between the overall track and the true track. Most people don't read the true track. They read the horizon cuts (overall track) which does not give the true track measurement. The true track is the only real measurement for tracking. If you read the overall track you could not tell the difference between a dog track and a coyote track. E.g. on a dog the inner toes are larger than the outer toes on a coyote the outer toes are larger. But this distinction will not show on the overall track.


You need to measure the length and width of all four tracks (2 in humans). When measuring animal tracks the length readings between tracks are measured from toe to toe because animals hit first with their toes. In humans it is measured from heel to heel because we land heel first.

  1. Establish the Line of Travel- This can be done by eye if the tracks are clear or by placing popsicle sticks at the heel of the tracks and connecting a string to the sticks.
  2. Length of Track - measure the length of the true track.
  3. Width - measure the widest part of the track.
  4. Stride - is measured from the heel of one foot to the heel of the other foot (i.e. right heel line to left heel line).
  5. Straddle - if you draw a line of travel between the left heels and a line of travel between the right heels the distance between these two lines is the straddle. There is zero straddle and positive straddle.
  6. Pitch - is the degree to which the foot angles out from the line of travel (pitched out). At the widest point of the track, draw a line bisecting the track along its long axis. The distance from where the line exits the front of the foot to the heel line is the overall pitch.

Overall Pitch - 1/2 track width = True Pitch

Ex. 4" wide track, 3" overall pitch 3 - (1/2 * 4) = 1" = true pitch

This is because if there is no pitch there would still be 2" from the line through the track to the heel line. So this measurement must be subtracted.


5% 1) Clear Print - when you can see the track clearly in soft soil, all toes visible.
95% 2) Pattern Classification - no clear print, you must tell track by general shape and size of track


The front and rear tracks on one side will be near each other. You need to note the number of toes in the front track and the rear track. Looking at the track you will also note the type of preferred gait used by the animal (in order to differentiate between front and rear tracks).

  1. Track Shape - the track shape is the overall shape of the track pattern.
  2. Direct Register - as the front foot is lifted up the rear foot on that side drops directly into the front track (cats and foxes). Also called perfect walking.
  3. Indirect Register - as the front foot is picked up the rear foot on that side drops slightly behind and to the right or left of the front track (depending on the sex of the animal).



  1. Ground Bird - spend most of their time on the ground and show a "walking" gait
  2. Perching Bird - spends most time in the trees - shows a "hopping" gait
  3. Mixed - if the track shows both walking and hopping it is probably a bird that splits its time between trees and the ground e.g. Crow


There are a number of different types of locomotion patterns. 90 - 95% of the time an animal will use this method of locomotion. In each case below the gait described is the normal walking pattern for that animal. As the animals speed changes this pattern will change (ex. moving slowly, in pursuit, being chased).

RF = right front LR = left rear, etc.

1) Continuum of Speed:

2) Diagonal Walkers - the animal moves the opposite sides of the body at the same time (e.g. RF & LR move simultaneously)
Deer Dog Cat - cat and fox direct register by being completely off the ground at one point

3) Bound Walkers - the front feet land together, then the rear feet behind 99.9% of the time these animals use this pattern even when moving slow or fast. Stride measured from rear toes to rear toes.
Weasel Family - All Members Except Skunks & Badgers

4) Gallop Walkers - the front feet land first, then the rear feet come on the outside of the front feet and land ahead. 99.9% of the time these animals use this pattern even when moving slow or fast. Stride measured from rear toes to rear toes. The pattern doesn't change with speed. The distance between sets of tracks increases.
Rabbits Hares Rodents - Except Porcupine & Ground Hog

If the front feet hit at a diagonal = ground dwelling rodent e.g. Rabbit, and the front foot that is further back is the one that hit first - sidedness (punch step). If the front feet hit side by side, it is a tree dweller e.g. Squirrel (just like tree dwelling birds - "hoppers")

5) Pacers - move the same side of the body at the same time (e.g. RF & RR) - these animals have wide, rotund bodies. These are the exceptions from the other groups. 95% of the time these animals use this pattern. As speed increases, they change their pattern.
Badgers Skunk Porcupine Oppossum Raccoon Bear

6) Variations on Pattern Classifications - 5% of the time. All animals can change their gait. In particular, Diagonal Walkers and Pacers will change their pattern as their speed increases.

In between these major patterns there is a continuum of discernable pattern variations.

  • From Pacer to Diagonal = 16 patterns
  • From Diagonal to Bounder = 32 patterns
  • From to Galloper = 16 patterns
  • For speed, a slow walk for a Pacer is faster than a slow walk for a Diagonal Walker.
  • A stalk is generally the slowest pattern and is slower for both a Pacer and a Diagonal Walker.
  • Slow Walk - animal pushes body weight forward.


Tracking by patterns allows you to track over hard ground over a long distance.

1. Diagonal Walkers

  • Stalk
  • Slow Walk
  • Pace when bored, annoyed, aggravated
  • Walk
  • Rarely hold a bound except in soft or rocky terrain - prefer to gallop on clear terrain hold a bound on for a few patterns before going into a gallop - prefer to trot or lope - can go straight from a walk to a gallop (e.g. if suddenly frightened)

Species Note: Deer prefer to gallop for high speed except for the Black Tail Deer and the Mule Deer that prefer to bound because they live in rocky areas.

2. Bound Walkers

  • For a shear burst of speed will gallop - seen just before a kill
  • Will diagonal walk when approaching hunting territory e.g. slowing down to be more quiet
  • Will stalk when hunting game
  • Will pace when aggravated, bored or agitated, threatening, seen just before going out on hunt

Note: This is an example of how you can tell the "emotional state" of an animal by looking at its tracks.

