10 A GUIDE TO THE BIRDS 



during July and August, the Solitary Sandpiper and the 

 Great Blue Heron toward the end of July, the Northern 

 Water-thrush and the Yellow-rumped Warhler in August. 

 By the tenth of September, the great stream of northern 

 birds sets in, reaching its height about the first of October, 

 though the Fox and Tree Sparrows do not arrive till late in 

 October. It is safe to say that by the fifteenth of December 

 all the land-birds that intend to move southward have done 

 so. In New England and New York, there is practically no 

 change in bird-life (unless it be a further diminution in num- 

 ber of some wintering species) until the middle of February. 

 The first arrivals from the south, the Crow Blackbirds, 

 Bluebirds, etc., reach the lower Hudson Valley by the end 

 of February, and the latitude of Boston early in March. 

 These are birds that have wintered within fairly easy reach, 

 in the Carolinas perhaps, or in Virginia. Stormy weather 

 delays them ; a warm spell with southwest winds brings 

 them early. All through March and early April other birds 

 which have wintered in the Southern States arrive. In the 

 mean time, birds that have wintered in the tropics have been 

 pushing into the Gulf States or into Florida, and at each 

 warm wave they advance, till in May they flood New York 

 and New England in a great wave. The first warm, fair 

 night following a hot day, or, better still, two successive hot 

 days, between the third and tenth of May, will generally 

 bring the first Orioles ; the next such spell of heat will 

 bring all the northern warblers and thrushes. If early May 

 is cool and clear for days, the birds do not arrive in a great 

 body, but slip through in little flocks, almost unnoticed. A 

 cold northeast storm following suddenly on a hot wave 

 makes the best conditions for observing migrants ; they are 

 held back in great numbers, and as they feed low in the 

 bushes in suoh weather, they can be easily studied. About 

 the city of New York, migration is practically over by Deco- 

 ration Day ; a day or two later, the last Black-poll Warbler 



