Tweeters,

I've been reading some of the recent accounts of predation by crows on
young birds. However, last Friday (May 31), from my office window in
Kamloops, I witnessed something I've never seen before. Two American
Crows attacked, killed and ate a full-grown (but newly-fledged)
American Robin. The attack took less than 2 minutes, and occurred
despite the frenzied attack of one of the parent Robins.

It is well-known that American Crows (and Northwestern Crows) are
proficient and persistent nest-robbers, taking eggs and small
nestlings, and Robins are one of their favorite prey species. I
witnessed several incidents of such predation when I was doing my
Master's thesis study on urban birds in Vancouver, BC. (This involved
Northwestern Crows.) However, I thought that crows (both species)
generally did not attack and kill full-grown birds-- fledglings or
otherwise-- because, unlike raptors, they are not well-equipped to
pluck birds.

Has there been a change in behaviour of one or both crow species over
the last 20-30 years, such that they now more frequently attack adult
birds, fledglings, and older nestlings? If so, it might help to
explain why crow populations have increased so dramatically. (In
Vancouver, Northwestern Crows have increased by a factor of at least 4
or 5 over the last 30 years.) Adding a whole new category of critters
to their diet might help to expand the "ecological niche" of crows.

I believe there are a couple of crow experts from UW on TWEETERS. If
you (or any other TWEETERS subscribers) have further comments, I'd be
interested in hearing them.

Wayne C. Weber
Kamloops and Delta, BC
contopus at shaw.ca