Monday, June 21, 2010

M.A.P.S. / Studying a Captured Bird

Most surprising of all the new information gained on my bird banding day was how gender and reproductive status are determined in species that look alike. The researcher blows on the belly to part the feathers, thus revealing either a female's "brood patch" or a male's "cloacal protruberance," both of which are red and swollen during the breeding season. The brood patch is a large featherless patch on the breast and belly with which the female warms her eggs or nestlings. The cloacal protruberance of the male is what it sounds like.

I found it comical to discover that the brood patch is assessed with descriptive terms like vascular, wrinkled, smooth, heavy, and molting, while the cloacal protruberance is assessed only for small, medium, and large. Make of that what you will regarding cross-species similarities, but don't deny that it makes you laugh.

Common Yellowthroat

Inspecting the feet

Measuring the wing of a cat bird

Determining flight feather wear

Blowing apart the feathers to assess "brood patch" or "cloacal protruberance"

Recording the data
The data collection was fascinating to watch. Each bird was inspected, measured, and assessed at close range for more than 30 specific bits of information, all of which were meticulously recorded, and many of which I had never before considered. My learning curve was high. Things like flight feather wear, molt limits, plumage; measurements of wing, skull, tail, body fat, eye color, mouth & bill, and much much more, for the purpose of determining age, gender, health, and reproductive status. Much of it was more technical than I was able to follow, though I found it intensely interesting---especially the myriad determinations about the plumage---the primary & secondary coverts (outer feathers), and inspecting the molt limits for primaries, secondaries, tertials, and rectrices to determine age, history, and health status.

If the captured bird already had a band on its leg, the number was recorded along with the new data, later to be entered into computer and compared with earlier observations of same bird. If not, it was given a band, a process to be described in next post. dkm

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