Pictorial Highlights, Summer 2009
|Rainbow over Powdermill|
|This SY Canada Warbler was captured during early June. An A1 molt limit can clearly be seen where the A1 was replaced during the 1st prebasic molt and A2, A3, and primary coverts are retained juvenile feathers. Such molt limits are more easily seen during spring compared to fall as juvenile feathers wear more quickly than feathers replaced during the pre-basic molt. Still, detecting molt limits in photographs is much more difficult than when examining the bird in good light.|
|This Northern Parula was a surprise capture during early summer and represented only the second capture of this species for the year. Although there a quite a few parulas breeding along the creek adjacent to the banding lab, they are seldom captured during the breeding season when they nest and forage high in the canopy. We unsuccessfully attempted to record a flight call from this individual as we are trying to increase our library of sounds for parulas to facilitate their identification from flight calls emitted during their nocturnal migration.|
||In North America millions of birds die each
year from collisions with windows. Learn more about this phenomenon
from an article called
9 Ways to Help Birds Avoid Window Collisions. We are exploring
ways to reduce the number of mortalities from window strikes.
To do this, we are assembling a "flight tunnel" at Powdermill which will be used to evaluate birds' ability to detect and avoid different window treatments.
Andy Mack (conservation biologist at Powdermill) and collaborators are spearheading this project, and ground breaking for the tunnel was initiated in June. In the photo Bruce Horner (left, Maintenance), Andy Mack (middle), and Mike Lanzone (right, Bioacoustics) watch as cement is being poured around the base of the tunnel. The tunnel was completed by the end of July and is shown in the second photograph.
|During June we found numerous Baltimore Checkerspot butterflies foraging around the banding area. This is often a difficult butterfly to find and is often associated with wet areas. The wet area around the banding lab appears to be very good habitat for this butterfly. The Baltimore is often easily approachable as (much like the Monarch) it is toxic to predators, which it advertises with its bright colors. I was able to get up to a foot away from this one and got some really nice photographs of it foraging on a Rubus flower.|
|It was a productive summer for Scarlet Tanagers as we banded 30 individuals. Pennsylvania is located in the core of the tanager's range, and they are commonly found throughout the state. Interestingly, its designation as a tanager may be somewhat of a misnomer and a result of convergent evolution rather than common origin. In fact, based on genetic evidence, the American Ornithologists' Union has now removed the genera Piranga (Scarlet, Summer, and Western Tanagers) from the true tanagers and placed them in the cardinal family (Cardinalidae). This ASY male Scarlet Tanager is somewhat unique as it has a bright red wing bar.|
|A young Scarlet Tanager waiting to be fed (photo below) as it sits in the shrub cover provided at the banding lab. Following breeding, we capture many family groups of birds that breed in the mature forest habitat. After fledging, adults and young may prefer dense understory vegetation that provides protection from predators and an abundance of food. In July Rubus plants (commonly found in early successional habitats) begin producing fruit, which is consumed by many birds, including Scarlet Tanagers.|
|A slightly older juvenile Scarlet Tanager captured at Powdermill in July had several orange colored body feathers molting in. This is probably a result of consuming fruit (e.g., honeysuckle berries) that contain carotenoid pigments that produce this color.|
|After fledglings gain independence, adults may continue to use these areas of dense understory vegetation for concealment while they molt. During the prebasic molt, adults replace all of their flight feathers, often rendering them nearly flightless. The degree of flight impairment has to do with the speed at which the feathers are replaced. Wood Thrush are known to replace numerous flight feathers simultaneously and have been noted to be unable to sustain flight for more than just a few meters. This SY male American Redstart is undertaking a somewhat more gradual molt, thereby minimizing negative effects on its flight performance. Notice the replaced feathers represent the bird's adult plumage while the unmolted feathers are those of the immature plumage (redstarts have delayed plumage maturation).|
|An AHY Ovenbird replacing several flight feathers simultaneously.|
|Another look at the molting adult Ovenbird.|
|At the end of summer we begin capturing large numbers of hummingbirds, and these are primarily HY individuals that have recently left their nest. Although male ruby-throated hummingbirds do not immediately acquire their red gorget, they still can be readily identified. The young male (left) has well defined streaking down its throat, whereas the female (right) has a white throat with indistinct or no streaking. In addition, the female is quite a bit larger than the male.|
|For both the male and female ruby-throats, HY individuals have bill corrugations and buffy edging on their crown feathers. Be careful, though, as these buffy tips can wear off.|
|Empidonax flycatchers are one of the first
passerines to depart for their wintering grounds, and we begin
regularly capturing migrating birds by the end of July. The two
birds in the photo below are both least flycatchers, and they were
identified by their small size, white throat, and emargination of
their sixth primary.
The bird on the left was identified as a HY by the broad buffy wingbars, and the bird on the right as an AHY individual with worn, white tipping on the median and outer greater coverts and worn flight feathers. Unlike the majority of North American migratory songbirds where adults undergo a complete prebasic molt on the breeding ground, in this species (and some other empids), the adult pre-basic molt (complete) primarily occurs on the wintering ground. The molt limit created from the prealternate molt is noticeable in the adult bird (right).