The Secret Life of Shorebirds
I just returned from field research on red knots at Padre Island National Seashore in Texas, a place better known as a nesting site for Kemp’s Ridley Turtles than for shorebirds. We nearly accomplished all our banding objectives in the first few days, but then the knots left. Still at low weight, it’s unlikely they left successfully prepared to reach their Arctic breeding areas. They could have flown over to the Laguna Madre, a large hyper-saline, state-sized bay on the backside of the island, but a cursory search turned up nothing. They might have moved up the Texas coast, but why do so when the donax (the small clam they rely upon to gain weight) were abundant? I returned home to Greenwich, N.J., stumped.
How does a flock of birds reach such decisions, and what roles do individuals play? Through observation, radio telemetry and other gadgets over my 35-year career, I have known individual red cockaded woodpeckers in South Carolina, black bears in Georgia’s Okefenokee Swamp, bald eagles in southern New Jersey and sharp-shinned hawks on the Cape May Peninsula. These projects and others had specific management or scientific goals, but sometimes it’s also like peeking into someone’s window: you can’t avoid observing the daily lives of animals. These indirect-yet-intimate relationships are rarely published, yet they provide a unique understanding that profoundly alters a wildlife biologist’s view of an animal’s life.
In my studies I saw animals making choices that distinguish them as individuals: some cautious, others brazen, some lazy, others industrious. How is that different from us? We pretend we are unlike all other human beings, yet we fall into categories. While we think we stand apart, we follow the same paths as others, over and over again behaving and thinking like our kind. Animals are often characterized as cogs in a population that is one cogs in an ecosystem, but aren’t we? Admittedly, they act on instinct in ways we don’t, but don’t people make money on Wall Street when they successfully predict our instincts and innate behaviors?
I’ve often thought about the relationships between shorebirds in a flock. A biologist will tell you flocks find food easier (many probing bills searching for clumped prey) and avoid predation better (many alert, wary eyes) than individuals. These two phenomena are not unimportant or unrelated. Shorebirds eat to satisfy their immediate needs, but also to build weight should food become scarce. Gain too much weight, however, and a peregrine falcon may pick you out of the crowd to satisfy its need. Flocking helps individuals balance these two important contingencies.
I know these things, and still, a flock is a perfect mystery to me. Who hasn’t watched a flock of birds flying and wonder at how perfectly they communicate. They become a single organism, a flying group of cells in perfect communion. Still, there is no surrender of individual will. This past February, while in Tierra del Fuego — the Western Hemisphere’s most important red knot wintering area — our team watched groups of hundreds of knots make up their minds to fly north and begin their 10, 000-mile journey to their Arctic breeding grounds. They flew high above us in ever widening circles, lifting then falling only to lift again, some flying so high we could only see them with our binoculars. Some took off into the sky appearing certain to fly north, then just as certainly turned around and landed. Others circled for nearly an hour, uncertain whether to go forward or to return, only to fly out of sight. Looking closely, though, you could see that much of the indecision started with one or two birds making a contrary move, often leading the rest to follow. Or not. It was mystifying.
We saw none of that on Padre Island. One day they were there, the next they were gone. Prior to our team’s arrival, 700 red knots used Padre Island National Seashore. The day we arrived, there were only 250. Two days later only five remained – another knot mystery unsolved.