338 BRITISH BIRDS. 
usually in September, shortly before the birds return to their winter 
quarters, a second annual complete moult takes place in adult birds. The 
autumn plumage is usually intermediate in colour between the spring 
plumage and that of the bird of the year. 
The Sylviinz are, so far as is known, confined to the eastern hemisphere, 
one species only having been known to cross Behring’s Straits into Alaska. 
The Sylviine might be again subdivided into three groups :—the migratory 
Sylviinee, of which there are about ninety species, principally confined to 
the Palearctic Region, with the wings long, pointed, and flat, andthe 
first primary less than half the length of the second; the non-migratory 
Sylviinee, of which there are several hundred species, principally confined 
to the Aithiopian and Oriental Regions, having rounded concave wings and 
the first primary more than half the length of the second ; and, lastly, 
the wide-billed Sylviinze, of which there are a hundred or more species, 
inhabiting the tropical portions of the Old World, having, in addition to 
the wide gape, the rictal bristles very largely developed, both characters 
being of importance in assisting the birds to catch insects on the wing. 
About a score species of the Sylviine have been found in our islands, 
belonging to five genera, the British examples of which may be distin- 
guished as follows :— 
a, Axillaries yellow. 
a‘, Bill slender, more or less dark underneath ...........000: PHYLLOSCOPUS. 
o", Bill stout, pale underneath |. ..:..':...5 Lee eke ovaep Hypovats., 
6. Axillaries buff, white, grey, or brown. 
c'. Tail nearly even, or, if much graduated, longer than the wing Sy.vza. 
d', Tail with the outside feathers considerably shorter than the 
central ones ; never longer than the wing. 
a’, Outside tail-feathers less than three fourths the length 
of the longest. No rictal bristles ...... erp eRe Te LocustTE.La. 
b*. Outside tail-feathers more than three fourths the length 
of the longest. ictal bristles moderately developed. ACROCEPHALUS, 
Genus LOCUSTELLA. 
The Grasshopper Warblers were originally included by the earliest 
writers who were acquainted with any of them in the comprehensive 
genus Motacilla, and were afterwards removed from it into the genus 
Sylvia with the rest of the Warblers. When the latter genus was broken 
up, the Grasshopper Warblers were associated by the elder Naumann with 
the Reed-Warblers in his genus Acrocephalus, in which Prof. Newton still 
