Fascinating, Chris. Many thanks for posting the report and the analysis.
Chris Rimmer wrote:
> I joined our field crew on East Mt. Tuesday night and Wed. Bicknell's
> Thrush (BITH) continue to be very active there, singing and calling. We
> mist-netted 4 previously unbanded males. This has been a "banner"
> summer for BITH, following 2 productive breeding seasons, when numbers
> of red squirrels were low (they are a major predator). Squirrel
> populations track fir cone crops, which generally follow a two-year boom
> or bust cycle in montane forests. The pattern occasionally skips a
> year, and 2005-2006 both featured low squirrel numbers, with the result
> that BITH (and other open-cup nesting species) enjoyed relatively high
> breeding productivity. BITH numbers have generally rebounded throughout
> the Northeast in 2007, with mountains like Burke -- a small peak on
> which we have detected no more than one BITH since the late 1990s, none
> last year -- supporting good numbers. I found 3 BITH on Burke in early
> June. I managed to mist-net all 3, and 2 were yearlings. A high
> proportion of the BITH we've captured on East, Mansfield and Stratton
> are also yearlings, reflecting 2006's solid productivity.
> This summer features a different story in terms of squirrel
> populations. Many of you will recall last fall's massive cone crop.
> The mountains are now overrun with squirrels! East Mt. in particular
> has obscene numbers, like nothing we have ever seen. They are
> undoubtedly depredating nests of BITH and other species, which means
> that many birds will renest after failing, accounting at least in part
> for the continued strong vocal activity, at a time of summer when things
> normally begin to quiet down. The good news is that the 2007 cone crop
> is all but absent, so BITH should have a relatively squirrel-free 2008.
> Pine Siskins and White-winged Crossbills continue to be present on East
> in small flocks. We caught a family of recently-fledged Boreal
> Chickadees and a female Black-backed Woodpecker that we had banded in
> 2005. Blackpoll Warbler numbers continue to be low.
> I spent the late mornnig and afternoon atlassing along the access road
> to East Mt, which like the summit is on the Seneca Mt. 6 block.
> Interestingly, Blackpolls were all over the place in suitable habitats
> of dense, small fir and spruce, at elevations of 6-800 m. I flushed a
> female off a nest with 2 eggs and had at least 6-7 pairs carrying food.
> I wish other species had been as easy to confirm.... I needed 11 new
> confirmations but only came away with 6. All were of adults carrying
> food and/or feeding fledglings, and included Black-throated Green
> Warbler, Black-and-white Warbler, Canada Warbler, Mourning Warbler,
> Common Yellowthroat, and Lincoln's Sparrow. Two interesting new species
> for the block included a female Tennessee Warbler and a (Western) Palm
> Warbler at the edge of a small bog -- both investigated my pishing, but
> neither had food or acted agitated as if a nest or young were nearby.
> Chris Rimmer
> Conservation Biology Dept.
> Vermont Institute of Natural Science
> 6565 Woodstock Road
> P.O. Box 1281
> Quechee, VT 05059
> 802-359-5001 ext. 230