Mansfield Update: YBFLs, NSWOs, and FOYs

A banded juvenile Northern Saw-whet Owl collects itself immediately after release, just before melting back into the night on Mt. Mansfield, 28 July 2020. © Avery Fish

Quiet now reigns on the Mansfield ridgeline, as VCE’s 2020 banding season winds down. The fervent June songs of Bicknell’s Thrushes and White-throated Sparrows have become sporadic whispers, while the more restrained melodies of Blackpoll Warblers and Dark-eyed Juncos have all but ceased. Most adult birds are undergoing flight feather molt, and most young-of-the-year have reached independence, so avian air traffic is decidedly lighter.

VCE’s penultimate summer field session on July 28-29 featured near-ideal weather conditions—warm and calm with partial cloud cover. Several of us sported shorts throughout the visit, a once- or twice-annual luxury. Mist netting was steady but slow overall, and we ended up with a total of 41 captures. Highlights included our third Northern Saw-whet Owl of 2020 on the dusk closing run (a station record), and several firsts for the year (in bold italics below). Yellow-bellied Flycatchers continued their strong showing, with an adult and immature bringing our season total to 14 individuals, another station record. And, 8 new Blackpolls (4 hatching-year birds) boosted our seasonal total to 57 captures, our highest tally since 2016 and an encouraging sign for a species that is experiencing widespread declines.

An adult (left) and hatching-year (right) Yellow-bellied Flycatcher banded on Mt. Mansfield, 29 July 2020. Note the difference in wing bars: whitish on adult, buffy-white on immature. © Michael Sargent

Our 41 captures over both days included:

Northern Saw-whet Owl — 1 juvenile
Downy Woodpecker — 1 juvenile
Yellow-bellied Flycatcher — 2 new bandings: female with refeathering brood patch and a hatching-year bird
Black-capped Chickadee — 1 hatching-year bird
Golden-crowned Kinglet — 1 bird in full juvenal plumage
Red-breasted Nuthatch — 1 hatching-year bird
Brown Creeper — 1 hatching-year bird
Bicknell’s Thrush — 1 new adult female w/refeathering brood patch in early primary molt
Purple Finch — 1 new yearling male missing primary #1
Dark-eyed Junco (Slate-colored) — 5 (4 new juveniles, 1 within-season recap female with regressing brood patch)
White-throated Sparrow—  8 (3 new HYs, 1 new adult male and female, 4 within-season recaptures)
Magnolia Warbler — 1 adult female in early primary molt
Blackburnian Warbler — 1 hatching-year male
Blackpoll Warbler — 10 (4 HYs, 6 adults [4 male, 2 female] all in primary molt)
Black-throated Blue Warbler — 2 (adult female in primary molt and hatching-year male)
Yellow-rumped Warbler (Myrtle) — 3 hatching year birds in various stages of postjuvenal molt
Black-throated Green Warbler — 1 adult female with primary 1 missing

A Golden-crowned Kinglet in juvenal plumage. Note its loosely-textured plumage and indistinct facial pattern compared to adults of this species. Mt. Mansfield, 29 July 2020. © Michael Sargent

A banded adult female Blackpoll Warbler looks askance immediately after release on Mt. Mansfield, 29 July 2020. © Michael Sargent

Our final summer session, pushed back to August 5-6 thanks to Tropical Storm Isaias, will likely feature a higher proportion of young birds, more non-local species in post-breeding dispersal mode, perhaps another diminutive owl or two, and…the possibility of something unexpected and storm-tossed. Sooty Tern, anyone? Yellow-breasted Chat?? Stay tuned.

Brooke Hindinger (left) with a banded male Black-throated Blue Warbler and Chris Hansen (right) with a hatching-year male Blackburnian Warbler. Mt. Mansfield, 29 June 2020. © Michael Sargent