Powdermill Banding Spring 2007

Spring 2007

Notes and Highlights for
May 22-27

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We banded 272 birds of 42 species during the week and processed 97 recaptures. Our total effort for the week was 1,665 net hours, giving a rather poor capture rate of just 16.2 birds/100 net-hours. It also was our impression that there were few migrants present in the banding area on any given day during the week, due probably to the lack of any weather systems to concentrate and ground them. Our best day in terms of banding total, species diversity, and capture rate was Tuesday, 5/22, when we banded 70 birds of 27 species at a rate of 19 birds/100 net-hrs. Species contributing most to our total this week were Cedar waxwing (87 banded), American Goldfinch (31), Gray Catbird (19), Indigo Bunting (16) Ruby-throated Hummingbird (13), Common Yellowthroat (12), Northern Waterthrush (8), Swainson's Thrush (8), "Traill's" Flycatcher (7), and five each of Magnolia and Canada Warbler.

Among the 32 visitors who signed our guest book this week were members of the Delaware Nature Society (photo below) on a field trip to Powdermill led by Joe Sebastiani (kneeling at right).

We also enjoyed a visit from a group of six interns from Hawk Mountain Sanctuary on 5/25, led by HMS Research Biologist and Intern Coordinator, Lindsay Zemba (photo below, standing at left). In the photo below, the six HMS interns from Veracruz, Venezuela, Cambodia, and the U.S. are joined by Molly McDermott (PARC's temporary bander-in-charge; back row, third from right) and two PARC interns from the Dominican Republic, Danilo Mejila (back row, second from right) and Maria Paulino (in front, far left).

The Powdermill banding crew this week was led by Molly McDermott, who is standing in as bander-in-charge during the latter part of the spring and all summer for Adrienne Leppold, who is away supervising a a field crew working on a seabird study for the Maine Coastal Islands National Wildlife Refuge. Helping Molly were her spring banding assistant, Pam Ferkett, the Powdermill Bobs (Mulvihill and Leberman), and volunteers Mary Shidel, Lauren Schneider, and Matt Shumar.

As mentioned above, Cedar Waxwings dominated our catch this week. Large flocks remained in the banding area all week, attracted by the flowering trees and shrubs, especially hawthorns and willows, whose flower parts they greedily consume at this time of year. A double-decker net just outside the banding lab accounted for the majority of our waxwing captures. With more than 80 banded, we observed the usual array of waxwing plumage variations, including wholly or partly orange tails (a result of the incorporation into developing tail feathers of rhodoxanthin, a red pigment found in the Tartarian Honeysuckle berries that are frequently consumed during molt, along with normal yellow carotenoid pigments). This variation is much more frequently seen in the juvenal tail feathers of young waxwings, because their tail feathers are grown in the nest when adults are feeding nestlings extensively on the early ripening (mid-June to July) honeysuckle berries. At Powdermill, at least, these same berries are much less widely available later in the fall when adults are molting their rectrices, and we rarely if ever see orange tipped rectrices in adult birds.

The bird pictured below, however, is an adult (ASY) bird, one that must have increasingly fed on honeysuckle berries as the molt of its tail proceeded centrifugally (i.e., from the central tail feathers to the outer ones). The same bird showed another infrequent plumage variation: small wax tips on its tail (especially the yellow central pair) in addition to those present on the tips of its adult secondary wing feathers.

The above-pictured bird's tail wax tips were nothing, though, compared to an adult male waxwing banded on 5/26 that had what may well be the most well developed tail wax tips we have ever seen!

The second most commonly banded bird this week after waxwings were American Goldfinches. A little known but useful means for separating SY and ASY goldfinches in spring is the existence of a prealternate molt limit among the greater coverts. The lack of any such partial molt of greater coverts in adult (ASY) goldfinches was first reported by Alex Middleton in his classic study of the molt of this species published in The Condor in 1977 (vol. 79: 440-445).

The photos below illustrate this: the top photo is of a SY female that has replaced one inner greater covert (GC 9); the middle photo is an ASY female showing no prealternate molt of greater coverts; the bottom photo is an SY male that has molted three inner coverts (GC 6-8). Although the molt limit is not as conspicuous in the male due to the black color of the retained juvenal GCs, the prealternately molted GCs 6-8 can be seen to be even blacker and far less worn than the adjacent unmolted (juvenal) GCs. The description of molt in AMGOs in Pyle (1997) is not entirely correct. It states that HY goldfinches molt 4-10 GCs during the first prebasic molt (they do not molt any) and 0 (35%) to six during the 1st PA molt (at Powdermill ca. 90% or more molt at least one GC), and that ca. 30% adults can molt up to two GCs in spring. We have not observed normal PA molt of GCs in any adult AMGOs at Powdermill, although asymmetrical adventitious replacement of GCs sometimes occurs.

