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Is intelligence a factor in how well birds adapt to urban environments? A recent study by a team of European biologists addressed that question, in a way, although the results are less interesting than the media coverage might suggest. 

The researchers, led by Alexei Maklakov and Simone Immler of Uppsala University’s Department of Animal Ecology, used relative brain size as a proxy for intelligence. That makes sense: there’s clearly a correlation among birds as well as mammals. Big-brained corvids and parrots are more behaviorally flexible than, say, chickens. To quote the abstract: “We provide the first evidence for the intuitive yet untested hypothesis that relative brain size is a key factor predisposing animals to successful establishment in cities…[We] show that passerine species that succeed in colonizing at least one of 12 European cities are more likely to belong to big-brained lineages than species avoiding these urban areas.” 

Of the 82 species of birds included in the study, corvids—the carrion crow, jackdaw, and Eurasian magpie—were among the most successful urban adapters. The Eurasian wren and nuthatch and the great, blue, and long-tailed tits, also relatively large-brained species, rounded out the top ten. Blue tits were the birds that learned to prise the caps off milk bottles and drink the cream at the top. (That’s not unlike the mix in my neighborhood, substituting American crow and western scrub-jay for the corvids, chestnut-backed chickadee and oak titmouse for the tits, Bewick’s wren for Eurasian wren, and red-breasted nuthatch for Eurasian nuthatch.) 

Smaller-brained city avoiders included two buntings related to the North American sparrows, two Old World warblers, and an Old World flycatcher. The warblers and flycatcher have no close New World relatives. Only songbirds were considered, which leaves out ubiquitous urban species like pigeons and occasional city-dwellers like woodpeckers and hawks. 

Some species, like the barn swallow, did better in urban settings than brain size would have predicted. Maklakov told a reporter that swallows couldn’t be considered true “urban adapters” and were “lucky enough to find niches in urban habitats that are by coincidence a pretty good approximation of their original habitat.” That strikes me as a bit of a rhetorical straddle. 

I haven’t read the actual article, which the journal Biological Letters has sequestered behind a paywall. So I don’t know whether 

the authors compared brain size and urban success within lineages of birds—among the corvids, for example. I recall seeing a lot of crows (carrion and hooded) and jackdaws in European cities, but far fewer Eurasian jays, which seem to be furtive, human-avoidant birds. In California, American crows and to a lesser extent western scrub-jays, yellow-billed magpies, and common ravens have made themselves at home in cities; Steller’s jays, not so much. 

Or take the New World tyrant flycatchers. Why are black phoebes and eastern phoebes more comfortable around people than eastern and western wood-pewees? Western bluebirds have been colonizing the Berkeley flatlands in the last few years; Rusty Scalf has identified three currently active nests. Are they larger-brained than related thrushes? 

To move beyond the passerines, how about hawks? Berkeley has a thriving breeding population of Cooper’s hawks, but only a couple of pairs of sharp-shinned hawks. Allen Fish of the Golden Gate Raptor Observatory says sharp-shins are more partial to conifers as nesting habitat, but conifers aren’t exactly scarce here. 

It’s also important to remember that large brains aren’t everything. 

Although some crow species have become successful urbanites, others are hanging by a thread. The Hawai’ian crow, for one, is extinct in the wild. You’d think it would have found a niche cleaning up after luaus, but a one-two punch of habitat destruction and persecution by ranchers and farmers did it in.