KEY TO THE WATER BIRDS OF FLORIDA. 189 
ORDER LONGIPENNES. 
LonG-WINGED SWIMMERS. 
Famity STERCORARIIDA. JcErs. 
Genus STERCORARIUS Brisson. 
STERCORARIUS PARASITICUS (Zzxz.). 
Parasitic Jeger. 
Length from base of hook on end of bill (unguis) to frontal feathers greater than from un- 
guis to tip of upper mandible. 
Adult (light phase of plumage): upper parts slaty gray, a tinge of pale yellow on the sides 
of the head and neck. Crown of the head and lores sooty black; under parts white, shading 
into slaty gray on sides and lower belly; two middle tail feathers pointed. 
Adult (dark phase), general plumage sooty brown; slightly paler below; crown dark 
brown. 
Immature (light phase): head and neck streaked with buff or gray; under parts mottled 
and barred with slaty gray; upper parts dark gray; some of the feathers edged with buff. 
Immature (dark phase) « general color slaty brown: neck marked with white; feathers on 
the belly barred with dull white. In all plumage the two middle tail feathers are pointed, and 
the tarsus is black in freshly killed specimens. 
Length, 17 to 20; Wing, 13: Tail (adult), 8.40, (immature), 6; Tarsus, 1.60: Bill, 1.20. 