3. Gallop Walkers

  • Prefer to gallop but will bound in soft terrain i.e. snow, mud or rocky terrain
  • Will diagonal walk if it needs to cover a shorter distance than a hop would cover, e.g. rabbit moves 2" over to feed
  • Will stalk when moving away from danger
  • Will pace when aggravated, threatening or bored


1) Sidedness - if one front foot is behind the other over 4 - 5 tracks that foot is on the dominant side. The animal will have a tendency to circle in that direction.

2) Sex - (this works for diagonal walkers only). Deer for example, just because a track is deep or splayed wide does not mean that animal is male. There are variations in the size of animals of the same species from location (different amounts of feed). Male deer (bucks) and female deer (does) have different bone structure. Doe - pelvic girdle > shoulder girdle (for birthing). Buck - shoulder girdle > pelvic girdle (to support antlers). In order to tell the sex of the animal you must compare the animal to itself. Find the front track on one side. The look for the rear track on that side. If the rear track is to the inside of the front track = male, a rear track to the outside = female. This system works only for adult animals. Immature animals have not finished bone development and may have rear track falling exactly behind front track.
Cats are another example because they direct register. Then how do you tell whether the rear foot is inside or outside the front? In cats (and foxes) the front foot is larger (by 1/3) that the rear foot. Thus the rear track will fall in the front track and be to the inside or the outside. Inside = male Outside = female.


1) The single most important factor in track degradation (and thereby aging) is weather and weather fluctuations.

2) Gravity is the second major factor in track degradation.

3) The third factor is the type of soil. The only way to learn to age tracks is to observe a track degrade over time with given soil conditions and weather conditions. Soils are classified from 1 to 10 with 1 being sand and 10 being clay (soft to hard). You must estimate the soil classification first. Then keep an accurate record of weather changes and by observing a track you will develop a sense of how a track degrades in that type of soil with those weather conditions. Weather conditions to be aware of are temperature, humidity, wind, precipitation, and hours of direct sunlight on the tracks.

4) Wisdom of the Marks - Do this once a month for three months and you will cover all seasons for the type of soil in your area (if possible do it with various types of soil). Clean out rectangular area of soil. Remove all rocks, transplant plants etc. Dig down 2 inches, break up soil into smooth texture, pat it down smooth and leave it to settle for 24 hours. Using a stick or object approximately 1/2 inch diameter make 5 marks in a row in the soil with varying pressure from a touch to enough to go 1/2 inch deep. Look at the marks carefully for 10 minutes to ingrain into your subconscious what they look like. Write down weather conditions. Come back 6 hours later and repeat the entire process making the new marks with the same implement and the same pressures in a row next to the first marks. You will now have fresh marks and 6 hour old marks to compare. Study both for 10 minutes. Come back in 6 hours and again 6 hours after that and again in 6 hours. This will give you a comparison of track degradation at 6 hours, 12 hours, 18 hours and 24 hours. Then go back every 24 hours for 6 days and you will see the track age and degrade over a week. After doing this summer, fall, winter, and spring you will begin to learn how to age tracks to within 2 hours of their being made. It is also advisable to do this whenever you move into a new area for tracking.


1) File card learning Method - Read about an animal in the Peterson's field guide an prepare a scan card on a 3 x 5 index card. By scanning these cards during "blow off time," you will quickly learn to recognize tracks.

2) Tracking Stick - This can be either primitive ( a stick with notches cut into it) or advanced a dowel with rubber bands ("O" ring washers work great). The stick should be about 3' x 1/4" and very straight. The tip should be sharpened to give a point. The stick is used to measure a track and give you a standard for comparing and looking for the next track.

  • Tip to 1st mark = length
  • 1st to 2nd = width
  • Tip to 3rd = stride
  • 3rd to 4th = straddle
  • 4th to 5th = true pitch

Since animals walk 95% of the time the tracking stick is a useful way to find the next track. If you lay the 3rd mark over the center of the last track the stick will point to the center of the area where the next track will be. To find the track add the straddle. If you don't find the track, ask yourself what does the landscape tell you? Uphill, downhill will shorten the stride debris - does the animal understep or overstep it? Soft earth will have an effect on stride length.

3) Track Pack - Carrying these items with you will help in learning to track.

  • Magnifying glass - large 2-4 x, jewelers loop 10x
  • Tape measurer - thin, metal 8'- to measure stride, straddle etc.
  • 6" plastic ruler - to measure track
  • Small notebook
  • Pen
  • Ziplock bags - for scat, bones etc.
  • Peterson's Field Guides
  • File Cards
  • Tweezers
  • Popsicle sticks and string
  • Price tags - for labeling.

All the information you need to find the next track is within the one you have. Never skip a track (cross-tracking) it doesn't teach you anything. If you hit "the wall" and can't find the next track, work at it, analyze it. This is how you learn to be a good tracker. If you spend 2 hours to find the next track, your skill will grow to a higher level.


In any tracking situation you need to be aware of what the local environmental hazards are in order to avoid accidents. This is a general list for a typical mid-Atlantic forest region.

Why Scientists Turned This Taxidermy Bird Into a Robot

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To revist this article, visit My Profile, then View saved stories.

This would be a whole lot harder if biologist Gail Patricelli didn’t have an excellent sense of humor. Because I’m expected to sit here like a professional and not guffaw at her invention: A real-life fembot, which is probably not what you’re imagining but instead a taxidermied bird stuck on wheels. It tears around a table in her lab, turning its head back and forth, stopping periodically to bend up and down, as if pecking at the ground. Patricelli laughs as she steers it around, which I take to mean I’m allowed to laugh too.

The fembot (Patricelli’s name for the contraption) is serious science, though, a machine that’s helping her tease apart the wild—and wildly complex—mating ritual of the sage grouse, a species under threat. Because it turns out it’s pretty easy to trick a male sage grouse into trying to mate with a robot.

