Pictorial_Highlights

POWDERMILL NATURE RESERVE
PICTORIAL HIGHLIGHTS
APRIL 22-28, 2002

Sunday, April 28, 2002:

Returning from just having opened nets (and without any carrying bags for the birds), an assistant briefly had his one hand full with the equivalent of six Common Yellowthroats in the bush!

Saturday, April 27, 2002:

The first of three Common Grackles banded today had just nabbed a red-spotted newt (an aquatic salamander) when it flew into our net and dropped the newt unharmed into the net. Newts have toxic skin secretions and are, for the most part, eschewed by predators--in fact, we have never before observed anything eating a newt. Who knows, maybe this grackle would have learned to avoid newts, too, if it had had the chance to finish its meal! One thing's for sure, with a gape like this grackle's (too bad yesterday's chat wouldn't say "Ahhh" like this!), that newt would have been gone in one gulp!

The third new species for Powdermill's spring 2002 banding list on 4/27 was our first Ruby-throated Hummingbird. Although RTHUs not uncommonly are spotted at feeders and ornamental flowering shrubs in the vicinity of Powdermill by the end of the third week in April, we have only banded eight other RTHUs in the month of April, and like today's bird, all of these have been the earlier arriving males.

It goes without saying that hummingbirds are the smallest birds that we band at Powdermill (males, which are smaller than females, often weigh less than 3.0 grams, or not much more than the weight of a penny). The tiny bands we use on them come printed on a sheet of pliable metal and each band must be carefully cut out and formed by hand (see second photo below). We have banded about 7,000 RTHUs in 40 years, but we have only ever had two of our banded RTHUs recovered away from Powdermill (one in Maine and one in Quebec). A good many of our banded individuals, however, have returned to Powdermill over the years, enabling us to study their survivorship and longevity (we have recorded female hummingbirds as old as 7 years of age). About ten years ago we (R.S. Mulvihill, R.C. Leberman, and D.S. Wood) published a paper in a leading ornithological journal, The Condor, which had a title that was almost absurdly long considering the diminutive object of our study: A Possible Relationship between Reversed Sexual Size Dimorphism and Reduced Male Survivorship in the Ruby-throated Hummingbird (Archilochus colubris).

Friday, April 26, 2002:

Two new species were added to the spring banding list today: Kentucky Warbler (left photo) and Yellow-breasted Chat (right photo; the first of this species that we have banded at Powdermill since May 11, 2000)--both were adult (ASY) males. Adult females and males of these two species sometimes differ only slightly in their plumage, but the extent and intensity of the black on this male KEWA far exceeded that of the most heavily marked female. Male YBCHs are told from females by their blacker lores (the feathered area in front of the eyes) and by the color of their mouth lining--it is inky black in males but mixed gray and pink in females (unfortunately, we couldn't get this YBCH to say "Ahhh" when we took its picture!)

The Brown Thrasher banded today (4/26) was an after second year (ASY) bird--its greater wing coverts were more uniformly dark and lustrous, and also of more equal length, i.e., there was no molt limit (top photo below). All of the greater coverts in this ASY bird appeared like the few molted inner greater coverts seen on the second year (SY) BRTH whose photo we first posted last week (bottom photo below). Note, also, the richer coloration of the carpal covert, primary coverts and remiges in the ASY bird. In comparing the two photos, it also appears as though the distinct white spots on the outer retained juvenal greater coverts in the SY bird (not present on the equivalent three outer coverts in the ASY bird) may be another useful criterion (along with color, lustre, and size) for helping to distinguish when these feathers are retained from the juvenal plumage in this species.

Thursday, April 25, 2002:

RBGRs, like the beautiful ASY male banded here today (photo below), often take feeder watchers by (pleasant) surprise when they show up for the first time on cool late April and May mornings along with the usual feeder crowd of chickadees, titmice, finches, and the like. Although we have not yet had our first, another brightly colored neotropical migrant that often finds its way to feeders shortly after returning to its temperate breeding grounds is the Indigo Bunting (maybe tomorrow!) Come to think of it, bird bander or not, what tomorrow may bring is the best thing about spring!

American Goldfinches were very numerous again today, 4/25 (60 banded), although they only comprised about half, rather than two-thirds or more, of our total catch. The distribution of AMGOs among age/sex classes was quite different from yesterday (see notes for 4/24 below)--numbers of males (29) and females (31) were about equal, and known ASY birds (33) outnumbered known SY birds (24). A few AMGOs could not be confidently ascribed to one age class or another. The photo below shows an ASY male AMGO banded today whose extremely dull epaulet coloration could easily be mistaken for that of an SY, but note that the other ageing criteria described and illustrated in yesterday's note (e.g., velvety black alula and flight feathers; carpal covert without a buffy terminal edge) supported the ASY determination (as did eye color and rectrix, or tail feather, shape).

Wednesday, April 24, 2002:

American Goldfinches (48 banded today) have made up two-thirds to three-quarters of our daily banding total since last Sunday. Among today's birds, males outnumbered females 30 to 18 and second year (SY) birds outnumbered after second year (ASY) birds 26 to 22. In the photo below, an SY male (top bird) is compared to an ASY male (bottom bird). In alternate (i.e., spring or breeding) plumage, both age classes have very bright body plumage and soft part (e.g., bill) coloration, but SY birds typically have dull greenish brown epaulets (i.e.,, lesser coverts) at the bend of the wing, while ASY birds usually have bright yellow "shoulders." This criterion alone, however, is not altogether reliable for determining age of AMGO males, because ASY males not infrequently have dull greenish lesser coverts, and SY birds sometimes will show precocious development of bright yellow lesser coverts.

In determining the age of male AMGOs, banders should look also for duller black retained juvenal alula and flight feathers in SY males (top photo below) and uniformly velvet black alula and flight feathers in ASY males (bottom photo below). Note, also, that the retained juvenal carpal covert ( the half-length covert just below the three-feathered alula and overlapping the innermost primary coverts), and sometimes also the alula, of SY males almost always has a thin buffy terminal edge, while ASY males have solid black carpal coverts and alula, although rarely these can have a white terminal spot. Finally, SY AMGOs often replace some inner greater coverts during the prealternate molt (giving a distinct molt limit between a few blacker inner greater coverts and the duller retained juvenal outer coverts--this is not shown in the photo below), while ASY birds typically do not molt any greater coverts in the spring.

With the exception of epaulet coloration, the ageing criteria discussed and illustrated for males also can be applied, albeit with somewhat greater difficultly and, therefore, more caution, to female AMGOs. Tail feather shape (broader and rounder in ASYs; narrower and more pointed in SYs) is another useful criterion to throw into the mix (but not to use in isolation) when determining age for female AMGOs in the hand.

Tuesday, April 23, 2002:

The only new species to band today was White-eyed Vireo.

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