[CT Birds] Cowbird observations (and English sparrows)
dbbingham at sbcglobal.net
Sat Mar 24 17:35:16 EDT 2007
Roy is right that in winter the cowbirds flock and they disperse in spring.
But they still tend to disperse to areas in which their niche for food is
found, and my point is that in 60 years of living in this location, that
niche has dramatically changed, mostly in that the numbers of domestic
animals (that used to outnumber people 10:1 or more) is drastically reduced.
Go to any horse farm or dairy or sheep farm later this spring and you will
see numbers of cowbirds in with the livestock (not the huge flocks of
winter, but numerous). Go to abandoned farms where there are no longer any
livestock, and the numbers of cowbirds, English sparrows and starlings seem
greatly reduced or gone altogether. It may just be in my neighborhood, and
this is a casual observation not a scientific survey, but it might be
worthwhile to study.
If I am right, then those people who have a horse in their back pasture are
bringing more than just hayseed and close-cropped pastures in to that local
environment. They may want to consider the other significant environmental
changes that they may also be inducing, inadvertently.
----- Original Message -----
From: "Roy Harvey" <rmharvey at snet.net>
To: "david bingham" <dbbingham at sbcglobal.net>
Sent: Saturday, March 24, 2007 7:41 AM
Subject: Re: [CT Birds] Cowbird observations (and English sparrows)
> Reading David Bingham's interesting observations about cowbird
> populations I think the seasonality factor has not been considered.
> As far as I have seen the large flocks he describes seeing in the
> days of the dairy farms happen outside of breeding season. Those
> large flocks have no particular affinity for edge habitat, so their
> abundance (or lack) in edge habitat in that season is not
> particularly significant. If local habitat has changed so that the
> large flocks are no longer seen it does not reflect on their
> population, simply that they are elsewhere.
> In breeding season the flocks disperse to the edge habitat where they
> can find other species' nests to parasitize. Density of cowbirds in
> that season will correlate with the density of the host species, so
> they will not be concentrated at that time of year and estimating
> numbers becomes much harder.
> Roy Harvey
> Beacon Falls, CT
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