The male sage grouse is perhaps the only thing more absurd than a female robotic sage grouse. When they gather to display in a mating arena known as a lek, they sound more like sci-fi than anything remotely bird-like—a shreeet of a passing laser blast, and a low pop of, well, your guess is as good as mine (see video above). Males also inflate patches of thin skin on their chests. “They have a whole bunch of muscles on their chest that allows them to manipulate this like an elaborate balloon animal show,” Patricelli says.

Females are comparatively drab, which makes turning one into a convincing robot easier, though far from simple. It begins with a specimen that met an unfortunate end by way of car or powerline. Meaning, it’s going to need some reconstructive surgery. “I do my best to try to make it look realistic,” Patricelli says. “I have learned a lot and spent a lot of time in the arts and crafts section.”

Her lab’s first-generation fembot rolled on model train tracks, but ended up getting stuck when quarreling males would kick dirt onto the rails. The next generation got off-roading tires. “They can move around and peck on the ground and look uninterested in mating anytime soon, or they can remain more upright looking back and forth looking like they're getting closer to being ready to mate,” says Patricelli.

Males fall for it, and hard. Which maybe isn’t saying much. “When there are no hens around, they often try to mate with dry cow pies,” says Patricelli. “So the bar's pretty low for us to fool the males.”

Still, if Patricelli rolls a fembot up and it doesn’t move naturally (the tires might seem like a giveaway, but you’d actually have a hard time seeing them on a grassy plain), males will spook and fly away. But by loading the already-realistic-looking fembot with complex behaviors, Patricelli can use it as a consistent stimulus to test a whole field of males.

See, Patricelli’s got a theory. To help understand the complex dynamics of sage grouse mating, she’s turned to economic models of negotiation, specifically the idea of an allocation decision, in which males are limited by how much energy they can spend on courtship.

“You can't help but think of a big open air bazaar, with a bunch of vendors out there that are all trying to sell their wares,” says Patricelli. Those would be the males. “They all want the customers to come visit them.”

The males have to keep an eye not only on potential patrons, aka picky mates, but on other vendors, their competition. If one particularly attractive male seems to be getting a lot of business, other females will take notice, not unlike a farmer drawing a crowd at a market. “We had our top male mate 37 times in one morning, and 23 of those matings were in a 23 minute long period of time,” says Patricelli. “So they're not looking for a long-term relationship.” Males, though, also have to choose who they court wisely, given how elaborate and energetically costly their displays are.

Patricelli can test this dynamic with some good old robotic trickery. “We send the robot out and have her not looking particularly interested in the male,” she says. This gets the male courting. “Then we have what's called an outside option in economics, where we have another hen heading out, and the male now decides whether to continue investing in that first courtship effort or shifting gears and focusing on trying to convince that second female to mate.”

“In economic theory, youɽ predict that he would only make that adjustment if the second hen is more valuable than the first one,” Patricelli says. With the fembot, the team can manipulate the visual signals the robot is giving to signal interest or non-interest, in order to test that hypothesis. (Results forthcoming—she and her team are still collecting data.)

Patricelli isn’t just exploring sage grouse mating dynamics, but the impacts environmental changes have on the lek. For one, the team has been trying to figure out where the sage grouse are most comfortable. Food availability in particular is a major concern. “We've done some experiments with her where we're looking at how they're foraging, and where they're foraging affects what happens on the lek,” says Patricelli. “That helps us understand the basic courtship dynamics, but it also gives us a better idea of what makes good sage grouse habitat.”

And boy, do they need it. Sage grouse habitats are being infiltrated by cheatgrass, an invasive species that grows thick—unlike native sagebrush, which grows spotty—which can fuel massive wildfires that destroy their homes. Habitat degradation has cut the sage grouse’s numbers from 16 million to around 200,000.

Add to that human development, which brings both physical destruction of environments and the attendant noise pollution. But Patricelli’s study of the birds’ sensitivity to noise on their leks has actually helped land managers consider better rules to ensure the birds can strut their stuff undisturbed.

Perhaps one day, all the sage grouse will hear out on the lek is the quiet whine of a fembot turning its head. Long live the future.

How the Tree Frog Has Redefined Our View of Biology

Karen Warkentin, wearing tall olive-green rubber boots, stands on the bank of a concrete-lined pond at the edge of the Panamanian rainforest. She pulls on a broad green leaf still attached to a branch and points out a shiny clutch of jellylike eggs. “These guys are hatchable,” she says.

From This Story

A parrot snake homes in on red-eyed tree frog eggs, which can respond to its approach. (Christian Ziegler) A beloved symbol of biodiversity, the red-eyed tree frog, shown here in Panama, has evolved a flexible strategy for survival. (Christian Ziegler) Frog eggs one day after being laid. (Christian Ziegler) Eggs four days after being laid. (Christian Ziegler) Eggs clinging to a leaf over water hatch. (Christian Ziegler) Free-swimming tadpoles. (Christian Ziegler) Karen Warkentin says that frog embryos' behavioral decisions may be more sophisticated than we imagined. (Richard Schultz (3)) Why the bulging red eyes? To surprise predators so the frog can jump away—scientists call it "startle coloration." (Christian Ziegler)

Photo Gallery

Red-eyed tree frogs, Agalychnis callidryas, lay their eggs on foliage at the edge of ponds when the tadpoles hatch, they fall into the water. Normally, an egg hatches six to seven days after it is laid. The ones that Warkentin is pointing to, judging from their size and shape, are about five days old, she says. Tiny bodies show through the clear gel-filled membrane. Under a microscope, the red hearts would just be visible.

She reaches down to wet her hand in the pond water. “They don’t really want to hatch,” she says, “but they can.” She pulls the leaf out over the water and gently runs a finger over the eggs.

