It\u2019s thrilling to see an unusual bird.\u00a0 Who is not excited about the chance to see a Snowy Owl or an American Oystercatcher in Maine?\u00a0 Yet there is the potential to experience wonder in watching our common birds.<\/p>\n
My case in point today is the American Crow.\u00a0 Here in Waterville, we are treated to an amazing spectacle late each afternoon.\u00a0 Hundreds of crows fly in from all directions to converge on a patch of forest behind the shopping center at Elm City Plaza in the fading daylight.\u00a0 The river of crows seems endless.\u00a0 No doubt, you have seen such behavior in your neck of the woods as well.<\/p>\n
Why do the crows congregate to spend the night together?\u00a0 We don\u2019t have a definitive answer but some intriguing suggestions have been proposed.<\/p>\n
Aside from humans with guns, the major threat to American Crows is predation by Great Horned Owls.\u00a0 Perhaps you have seen American Crows mob a roosting Great Horned Owl during the day.\u00a0 The crows are brutal, swooping down on the owl and pecking it.\u00a0 Usually the owl is forced to fly to find a more peaceful place to sleep.<\/p>\n
Roosting might therefore offer protection from owl predation.\u00a0\u00a0 It is awfully hard for an owl to approach when a thousand or more crows are keeping a vigilant watch.<\/p>\n
Another possible explanation comes from a somewhat controversial idea called the information-exchange hypothesis.\u00a0 The premise is that crows can learn about good food sources from each other.\u00a0 We have to be careful to avoid ascribing a human perspective to this information sharing.\u00a0 In the natural world, behavior that appears to be altruistic turns out to be selfish behavior.\u00a0 In nature, individuals that watch out for themselves and their kin fare better than altruists.\u00a0 How does helping unrelated individuals survive increase the chance of getting your genes into future generations?<\/p>\n
Honeybees through their remarkable waggle dance let other members of a hive know where good nectar sources are.\u00a0 But all individuals in the colony are related to each other so sharing information indirectly benefits all colony members.<\/p>\n
A roost of crows consists mostly of unrelated individuals.\u00a0 Crows are not so kind-hearted as to somehow share the location of a food bounty with unrelated individuals.\u00a0 However, it may be possible for crows to discover the whereabouts of good food.\u00a0 Crows may be able to assess the nutritional status of a crow as it comes back to the roost.\u00a0 Perhaps it is full of energy.\u00a0 If so, a crow in need of a good meal may follow the well-fed crow in the morning.\u00a0 This behavior can be seen as a type of parasitism.\u00a0 The definitive study to test for this type of information sharing in crows has yet to be done.<\/p>\n
One other explanation for crow roosts is the patch-sitting hypothesis.\u00a0 This explanation entails roosting near a site where there is a reliable source of food.\u00a0 The food does not need to be the most nutritious food but will provide roosting crows with a breakfast to get them going in the morning in search of more substantial food and a snack in the evening before they go to sleep.\u00a0 Like the information-center hypothesis, this hypothesis needs more study as well.<\/p>\n
Crow roosts are seasonal, occurring in the fall and winter.\u00a0 Some of these aggregations must be truly spectacular.\u00a0 I know of one report from Oklahoma of two million crows in a single roost!\u00a0 Roosts from 100 birds to tens of thousands are much more common.<\/p>\n
We are seeing a trend of American Crow roosts occurring in urban environments rather than in more rural or undeveloped habitats.\u00a0 Some have speculated that the crows are taking advantage of the slightly warmer temperatures found in cities.\u00a0 Just a few degrees of warmth can make a big difference.\u00a0 Plus the lights of a city make it easier to see Great Horned Owls at night.<\/p>\n
[Originally published on Mar 4, 2012]<\/p>\n\n
It\u2019s thrilling to see an unusual bird.\u00a0 Who is not excited about the chance to see a Snowy Owl or an American Oystercatcher in Maine?\u00a0 Yet there is the potential to experience wonder in watching our common birds. My case in point today is the American Crow.\u00a0 Here in Waterville, we are treated to an […]<\/p>\n","protected":false},"author":146,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_s2mail":"","ngg_post_thumbnail":0,"footnotes":""},"categories":[4625,420],"tags":[],"builder_content":"","_links":{"self":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/486"}],"collection":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/users\/146"}],"replies":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/comments?post=486"}],"version-history":[{"count":1,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/486\/revisions"}],"predecessor-version":[{"id":487,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/486\/revisions\/487"}],"wp:attachment":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/media?parent=486"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/categories?post=486"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/tags?post=486"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}