Flight, Feathers, and Freedom What birds mean to us and why we should treat them better.

This morning as I walked along the lakeshore,

I fell in love with a wren

—Billy Collins, 2003

On July 16^th a peregrine falcon, Falco peregrinus, flew above me and perched on a high, bare branch at the corner of North Bemiston and Pershing, just inside the Clayton, Missouri, city limits. It smoothed its feathers and then called several times, but not loudly enough to bring on the blue jays. In the next six weeks I saw one, two, or three more peregrines together about once a week, either on morning walks, or soaring above our University City backyard, less than a mile from the first sighting.

When that first peregrine lifted from its perch and was soon soaring high above me, it seemed to symbolize all that I love about birds, their beauty, their freedom, and their essential wildness, even against this semi-urban landscape. A part of that feeling is a sense of connectedness through these birds to an earlier America when the local urban center was across the river in Cahokia, or even before humans arrived on this continent.

But with these particular peregrines there is no such connection. By 1962 the Midwest subspecies of peregrine falcons was extinct. It had fallen to the very DDT pesticides that Rachel Carson warned us about, with eggs so weak that a brooding mother crushed them. I was able to see a peregrine perched so naturally only because University of Minnesota scientists Patrick Redig and Harrison Tordoff and their team began breeding and releasing peregrines, working out of Minneapolis and releasing beginning in 1982. These releases followed an earlier breeding and releasing program in the East. The Minnesota birds were a genetic mix of four different subspecies collected from western United States and Alaska, the Arctic, and Europe. They have persisted even though none had the large size and other characteristics of the Midwestern bird race we lost forever.

These peregrine falcons, therefore are not what they seem. The species has suffered from our distortion of their environment. The local subspecies is gone, but the species has survived in the form of other subspecies brought in at great effort and cost, at one point estimated at $2,500 per bird. We love birds, but our actions so often harm them. They also sometimes help. Peregrines, which once nested mainly on cliffs, now find convenient nesting sites on downtown buildings. The oldest record of this ancient relationship comes from another bird that has moved from cliffs to buildings, the rock dove or city pigeon. But our complex relationship with birds has ancient roots.

Food might be the earliest hominid use of birds. As long ago as 67,000 years, Neanderthals showed clear evidence of cooking and eating rock doves, the antecedents of our city pigeons. Ruth Blasco from the Centro de investigacion sobre la evolucion humana in Burgos, Spain, and her team found cuts and charring in patterns characteristic of cooking on the bones of rock doves from Gorham’s Cave in Gibraltar. Like the peregrine, these birds now nest on city buildings, but their original nesting sites were rock ledges on cliffs and in caves, where accessible nests would have been easily plundered.

But birds were not just food even for the Neanderthals. More than a thousand miles northeast of the Gibraltar cave is the Grotta di Fumane in the Veneto, Italy. In this cave, Marco Peresani from the University of Ferrara in Italy and colleagues found evidence that 44,000 years ago, Neanderthals removed feathers from bird wings. Since the removed feathers came from areas of the wing lacking significant flesh, the feathers themselves were the target. They came from large birds: lammergeyers, Eurasian black vultures, golden eagles, red-footed falcons and Alpine choughs. The investigators speculate that Neanderthals used these feathers for their own adornment.

Six hundred miles west of the Veneto cave is the Lascaux cave of southern France, famous for its Paleolithic paintings of animals dating to 17,000 years ago. Most of the paintings are of the large animals so important in the lives of the humans: horses, cattle, and bison. In contrast, there is only one bird, a simply drawn bird on a staff. It is adjacent to the cave’s only drawing of a man. Above the bird is the cave’s only drawing of a man, with two arms, two legs, a head, and a phallus. But he has a bird head and four digits on his hands, like a bird. His supine position and bird mask argue that he is dying, or in a trance. If those that have studied this image are correct, both the bird mask and the stick-bird represent grouse. Black grouse in the region have mating arenas where males dance to attract females. Perhaps these early humans used these birds for food, but the art suggests that they also seem to have attached some kind of non-utilitarian meaning to them.