Sproing! A tiny tadpole breaks out. It lands partway down the leaf, twitches and falls into the water. Another and another of its siblings follow. “It’s not something I get tired of watching,” Warkentin says.

With just a flick of her finger, Warkentin has demonstrated a phenomenon that is transforming biology. After decades of thinking of genes as a “blueprint”—the coded DNA strands dictate to our cells exactly what to do and when to do it—biologists are coming to terms with a confounding reality. Life, even an entity as seemingly simple as a frog egg, is flexible. It has options. At five days or so, red-eyed tree frog eggs, developing right on schedule, can suddenly take a different path if they detect vibrations from an attacking snake: They hatch early and try their luck in the pond below.

The egg’s surprising responsiveness epitomizes a revolutionary concept in biology called phenotypic plasticity, which is the flexibility an organism shows in translating its genes into physical features and actions. The phenotype is pretty much everything about an organism other than its genes (which scientists call the genotype). The concept of phenotypic plasticity serves as an antidote to simplistic cause-and-effect thinking about genes it tries to explain how a gene or set of genes can give rise to multiple outcomes, depending partly on what the organism encounters in its environment. The study of evolution has so long centered on genes themselves that, Warkentin says, scientists have assumed that “individuals are different because they’re genetically different. But a lot of the variation out there comes from environmental effects.”

When a houseplant makes paler leaves in the sun and a water flea grows spines to protect against hungry fish, they’re showing phenotypic plasticity. Depending on the environment—whether there are snakes, hurricanes or food shortages to deal with—organisms can bring out different phenotypes. Nature or nurture? Well, both.

The realization has big implications for how scientists think about evolution. Phenotypic plasticity offers a solution to the crucial puzzle of how organisms adapt to environmental challenges, intentionally or not. And there is no more astonishing example of inborn flexibility than these frog eggs—blind masses of goo genetically programmed to develop and hatch like clockwork. Or so it seemed.

Red-eyed tree frog hatchlings were dodging hungry snakes a long time before Warkentin started studying the phenomenon 20 years ago. “People had not thought of eggs as having the possibility to show this kind of plasticity,” says Mike Ryan, her PhD adviser at the University of Texas in Austin. “It was very clear, as she was doing her PhD thesis, that this was a very, very rich field that she had sort of invented on her own.”

Karen Martin, a biologist at Pepperdine University, also studies hatching plasticity. “Hatching in response to some kind of threat has been a very important insight,” Martin says. “I think she was the first one to have a really good example of that.” She praises Warkentin’s sustained effort to learn big biology lessons from frog eggs: “I think a lot of people might have looked at this system and said, ‘Here’s a kind of a quirky thing that I could get some papers out of, and now I’ll move on and look at some other animal.’ She dedicated herself to understanding this system.”

Warkentin’s research “causes us to think more carefully about how organisms respond to challenges even very early in life,” says Eldredge Bermingham, an evolutionary biologist and director of the Smithsonian Tropical Research Institute (STRI, pronounced “str-eye”) in Gamboa, Panama. Warkentin, a biology professor at Boston University, conducts her field studies at STRI. That’s where she showed me how she coaxes the eggs to hatch.

The tadpoles leaping from the wet leaf still have a little yolk on their bellies they probably won’t need to eat for another day and a half. Warkentin keeps rubbing until only a few remain, stubbornly hiding inside their eggs. “Go on,” she tells them. “I don’t want to leave you here all by yourselves.”

The last of the tadpoles land in the water. Predatory bugs known as backswimmers wait at the surface, but Warkentin says she saved the tadpoles from a worse fate. Their mother had missed the mark, laying them on a leaf that didn’t reach over the pond. “If they were hatching on the ground,” she says, “then they would just be ant food.”

Warkentin was born in Ontario, and her family moved to Kenya when she was 6. Her father worked with the Canadian International Development Agency to train teachers in the newly independent country. That’s when she got interested in tropical biology, playing with chameleons, and watching giraffes, zebras and gazelles on the drive to school in Nairobi. Her family returned to Canada several years later, but at 20 she went hitchhiking and backpacking across Africa. “That was something that seemed perfectly reasonable in my family,” she says.

Before she started her PhD, she went to Costa Rica to learn more about the tropics and look for a research topic. The red-eyed tree frog’s terrestrial eggs caught her interest. She visited the same pond over and over again, and watched.

“I had the experience—which I’m sure other tropical herpetologists have had before and maybe didn’t think about—if you have a late-stage clutch, if you bump into them, they’ll hatch on you,” Warkentin says. “I bumped into a clutch, and they all were bailing out.”

She had also seen snakes at the pond. “What I thought was, wow, I wonder what would happen if a snake bumped into them,” she says, and laughs. “Like, with its mouth?” Indeed, she found that if a snake appears and starts attacking the clutch, the eggs hatch early. The embryos inside the eggs can even tell the difference between a snake and other vibrations on the leaf. “This is the thing, of going out in the field and watching the animals,” she says. “They’ll tell you things you didn’t expect sometimes.”

Biologists used to think this kind of flexibility got in the way of studying evolution, says Anurag Agrawal, an evolutionary ecologist at Cornell University. No longer. It’s exciting that Warkentin has documented wonderful new things about a charismatic frog, but Agrawal says there’s a great deal more to it. “I think that she gets credit for taking it beyond the ‘gee whiz’ and asking some of the conceptual questions in ecology and evolution.”

What are the advantages of one survival tactic over another? Even a 5-day-old frog has to balance the benefit of avoiding a hungry snake against the cost of hatching early. And, in fact, Warkentin and her colleagues have documented that early-hatching tadpoles were less likely than their late-hatching brethren to survive to adulthood, particularly in the presence of hungry dragonfly nymphs.

