Cerulean Warbler

It's a female, on its nest, characteristically high above the ground, captured from a considerable distance, on Mount Holyoke in Hadley. Using a doubler (2x extender) on my 100-400 lens required manual focus, which was almost impossible; I quickly realized that the branch's motion made it a lottery, and in fact this was my only clear image.  Without the doubler the lens focused, but the images were not quite as sharp and the bird's position not so revealing. Ceruleans are very uncommon in New England; in fact this may be the only nesting site in Massachusetts, and it attracts birders from considerable distances.  It was a dull, cloudy day.