These early stories tell of nascent human interaction with birds, but they do not tell us what people did to bird populations as a whole. The signature adaptation of birds is flight and that generally makes them hard to catch for humans and other predators.  Birds are most vulnerable to human hunting on islands lacking major predators, where they have evolved to lose their wariness and even their ability to fly. Polynesians arrived in New Zealand about 700 years ago, settling the last significant land mass lacking humans. There they encountered birds including the crested moa, long-billed wrens, Haast’s eagle, New Zealand geese, and Waitaha penguins. All are all now extinct. In total 25 species disappeared after the Maori arrival and before Europeans arrived. Many of them were flightless and had no way of escaping hungry humans. Even the giant moas, some 12 feet tall and 5000 pounds were extirpated.

Though even small human groups with stone-age tools can have devastating impacts on birds, the biggest challenges to our birds have come on continents settled by Europeans with guns. But the reasons for exploitation remain the same. Some birds, like the passenger pigeon, were hunted for food. Others were hunted for art, now in the form of lady’s hats bedecked with feathers.

Passenger pigeons specialized in foraging in huge groups on mast crops, like acorns. Mast cropping is an evolved tree strategy to avoid losing all their seeds to predators. They produce no seeds at all for a number of years, then all the trees synchronously fruit, overwhelming local seed predators so some seeds survive. Oak trees mast, as do many species of bamboo. Only a powerful flyer in huge flocks could specialize in moving around the country seeking local masts. Huge flocks meant easy hunting and powerful flight meant large tasty breast muscles.

People hunted passenger pigeons wherever both occupied the same space, but it was only the commercialization of the hunt of both adults and young in the late 19^th century and substantial habitat destruction that finished them off by 1914. This horrific extinction of what has been called the world’s most abundant bird contributed to a growing American enthusiasm for conservation.

But it was not only passenger pigeons that fomented the public will for conservation. The other impetus came from using feathers for art, if fancy hats can be considered art. In the late 1800s women’s hats were often adorned with feathers or even entire stuffed and mounted birds from around the world. Snowy and great egrets were among the favorites for their pure white whispy plumes. Feather collectors killed thousands of birds, often stripping entire rookeries of their adults and leaving chicks to starve or be eaten by crows and other predators.

A movement to stop the living feather harvest coalesced in 1896 when wealthy socialite Harriet Hemenway founded the Massachusetts Audubon Society and with her cousin Minna Hall convinced many Boston women to stop buying hats with feathers. Then in 1900 the Lacey Act passed, prohibiting trade in illegally acquired wildlife, fish, or plants. This was followed 18 years later by the Migratory Bird Treaty Act, which protects some 800 migratory birds from harvest of any kind and includes their feathers and bodies, dead or alive. In 1901 water birds were specifically protected from being killed for their feathers.

Around the same time, in 1900, Frank Chapman began the first Christmas Bird Count to take the place of the Christmas side hunt, in which teams of men competed to kill as many birds and small mammals as they could.

•  •  •

We love birds for their beauty, their feathers, and their flesh, but what do we really know about these light creatures that seemingly float so effortlessly above us? Birds evolved more than 150 million years ago, in the Mesozoic from feathered theropod dinosaurs. Their great glory is that they can fly, a trait that depended on early dinosaur feathers probably originally adapted for warmth. Birds first lifted aloft at a time when the earth’s atmospheric oxygen levels had increased, making air more dense which in turn made flight easier.

Flight is a seemingly magical trait that has evolved only four times, first in insects 350 million years ago, then in huge pterosaurs, now extinct, 228 million years ago, then in birds 150 million years ago, and finally in bats 60 million years ago. It is a trait that requires severe physiological and morphological adaptations to defeat gravity. Flight requires strength, lightness, and exceptional power. In birds, feathers, hollow bones, efficient one-way paths for air through the lungs, and a hot body are all involved. Flight may be challenging to achieve, but once accomplished it makes for fabulous success. Like birds, the other extant flighted groups are very successful. There are more insect species than all other animal groups combined. There are more birds than any other group of terrestrial vertebrates. Within the mammals, bats make up 20 percent of species, more than any other group except rodents.