Plasticity not only lets frogs cope with challenges in the moment it might even buy time for evolution to happen. Warkentin has found that tadpoles also hatch early if they’re at risk of drying out. If the rainforest gradually became drier, such early hatching might become standard after countless generations, and the frog might lose its plasticity and evolve into a new, fast-hatching species.

One of the mainstays of evolutionary thinking is that random genetic mutations in an organism’s DNA are the key to adapting to a challenge: By chance, the sequence of a gene changes, a new trait emerges, the organism passes on its altered DNA to the next generation and gives rise eventually to a different species. Accordingly, tens of millions of years ago, some land mammal acquired mutations that let it adapt to life in the ocean—and its descendants are the whales we know and love. But plasticity offers another possibility: The gene itself doesn’t have to mutate in order for a new trait to surface. Instead, something in the environment could nudge the organism to make a change by drawing on the variation that is already in its genes.

To be sure, the theory that plasticity could actually give rise to new traits is controversial. Its main proponent is Mary Jane West-Eberhard, a pioneering theoretical biologist in Costa Rica affiliated with STRI and author of the influential 2003 book Developmental Plasticity and Evolution. “The 20th century has been called the century of the gene,” West-Eberhard says. “The 21st century promises to be the century of the environment.” She says mutation-centric thinking is “an evolutionary theory in denial.” Darwin, who didn’t even know genes existed, had it right, she says: He left open the possibility that new traits could arise because of environmental influence.

West-Eberhard says Warkentin’s group has “demonstrated a surprising ability of tiny embryos to make adaptive decisions based on exquisite sensitivity to their environments.” That kind of variation, West-Eberhard says, “can lead to evolutionary diversification between populations.”

Although not everyone agrees with West-Eberhard’s theory of how plasticity could bring about novelty, many scientists do now think that phenotypic plasticity will emerge when organisms live in environments that vary. Plasticity may give plants and animals time to adjust when they’re dumped in a completely new environment, such as when seeds are blown to an island. A seed that isn’t as picky about its temperature and light requirements might do better in a new place—and might not have to wait for an adaptive mutation to come along.

Also, many scientists think that plasticity may help organisms try out new phenotypes without being entirely committed to them. Early hatching, for example. Different species of frogs vary greatly in how developed they are when they hatch. Some have a stumpy tail and can barely swim others are fully formed, four-limbed animals. “How do you get that kind of evolved variation?” Warkentin asks. “Does plasticity in hatching time play a part in that? We don’t know, but it’s quite possible.”

The town of Gamboa was built between 1934 and 1943 by the Panama Canal Company, a U.S. government corporation that controlled the canal until 1979, when it was handed over to Panama. Gamboa, on the edge of a rainforest, is part ghost town, part bedroom community for Panama City and part scientific summer camp. Quite a few residents are scientists and staff at STRI.

When I visited, Warkentin’s team had up to a dozen people, including several undergraduates she refers to as “the kids.” One morning a posse of vigorous-looking young people in knee-high rubber boots, backpacks and hats departs Warkentin’s lab and strides across the field behind the school, past the tennis courts.

James Vonesh, a professor at Virginia Commonwealth University, who did a postdoctoral fellowship with Warkentin and still collaborates with her, points out his favorite sign in town, a holdover from the Canal Zone era: “No Necking.” It’s painted on the front of the stands at the old swimming pool, now part of the local firefighters’ sports club. Then he explains to one of the kids what “necking” means.

They walk down a road into a nursery for native plants, cross a ditch on a footbridge and arrive at Experimental Pond. It was built of concrete to specifications provided by Warkentin and Stan Rand, a revered frog researcher at STRI, who died in 2005.

On the pond’s far side is the group’s research area, bounded by a ditch on one side and a stream, then rainforest, on the other. There’s a metal-roofed shed with open sides, surrounded by dozens of 100-gallon cattle tanks used in experiments. They look like buckets set out to catch an array of extremely large leaks. Vonesh talks about the plumbing system with more enthusiasm than seems possible. “We can fill a cattle tank in three or four minutes!” he exclaims.

All that fast filling means the researchers can do quick experiments other aquatic ecologists can only dream of. Today they’re dismantling an experiment on predation. Four days ago, 47 tadpoles were put in each of 25 tanks along with one Belostomatid, a kind of water bug that eats tadpoles. Today, they’ll count the tadpoles to find out how many the Belostomatids ate.

A giant blue morpho butterfly flits by, its iridescent wings a shocking splash of electric blue against the lush green forest. “They come by, like, the same place at the same time of day,” Warkentin says.

“I swear I see that one every morning,” Vonesh says.

“It’s the 9:15 morpho,” Warkentin says.

Warkentin explains the experiment they’re finishing today. “We know that predators kill prey, obviously, and they also scare prey,” she says. When new-hatched tadpoles fall into a pond, water bugs are one of the threats they face. The tadpoles’ plasticity might help them avoid being eaten—if they can detect the bugs and somehow respond.

Ecologists have developed mathematical equations describing how much prey a predator should be able to eat, and elegant graphs show how populations rise and fall as one eats the other. But what really happens in nature? Does size matter? How many 1-day-old tadpoles does a fully grown water bug eat? How many older, fatter tadpoles? “Obviously, we think small things are easier to catch and eat and stick in your mouth,” Vonesh says. “But we really haven’t incorporated that into even these sort of basic models.”

To figure out how many tadpoles got eaten, the undergraduates, graduate students, professors and a postdoctoral fellow have to get every last tadpole out of each tank to be counted. Vonesh picks up a clear plastic drink cup from the ground by his feet. Inside is a water bug that was feasting on tadpoles. “He’s a big guy,” he says. He reaches into a tank with the net, pulling out tadpoles one or two at a time and putting them in a shallow plastic tub.

