Spring 2006 Notes and Highlights for the Month of April

• April highlights were certainly not few and far between.  In addition to holding two very successful beginner bander workshops the first two weeks of the month, the captures of many species (and a couple record setting numbers) helped make April very eventful.  This was the first time in 10 years we have banded more than five Northern Rough-winged Swallows in a spring (and it's still only April) and we set a new high daily total for Ruby-crowned Kinglet with 70 banded on 30 April 2006 (the previous high daily total was 57 on 20 April 2000).  More of the April highlights can be found below accompanied by photos.

• Overall, seventeen of the 26 species banded this month were wood warblers.  American Goldfinch topped the list with 284 banded, Ruby-crowned Kinglet came in a close second with 276, and Dark-eyed Junco came in third with 149.  Such a successful April would not have been possible without the help of the many staff, volunteers, and visitors.  For this reason we would like to thank our seasonal banding assistant, Keri Parker, Powdermill administrative assistant, Cokie Lindsay, Louisiana Waterthrush intern, Christian Meny, and volunteers, Jessica Scopel, Pam Ferkett, Brian Jones, Jamie McDougal, Emma DeLeon, Glenn Stauffer, Fred McCullough, Carol Leppold, Molly McDermott, and Matt Shumar.  We also welcomed a post-doc researcher from Switzerland, Simone Immler, for a two week stay at Powdermill and thank her for all the assistance she provided us on a daily basis while she was here collecting data for her project.  Read more about her and her research in next week's update.

• With so many highlights this month, it makes sense to start at the beginning.  So, on April 1st we captured our first Chipping Sparrow for the year....

• Four days later we welcomed our first beginner bander workshop group to Powdermill for their week long stay and first introduction to bird handling and banding techniques.  And, what an introduction it was!

• While it turned out to be a beautiful (and productive) first day, the morning temperatures were in the 30's and wet snow blanketed the ground.  Once we were able to open nets, though, we were quite busy and had banded 101 birds by the end of the day.  After an introduction like that, we welcomed the more seasonal temperatures throughout the rest of the week and also the more manageable numbers for the beginner group.  All involved had a great time and found it an awesome learning experience.

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In the photo below, from left to right, is:  Keri Parker (PARC Spring Banding Assistant); Jeff Michaels, Bob Mulvihill (PARC Field Ornithology Projects Coordinator); Beth Girard, Jonathon Gottsche, Mike Lanzone (PARC Assistant Field Ornithology Projects Coordinator); Cailin O'Connor (holding Keri's newly adopted dog, Kody); Adrienne Leppold (PARC Bander-in-Charge) with Puppy, and Bob Leberman (PARC Senior Bird Bander Emeritus).

• While the first week of April at Powdermill typically is not very noteworthy for its bird diversity, our workshoppers still were treated to a nice variety of birds.  Our first Rusty Blackbirds for the season presented a nice comaprison between a male and female and also provided us an opportunity for a brief discussion on ageing and the importance of being familiar with an individual species' molt pattern before arriving at an age determination.  The top photo is an AHY female and the bottom photo is an SY male.  The underwing photo is of the same immature male pictured below.  It is important to know that most icterids can have a complete first prebasic molt in the fall.  Because of this, it is often difficult to distinguish adults (ASY) from immatures (SY) at this time of year.  The only reason we were able to do so in the case of this male was because he had a few retained (browner) juvenal underwing coverts (shown in the third picture below), as is often the case in this family of birds.

• Tail feathers from both of these birds were collected to aid researchers at the Smithsonian's Migratory Bird Center who are invesitgating possible causes behind long-term declines in this quintessential boreal breeding bird (for more information, click here).

• The first Tree Swallow of the season was a recapture of a returning breeding resident male (sex known based on previous handlings), but the workshoppers got a chance to band their first one just before they left on Sunday, April 9th.  Like icterids, young swallows can have a complete first prebasic molt, leaving us no cues as to the age of this bird.  Furthermore, an adult female could have similar bright iridescent plumage, which left us unable to accurately sex the bird as well.  So, in the end, this bird was recorded at this recapture simply as an AHY of undetermined sex.