Flight and the ability to escape predators are what allow birds to live in plain view of us, going about their daytime lives a flit away from potential human harm. This view and the songs are what give us an avian link to wildness, something we treasure. By contrast, the mammals that live among us, generally come out only under cover of dark.

However, birds are not always in the air. A newly hatched nestling cannot fly. This is true even for precocious shorebirds or ducklings that can hop about or swim, right out of the egg.  Songbird young are even more helpless. The time in the nest is perilous, for any snake, squirrel, or other hungry animals can eat them. But it takes time to develop. For example, black-throated blue warblers incubate their eggs for 12 to 13 days before they hatch. The female does nearly all the incubating. During these few days, all of the development happens. The developing embryo is buffered by the egg white and nourished by the yolk. After they hatch, black-throated blue warbler chicks remain in the nest another 8 to 11 days. Their adults feed them insects and other invertebrates, bringing them to nearly the mass of the adults. But they do not yet know how to find their own food and are only very weak flyers. It takes about another 20 days for them to gain these skills.

Birds are favorite topics for behavioral ecologists who have discovered many fascinating things about them, making them great subjects for nature films. Mating and parentage are among these. One of the big differences between birds and mammals is that bird babies of most species need both parents to feed them. Or to put it more accurately, the babies need two adults to feed them. Until we had DNA fingerprinting to figure out exactly who the parents were, people viewed the adult birds caring for young as the ideal nuclear family with mom and dad caring for ever-cheeping young. In 1853 Reverend Frederick Morris famously entreated that his parishioners “Be thou like the dunnock—the male and female impeccably faithful to each other.” However, this little brown bird that is common throughout Europe has a mating system so promiscuous that males and females alike sneak away for other mates. In fact, a dunnock male so assumes a female has recently mated with someone else that, before mating, he pecks her cloaca until she releases a droplet of the previous male’s sperm.

That birds of many species have social fathers and sometimes mothers caring for young that are not their genetic offspring was one of the stunning findings of the early days of paternity testing based on DNA techniques. This was not only the case for socially monogamous birds like the black-throated blue warblers. It was also true for species where some males had harems of females, like the noisy great-tailed grackles of the southern United States.

Kris Johnson and students studied this shiny black bird on the Rice University campus. She had to wear different hats during her study because these grackles grew to recognize her as she went up in a cherry picker to collect, sample, then return nestlings to their nests. She bled them to get a tiny sample of blood for DNA (bird blood has nucleated red blood cells carrying DNA unlike our own). She weighed them and she put little-colored leg bands around their ankles to recognize them later on. She then figured out if the social parents were the genetic parents, or if the social parents doing all the work were tending someone else’s genetic offspring.

Even in this species where males do not feed the babies and offer little more than nest defense Johnson found that the male in whose territory a female nested is not necessarily the father of her chicks. This is even true for a lone nest in a pine tree, which has a male that stands out in attentiveness to his nest, his mate, and his chicks. It turns out he is not the father of a single one of the chicks he guards so carefully. Instead, the genetic father is a male in the neighboring live oak, who has a dozen or so nests and females of his own. Perhaps after all the vicar was right. These birds are exemplary, caring or protecting the young in their nest without regard to parentage.

There are many other aspects to the biology of birds, from migration, to cooperative breeding, but here I will get back to our interactions with birds, starting with ways we interfere with their lives.

One sunny day as I stood in the backyard admiring the late summer flowers, I heard the dull bump of something hitting our dining room window. One feisty hummingbird had chased another away from our feeder and into the window. I picked her up. She lay stunned in my hand, allowing me to admire her iridescent greens and whites. After a minute or so, she rearranged herself and perched on my thumb. Then she buzzed off into the flowers. I hope she was the same bird I saw at the feeder a few minutes later.

I wish this were always the outcome of birds hitting glass. It is not. In 2014 bird conservationist Scott Loss of Oklahoma State University and colleagues published a paper on bird deaths from crashing into human structures in the United States. It is the kind of study I can hardly bring myself to read, at the thought of all those birds dying. Loss and colleagues found more than 92,000 fatality records for birds. Because they were compiling from many data sources, the original observers used various terms, including dead, collected, disabled, squashed, fractured, or injured. Not counted as dead were original terms stunned, exhausted, weak, disoriented, or sent to rehabilitation.

