Date: 6/28/18 1:47 pm
From: Chris Rimmer <crimmer...>
Subject: [VTBIRD] Mansfield week 5
VCE reached the halfway mark of our 2018 field season on Mt. Mansfield this
week, completing our fifth banding session on Tuesday evening and Wednesday
morning. We ran 25 nets under favorable conditions -- mostly calm, cool
temperatures, filtered sun. Both sunset and sunrise were spectacular.
Overall, singing was reduced from earlier in the month, though Am. Robins,
White-throated Sparrows and Purple Finches were in full voice. I'm quite
certain we've never encountered as many robins and finches up there as we
have so far this year, with 10 and 11 adults banded, respectively. Pine
Siskins are still present in good numbers, with a flock of 30 birds roaming
around the uppermost parking lot on Wed. morning. We finally captured 2
Magnolia Warblers, our first of the season, and we netted our (more or
less) annual Sharp-shinned Hawk. No real surprises this week. Still no
Winter Wrens, and numbers of both Swainson's Thrush and Yellow-rumped
Warbler seem relatively low.

We're on course for a "typical" or above-average Bicknell's Thrush (BITH)
year, with 40 captures so far, of which 21 are new bandings and 19 birds
banded in previous years. Reflecting, at least in part, last summer's
absence of red squirrels (major nest predators that follow cone crop
cycles) on the ridgeline, and presumed solid 2017 nesting success by BITH
and other open-cup nesting species, our captures of new birds are dominated
by yearlings (second-year, or SYs), which accounted for 19 of our 21 new
bandings. As always, the sex ratio is skewed towards males (22 vs. 12
females among birds of known sex), reflecting the chronic imbalance that
occurs in this species, with its strange polygynandrous mating system

Our next visit will be on July 10-11, at which point I expect we'll see and
capture juveniles of early-breeding species like robins, juncos,
white-throats, and PUFIs. We'll also likely capture more dispersing failed
and non-breeders from lower elevations, and some early-molting adults. It's
hard to believe our field season is halfway to completion!

Among the 62 birds we captured over both days:

Sharp-shinned Hawk 1 new adult male
Yellow-bellied Flycatcher 1 new adult of unknown sex
Red-breasted Nuthatch 1 free-flying juvenile, flight feathers
completely grown
Ruby-crowned Kinglet 1 within-season retrap male
Bicknell's Thrush 15 3 new SY males, 1 new SY female, 3 returns (1
from 2014, 2 from 2016), 8 within-season retraps
Swainson's Thrush 2 1 new SY male, 1 within-season retrap female
American Robin 2 new male and female
Magnolia Warbler 2 new males
Blackpoll Warbler 10 5 new, 1 return from 2017, 4 within-season retraps
Black-throated Blue Warbler 1 new bird
Yellow-rumped Warbler (Myrtle) 2 new yearling females
Dark-eyed Junco (Slate-colored) 5 4 new birds, 1 within-season retrap
White-throated Sparrow 7 1 new, 6 within-season retraps
Purple Finch 5 1 new female 1 new SY male, 2 new and 1 retrap ASY males
Pine Siskin 7 new; 1 adult female, 6 free-flying juveniles


Chris Rimmer
Vermont Center for Ecostudies
PO Box 420 | Norwich, Vermont 05055
802.649.1431 x202

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