Jane and All,
Berndt does discuss raven roosting, and there is also some good info in the book, "In the Company of Crows and Ravens", by Marzluff and Angell. For both crows and ravens, roosts are thought to be places where information is exchanged, for example where a new deer carcass was found that day. Also, apparently many crow roosts are located in more urbanized areas because the birds have learned over time where human hunters are least likely to be encountered.
I haven't found any raven roosts in our area yet, but on last year's Xmas count I watched a group of 25 ravens fly over Braintree Hill at sunrise, heading down into the valley for the day.
Rick Enser, Braintree
From: Jane Stein <[log in to unmask]>
To: [log in to unmask]
Sent: Thursday, December 1, 2011 1:19 AM
Subject: Re: [VTBIRD] crow roost
Interesting stuff, Rick. Thanks for describing this. It's particularly fascinating to me that all that raucous meet-and-greet is pretty much restricted to the pre-roosts and the big final roosts are a good deal more sedate.
In the Boston suburbs I used to live in, those big final roosts do seem to persist for many years in the same location, but the pre-roost locations change every few years, sometimes even just months. Perhaps suitable final roosts are difficult enough to find among denser human habitation that the birds get the noisy greetings out of their systems earlier so they can be quieter there to avoid inviting disturbance and/or predator attacks. (What, owls?) Whatever the reason, I think it's likely not a coincidence that the noisy pre-roosts aren't permanent and the quieter roosts more or less are.
Do Ravens also have these pre-roost locations? I'm trying and failing to remember my Berndt Heinrich on the subject...
On 11/30/2011 11:56 PM, Richard Enser wrote:
> Spent many hours watching crow roosting behavior in Rhode Island
> where there were two major roosts of 10,000+ birds. Unfortunately,
> the advent of West Nile virus caused these roosts to disintegrate,
> but apparently they are beginning to regain their former numbers.
> Most interesting was watching single birds, what we called "scouts",
> leaving pre-roost locations to assess the safety of several final
> roost sites. Returning scouts could be heard calling as they
> approached the preroosting flock, and apparently if the message was
> positive the entire flock would then depart to the final roost. In
> Westerly, Rhode Island the final roost was located in a small
> (5-acre) mature red maple swamp in the midst of a highly urbanized
> residential neighborhood and you could watch the birds dropping into
> the canopy just before dark, still calling as they approached but
> becoming silent as they settled in. Roosts were mixed, about 100:1
> Common/Fish Crow.
> It would be interesting to map out all of the Vermont roosts. There
> is also one in the Randolph area - my last count was about 300 birds
> preroosting in the vicinity of Vermont Tech College.
> Rick Enser, Braintree
> ________________________________ From: Jane
> Stein<[log in to unmask]> To: [log in to unmask] Sent: Wednesday,
> November 30, 2011 10:09 PM Subject: Re: [VTBIRD] crow roost
> I find it impossible to watch crows for any length of time and not
> believe there's much more sophisticated communication going on than
> just noise-making.
> On 11/30/2011 9:14 PM, Ronald Payne wrote:
>> I counted 430 Crows passing by Otter View Park in Middlebury headed
>> in the general direction of Chipman Hill. Loved the Crow bussing
>> comment, Jane. -- Ron Payne Middlebury, VT
>> On Wed, 30 Nov 2011 18:06:35 -0500, Eric Masterson wrote: There is
>> also a neat crow roost somewhere in the Lebanon/White River
>>> area. Counted 500 heading west over exit 18 on i89 today.