Birds: To See Them Is Not to Know Them
There is so much more to the lives of birds than we can see on the surface.
I have been a field biologist and ornithologist for 25 years, so you might think I have high standards when it comes to connecting with the wild and am satisfied only with sightings of hard-to-find birds. During the winter, at my farmhouse in rural Pennsylvania, I have a bird feeder on the porch only a few feet from the dining room window, and admire the nearly nonstop visits by ordinary birds such as hairy woodpeckers, downy woodpeckers, black-capped chickadees, tufted titmice, white-breasted nuthatches, slate-colored juncos, blue jays, and northern cardinals.
These are some of the common feeder birds that I have seen thousands of times before, but every sighting brings an important token of a renewed connection with nature and, occasionally, a surprising observation. The experience of quietly viewing nature through a window, from the warmth and safety of your home, is obviously enhanced enormously by luring colorful and interesting birds to the scene with a concentrated source of food. Here, I argue that a deep knowledge and understanding of the natural history and behavioral ecology of birds provides us with a more meaningful experience than simply seeing birds as beautiful, entertaining ornaments for our backyards.
Chickadee winter flocks are comprised of breeding pairs who, during the summer, defended nesting sites and territories from each other. In fall, the breeding territory boundaries break down, and chickadee pairs come to together and cooperate to defend a much larger winter territory from neighboring flocks. That year's young birds, facing their first cold winter, join the adults. A chickadee flock is a complex social network and has a clear-cut pecking order, with older and larger birds in the top positions, and socially dominant over younger newcomers. There is a parallel hierarchy, one for males and one for females, and the top-ranked birds of each sex usually pair up and breed together the following spring. Social rank determines access to winter food and hence winter survival. Low-ranked birds are subordinate and promptly leave the feeder when a more dominant bird arrives, so as to avoid physical aggression and possible injury. Those low-ranked birds that do survive the winter often cannot breed because the top-ranked birds claim all the available nesting territories and there is not enough forest to go around for subordinate pairs.
Most young birds live as the lowest-ranked birds and wait in line for a higher social position, gradually moving up in rank in the winter flock as older birds die. Nevertheless, about a quarter of young chickadees take a different tack, drifting between flocks on a daily basis rather than having a single home flock. If a top-ranked chickadee disappears, then a wanderer quickly appears and jumps the queue, claiming the vacant position.
During the breeding season, the stakes shift from food and social status to sexual competition. According to DNA testing, although chickadees are socially paired and seemingly monogamous, many offspring are the result of females mating outside the pair bond. Female chickadees eavesdrop on male-to-male interactions by listening to dawn song contests between neighboring males that duel using their fee-bay song. A female can discern which male is dominant during boundary disputes, and then the next day she visits that neighbor to sneak copulations.
As I sit writing, watching the chickadee action at my feeder only a few yards away from my laptop, I don't just see cute, tuxedo-clad, bundles of energy. I see a social network of dominant and subordinate birds, an underworld strategy of flock switchers, and future philanderers. How can I not be awed by the world of the chickadee? Whether in your backyard or a wilderness area, knowing versus seeing birds is an entirely different experience with nature.
This can be thought of as a kind of nature literacy. If you pick up a book in a completely foreign language you may be able to enjoy the illustrations, but since you can't read the text you will get little out of the experience. By learning the natural and evolutionary history of birds, you become nature literate and can understand what you are seeing. Just as watching high-definition scenes of nature on television does not fully substitute for a window view of real nature, I would argue that viewing nature without knowing it does not fully satisfy the human need for other-than-human experiences. There is more to nature than attractive, peaceful scenery. There is a complexity and deep evolutionary history that teaches us what nature, and ourselves, are really all about.
Our ancestors had no understanding of evolution, prior to Charles Darwin's theory of natural selection, but they did have a comprehensive knowledge of the ecology of the plants and wildlife around them because it was a matter of survival. Today, many North Americans who live in suburban and urban areas are largely illiterate when it comes to nature. In Toronto, I have seen my neighbor's children scream in fear at the sight of a moth, and I know several parents who believe that the long-legged, harmless crane flies that hatch out of the lawn in late summer are in fact giant mosquitoes that must be dispatched at once with a tennis racquet or chemical attack. Yet I have met few people disinterested in learning more about the other-than-human world around them.
