Blue-winged Warbler

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Hooded mergansers at the Assabet River National Wildlife Refuge, photographed by Dan Trippe.
Dan Trippe photographed hooded mergansers, ring-necked ducks, a belted kingfisher, pine warblers, American woodcock chicks, a blue-gray gnatcatcher, barn swallows, a palm warbler, a yellow-rumped warbler, a common grackle, an...