Thursday, November 18, 2010

American Crow

 
American Crows are abundant across North America.  Picking what to write about crows is difficult. They are intelligent.  They employ a number of information-laden calls, they recognize individual people (although few people can recognize individual crows), and, generally speaking, crows are less wary in cities than in the countryside. I encountered these crows as they foraged in a Northfield field (the day before the snow arrived).

For the past several years, we enjoyed a huge winter crow roost in our backyard.  The birds reminded us of the flying monkeys in the Wizard of Oz.  I do not know why the roost was abandoned this year.  Crows seem to be exceptionally prone to West Nile Virus.  This Old World disease appeared in New England and spread across the country.  I once wrote a paper demonstrating that banding returns show that crow populations are are not isolated, but potentially can come in contact with infected birds across the continent.

Young crows help their parents raise subsequent broods, sometimes for two or three years.  Not all young are helpers, and we do not know why some young help while others raise their own offspring.  Do the baby-sitting helpers eventually become better parents? Do parents pass genes to some offspring that effectively enslave some young, thereby increasing the parents' reproductive success compared to crow families without helpers?

1 comment:

  1. Dan - I've been trying to "habituate" crows - assuming that is even remotely possible - for a few years now. It took several year just to get them to accept food on the deck off the back of the house. Yesterday - for the first time - two crows allowed me to watch from the window while they fed. I leave dog food on the railing for them. I'm sure they recognize me now because they come immediately to feed after they see me leaving the food. Great fun.
    Larry S

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