In the natural world, competition for sex and resources is near universal. Sex, adultery, divorce, and daily threats and acts of violence are common in the bird world of the backyard. Male birds are under pressure to impress mates, females hold out for the highest-quality males, parents must share the burden of child care, and neighbors fight over space and food. The details of how these sexual and personal conflicts are resolved are the product of a long history of natural selection that favored winners over losers, gradually changing the genetic makeup of a population one generation at a time. An evolutionary lens can be used to better appreciate the melodies of the robin, flash of red on the cardinal, and amazing journeys of our songbirds that arrive so casually in spring after traveling thousands of kilometers.
Birdsong is music to our ears, but to birds it is also a sophisticated weapon to keep competitors at bay. Songbirds often have individually distinctive songs, and gauge their aggressive response to a singer according to prior social interactions with that bird and the possible threat it poses. Not every song is created equal, and some song types are saved for the most aggressive interactions. The trill, for instance, comprises almost identical notes repeated in a fast succession that requires a precise coordination of vocal muscles and airflow. The sound produced is a trade-off between how quickly a bird can repeat the individual units versus the frequency range that each unit spans, such that rapid broadband trills indicate high male quality and signal that the singer should be treated as a serious challenge. Females also listen to songs, and prefer males with more complex songs or a bigger repertoire. My research on hooded warblers has shown that males with a weak song performance have mates who sneak off territory to obtain extra-pair copulations from neighboring males that sing at a higher rate. Most songbird neighborhoods are social networks where individual qualities are broadcast through song. A male territory owner recognizes his rivals individually, and continually updates his assessment of each rival's immediate and future threat, and meanwhile females are eavesdropping on male performances.
The stunning color patterns of songbirds are also used in communicating threat and individual quality. The common yellowthroat is a little warbler, and males have a Zorro-style black mask and challenge rivals with a ringing witchity-witchity-witchity song. The mask is used as a status signal, and males with bigger masks are socially dominant over other males as well as preferred as mates by females. In some birds, like northern cardinals and house finches, it is the red coloration that reveals so much about the wearer. The intensity of red and orange colors indicates a bird's ability to find and consume foods rich in carotenoids. Eating carotenoid-rich foods does not guarantee a male will have sexy colors, because these chemicals are also used in the immune system. Females prefer red males because only a healthy male can afford the luxury of showing off carotenoids in his feathers.
People who provide nesting boxes for purple martin colonies spend many a lazy evening admiring the acrobatics of their tenants. There is no doubt that purple martins are masters of the sky, plucking dragonflies out of the air with ease and then flying into the impossibly small hole of their nesting compartment at breakneck speed. The martin's long tapered wings and streamlined body say it all: flying machine. The past few years I have collaborated with the Purple Martin Conservation Association to track martins to their wintering grounds in South America--the first time this has ever been done with songbirds. Martins are described in the scientific literature as leisurely migrants, but our birds from northern Pennsylvania typically fly to the Gulf Coast states, across the Gulf of Mexico, and arrive at the Yucatan Peninsula within five days of leaving Pennsylvania. This is a trip of 2,400 kilometers, including an 800-kilometer overwater flight, in less than a week. In spring, most return from the Amazon basin of Brazil (7,500 kilometers) in only three weeks, averaging 350 kilometers per day. When viewing an iridescent black-blue male advertising his nest site with his complex, gurgling song or a female forcibly evicting another who dared to enter her nest cavity, it is hard to believe these birds have just flown from South America. Aristotle was so puzzled by the sudden appearance of swallows in spring that he assumed they buried themselves in the mud to survive winter, much as turtles and frogs do.
Nature literacy not only enriches our own experience of nature, it is also a powerful weapon for conservation and environmental sustainability. Margaret Morse Nice, a pioneering ornithologist famous for her bird behavior studies in the 1930s, wrote in her autobiography: "I thought of my friends who never take walks... "for there was nothing to see." I was amazed and grieved at their blindness. I longed to open their eyes to the wonders around them; to persuade people to love and cherish nature.
She argued that the more we know and understand nature, the more we will care about what is being lost. Although many people do not have the time or means to travel to wild places, the songs, colors, and behaviors of common birds have much to teach us about the wild. The wild in this case is not one of remoteness or exotic scenery but rather of evolutionary adaptation that took place long before humans dominated the planet.
Reprinted from The Rediscovery of the Wild, by Peter H. Kahn Jr. and Patricia H. Hasbach Copyright (c) 2013 Massachusetts Institute of Technology, Published by The MIT Press.