Here we see a common sight, a swarm of Barn
Swallows swooping and diving (show picture). This is a specialized behavior
that helps them to feed almost exclusively on flying insects. Their boomerang
shape allows them to glide effortlessly. They’re also actually a species that
has co-evolved and been very successful living with humans, similar to the
American Crow, who is another common species here. They like open spaces and
have changed from building nests in caves to building them on the sides of
buildings, usually barns, which gives this swallow its name. They tend to spread
wherever humans colonize, suggesting a positive relationship between us and the
Barn Swallow. These nests are usually cup-like and made out of mud and sticks
so that it sticks to the sides of buildings. Another interesting behavior is
that, as you can see, these birds are pretty social and swarm together whereas
a lot of the other birds you see, other than crows, are frequently seen foraging
in solitude. Barn Swallow parents sometimes get help from other birds to feed
their young. These helpers at the nest are usually older siblings from previous
clutches, but unrelated juveniles may help as well. At Nisqually National
Wildlife Refuge, we saw the Barn Swallows working together to build their
nests, as well. I saw around three birds, on average, working on one nest at a
time.
As
I mentioned, the American Crow is quite a social bird as well. They form groups
and roost together to forage and defend territory. The urban ones display a
marked intelligence. Our field guide remarks that the crow has flourished
because "much of its survival strength lies in its ability to adapt to a
variety of habitats, food resources, and environmental conditions." As
such, this species persists here in the Pacific Northwest almost year-round. We've observed
crows in Discovery Park, and they appear to be fairly nonchalant and
unconcerned of predators. I speculate that, based on these two kinds of birds,
perhaps birds that are more social or cooperative survive better under the
pressures of human influence. Or, looking at it another way, humans may have
actually created a new niche, the urban environment, where some species are
actually more successful than they may otherwise be.
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| Barn Swallow |
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| American Crow |
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