Photographed at Port Mahon, Delaware in May. There are Dunlin nearby in full breeding plumage, but this one just doesn't look quite like the molts or juveniles I see in the guides?
Hi Joe, There is quite a bit of variation in timing of moult in birds. For example, I study phalaropes and Bonaparte's Gulls as they migrate through my region in the fall. In the early part of migration you see birds that have moulted already into their Basic, winter plumage, and those that haven't. It's possible that this bird is just late. But I'd like to hear others' views. Do young sandpipers moult later than adults? Do they take more than a year to attain adult plumage?
Most shorebirds take more than 1 calender year to reach maturity, with many only partially moulting or remaining in their non-breeding garb. Although some adult females can be quite dull, the mix of summer/winter feathers & particularly the worn, drab primaries & coverts indicates this is a 1st summer individual. While some immature birds remain on wintering grounds, others migrate north with the adults to breed.
Timing of moult is dependant on where 1st summer Dunlins are during the summer months. If they remain on their wintering grounds, then most are probably already in full winter plumage well before the older birds start their return journey southwards. If they travel to summer haunts, then the pattern is much like adults, i.e. it begins almost immediately on arrival in the Arctic. Primary moult is even more gradual & may not be completed until south-bound migration is underway, i.e. from mid-August to mid-September. This scenario applies to pacifica, arcticola & hudsonia, but not the race arctica which moults from summer plumage on its wintering grounds.
Cheers: Wayne
Last edited by Wayne Richardson; 06-22-2009 at 12:06 PM.
Reason: grammar