“You ready?” asks Randall Jimenez, a graduate student at National University of Costa Rica.

“I’m ready,” Vonesh says. Vonesh tips the tank as Jimenez holds a net under the gushing water. The guys watch the net for any tadpoles that Vonesh missed. “See anybody?” Vonesh asks. “Nope,” Jimenez says. It takes almost 30 seconds for the water to flow out. Most of the researchers wear tall rubber boots to protect against snakes, but they’re useful as the ground rapidly turns to mud.

A flock of grackles wanders nonchalantly through the grass. “They like to eat tadpoles,” Vonesh says. “They like to hang out and pretend they’re looking for earthworms, but as soon as you turn your back, they’re in your tub.”

Vonesh takes his tub of tadpoles to the shed where Warkentin photographs it. A student will count the tadpoles in each picture. Insects and birds sing from the trees. Something falls—plink—on the metal roof. A freight train whistles from the train tracks that run alongside the canal a group of howler monkeys barks a raucous response from the trees.

To scientists like Warkentin, Gamboa offers a bit of rainforest about an hour’s drive from an international airport. “Oh, my god. It is so easy,” she says. “There’s a danger of not appreciating how amazing it is. It’s an incredible place to work.”

During the day, the iconic red-eyed frogs aren’t hopping about. If you know what you’re looking for, you can find the occasional adult male clinging to a leaf like a pale green pillbox—legs folded, elbows tucked by his side to minimize water loss. A membrane patterned like a mosque’s carved wooden window screen covers each eye.

The real action is at night, so one evening Warkentin, Vonesh and some guests visit the pond to look for frogs. The birds, insects and monkeys are quiet, but amphibian chirps and creaks fill the air. One frog’s call is a clear, loud “knock-knock!” Another sounds exactly like a ray gun in a video game. The forest feels more wild at night.

Near a shed, a male red-eyed tree frog clings to the stalk of a broad leaf. Tiny orange toes outspread, he shows his white belly and wide red eyes in the light of multiple headlamps. “They have these photogenic postures,” Warkentin says. “And they just sit there and let you take a picture. They don’t run away. Some frogs are, like, so nervous.” Maybe that’s why the red-eyed tree frog has gotten famous, with its picture on so many calendars, I suggest—they’re easier to photograph than other frogs. She corrects me: “They’re cuter.”

Scientists think the ancestors of modern frogs all laid their eggs in water. Maybe the red-eyed tree frog itself could have evolved its leaf-laying habits as a result of phenotypic plasticity. Maybe an ancestor dabbled in laying its eggs out of the water, only on really wet days, to get away from aquatic predators—a plastic way of dealing with a dangerous environment—and that trait got passed on to its descendants, which eventually lost the ability to lay eggs in water at all.

Nobody knows if that’s how it happened. “That was a very long time ago and no longer amenable to those kinds of experiments,” Warkentin says.

But intriguing experiments on another kind of frog—one that might be still navigating the transition between water and land—are underway. Justin Touchon, a former PhD student of Warkentin’s, studies how the hourglass tree frog, Dendropsophus ebraccatus, lays its eggs, which are less packed with jelly and more prone to drying out than red-eyed tree frogs’. A female hourglass tree frog seems to choose where to lay eggs based on dampness. At ponds shaded by trees, Touchon found, they’ll lay eggs on leaves above the water, but at hotter, more exposed ponds, the eggs go in the water.

In a study published last month, he found that eggs were more likely to survive on land if there was a lot of rain, and more likely to survive in water if rainfall was scarce. He also looked at rain records for Gamboa in the past 39 years and found that while overall rainfall hasn’t changed, the pattern has: Storms are larger but more sporadic. That change in the environment could be driving a change in how the hourglass tree frogs reproduce. “It gives a window on what caused the movement to reproducing on land to occur,” Touchon says—a climate that shifted to have lots of steady rain could have made it safer for frogs to lay eggs out of the water.

Warkentin’s group is based on the ground floor of the Gamboa Elementary School, which closed in the 1980s. One morning, Warkentin sits on an ancient swivel chair with dusty arms at a retired office desk, doing what looks like a grade-school craft project.

On the floor at her left sits a white bucket with rows of green rectangles duct-taped to the inside. She reaches down and pulls one out. It’s a piece of leaf, cut with scissors from one of the broad-leafed plants by the experimental pond, and on it is a clutch of gelatinous red-eyed tree frog eggs. She tears off a strip of tape and sticks the piece of leaf onto a blue plastic rectangle, cut from a plastic picnic plate.

“You can do an amazing amount of science with disposable dishware, duct tape and galvanized wire,” she says.

She stands the card in a clear plastic cup with a bit of water in the bottom, where the tadpoles will fall when they hatch, and goes on to the next piece of leaf. The tadpoles will be part of new predation experiments.

There’s great explanatory value in simple models—but she wants to understand how nature actually operates. “We’re trying to grapple with what’s real,” she says. “And reality is more complicated.”

Bird seen 'frozen' in mid-air while 'twitching' in mysterious footage

The white pigeon remained in a flying position but appeared completely motionless in mid-air. While some viewers joked it was a flaw in Matrix, others suggested the bird had become trapped by thin wires

A bird has been filmed apparently frozen mid-flight in mysterious footage, sparking a wave of wild theories online.

The baffling incident took place in a quiet neighbourhood of Tuluá Valle, in Colombia, on Thursday, July 9, and was filmed by locals.

Footage first shared by Twitter user "Hechizero" shows the white bird appearing to remain motionless with its wings spread apart in the sky above a two-floored house.

Stunned pedestrians and curious bikers stop and look up to find the unusual sighting.

