MIGRATION 



11 



and Olive-backed Thrush have left the latitude of Boston. 

 Only two or three rare migrants, the Mourning Warbler, 

 for instance, occur regularly in June. 



The above paragraphs deal chiefly with the migration of 

 land-birds ; the shore-birds and the sea-birds have some- 

 what different periods of migration. The sandpipers, plovers, 

 and terns spend the winter to the southward, and return to 

 their breeding grounds for the most part during May. A 

 few species remain to breed off the coasts of New York and 

 New England, but the vast majority pass farther north. 



By the middle of July, many of the sandpipers begin to 

 come back, and there is a heavy migration of the shore-birds 

 during August and early September. Numbers of the ducks, 

 loons, grebes, and gulls are winter visitants to our coasts ; 

 they begin to pass north in April, and by the end of May 

 all that are going north have left. The gulls begin to come 

 back in August, some of the sea-ducks, loons, and grebes in 

 September, and throughout October there is a steady south- 

 ward movement ; by the first of December the bulk of those 

 that winter farther south have already passed by. 



There are several facts about the migration of birds that 

 it is well for the observer to keep in mind. In many species 

 the males precede the females by several days, — in the case 

 of the Bed- winged Blackbird by several weeks. If a species 

 is a summer resident of any locality, and also a migrant to 

 more northern regions, the first arrivals are almost always 

 residents which return to the old breeding-places. The earli- 

 est Black-throated Green Warbler, therefore, will be found 

 in some grove of pines where the bird breeds, and two weeks 

 later, perhaps, the orchards and open woodland will be full 

 of migrant Black-throated Green Warblers, passing north in 

 company with other northern warblers. The resident birds, 

 moreover, vary greatly in promptness ; some one Catbird will 

 be noted as an early bird, singing in his favorite thicket sev- 

 eral days before his neighbors arrive. The period of migra- 



