Life and Work
The challenges faced by breeding birds
Chris Petrak fills his time with photography and birding. He has published a second collection of his essays, More Tails of Birding. It is available in local bookstores and at www.pondvillepress.com. He blogs at www.tailsofbirding.net.
Originally published in The Commons issue #166 (Wednesday, August 22, 2012).
WILLIAMSVILLE—The breeding season for the birds is just about over. In my yard it has been a successful and entertaining season, with a succession of young birds being fed in the trees and bushes and around the feeders. But what I see in my yard is just a fraction of the activity, challenges, and drama of the breeding birds.
As an example, let’s begin with a few dry facts about the American Robin. The male and female build a cup nest from scratch. Typically, four eggs are laid and are incubated by the female for two weeks. The young are fed in the nest for two weeks and are then fed by both parents as fledglings. A pair of robins will raise two or three broods each year.
Now consider: if every egg hatches and every hatchling fledges and every fledgling survives, this would mean that a single pair of robins would add eight to 12 new robins to the robin population in a single year. If all robins were similarly successful, the robin population would increase on average five times in one breeding season. Clearly, we would soon be overrun with robins.
But that degree of nesting success rarely occurs.
The eggs and the nestlings of birds are threatened by many predators: weasels, raccoons, red squirrels, snakes, jays, crows, hawks, and owls (to name just a few). And don’t forget your house cat among the predators. Birds are hosts to many parasites: bird-lice, fleas, louse flies, ticks, and mites all dine on the birds and their young.
Storms can damage nests. If the nest has been built anywhere near humans, deliberate or inadvertent disturbance may occur. Once the young are out of the nest, the dangers increase. Young birds are squawking and fluttering to attract the attention of their parents so that they can be fed, but this may also attract the attention of all of those nest predators and more.
Food supplies affect the ability of birds to successfully raise young. A few years ago, cuckoos were common in our area, in conjunction with a variety of caterpillars chewing up the leaves of the trees. Several years ago, our yards were overrun with chipmunks. That same summer, Barred Owls had remarkable success in raising their young.
But then came the winter when the food disappeared beneath the snow pack and the young owls were unable to feed themselves. A few were found and taken to wildlife rehabilitation centers; the others perished. This summer has been another banner year for chipmunks, and probably for owls and hawks as well. What will happen to those young if the coming winter is typically harsh?
The likelihood that a nesting pair of birds will successfully hatch and raise a full clutch is quite low: an egg might not hatch, a nestling may be out-competed for food by its nestmates, a fledgling might be too quiet or too weak to attract a parent with food or simply get too far away from its parents. Cornell Lab of Ornithology has citizen scientists doing nest-box studies. For the Eastern Bluebird, for example, nesting success is about 72 percent; this is the percentage of nests that produce at least one fledgling.
* * *
When I see young birds being fed around my feeders or in the trees around my home, I am seeing young that have already beaten many odds but who have many long odds still to overcome.
In mid-July, I was entertained by a pair Evening Grosbeaks. One was the mother; the other, a youngster. He was constantly calling for her. When she fed him and flew off, he followed her noisily. Eventually, he followed her to the birdfeeder, where she ate and occasionally fed him. Bit by bit, he got the idea that he could get food on his own, although he gave up mom’s service only reluctantly.
The next day, the young grosbeak was at the feeder by himself and feeding himself, endlessly scarfing down seed and even chasing off other, sometimes larger, birds. But he had no sense of fear. I approached to within three feet and felt as though I could have picked him up, he was so tame — or, perhaps, clueless.
Instead, I clapped my hands and shouted. This measure finally induced him to fly off. Young Downy Woodpeckers on the suet feeder also show a cluelessness to danger, so I’ve taken to chasing them off as well in an attempt to teach a bit of wariness.
They need wariness, as the pile of dove feathers on the back lawn one morning testified. Probably a young Mourning Dove roosted on the tree branch too long and became a meal for a hawk or owl. But in doing so, that dove fulfilled its life purpose; it became a part of the food chain.
* * *
Therein is a truth that is an unpleasant one for many people. We look on the birds at our feeders as entertainment, cute bundles of energy and activity. We give them human attributes. The titmice are sweet, the chickadees acrobatic, and the nuthatches comic. The crows are noisy, and the jays are greedy bullies. But they are all “our” birds.
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