The camera pans to show the bird and it appears to be twitching in subtle motions.

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The clip was recently shared onto Instagram by another user, who wrote in the post: "There is a static pigeon in the air next to a 4G antenna and there are apparently no wires nearby. Tuluá Valle."

Viewers were quick to flock in with their suggestions for what caused the sight.

"It&aposs a flaw in Matrix," one joked.

"Morpheus has returned," a second one made a reference to the blockbuster.

"Drones, it&aposs a drone bird, that&aposs it," another guessed.

But other viewers had the more reasonable explanation that the bird had actually been caught by thin wires that are not seen on the video.

One attached a stock picture and wrote: "It could be cables even thinner than those in this image, the poor thing got stuck, you see at first how it sways a little."

A second viewer suggested: "There are four cables that are not well perceived, these come from another pole for electricity, the pigeon got stuck there."

In February, a mum caught a similar sighting on camera when she drove her children to school in Gallump, New Mexico, US.

A black crow was seen apparently suspended in the sky near some overhead wires above the train tracks.

If the bird had not been trapped by the wires, it could have been performing stationary flights.

A study by Standford University explains birds can remain motionless in the air as long as they fly into the wind at a speed equal to that of the wind.

They can perform stationary flights as long as they are flying with headwinds.

Amazing lizard breath: Dinosaurs probably breathed better than you do

Little-known fact: When it comes to extracting oxygen from the air we breathe, we humans are just OK.

Birds are more efficient breathers than us. So are alligators and, according to a new study, monitor lizards, and probably most dinosaurs were as well.

Humans are what are called tidal breathers. When we breathe in, fresh air moves into our lungs along progressively smaller airways, eventually ending in little sacs called alveoli, where our bloodstream picks up oxygen and deposits carbon dioxide. Then the “old” air moves out of our lungs along the same path it came in.

But birds, alligators and monitor lizards are “unidirectional” breathers. After the air moves into their lungs, it begins to follow a system of tubes similar to arteries, capillaries and veins. In this system, the air moves through the air tubes in only one direction.

[Updated, 12:10 p.m. PST Dec. 12]: Unidirectional breathing is complex. For more information on how it works, check out this reference page, sent in by a reader. Animations, videos, and graphics all illustrate unidirectional breathing.]

And, it turns out, their system is more efficient at extracting oxygen from the air than ours is.

Scientists discovered that birds are unidirectional breathers in the first half of the 20th century, after researchers noticed that pigeons breathing the sooty air of train stations showed just one black area on the lung. If the pigeons breathed like we do, scientists would have expected the entire lung to be black.

“The fact that only one part of the bird lung was dark suggested the air was flowing in one direction and that the first part of the lung to receive the contaminated air was filtering the particles,” said Colleen Farmer, an associate professor of biology at the University of Utah.

It isn’t that surprising that birds have developed a more efficient breathing system. Scientists hypothesize it may have evolved to help them support their high metabolic rates, or to help them survive when they fly at high altitudes, where oxygen is scarce.

But in 2010, Farmer published a study showing that alligators are unidirectional breathers as well.

“That’s when I realized it had to have a function other than supporting the high metabolic rates associated with birds,” she said. “I knew cold-blooded animals spend about 80% of their lives holding their breaths -- and so I formulated the hypothesis that this breathing would be important for mixing gases in the lungs during a breath-hold.”

On Wednesday, Farmer published a study in the journal Nature that shows monitor lizards are unidirectional breathers as well. She believes that further studies will show that all lizards and snakes are also unidirectional breathers.

"[Unidirectional breathing] appears to be much more common and ancient than anyone thought,” she said in a statement.

The scientists are still not sure exactly when unidirectional breathing first developed, but if it all evolved from one ancestor rather than concurrently, it is possible there have been unidirectional breathers walking the planet for 270 million years -- 100 million years before the first birds and 20 million years earlier than anyone thought.

And although it is impossible to directly study whether extinct animals like dinosaurs were unidirectional breathers, Farmer said that since alligators, birds and probably most lizards breathe this way, it’s likely the system was inherited from an ancestor the dinosaurs shared as well.

Farmer said the next step in her research is to determine just how common unidirectional breathing is or was.

“We want to look at a bunch of lizards and snakes and turtles and amphibians,” she said. “We have a lot of work ahead of us.”

You just read a story about hyper-efficient dinosaur breathing! Follow me on Twitter for more like this.

Birds placing sticks on train tracks? - Biology

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A new page featuring early demos from a tape Dan labled, "Ruffs."

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A COVID-19 Serial Memoir by Jean Fogelberg


We're so gratified by the amazing response to this wonderful recording of Dan shining, as he did, while performing solo in front of a live audience. Thank you to those of you who have written to us about your love of the CD set, and those who have posted such glowing reviews online.

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"Garth Brooks, Vince Gill and Amy Grant, Zac Brown Band, the late Donna Summer and Eagles are among the artists contributing to A Tribute to Dan Fogelberg , a long-gestating encomium to the singer-songwriter. Fogelberg&rsquos widow, Jean, produced the album, along with producer Norbert Putnam, Irving Azoff and Chuck Morris, all of whom played seminal roles in Fogelberg&rsquos career. Fogelberg died 10 years ago from prostate cancer.

Among the highlights are Brooks&rsquo muscular, robust version of &ldquoPhoenix&rdquo and Summer&rsquos gorgeous version of &ldquoNetherlands,&rdquo which features her singing over the original lush orchestrations. Train and Michael McDonald reinvent &ldquoSame Old Lang Syne&rdquo and &ldquoBetter Change,&rdquo respectively, while Zac Brown Band turns in an emotionally charged live take on &ldquoLeader of the Band&rdquo and Gill and Grant reimagine &ldquoLonger&rdquo as a sweet duet.

