A bird chooses a roosting site, a place to sleep and rest, with care.\u00a0 The roosting site can mean the difference between life and death on a cold winter night.<\/p>\n
You know from watching your bird feeders that birds quit coming to feed about a half hour before dusk.\u00a0 In the dim twilight, birds find a roost site and hunker down for the evening.\u00a0 Of course, nocturnal birds like owls have a topsy-turvy schedule so go to roost around dawn.<\/p>\n
Particularly in the winter, the roost site should provide some protection from the elements.\u00a0 Heat is easily lost to convection, the movement of a cold fluid over a solid structure.\u00a0 Meteorologists are always warning us about wind-chill; convective heat loss provides the explanation of wind-chill.<\/p>\n
The obvious way to minimize wind-chill is to get out of the wind.\u00a0 Many birds choose a roost site in a conifer where the needles reduce the wind.\u00a0 Roosting close to the trunk has triple benefits.\u00a0 The area next to the trunk will experience the least wind because of the dense foliage extending outward from the trunk.\u00a0 A central roost in a conifer maximizes the safety of a roosting bird from owls or other nocturnal predators.\u00a0 Finally, the trunk of a tree emits a modest amount of infrared radiation (sensible heat) that can provide just enough heat to get a chickadee through the night.<\/p>\n
Some birds roost in cavities.\u00a0 Woodpeckers maintain a roost cavity, often separate from the nesting cavity, were they spend the night in relatively cozy comfort.\u00a0 Ruffed Grouse and Common Redpolls take advantage of the remarkable insulating properties of snow by roosting beneath the snow surface.\u00a0 Having a grouse fly up from the snow as you walk by on a nighttime snowshoe hike is a heart-stopping experience.\u00a0 To get into the snow, the grouse flies into a snow bank to create an instant den for the night.<\/p>\n
Some birds roost alone.\u00a0 Black-capped Chickadees provide a local example.\u00a0 Others huddle at a roosting site.\u00a0 The energetic advantage is clear.\u00a0 By huddling with other birds, some of the heat lost to the cold can be absorbed by a neighboring bird in the huddle rather than lost to the atmosphere.<\/p>\n
My favorite anecdote of huddling in birds comes from an English garden.\u00a0 After a particularly cold night, a homeowner checked the contents of a small nest box measure 4x4x5 inches.\u00a0 What a surprise it must have been to find 61 Common Wrens (similar to our Winter Wren) huddled together to snugly pass the night.<\/p>\n
I have received lots of questions this winter about the massive American Crow roosts that are often in heavily populated areas.\u00a0 I wrote a column about crow winter roosts last year.\u00a0 You can read it at: http:\/\/bit.ly\/1cIYz0f<\/p>\n
American Crow roosts vary in size from several hundred birds to two million.\u00a0 Crows are one-upped by the Red-billed Quelea, an Old World sparrow related to the House Sparrow.\u00a0 Quelea roosts reach the tens of millions of birds.\u00a0 Alas, the most social of roosting birds is not longer with us.\u00a0 Roosts of the extinct Passenger Pigeon numbered in the billions and covered many square miles.<\/p>\n
Communal roosts may involve several species.\u00a0 Several species of herons and egrets may roost together.<\/p>\n
For any roosting bird, you may wonder if they ever fall off their perch at night.\u00a0 Birds have special flexor tendons that cause the toes (usually three pointing forward and one pointed back) to lock into place when the legs are bent.\u00a0 The weight of the roosting bird keeps the legs bent and the flexor tendons firmly locked through the night.\u00a0 When the bird awakes in the bird, it straightens its legs and the flexor tendons relax, freeing the toes from the perch.\u00a0 The same flexor tendons in birds of prey prevent prey from escaping by locking the talons into the unfortunate prey item.<\/p>\n\n
A bird chooses a roosting site, a place to sleep and rest, with care.\u00a0 The roosting site can mean the difference between life and death on a cold winter night. You know from watching your bird feeders that birds quit coming to feed about a half hour before dusk.\u00a0 In the dim twilight, birds find […]<\/p>\n","protected":false},"author":146,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_s2mail":"yes","ngg_post_thumbnail":0,"footnotes":""},"categories":[4625,430],"tags":[],"builder_content":"","_links":{"self":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/648"}],"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=648"}],"version-history":[{"count":1,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/648\/revisions"}],"predecessor-version":[{"id":650,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/648\/revisions\/650"}],"wp:attachment":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/media?parent=648"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/categories?post=648"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/tags?post=648"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}