This kind of study requires a fair number of assumptions because the observed deaths are a small number of the total deaths. In order to extrapolate up to total numbers, the authors had to estimate how many of each type of building exists in the country. They had to consider differences between springtime and winter and the other seasons, particularly considering migration.

The numbers of bird deaths from hitting our homes came to an average of 253 million per year in the United States. This is a number that is hard to understand, so perhaps the per home number is better. Each year an average of 2.1 birds hit your home and die. I am glad that my little ruby-throated hummingbird did not become one of those numbers, but I am concerned that homes with feeders have more deaths, another result of this study.

But low homes are only one kind of building. To the 253 million they kill, we can add 339 million from medium-high buildings, and 508 million from high-rises, for total bird deaths of over a billion per year from crashing into buildings. Clearly, the positive effect of buildings as nesting places for peregrines does not begin to capture their overall impact.

Which birds are most likely to crash into buildings? My ruby-throated hummingbird ranks second only to purple finches as most likely to crash into homes like mine. Ovenbirds (a diminutive warbler), brown creepers, and house finches round out the top five. Medium-high buildings take down golden-winged warblers, painted buntings, ruby-throated hummingbirds, black-throated blue warblers, and swamp sparrows, while high rises extirpate Townsend’s solitaires, black-throated blue warblers, Connecticut warblers, brown creepers, and ovenbirds.

Buildings are not the only causes of bird death by collision. There are automobiles, power lines, communication towers, and wind turbines. Fortunately, the modern single tower wind turbines kill far fewer birds than the older lattice-style towers. Wind turbine deaths present a painful dilemma for environmentalists interested in low-carbon energy and wildlife, so it is good the more modern design is better for birds.

Besides things to hit, birds die from contact with agricultural pesticides, ocean oil and gas activities, and industrial fishing nets. The numbers from these causes come to more than 240 million. But the highest cause of bird death of all is a very familiar one.

My daughter came home from a long day in the office at the University of Texas’s famous tower to find her three cats staring rapturously up at the fireplace. Feathers were everywhere. Quickly she spotted the gnawed carcasses of several house sparrows. Apparently, they had flown down the chimney into the jaws of Carlos, Tina, and Adelie who were now waiting expectantly for more.

My daughter knows better than to let her cats outside where they can get infections, risk death by car, and kill birds. Unfortunately, this is not true for millions of other cats who are responsible for the deaths of 2.4 billion (10⁹) birds per year in the United States. The greatest threat to birds is feral cats. These wild cats account for about 69 percent of bird deaths. I guess it was a good thing my daughter rescued Carlos as a kitten from the forested roadside where she spotted him before he spent a feral life killing birds.

To some degree, we can estimate counts of the birds that have perished because of cats, buildings, and oil slicks. But it is much harder to measure how many birds have perished silently alone, unable to find a place to live or food to eat. I wondered what had happened to all the birds that once lived in the forests and prairies of Michigan, Illinois, and Missouri, the states I cross when I visit my parents.

I flew from Lansing home to St Louis via Chicago. After a Lansing takeoff, I looked down on the forested corridor along the Grand River. As we moved along towards Chicago, I saw a mosaic of corn, soybean, wheat, and brown, empty fields. But also in every road-defined grid were a few squares of forest. Sometimes their uneven borders indicated a creek or swampy soil. As we got closer to Lake Michigan, flying between Kalamazoo and South Haven, the wild areas increased. The field borders became more uneven. I looked down on many small lakes, sometimes glistening. Loggers cut nearly all the trees down in Michigan around the turn of the last century, but there is plenty of second growth in this corner of Michigan.

The landscape under the flight from Chicago to St Louis was different. Forest remnants had disappeared. Corn, soy, and occasionally wheat fields bordered each other with lines as straight as fudge cuts in a pan. Here forests bordered only the rivers and streams in curves and wisps. I guess prairies are more profitable to exploit than the sandy southern Michigan forests.

