230 Parmer, The Maryland Vellow-throat. fuly 
The northern birds have short secondaries while the non- 
migratory and especially the lowland birds haye long secondaries. 
Causes of the Differences. 
Freshly molted autumnal specimens of the four United States 
forms are not greatly unlike in color, but voscoe is the richest and 
deepest colored. These richer and browner colors are evidently 
due to its moisture, lowland, semi-tropical habitat, while its size 
and well-rounded wing are evidence of its non-migratory habit, 
its practically insular home and abundant and easily obtained 
food. It is a rather shy, retiring bird not easily coaxed from its 
leafy retreats. It inhabits a region of the least relative radiation 
and is not a sun-loving bird. 
The smaller, paler ¢zchas is at home in summer about the 
marshes and low places of the Coastal Plain and Piedmont 
Plateau, where it is exposed to more sunlight, less rich and gen- 
erally drier conditions. The shortness of its migration accounts 
for its similarity in wing contour to voscoe. It inhabits a region 
of great relative radiation of heat and moisture, rendered stronger 
by the effects of civilization upon forest growths, the bird having 
undoubtedly greatly extended its range as the country became 
deforested, as for instance in the mountains of Pennsylvania up 
to 3000 feet. It greatly enjoys sunlight. In winter it seeks as 
nearly as possible similar conditions. Its very close relative, too 
near perhaps to be subspecifically separated, the Mississippi 
Valley bird, is,in comparable specimens, more highly colored and 
often larger. It inhabits a moister and richer region and its 
winter residence in Mexico and Central America causes a 
longer migration, hence its longer wing and greater size. The 
usually greater extent of yellow on the under body as compared 
with eastern specimens shows less wearing and consequently the 
less harsh character of both its winter and summer habitats. 
Specimens of ¢véchas that I took in Chotank Creek marsh, King 
George County, Virginia, in July, 1898, had the yellow of the 
throat extending to a point down the centre of the under body, 
while the sides are even more worn than in ordinary birds. 
