KEY TO Tin-: WATER BIRDS OF FLORIDA. 



ORDER LONGIPENNES. 



Long-Winged Swimmers. 



Family STERCORARIID.E. J.egers. 

 Genus STERCORARIUS Brisson. 



57 



STERCORARIUS PARASITICUS {^Linn.). 

 Parasitic Jaeger. 



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 

 Ijrown. 



Immature {liglit pliase) : head and neck streaked with l)uff 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), S.40, (immature). 6 : Tarsus. 1.60 : Hill. 1.20. 



