June 11, 2010

Q: Why are there so many crows in Seattle?

The Burke Museum partners with the Seattle PI's Big Blog to answer commonly asked questions about the natural and cultural history of our region. Read past entries from the Ask the Burke column here.

The following was posted to the Seattle PI's Ask the Burke column on June 11.

Q: Why are there so many crows in Seattle?

A: The crow population has increased dramatically in Seattle over the past 40 years. Increases in human population have reduced forest cover, creating open foraging areas preferred by crows, and generated food sources such as garbage that crows are quick to exploit.

Nighttime communal roosting of crows is particularly noticeable and sometimes disruptive. Crows probably roost communally for the same reason many other birds do—to avoid predation and share information about food resources. Starting in April in the Seattle area, crows become less noticeable because they are breeding; they disperse onto other territories, and females stay on nests. As winter approaches, crows form huge roosts, where they congregate at sunset. They typically commute along regular flight paths, stopping at traditional pre-roosting sites along the way and often vocalizing loudly. In the morning, birds disperse and follow each other to foraging sites.

Ongoing surveys by the Seattle Audubon Society provide historical records of the growing crow populations in this area. During the 2009 Christmas Bird Count, Seattle Audubon observers recorded a remarkable 18,180 American Crows in the greater Seattle area, or about 35% of all total bird species observed in that time. The total number of crow sightings from 2009 is about 26 times greater than the long-term average from 1973-2008; in other words, the population has grown significantly as Seattle has become more urban.

To read more about crows, including tips for how to prevent conflict with these birds, check out the Seattle Audubon’s very informative site.

Photo: American Crow, corvus brachyrhynchos. Photo by Stuart MacKay.