L.A.'s crows explained

Crow on wireDesigner and blogger Marc Grobman (the guy campaigning to de-uglify Donald Sterling's Times ads) became so curious about the crows invading his Santa Monica neighborhood each winter that he went right to the source for information. Kimball L. Garrett, is ornithology collections manager at the Natural History Museum, author of Birds of the Los Angeles Region and the go-to guy on everything avian from West Nile Virus to the parrots and parakeets that adorn our sky with flashes of green and red. Excerpt of their interview:

MSG: So, what are these birds doing?

KG: Crows (technically these are American Crows, Corvus brachyrhynchos — there are many other species of crows and ravens in the world) are very social birds. They tend to roost in groups, forage in groups, and gather for “socializing” at various times of the day. They also harass and chase predators (such as hawks) in groups. On the other hand, crows do not nest in large groups, but instead separate into pairs or small cooperative breeding groups of up to a dozen birds — in these groups there is usually a breeding pair, plus one to several “helpers” which are usually young from previous broods.

What you are seeing are social gatherings of wintering crows (social groups, as noted above, are much smaller in the breeding season). Some nighttime roosts may contain up to several hundred birds (thousands in some parts of the country). There is a lot of social interaction that goes on as birds gather near the roost sites — calling, chasing, jousting, etc. The seemingly useless behaviors such as pecking at roofs, picking up sticks, etc. may be “play” behavior mainly by juveniles — they’re just sort of acting out their repertoire of behaviors, getting more proficient at maneuvers and behaviors important for survival.

MSG: Where do they go during the day?

KG: Crows are mostly out foraging during the day. They’re omnivores and extreme generalists, so they might feed in a variety of areas and on many different kinds of foods. e.g., garbage at landfills, schoolyards, parks and beaches (we’re good at providing a lot of that), pet food left outdoors, fruits, walnuts (they’ve been observed dropping walnuts into streets and waiting for cars to run over them to crack the shells), insects, small vertebrates, bird eggs and nestlings (they’re notorious nest-robbers), etc. They fan out over a large area to feed, so you tend to see the large concentrations back toward the roost areas.

MSG: Is this a Westside phenomena or is this happening all around Los Angeles? Everywhere?

KG: American Crows are found over most of the US and temperate Canada (except for some of the southwestern deserts). In our region they’re pretty much everywhere on the coastal slope and foothills, but they’re scarce or absent from the deserts (where Common Ravens predominate). Crow behavior is more or less the same throughout the species’ range (though some northern migratory populations might not show cooperative breeding as frequently). Areas of high abundance of crows in the L. A. region include the interior valleys (San Fernando, San Gabriel, Pomona, etc., and most of the coastal lowlands (e.g. L. A. basin, Long Beach, etc.).

MSG: I read in your book that Crows are on the rebound — is that true? Were they endangered? Are they displacing other local birds or other fauna

KG: American Crows probably used to be less common overall and definitely more localized in their distribution than they are now. Basically they need trees — for nesting and for roosting. They prefer large stands of tall, dense trees for roosting. If you consider what much of the Los Angeles region looked like 200 years ago, you can understand why crows were probably relatively uncommon and localized — there were few if any trees in large expanses of the lowlands. Now we’ve planted trees everywhere, and the crows don’t care that they’re non-native eucalyptus, pines, ficus, deodars, silk-oaks, etc....Because crows have become so abundant, and because they do prey on eggs and young of a variety of other bird species, there is some evidence they are negatively impacting some of our local bird species. However, recall that crows are abundant because of our changes to the landscape — thus, we’re really the culprits (as expected) and the crows are the symptoms!

MSG: Are they considered a nuisance? They seem really intimidating and make quite a mess. I like them but I imagine others might not!

KG: Many find crows fascinating, and they are considered highly “intelligent” as birds go (insofar as we can really assess intelligence in birds). This stems from their adaptability and generalized ecology. That’s the up side. The down side is they can be noisy and their roost sites can be messy — some people don’t seem to be able to deal with such doses of nature.

More there. Crows are also a big topic in the Santa Monica Mirror these days.

Photo: Crunchbot/Flickr


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