Beaks, Bones and Bird Songs: How the Struggle for Survival Has Shaped Birds and Their Behavior - Roger Lederer (2016)

INTRODUCTION

image

It’s Tough To Be a Bird

There are some four million different kinds of animals and plants in the world.
Four million different solutions to the problems of staying alive
.

—DAVID ATTENBOROUGH

Look outside your window, take a walk, go fishing, watch a video, or do anything else that allows you to see birds in the wild. You may get the impression that birds are blithely going about their business, happily chirping, singing, and scratching among the leaves, flitting from branch to branch, clambering up a tree trunk, or soaring through the sky barely moving a feather. Looks like an easy life. Cultural symbols like the dove representing peace, the bluebird signifying happiness, and the robin as the harbinger of spring reinforce the idea that birds have not a care in the world. But we don’t often see the arduous challenges a bird faces every moment of every day.

Of the many hours I have spent in the field, watching birds flying, feeding, resting, and nesting, I was most affected by those moments when I saw birds searching for food in blowing snow, sitting on the surface of an ocean fighting threatening waves, and flying in serious winds. I wondered: how do birds make it from hatching to adulthood and from year to year after that?

Birds have to be on task all the time. They have to use their senses to find food, migrate, withstand the weather, avoid predators, compete with each other and alien species, and face a myriad of other trials. This book is about the abilities, adaptations, and behaviors birds possess and employ to survive from one day to the next. It is only the most physiologically, anatomically, and behaviorally well-tuned birds who successfully meet these challenges and go on to the most important goal in their life, reproduction.

image

The phrase “free as a bird” implies a carefree existence and the liberty to go anywhere, anytime, but birds are not as free as their aerial life implies.

Accurate figures for mortality and longevity of wild birds are nearly impossible to determine, but there are trends. Only about 50 percent of White-eyed Vireos in the southeastern United States return to their breeding grounds from their winter quarters, and merely 36 percent of Downy Woodpeckers, resident all year throughout much of North America, survive from one year to the next. Songbird adults have a 40–60 percent survival rate from year to year. Of their young, perhaps only 10 percent make it from egg to adulthood the following year. This means that a two-year-old songbird is a one out of twenty miracle. This short life expectancy is a result of the many dangers birds face. And while bigger birds have a lower mortality rate than smaller birds, they all face hazards every day. Unlike humans, birds don’t seem to get closer to their demise as they age; instead of slowly declining, most birds, after reaching maturity, have an equal chance of dying suddenly at all times of their precarious life. Sick or injured birds are rarely seen in the wild as illness or injury puts them at immediate risk of death, so you only see healthy birds on your bird walks.

Evolution has been at work on birds for more than 200 million years, shaping them into adept and adroit organisms. But birds today not only face the challenges that natural selection throws at them, but an entirely new set of obstacles, thanks to us. Things started to change for birds shortly after humans came on the scene. Early humans incorporated birds into their diet. Then agriculture came along, usurping habitat but also inadvertently providing food for birds. As civilization matured, bird feathers, bills, and bones became adornments for human culture; later, birds were domesticated for meat or eggs. Bird hunting became more efficient with the advent of guns and as civilization spread, habitat shrank. Massive destruction of wildlife of all sorts was common, including the commercial hunting of many bird species for food and feathers, until the passage of the Lacey Act in the United States in 1900—the first federal law protecting wildlife. The Migratory Bird Treaty Act of 1918 further protected migratory birds. These laws made a difference in North America, but many bird species live in or migrate through areas of the world that don’t pay much attention to the needs of birds or their protection. Today about 1400 of the world’s 10,000 bird species are threatened with extinction.

We have destroyed habitats and replaced them with cities, highways, tall windowed buildings, transmission towers and lines, microwave antennas, wind turbines, and lights—along with millions of cats. Birds have always contracted diseases, but humans have altered the environment and allowed pathogens to spread more quickly. A solar plant in the Mojave Desert concentrates the sun’s rays so strongly that birds are incinerated if they happen to fly through it. Birds have evolved rather amazing and often unique adaptations to the environment, but as the world changed, those adaptations became increasingly less effective. Birds never evolved defenses against windows or lights, buildings or towers, or the large number of our feline friends. Climate change has caused changes in bird migration patterns, but what the long-term effect will be is unknown.

With ornithological science as the background, this book will explore the common and unusual ways birds put into operation their physical and behavioral adaptations. What everyday challenges does a bird face and how does it survive? Seeing ultraviolet, finding food without seeing or touching it, flying thousands of miles nonstop, maneuvering deftly and speedily through thick forests, navigating by smell, surviving extremes of weather, sharing community resources, and changing their songs in noisy cities are just some of the amazing things birds do to simply make it to tomorrow and cope with the challenges of a changing planet.