ALWAYS IN SEASON/ Mike Jacobs: Birds compete for nesting sites
A kind of competition has developed between the birds. It involves barn swallows and eastern phoebes, and the stakes are high. Both birds want the same nest site. The phoebes showed up first, as they do every year. The swallows arrived a few days...
A kind of competition has developed between the birds. It involves barn swallows and eastern phoebes, and the stakes are high.
Both birds want the same nest site.
The phoebes showed up first, as they do every year. The swallows arrived a few days later.
The swallows are more numerous. They have what amounts to a colony at our place west of Gilby, N.D.
The phoebes, on the other hand, are a single pair.
Both of these species choose nest sites on vertical surfaces protected from above. Both sometimes nest inside buildings.
The relative numbers would be a disadvantage to the phoebes, but that may be offset by their slightly earlier arrival.
The phoebes are notably fussier about their nest site, too. They prefer a dark, well-hidden place. Barn swallows are not at all secretive. Nor do they avoid the sun. It's rain that they worry about.
Both of these species build their own nests, and these are easy to distinguish. Barn swallows build almost exclusively with mud, with perhaps a few strands of grass inserted as binding. The phoebe's nest is a more complicated affair, involving mud, grass bits of twigs and even cloth. A phoebe nest is intended to be more substantial than a swallow's.
Phoebes are famously faithful to nesting sites, with the same pair using the same nests in successive years. No less a bird man than John James Audubon first documented this. In 1804, he tied silver threads around the legs of nestling phoebes. He recorded their return in following years.
Swallows are known to be site faithful, too, so it's likely that the swallows and phoebes at our place are descendants of the same birds that nested here when we arrived almost 20 years ago, soon after the Flood of '97.
The swallows have ceded the territory to the phoebe couple without much of a fuss. Swallows generally build new every year, and our property provides many more sites to their liking than it does to phoebes.
Phoebes have one other nest site competitor, a somewhat surprising one. A pair of American robins has usurped one of the spots phoebes once used. This is on a broad board just under the eaves of one of our outbuildings, a snug, dark place.
The upshot of all this is that all three species are here and secure, although they've traded nesting sites, at least for this year.
Crows vs. owls
A rather more dramatic competition broke out between a family of crows and the resident great-horned owl. Owls are early nesters-and indifferent nest builders. Instead of building new, the owls typically move into a platform nest left behind by its builders, who move away for the winter.
Again the species that nests earlier has an advantage.
The crows had not gone far, however. Probably they joined the congregation of crows that forages through Grand Forks in the winter months. From our place, that would be a one-way trip of about 25 miles, as the crow flies.
So the crows were back at their nest site before the owl hatched her eggs.
The crows had a numerical advantage over the nesting owl. Owls are generally solitary. Crows have a fairly complicated social system in which younger birds assist at the nests. Often, though not always, these are the nests in which they were fledged.
The crows employed a very aggressive strategy in their effort to dislodge the nesting owl. This involved strafing the nest, dive bombing the owl and screaming all the while. The owl eventually fled. Presumably, the crows destroyed whatever she left behind, and they are now in comfortable control of the nest site.
A similar story has played out not far from Grand Forks, where a great-horned owl moved into a nest that has been used for many years by Swainson's hawks.
Unlike the crows, Swainson's hawks are long-distance migrants. They spend summers on the Great Plains of North America and winters on the Argentine pampas.
The interaction of hawks and owls has created a good deal of interest among local birders. I don't know the outcome.
Both the owl and the hawks had their advocates among those watching the nest. I didn't take sides. Nature will take its course, and it's best not to interfere, even emotionally.