Date: 9/24/17 5:23 am
From: Scott Weidensaul <scottweidensaul...>
Subject: Re: 9/23 warblers & thrushes, berks
It's been interesting the past few years to see the noticeable upswing in Cape May warbler numbers, as well as lesser increases in bay-breasted and blackpoll. This is a region-wide trend, from all evidence, and is likely tied to the long-term cycle shift in native spruce budworm outbreaks in the Canadian boreal forest, which occur every 30 or 40 years. These "budworm specialists" see their numbers rise and fall in synch with the caterpillar infestations, which provide abundant food for their chicks. Cape Mays and bay-breasteds in particular are tied to budworm cycles, with major declines since the late 1980s when the last regional series of outbreaks (roughly 1966-1992) subsided.

Now we're seeing budworm numbers rising again in what may be the beginning of another series of outbreaks, and the warblers appear to be responding. It will be interesting to see if another, less recognized member of the budworm-specialist group also increases in abundance -- evening grosbeaks. While the winter adults are seed-eaters, they depend on arthropods to feed themselves and their chicks in summer, especially budworms. Some researchers have linked the explosion of irrupting grosbeaks in the East from the 1960s through the late 1980s with the last major budworm outbreaks, and it's true that since budworm numbers have begun climbing, we've seen at least an uptick in the number of evening grosbeaks in the Northeast. It's much too soon to say if we'll again have hordes of EVGRs at our feeders, as we did in the 1970s and '80s…but we can hope.

Scott Weidensaul
Schuylkill Haven, PA



On Sep 23, 2017, at 10:50 PM, Rudolph Keller wrote:

> As Carole Winslow found in western PA, lots of birds in Berks & Schuylkill have been moving on not much of a north wind during the last few nights. South Lookout at Hawk Mt. Sanctuary is a good place to stand in the hour before sunrise listening for nocturnal migrants coming down from their red eye night flights. This morning I counted over 1100 calls, mostly of Swainson's Thrush. I was a little surprised to hear only 4 Gray-cheeked Thrush calls in that large crowd. Warbler counts at North Lookout have been good in the last few days. This morning's standout in that group was a remarkable count of 203 Cape May Warblers, plus lots of Tennessee, Black-throated Green and Scarlet Tanager. When that many birds pass, darting in and out of foliage, in such a short time, I feel as though I'm looking through a kaleidoscope, with each turn of the glass revealing a new pattern of colorful fragments. The list is below.
>
 
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