Date: 7/9/17 7:06 pm
From: Geoff Malosh <pomarine...>
Subject: Re: Cliff Swallows extirpated in Allegheny County?
Oscar and all,

To say that Cliff Swallow is "extirpated" in Allegheny County is putting it strongly, implying that the species is gone from here as a breeder forever; more correct would be simply to say that there are no longer any known nests in the county at present, as has been the case at times in the past too. Cliff Swallows are notorious for sudden and unexplainable shifts in distribution and nest site fidelity, and while it is certainly true that the species has been very rare as a breeder in Allegheny, Beaver, and Washington counties in recent decades, the North Park birds quite likely won't prove be the last to be found here. Certainly some Cliff Swallow colonies in Pennsylvania are very long established and are active every year, for decades on end. The colony that nests on the underside of the PA-528 bridge at Lake Arthur, Butler County is one such example. But smaller colonies like the one that appeared at North Park Lake just as frequently prove to be ephemeral as they do to be 'permanent'.

The entire history of the species in Pennsylvania has followed this kind of unpredictable, almost erratic status and distribution. Originally a native only of western North America, historically, Cliff Swallows nested only on naturally occurring cliff sides. The species did not expand into eastern North America until the early 19th Century, as the man-made structures they adapted to use as nest sites (bridges, barns, dams, buildings) themselves expanded westward. They did not appear in Pennsylvania until about 1830, but ever since then they have exhibited, more or less, their modern-day tendency to suddenly and inexplicably abandon nest sites from year to year, as well as a tendency to ebb and flow even in raw abundance. It's quite likely the North Park birds were indeed driven out by House Sparrows (a known threat to Cliff Swallow nests), but sometimes Cliff Swallows just move on for no obvious reason too. So it's a fair enough possibility that another colony will pop up at North Park or somewhere else around here again, someday, and will probably seem to arrive completely out of the blue at that.

Geoff Malosh
Allegheny County

-----Original Message-----
From: Bird discussion list for Pennsylvania [mailto:<PABIRDS...>] On Behalf Of Oscar Miller
Sent: Friday, July 07, 2017 3:44 PM
To: <PABIRDS...>
Subject: [PABIRDS] Cliff Swallows extirpated in Allegheny County?

On 5 July 2017 Wednesday I checked the Cliff Swallow colony on the structure at the dam of North Park Lake. Unfortunately there were no active nests present. In 2015 there were seven active nests. In 2016 there were only 2 active nests, with House Sparrows taking over 5 nests. Lots of House Sparrows nesting in holes in the structure which has not been well maintained were probably too much competition. This year there are two active Barn Swallow nests but no Cliff Swallows…Sadly, this might have been the last known site for nesting Cliffs In Allegheny County. Does anyone know of any other sites in Allegheny? Thanks, Oscar Miller
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