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• April is the month for Brown-headed Cowbirds at Powdermill.  Although we have banded cowbirds in every month of the year, fully two-thirds of all our cowbirds (2,945 out of 4,482) have been banded in April.

• All too often, we hear disparaging remarks from our visitors concerning cowbirds--e.g., "the only good cowbird is a dead cowbird!"  Their bad reputation stems from their atypical reproductive strategy, a strategy called obligate brood parasitism.  This means that after adult cowbirds mate, females lay their eggs in nests of other species that in turn act as "hosts," or foster parents, for the cowbird nestlings.  Adult cowbirds provide no parental care to their young whatsoever.

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The impact of this highly specialized breeding strategy can be negative on the host species, because female cowbirds often will remove a host egg before laying one of their own, and the usually larger cowbird nestling will sometimes force one or more of the smaller host young out of the nest completely or simply command the far greater share of food brought to the nest.  Because cowbirds, a native songbird species, historically occurred in open prairie habitats, they are a relatively new component of the breeding bird communties in the formerly very heavily wooded eastern deciduous forest.  As that forest was removed, and as it continues to be fragmented by humans for their use, cowbirds have been able to expand eastward, in the process encountering many new potential "host" species for their young.  The cowbird almost always is implicated in declining trends for many species of eastern forest nesting songbirds, and this has made them aves non grata among many bird watchers and bird conservationists.
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At Powdermill we take a very different view of this interesting native songbird species.  Because it is a legally protected migratory species, we believe that cowbirds should not be persecuted for an evolutionary strategy that they have evolved over eons, a strategy originally well-adapted for a nomadic life following huge buffalo herds in the prairie Midwest and, as it turns out, successful in present day contexts, too.  In fact, while they are "Wanted," dead or alive, by many purported bird "lovers,"  we believe that the cases where species must be actively protected from productivity losses associated with cowbird parasitism are few and far between--limited, for example, to genuinely endangered and highly geographically restricted species like Kirtland's Warbler, Golden-cheeekd Warbler, and Black-capped Vireo.
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In the course of a single nesting season, a female cowbird produces 30-40 eggs over as many or more days, and she must find almost as many nests of potential host species at just the right stage of laying in order for just a few of her offspring to have the chance to survive to independence--this is about the same number of young that many cowbird host species themselves will raise in a single season by tending just one or two nests containing four or five eggs each.
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Locally, there can be some significant exceptions where cowbird nesting success almost completely eclipses the nesting success of its host species.  That is, some small forest fragments in predominantly agricultural landscapes are large enough to attract forest nesting host species, like Wood Thrush, but these hosts experience exceptionally heavy cowbird parasitism pressure due to the fact that a very large population of cowbirds is supported by the surrounding agricultural landscape.  In these settings, host species may effectively raise only cowbird young, with the result that from the host species perspective, the breeding location constitutes a deep "population sink."  Again, though, the irrefutable negative impact of cowbirds on some host species in such settings is symptomatic of the generally negative effect on many ecological processes of conversion of forest to other land uses by human beings.  These negative impacts are by no means limited to elevated rates of brood parasitism by cowbirds on some songbirds.

• Arriving along with the three participants for the second beginner bander workshop offered from 11 April - 15 April were our first wood warbler of the spring, this SY male Yellow-rumped Warbler,

 
and this handsome adult (ASY) male Eastern Bluebird.


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• While the focus for our beginner workshops is primarily on handling techniques, net extraction, and banding ethics, (in the photo below, Adrienne Leppold instructs workshopper Erin High on the proper way to band a Belted Kingfisher),

 

 
 




we inevitably incorporate a little bit of explanation of the banding age codes, molt sequences, and ageing techniques.  In the photo below, Adrienne explains thrasher molt to workshoppers (from left to right) Erin High, Andrea Adams, and Jason Reppart.



• Other new species for the spring that were banded during the first half of April included Blue-gray Gnatcatcher (top) and Hermit Thrush (bottom).  Our first (of 15 banded so far this spring) BGGN was an adult female (males have prominent black "eyebrows" in alternate, or breeding, plumage.

click here for more April Highlights

Last Updated on 05/05/06
By Adrienne J. Leppold and
Robert S. Mulvihill