ML251507641
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Observation details
Two birds in with the Ring-billed Gulls at the north end of the sandbar. Relatively small bill, white under the primaries. Enjoyed these birds with the good company of Lois and Al Richardson. Photos and audio. The white-headed bird is a first summer bird with retained juvenile outer primaries, secondaries, and outer rects. It is well advanced in it second prebasic molt, growing in mid/outer primaries and replacing outer secondaries. Pink fleshy legs. SPB in WRP nomenclature. The other bird is an ASY (DPB in WRP system) with a dark hood and orangish-red legs, but I didn’t have a close enough look of it in flight to try to distinguish between second summer and older; feather wear also complicates things. It is also undergoing a prebasic molt, but has started molting more recently than the younger bird; inner primaries growing in. The ages of the birds make it interesting to consider what leads to Bonaparte’s arriving in Western Mass in July/August, before larger movements in fall. Howell and Dunn (2007) note a bimodal migration through the eastern region with the first peak in August and a (much larger) peak in late Sept/early Oct. Interesting to consider what is the mechanism behind this bimodal migration. Perhaps the earlier movements are nonbreeders and failed breeders. The white headed bird is certainly a non-breeder, so perhaps it has migrated part of the way or all of the way to the breeding ground and is returning to nonbreeding grounds on an earlier schedule as nonbreeders sometimes do. Perhaps the dark-headed bird is a nonbreeding second summer and so the same story holds true for it as well (the two birds likely arrived together....I checked this spot earlier in the morning and neither was present). Or perhaps the dark-headed bird was a failed breeder and is moving earlier as a result. Howell, S.N.G., Dunn, J. 2007. A reference guide to gulls of the Americas. Houghton Mifflin: New York, New York.
Technical information
- Recorder
- Microphone
- Accessories
- Original file size
- 4.26 MB