Increases in agricultural fields harm forest birds, but we need a comprehensive analysis of how humans have changed the birds overall. Globally, we are facing the sixth extinction on our planet. We are losing individuals, species, and habitats. A massive analysis of land plants and animals, including insects, other invertebrates, vertebrates, fungi, and plants used 320,924 measures of local species richness at 11,525 sites around the globe presented originally in 284 publications. The study had 41 authors beginning with Tim Newbold of the United Nations Environment Programme World Conservation Monitoring Centre. They found that in the most vulnerable habitats species richness has declined by 76.5 percent and overall it has declined by 13.6 percent. In their dataset birds were particularly well represented. The habitat I flew over from Lansing to St. Louis mostly fit in their definition of intensely used cropland. This is a category of monoculture with large fields, annual ploughing, inorganic fertilizers, pesticides, irrigation, and no crop rotation.” The little patches of Michigan woodland fit their definition of vegetation that was recovering after destruction. Except for Chicago, the cities we flew over fit their light use category: “suburban or small managed or unmanaged green spaces in cities.” While many birds have decreased, the red-winged blackbird has increased, adapting to habitat made more common with intensive agriculture, so that it is now the most common bird in Illinois.

The impact of human habitat change varies by the bird, something Peter Marra, head of the Smithsonian Migratory Bird Center, and his team have studied. For example, a study of six common species from rural to urban Washington DC found that robins, catbirds, cardinals, and song sparrows survived best in the mid to distant suburbs. They argued that this was because of food availability. The other two species they studied, Carolina chickadees, Carolina wrens, and house wrens did worse in more urban areas. Another study showed that cardinals actually thrived in the urban areas.

As habitat fails, birds lose a place to live. Birds of a migratory species typically return to the same place year after year. What do they do if their forest or field is now a parking lot? How drastically has our habitat destruction reduced the birds? It might be easier to ask what is left. Of the mosaic of forest in southern Michigan only four small spots are listed as unlogged native forest, according to Donald Dickmann, forestry professor at Michigan State University. One of them is Baker Woodlot, on the Michigan State Campus, and a place I have explored nearly all my life. In the 1950s and 1960s these woods contained red-backed salamanders, but that has not been the case for decades. I wonder how many birds have left this 78-acre reserve. Human modification of the environment has reduced numbers of some bird species and raised others, for an overall decline in bird diversity.

But we have done other things to birds. The human-changed geography of the landscape has actually caused some species to evolve new, measurable characteristics. One of the more interesting is what has happened to cliff swallows.

Field biologists Charles Brown and Mary Bomberger Brown base their studies at Cedar Point Biological Station in the middle of Keith County, Nebraska where prairie has not given way to irrigation circles. They have followed the cliff swallow colonies there for 35 years.  These graceful birds breed in colonies across most of the United States, eating billions of mosquitoes and other flying insects while soaring and swooping away from their mud nests. Sadly, sometimes these lovely birds swoop too low, or fly up too slowly and into a car.

Collecting road kill is pretty much a biologist’s specialty, for few others stop to inspect the roadside tragedies that line our highways. Charles Brown and Mary Bomberger Brown only stopped for certain road kills, the sad carcasses of cliff swallows. After all, a dead bird might have a little leg ring indicating it was part of their study. The dead birds could be measured and skinned to form part of a collection

As so often happens in field biology, their all-encompassing approach to their birds had a serendipitous benefit. They could substantiate their impression that deaths were declining over the years with reliable numbers. These numbers indicated a real decline in the number of dead swallows they picked up along the roads. They ruled out the idea that they might have driven less, picked up fewer birds, or that there was a trend towards less traffic or differences in car design. The number of cliff swallow nests had actually increased over the period. So did the numbers of cliff swallows recorded by the Breeding Bird Survey. What could the reason be? The theory that the researchers favor is that cliff swallows have evolved over this period to more effectively avoid cars. But first some background.

Cliff swallows historically nested on vertical walls of overhung cliffs. They nest in colonies where they can jointly watch out for predators, giving alarm calls to mob a snake, or benefiting from being in the middle of the group to avoid one. From the cliff swallow’s point of view, our highways are a huge extension of habitat, for nearly all bridges have overhung vertical surfaces. As the birds expanded across the landscape, agility became increasingly valuable. Agility benefits from shorter wings. From 1984 to 2011, wing length decreased from nearly 111 centimeters to nearly 107 centimeters in the birds the scientists measured from the colonies. By contrast wing length of those birds found as roadkill increased from 108 centimeters to 111. It seems that longer wings are disadvantageous in human environments, probably because they reduce maneuverability.

