The rain stayed just offshore this morning allowing me to get today's banding sesssion in. I banded 14 new birds with 5 recaptures of 8 different species. Prairie Warblers were the most numerous species again and I banded the first EASTERN TOWHEE and "TRAILL'S" FLYCATCHER of the season.
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| Eastern Towhee (After hatch-year, female) |
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| "Traill's" Flycatcher (Hatch-year, sex unknown) |
Because it was a rather slow morning I was able to take some extra time with the Prairie Warblers and took some photos that will help explain how bander's age and sex this species. Before assigning a sex to a Prairie Warbler you first need to determine it's age. This can be done by looking for molt limits within the alula feathers on the wing. A molt limit is the location within or between feather tracts of the wing where two generations of feathers are adjancent to each other. If a molt limit occurs then that bird has retained some juvenile feathers therefore it can be aged as hatch-year meaning it was born this summer. In most hatch-year warbler species, molt limits will occur within the alulas or between the carpal covert and A1 (the tiny 1st alula feather).
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| Alulas and carpal coverts of Prairie Warbler |
In the photo above there is no difference in the color within the alulas or carpal covert. They are all dark black centered and A1, A2, and the carpal covert all have bright yellow edging indicating that this is an adult bird. A3 usually won't have as bright of edging as the other but the feather center will be just as dark.
In the photo below you can see there is a clear difference in color between A1 and the carpal covert. The carpal covert was replaced this summer during the 1st prebasic molt and the alulas were retained as juvenile feathers. For this Prairie Warbler, the molt limit is between A1 and the carpal covert making this a hatch-year bird.
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| Molt limit between carpal covert and A1 in hatch-year Prairie Warbler |
Once you have figure out the age of the Prairie Warbler, next you want to look at body plumage characteristics in order to determine the sex. Adult males will be the brightest in color and will have dark black facial markings as well as large red centers on the on the upper back feathers.
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| Dark black facial markings of adult male Prairie Warbler |
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| Large red centers on back of adult male Prairie Warbler |
Adult females and hatch-year males can look very similiar in plumage. They usually have a little black in the face (but not always). The red spots on the back feathers will be larger in males than in females but both can be moderate in size. Some adult females will have very small red centers.
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| Prairie Warbler (Hatch-year, male) |
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| Moderately size red centers on back of hatch-year male Prairier Warbler |
Search "molt limit" on Google. Wind up here. It would be awesome if all the molt limit photos from the blog were centralized somehow. Cheers-V
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