(Quick note – I always strive to use either my own photos or those of my contributors but sometimes you just don’t have the photos you need!)
Two Common Nighthawks (Chordeiles minor) in a week!
With an English binomial such as this – you wouldn’t think it would warrant any excitement. But so far as I can remember the last time I saw a Common Nighthawk within Seattle City limits was when I was in my early teens. Never were they common but clearly they’ve declined because I was able to find them periodically in specific locations in the city as a child.
My presumption is immediately that humans have disturbed habitat that Nighthawks might have once used. Make’s sense, most birds do not thrive with human density, especially ground nesters, inherently at risk from foot traffic, cats, and other feral animals. Killdeer are not apparently at risk and similarly ground nest. I don’t have a statistically based explanation, but I suspect that their babies being precocial (soon upon hatching they are capable of moving and finding food) and that they spend most of their lives walking is far more adaptable than the short legged, air adapted Nighthawk. Without so much development however, the open spaces humans have created should provide ample foraging for the birds, historically I would guess they were in once common. I also know that Common Nighthawks will use rooftops for nesting areas in cities, so why not now? A lot of assumptions based on general facts I know are being foisted onto these Goatsuckers. Time for a little more research.
Wait – did you say Goatsuckers? You mean like the Chupacabra? That’s an oddly profane sounding name for such an unassuming, cryptically plumaged group of species. The history behind the unusual name comes from ancient Europe. It was believed, erroneously, that Nightjars flew into barns and sucked their goats dry of milk. In Latin, Caprimulgidae (the family nighthawks belong to), literally means “goat sucker.” They are closely related to both Owls and Swifts but there’s been a decent amount of debate about their firm placement in bird phylogeny, which I often find a bit semantic beyond the fact that I enjoy pondering evolutionary development.
This order of birds, while having short legs ill adapted for terrestrial mobility, are excellent aeronauts and inhabit a multitude of habitats minus the colder clines and aquatic regions of the world. Although the order in general is unified by typically cryptic plumage and large nocturnally biased eyes, there are a huge variety of iterations. There’s the atypically gregarious, cave dwelling, Oil Birds (they may actually be of a monotypic separate, order), which use a form of echolocation in low light. And the spectacularly plumed Lyre-tailed Nightjar (which I’ve briefly seen in Ecuador). Saying I’m a fan is silly because I can geek about any order, family, genus, or species – but I am none-the-less.
So, has there really been a decline in Common Nighthawks since I was a kid? It’s hard to say specifically. When I start doing research on bird populations in the United States my knee jerk reaction is to look up past Christmas Bird Counts, which in Seattle has been going for 80 years. Unfortunately this doesn’t work. Common Nighthawks don’t winter here and are late migrants. My assumption with the two birds I noted is that they were migrants, just arriving (as good an explanation as any). But that doesn’t answer my question of their decline.
Another source I’d typically venture towards is the building base of data on Ebird, the Cornell Lab of Ornithology and National Audubon’s online checklist program. It is designed to provide a way for people to compile their data and in turn help keep better records of populations. Under Common Nighthawk in King County, I found a handful of sightings in the last 20 years and the seasonal abundance bar graph shows them as just short of extremely rare from June through September. This isn’t a definitive answer however. A lot of people, myself included, are not great at entering their sightings in their spare time (exactly why I don’t think I’d be a fantastic scientist).
Looking in Eugene Hunn’s Birding Seattle and King County, a book published in 1982 confirms that these birds were not common even then. He suggested, partially in jest, that they should be considered an endangered species in Seattle. The book cited an old Auk (the American Ornithologist’s Union Journal) article from 1902 called “A List of the Land Birds of Seattle, Washington, and Vicinity” by Samuel F. Rathbun. He listed them as “abundant summer residents.” Hunn’s book also mentioned that they used to commonly nest on the rooftops of downtown Seattle. Yet, still no explanation.
Seattle Audubon’s Birdweb finally started to give my assumptions a bit of traction. The subspecies of Common Nighthawk that inhabits Western Washington was probably uncommon pre-European settlement according to their sources. Then the white folks showed up and business as usual – all the trees disappeared and for a long time there was nothing but large open spaces. Prime real estate. From the early 1800s to the early 1900s they appear to have been fairly common. Then in the early 1900s, we started to develop the city, sizable trees grew back, and those spaces started to dwindle. What about all those rooftops? Well Birdweb suggests, quite astutely that with an increase in human density came a certain sect of birds that enjoy the leftovers of big cities. Glaucous-winged Gulls probably wouldn’t think twice before gobbling up a Nighthawk egg but they just as likely out-competed them for nesting areas on the still abundant rooftops. What few birds were left might have slowly diminished due to increasing numbers of American Crows. A story that while unsupported by any research I could find, makes a good deal of sense to me.
Stories like these are what make the world of Natural History so captivating. Because we are so impactful. Understanding how human history collides with nature is essential to our appreciation and for it’s conservation. Much of our own history we hardly understand and significant research is required to even know a city 100 years in the past. Consider a species that doesn’t have our words, our documentation (I’ll expand on this with an entry on the Burke Museum in the near future). This was a pretty cut and dry, decently documented account of the boom and bust of a bird that exploited an opened niche and disappeared when that habitat was gone. Stories like this have played out like this for eons and they’ll continue indefinitely so far as I know. I’ll just be happy if I get to know a few of them.