One of the biggest ways in which we have changed birds is to move them around. Some are accidental establishments of pets released into the wild. In North America and Europe, monk parakeets, are common in warmer cities like Houston and Barcelona, but also thrive as far north as Chicago or Brussels. Rose-ringed parakeets, from Africa and Asia, have been similarly successful in moving far north, perhaps because they also nest socially. But there are other cases where people released birds with the express purpose of establishing them in nature.

Just this year, Tim Blackburn of University College in London and his team explored all known bird introductions from the year 1500 to 2000 and found records of nearly 3700 cases. Most are in the last 25 years but numbers began to rise from 1851. One of the big increases was the introduction of Shakespeare’s birds by Eugene Schieffelin in 1890, most notoriously a winter release to Central Park, New York City, of 60 starlings, which now number 200 million in the United States and have displaced woodpeckers from their nesting holes. But there are thousands of other cases of live birds transported to new environments, particularly by British colonists to the United States, New Zealand, and Australia. It may seem stunningly naïve today, but acclimatization societies in the colonial era formed explicitly to move birds back to Britain and from Britain to distant homes. This was not done only for familiarity, but also for food,  sport, and feathers. For example, colonial New Zealanders of any class could hunt quail and pheasant once they were introduced. Back in England, only the titled could do so.

An earlier bird transplantation involved moving the great-tailed grackle from the Mexican coast to the highlands. During 1486–1502, Aztec emperor Ahuitzotl introduced the noisy great-tailed grackles from coastal Veracruz to Mexico City, over 200 miles west and 7,350 feet higher. This was figured out by some of the earliest bird scholars anywhere. Bernardino de Sahagún and his group reported this movement as part of a study of the birds of Tlatelolco, in the valley of Mexico in a scholarly report in 1577! Apparently, the emperor moved these birds because he missed the bird sounds of his coastal home. It might have been hard for great-tailed grackles to get established so high, but another action helped. The emperor claimed the birds as his royal symbols. He forbade any hunting or interfering with the birds. Under these conditions, they thrived and spread.

•  •  •

I began this piece with the ways that humans have used birds for food and for art. Then I moved on to the many ways that our distortion of the natural environment has harmed birds. This includes both harming birds directly and also harming them by moving them around. There is one more topic essential to understanding our relationship to birds that is founded on how much people love birds. That is birdwatching and citizen science. The National Audubon Society has over half a million members in more than 500 chapters in the United States. It is responsible for conserving millions of acres of essential habitat for migrating birds, in various programs, including direct ownership, and working with landholders interested in conservation practices.

Another conservation organization focused on birds is Ducks Unlimited, that began in 1937 after waterfowl were threatened by drought-based wetland loss. Their sole mission is habitat conservation, whether it be by purchasing land, or partnering with individuals, or other landowning groups. They have conserved over 5.5 million acres in the United States alone. If we count land in North America including Canada and Mexico that they have directly conserved or influenced, it comes to 245,312 square miles or nearly the area of Texas (268,597 square miles). Ducks Unlimited has more than 620,000 adult and more than 45,000 youth members as of the beginning of 2017.

Conservation of habitat is essential for birds to thrive. Many argue that for us to thrive we must get outside and connect with wildness. One way to do this is on all the lands that have been preserved. Another is to participate in documenting what is happening to bird populations. Thousands of people log the numbers and locations where they see birds. The Cornell Laboratory of Ornithology in Ithaca New York leads in organizing these efforts, particularly with eBird. Scientists can use the data collected by these citizen scientists to understand bird numbers and locations. They can track migration of any species as they move north. They can see what species are declining or increasing and where. Observations entered into eBird make them valuable to the entire scientific community, but this is not why people get outside with their binoculars and look skyward, or into the leafy treetops. It is not why people listen to birdsong when they step out the door. Birds like no other organism connect us to the wild world, one that was once all we knew.