We couldn't resist snapping a quick side-by-side photo of two small, mostly yellow, black-capped birds (Wilson's Warbler, left; American Goldfinch, right) banded during the same net round on 5/23.

In our early May highlights we showed a closeup picture of dark "gunk" on the tip of the beak of a White-crowned Sparrow. Like the WCSP, the photo of the female American Goldfinch below belies this species' fondness for dandelion seeds. When probing into the unopened seed heads, birds that feed on dandelions in spring encounter the gooey white substance found in the plant's hollow stems, a substance that dries to a rubbery consistency and which apparently is difficult for the birds to clean off from their bills.

We banded just our second Yellow-bellied Flycatcher of the season this week, an SY bird, on 5/24. A more usual spring total by this date would be 20 or more. Some of you will recall that we consider the YBFL to be literally the "cutest" of the eastern Empidonax flycatchers, because of its comparatively infantile proportions (i.e., disproportionately big head and eyes; small bill and body).

For the same reasons, a Philadelphia Vireo banded on 5/24 looked far cuter than the Red-eyed Vireo caught with it on the same net round.

Speaking of vireos, an encounter with another vireo species reminded us on 5/24 of why our banding station protocol encourages examination of the breeding condition of birds at the net and allows for selected birds, e.g., previously banded females with fresh brood patches and/or in gravid condition, to be recorded and released at the net and not brought back to the central banding lab for banding or full processing.

A White-eyed Vireo retrapped early in the morning on 5/24 was bagged by a less experienced volunteer and returned to the banding lab where it was discovered that she had laid in the bag an egg she undoubtedly was on her way to a nest to lay when she was caught in our mist net. Her elongated, sparsely spotted egg weighed 2.2 grams. Interestingly, the bird still appeared very gravid despite having just laid an egg. And, at 14.9 grams, her weight after having already laid one egg showed that she did indeed have a second very well-formed egg in her oviduct (this notwithstanding the fact that birds lay just one egg a day).

A WEVI with little or no fat and no egg might weigh 11-13 grams. Considering the added weight of the egg that she laid in the bag, this female WEVI must have weighed an amazing 17.1 grams when she was caught in our mist net. The highest body mass recorded in Mulvihill et al. (2004, Relationships among body mass, fat, wing length, age, and sex for 170 species of birds banded at Powdermill Nature Reserve, EBBA Monograph No. 1) based on 685 WEVI banding records is 16.8 grams, and this was for a bird with maximum fat deposits.

What is undoubtedly one of the last Lincoln's Sparrows of the spring season was banded on 5/24. The LISP is a especially finely marked bird whose neatly tailored appearance rarely comes across well in field guide illustrations or photographs. The photo below is our latest attempt, and we think it's a bit closer to doing justice to the understated beauty of this bird than any we've taken before.

We observed a couple of unusual cases of eccentric wing molt this week: an SY female Scarlet Tanager banded on 5/23 (top photo below) had replaced (presumably during her first prealternate molt) three outer primaries (note the darker gray color and blacker shafts) and four inner secondaries on both wings (as well as all of her rectrices); on 5/27 we banded an SY female Indigo Bunting (bottom photo below) that appeared to have undergone a very nearly complete first prebasic molt including all but the innermost (juvenal) primary and several inner primary coverts.

On 5/22, we banded this unusually dull SY male Canada Warbler that had just a trace of a black "necklace."

Female Black-throated Blue Warblers arguably are among the most confusing fall and spring warblers. But many of them are substantially less well marked than this SY female banded on 5/24, with her very prominent white wing spot and eye markings.

It has been a good spring flight of Mourning Warblers at Powdermill. This ASY male and SY female banded on 5/26 brought our spring total to 21 (our long-term spring average is 14).

It's also been a very good spring migration for Indigo Buntings (51 banded through 5/27 compares with a long-term spring average of about 30). We couldn't resist taking yet another photo of a brilliant ASY male, this one banded on 5/26.

On the last banding day of the week, we caught what surely is the quintessential blue bird: an ASY male Eastern Bluebird.

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Last Updated on 05/27/07
By Robert S. Mulvihill