The album comes during a resurgence in Fogelberg and his music. In September, Part of the Plan, a musical based on Fogelberg&rsquos songs, opened at the Tennessee Performing Arts Center to strong reviews."


On 10th anniversary of his death, Eagles, Vince Gill and more pay homage to influential artist on new LP

&ldquoI always thought my music had to be flawless,&rdquo Garth Brooks told the Boston Globe in 1991. &ldquoOne of my biggest influences was [Dan] Fogelberg, and if you ever listen to his stuff, it&rsquos particularly flawless &ndash all the harmonies are perfect.&rdquo

"Dan Fogelberg&rsquos legacy was, without a doubt, bolstered by Brooks&rsquo endorsement, but the singer-songwriter best known for such mellow pop hits as &ldquoHard to Say,&rdquo &ldquoLonger&rdquo and &ldquoLeader of the Band,&rdquo as well as harder-edged rockers including &ldquoPart of the Plan,&rdquo &ldquoPhoenix&rdquo and &ldquoAs the Raven Flies,&rdquo had long been an influence on country music, having emerged from California&rsquos country-rock scene in the Seventies, which gave rise to the Flying Burrito Brothers, the Eagles, Linda Ronstadt and more. Fogelberg was just 56 years old when he died after a battle with prostate cancer, at his Deer Isle, Maine, home, on December 16th, 2007, 10 years ago this Saturday. But several important projects, long in the making, continue to celebrate his artistry and influence.

Although it took almost a decade to come to fruition, the singer&rsquos widow, Jean Fogelberg, organized a CD tribute to her late husband, with Brooks the first to be contacted and the first to commit to the project. Acclaimed producer-musician Norbert Putnam, whose work with Fogelberg includes his 1972 debut LP, Home Free, recorded in Nashville, is among the producers on A Tribute to Dan Fogelberg, released last month. On it, the tunesmith&rsquos songs are interpreted by Brooks and his wife, Trisha Yearwood (&ldquoPhoenix&rdquo), Vince Gill and Amy Grant (&ldquoLonger&rdquo), Zac Brown (&ldquoLeader of the Band&rdquo), Jimmy Buffett (&ldquoThere&rsquos a Place in the World for a Gambler&rdquo), Michael McDonald (&ldquoBetter Change&rdquo), Alabama&rsquos Randy Owen (&ldquoSutter&rsquos Mill),&rdquo Nitty Gritty Dirt Band (joined by Richie Furay on &ldquoRun for the Roses&rdquo) and more. Perhaps most poignantly, two of the artists involved, Donna Summer and Dobie Gray, have also died since recording their contributions to the remarkable collection, which merely hints at the depth and breadth of Fogelberg&rsquos lyrical and melodic gifts.

Head bobbing gives pigeons a sense of perspective

A pigeon tracking one of the moving dots before pecking it. Photo credit: Yuya Hataji.

A pigeon tracking one of the moving dots before pecking it. Photo credit: Yuya Hataji.

Having your eyes stuck on the side of your head is great to avoid turning up on someone else's menu. Providing almost 360 deg vision, wide-set eyes give pigeons the best chance of escape. But they also have lousy stereo vision. With little overlap between the views of both eyes, no one knew whether the birds are able to perceive depth or are trapped in a flat panorama: cue the comical walk. Pigeons are easily recognised from their eccentric gait, bobbing their heads to and fro. The head movement allows the goofy birds to stabilise their vision when strutting forward, by essentially holding the head still when the head bobs back. The question was, could the birds take advantage of the rapid rebound, when the head bobs forward, to help them to gauge the depth and distance of objects? To find out, Yuya Hataji, Hika Kuroshima and Kazuo Fujita, from Kyoto University, Japan, played some sleight of hand on the birds to find out whether their ungainly deportment allows them to distinguish near from far.

But first the team had to train the pigeons to peck at a dot on a TV screen to tell the researchers whether it was small or large. After showing each pigeon five static individual dots on a grid, each the same size, the team then provided the bird with a choice of squares that they could peck to tell the researchers whether the dot was small (selecting the left square) or large (right square). ‘The pigeons learned to do this in a few sessions since we have a lot of experience training pigeons on similar perceptual tasks’, says Hataji. Once the discs had got the birds’ attention and the animals were reliably distinguishing between the small (14.9–20.5 mm) and large (21.7–29.7 mm) dots, Hataji turned up the pressure. Now the discs began roving across the screen, so that the pigeons had to move their heads to keep track of them. Hataji rigged two cameras to monitor the birds’ head motion, and adjusted the movement of the dots depending on whether he wanted the dot to jump out of the screen – moving it in the opposite direction from the pigeon's head – or slide behind the screen – moving the dot in the same direction as the pigeon's head. Then he filmed each pigeon to find out how close it got to the screen before pecking at the dot. ‘Pigeons hold their head at a constant distance before pecking’, says Hataji, so if the bobbing head movements were helping the pigeons judge distance, then they would crowd the screen when the dot appeared farther away and stand well back when the dot jumped out at them.

Impressively, the pigeons could tell when the dots were in front of or behind the screen. The resourceful birds are able to determine how near or far objects are, thanks to their goofy head movements. Objects in the foreground seem to move differently from farther back objects as the pigeons move their heads, telling the birds which objects are near and which are distant. In addition, the birds were still able to differentiate between small and large dots, so head movements don't contribute to the bird's ability to determine size, although they did ponder longer before landing a peck when presented with intermediate-sized dots that were more difficult to categorise.

Despite their bird-brained reputation, pigeons take advantage of their unconventional gait to overcome their wide-eyed disadvantage. Bobbing their heads to and fro gives the birds a sense of perspective, allowing them to land pecks whether the target is near or far.

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