Date: 9/6/18 5:22 pm
From: Ian Nisbet <icnisbet...>
Subject: [MASSBIRD] more thoughts about Barn Swallow nest sites
About 40 years ago, I quizzed many of my colleagues (in Europe as well
as in North America), asking whether they had ever seen a Barn Swallow
nest in a natural site.  None of them answered Yes to that question. 
The account of the Barn Swallow in the Birds of North America (1999)
says that the species originally (pre-humans) nested primarily in caves,
but has "almost completely converted" to nesting in artificial sites. 
It cited a 1986 review paper which stated that since the 1960s, the only
records of nesting in natural sites in eastern North America had been
from West Virginia, New York, and the Canadian Maritimes, and the only
place where they continued to nest in natural sites was in the Channel
Islands off California.  I think that the Barn Swallow is more dependent
on artificial sites than any other species in North America: it is easy
to find nests of Tree Swallows, House Sparrows and Starlings, for
example, in natural sites.  Has any Massbirder seen a Barn Swallow nest
in a natural site?

The BNA account mentioned associations of Barn Swallows with pastures
and grazing animals, but the close association with cattle has been
reported primarily in Europe.

On 9/6/2018 4:52 PM, Ian Nisbet wrote:
> In many parts of the northern hemisphere, Barn Swallows are closely
> associated with cattle, and declines in Barn Swallow populations have
> been linked to declines in numbers of dairy farms where cows graze
> outdoors.  My guess is that as suburban development encroaches on
> dairy farms in New England, Barn Swallows will continue to decline
> whatever we do to preserve nesting sites.
> Ian Nisbet
> North Falmouth
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