The American Crow – Communal Roosting

Birds do not weigh that much, their hollow bones and sleek, aerodynamic figures are optimized for a life in the sky. With that in mind, imagine a tree so dense with loud, dark-feathered fowl that at any moment its limbs are in danger of breaking under the weight. This tree, having lost its leaves for the winter has grown a new type of foliage in the last few hours as crows (Corvus brachyrhynchos ) pour in from all over the region to share the safety and warmth of a communal roost.

Now imagine that this is only one tree amongst several dozen trees and that every single move you make is being carefully observed by thousands of pairs of eyes.

Last Wednesday the AIAO staff, along with friends and family, went on a reconnaissance mission to find such a place. Equipped with two-way radios, cell phones and video cameras, the search team consisted of three cars and about nine people – all of them scanning the skies for the first signs of this local migration.

Crows will often travel together in groups of 4-10 (commonly called “murders”) in order to increase their chances of finding food and spotting predators. Sometimes they also fly solo – like people, each animal will have it’s own preferences and personality. These individuals and small family groups are going to provide you with the first clues as to where your local roost is. There is not a lot of research as to why the crows gather in this way but it is theorized that they do so for both the benefits of shared body warmth as well as protection from predators. From a humans perspective, four thousand crows in one place can be both magical and highly intimidating. Crows will often harass larger birds of prey even when not in a large group so the wise owl would b e keeping a low profile during such an event.

From an open field or a high point such as a mountain or the top of a building you will be able see the first signs of gathering about two and a half hours before sunset. By triangulating the flight path of these smaller groups you can get a vague idea of where to start looking.

The chase started for our team when, while stationed behind a large hardware store in Holyoke, a group of about 50 crows started streaming over our heads, all headed for the same place. Small groups will congregate into larger groups and these multiple-family caravans will combine at Staging Areas (video) where they call out and wait for others to join them. A staging area will have somewhere in the area of hundreds of crows.

With the chase on, all three cars took off, stopping occasionally at graveyards, fields and high points to get a better view of the skies and to adjust their driving directions. The most challenging part of this part of the chase is avoiding dead ends and high-traffic areas. One wrong turn can leave you crow-less and direction-less with the lowering sun threatening to take away your view of the sky.

Finally, after about two hours we found ourselves under a canopy simply writhing with activity. Crows of all different species had come together in the thousands to what we thought was the final roosting area…

And then, at some unknown signal – they all flew away.

Ten more minutes of driving brought us to the final roosting area. Four thousand crows from all over the region would be a modest estimate of what we found here yet even in their large numbers they still kept their distance from us, parting their masses over our heads as we walked through their roost.

And by morning, they were gone.

 

For more information, check out: http://www.crows.net/roosts.html

 

Published by:

Christopher J. Poulin

Adventure In Adventure Out, Field Instructor