Nesting Time

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The Bicknell’s thrush looked like a greedy patron at a salad bar. Stuffed into her bill were a crane fly, a moth, a pupa of some kind, and what looked like a caterpillar. But that apparently wasn’t enough food. She returned later and gathered a heaping plate of earthworm.

Yet the thrush wasn’t being greedy at all. Instead, by collecting all that food, she was offering a vivid lesson in the art of early summer birdwatching: you need not actually see a nest to know that birds are breeding nearby.

Most of the time, songbirds eat their meals on the spot. But many carry food this time of year. In all likelihood, they are bringing it to a prospective mate as part of courtship, to a mate sitting on a nest, or to feed young, either in the nest or newly fledged. And keeping those chicks nourished is a relentless task. Feeding trips are frequent. So a bird carrying food will often lead you to its nest.

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But be aware that some of what goes in must also come out. A songbird flying with what appears to be a small white balloon in its bill is carrying a “fecal sac” – a “diaper” of nestling feces being removed from the nest and dropped out of sight. It is a clever way to keep the nest clean, free of bacteria, and less vulnerable to predators attracted by the odors.

For other birds, however, evidence of nesting isn’t so subtle. “Duck and cover” was a Cold War drill for generations of school children learning to fear the bomb. But nothing gives it new meaning like a northern goshawk.

I once trespassed onto the territory of a goshawk pair. One of the adults, shouting a rapid and raspy “kehk-kehk-kehk-kehkkehk,” came at me like a missile. Ordinarily, when an angry critter zooms my way, I prefer to stand my ground and enjoy the show. Not so with a goshawk. I ducked, covered, turned, and fled like a snowshoe hare. The enraged hawk passed close enough for me to feel wind from its wings. There could be no doubt about a nest nearby.

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Other birds, presented with an intruder near the nest, prefer deception over aggression. The killdeer, trying to appear as easy prey, will feign a broken wing and limp away in order to distract a prospective predator from its nest. An ovenbird once did a similar ruse for me. Other species may scoot along the forest floor like a small mammal to divert the attention of a predator. We call these tricks distraction displays.

But there can be no fakery in a bill full of food. The Bicknell’s thrush had mouths to feed. So I kept watching. She vanished into the bough of a balsam fir, and I could hear the chirps of hungry young. From a safe distance, I was able to watch her shove her haul of earthworms down
their throats. Now if only northern goshawks would calm
down and practice a little détente.

Bryan Pfeiffer is an author, wildlife photographer, field guide and consulting naturalist who specializes in birds and insects. He lives on Bartlett Hill in Plainfield, Vermont.

 
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