Saturday, August 7, 2010

Morning Flight and State Park Shorebird Show

The early morning movement of migrants at Higbee's Beach was well worth the early start today, with plenty of birds to enjoy. Cedar Waxwings, Common Grackles, Brown-headed Cowbirds and Red-winged Blackbirds milled around over the fields and dropped in to feed on the ample Black Cherries. Blue-grey Gnatcatchers, Indigo Buntings and Yellow Warblers were the most common species around the fields and a small movement of warblers over the dike included Yellow, Black-and-white, Prothonotary and Prairie warblers, American Redstart and Northern Waterthrush. A Worm-eating Warbler was in trees in the first field. Other birds passing the dike this morning included Black Tern, Bald Eagle, four Green Herons, Tricolored Heron, Marbled Godwit, Whimbrel, small parties of Eastern Kingbirds and Orchard Orioles and a single Lark Sparrow.

The shorebird bonanza at Bunker Pond continues with Karl Lukens reporting one Marbled Godwit still present this morning. The close proximity of some of the birds offers great opportunities for study, both to compare the species side by side and to dip into the murky minefield of molt!

Typically, the first returning shorebirds in July and early August are adults - like this Least Sandpiper. Note the pale, olive-yellow legs, and note how tough the color can be to see when in the bird's shadow. Incidentally, note also in this picture all the small snails in the mud; these and other small invertebrates are collectively known as benthic invertebrates which build up large populations in mud at the bottom of pools during the summer and provide food for migrant shorebirds. There needs to be ample water in the pools to allow these populations to build up and the dryness of the Migratory Bird Refuge throughout the summer has probably greatly reduced this population, resulting in shorebirds favoring Bunker Pond. [Photo by Mike Crewe]

This close up of the same Least Sandpiper clearly shows the difference between the old and new feathers. This bird's breeding plumage consists of feathers that are dark brown with buff bases and whitish tips. The whitish tips have worn off, leaving angular, dog-toothed feathers. The fresh non-breeding plumage feathers are pushing through and are pale gray with darker shafts; these new feathers are still broadly square-ended with whitish tips. This mix of feathers shows this bird to be an adult; juveniles would still have all feathers of the same age, giving a more even and neater appearance. [photo by Mike Crewe]

Adult Semipalmated Sandpiper (note the dark grey/black legs). The strong contrast between black-centered breeding plumage feathers and pale gray non-breeding plumage feathers makes the molt particularly easy to see in this species. [photo by Mike Crewe]

Larger shorebirds share the same molt strategy. Here, an adult Lesser Yellowlegs on Bunker Pond shows a checkerboard back pattern of dark breeding- and pale non-breeding feathers. [Photo by Mike Crewe]

An adult White-rumped Sandpiper (right) faces off against an adult Semipalmated Sandpiper. Contrasting back patterns again visible on both species. Shorebirds often bicker and grumble with each other as they defend particularly good feeding spots - indeed, you don't have to watch Least Sandpipers for long on Bunker Pond before you see a right humdinger of an arguement going on! [Photo by Mike Crewe]

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