'J 2 LooMis on Birds of Chester County. South Carolina. [jLinuMry 



three, however, are essentiull} Apiil birds ;is to the time of their 

 first arrival. Some of the constant winter visitors diminish 

 greatly during the closing fortnight, successive \\aves character- 

 izing their decline. The aftermath of the Robin migration, too, 

 continues in a similar manner through this month. Other spe- 

 cies, again, simply tlisplay fluctuations. Some of the irregular 

 and uncommon birds, wintering chiefly in the region below, as 

 the Brown Thrasher, now become prominent, unless delayed. 

 The breeding season proper normally opens in this month, par- 

 ticularly during the last half of it. 



The ordinary spasmodic returns at this time of the vear to 

 cooler temperature have not been found to exercise great influ- 

 ence upon the migrations, the birds usually being but little af- 

 fected by such vicissitudes. When once under headway the\ 

 stubbornly hold their ground. Prolonged inclemency, which is 

 now exceptional, is more potent, however, impeding the move- 

 ment during its prevalence. While the most forward seasons 

 have been the mildest, it has not in\ariably been true that an open 

 spring was accompanied by corresponding early migratory mo^'e- 

 ments from the south. Other agencies, aside from local cold, 

 have sometimes, apparently, arrested advance. The backward 

 spring following the phenomenally mild winter of 1889-90, con- 

 sideied in connection with other years, showed that the later mi- 

 grations, those of the Black-and-white Warbler, etc., are directh' 

 accelerated or retartled by the immediate meteorological condi- 

 tions, and not by the remote ones. Late dates of first arrival, in 

 individual species, are not to be accounted for solely, I believe, 

 bv phases of the weather, as is evidenced by the case of the Yel- 

 low-throated Warbler which varies considerably in its coming in 

 diflerent years when other early migrants are on time. Other 

 causes, as a variation within narrow limits in the line pursued by 

 the vanguard, may bring about these apparent delays. It may 

 further be stated, in general, if the van of migration was held 

 back immediately below a point, the territory nearest above might 

 be passed over for the time being, and a locality further north be 

 the first stopping place, and hence exhibit an earlier record. 



The migrations gather force through April onward until about 

 the first of May, or the first week of May, when the falling ofl" 

 commences. The winter birds (migrants really) now finally dis- 

 appear ; some, as the Slate-colored Junco, about the first or 



