Auk 
236 PatmMeErR, The Maryland Yellow-throat. analy 
occidentalis, migrates comparatively little except along its northern 
habitat. The birds which summer at a high altitude evidently 
simply descend to lower stations along our southern borders, 
where they spend the winter in favorable situations. Migration 
evidently has little effect on their feather growth, their size being 
due to the generally high elevation of the summer habitat, a truth 
shown in many other species. 
Little is known of the movements of me/anops, but there would 
seem to be little difference from occédentalis ; its richer coloration 
implies a more southern and less boreal habitat. 
The effects of a long migration are well shown in other species 
of Geothlypis in North America. 
In G. agilis, the most northern breeder and probably also the 
most southern in its winter habitat, we have the largest form, and 
the outer primary (on immature birds the 2nd) is the longest, the 
others graduating to the innermost. In G. philadelpha and G. 
tolmiei, more southern yet high ground breeders, the wing is 
slightly more rounded, the 3rd, sometimes the 2nd, being the 
longest; the bill is smaller than in agz/s and the bird is smaller. 
In G. formosa there is little difference in the lengths of the 
three outer primaries; but the outermost is always slightly the 
shorter, the longer being usually the 2nd. ‘Their migration is 
less extensive than those given above. 
As the more southern and therefore more tropical forms do 
not migrate extensively we find in consequence a more rounded 
wing with short outer primaries, the fourth (often the third when 
the feathers are worn) being the longest. It seems evident then 
that the comparative lengths of the wings, and especially of the 
outer primaries and the secondaries, are an index of the compara- 
tive length or absence of migration in the respective forms. The 
comparative differences of size, length of wing, primaries and 
tails are in this genus simply effects of latitudinal and altitudinal 
habitats modified when necessary by insular characteristics, or 
length, character, or absence of migration, hence more of sub- 
specific or specific than of. generic or subgeneric values. Accord- 
ing to this view a genus Oforonis does not exist. 
