19 



times a sudden rise in temperature with its accompanying bird-wave 

 will bring a species a week or more earlier than the average time, or 

 a cold, wet spell of weather will delay its arrival correspondingly. 



MIGRATION IN THE VICINITY OF PHILADELPHIA. 



The spring migration in the vicinity of Philadelphia begins early in 

 February with the arrival from farther south of scattered bunches of 

 Robins, Bluebirds, Purple Grackles, and a few other species which 

 often occur in small numbers during the winter. 



About the middle of the month, on the first clear spring-like day 

 when the temperature rises to 60° or 70° F., a well marked wave 

 takes place. Purple Grackles, Red-winged Blackbirds, Robins, 

 Bluebirds and a few Flickers are the principal species, the Grackles 

 being the most numerous. The greater part of these early migrants 

 seem to pass farther north. 



From the time of occurrence of the first well-marked wave, the 

 species above mentioned continue to pass in increasing numbers dur- 

 ing favorable weather, but there is usually no other decided wave 

 until about the middle of March. 



During this month, in addition to the species already mentioned, 

 the principal migrants are the Meadowlark, Pewee, Field Sparrow, 

 Fox Sparrow, Cowbird, Dove, Canada Goose and Killdeer Plover, 

 together with a few Yellow-bellied Sapsuckers, Savanna Sparrows, 

 Vesper Sparrows, Myrtle Warblers and Rusty Grackles. None of 

 these birds, however, arrive — at least in abundance — before the 

 middle of the month. 



Up to April 1 no migrants have been recorded in the records 

 that we have examined which do not occur occasionally in winter, 

 either at Philadelphia or a little farther south in N ew Jersey, except 

 the Canada Goose and Chipping Sparrow, which latter species has 

 been once or twice noticed during the last week of March. 



After the first of April, however, the strictly summer species and 

 transients begin to arrive. There are generally several Aveli marked 

 waves during the month, their most characteristic species being the 

 Hermit Thrush, Ruby-crowned Kinglet, Chipping Sparrow, Chimney 

 Swift, Barn Swallow, Bank Swallow, Myrtle Warbler, House Wren, 

 Thrasher, Chewink, Black and White Warbler, Maryland Yellow- 

 throat and Solitary Vireo. 



A number of other species sometimes arrive during the last week 

 of April, when there often occurs a wave which seems to be a foi'e- 



