42 WATER BIRDS 



robbed three times in succession, leave the vicinity with 

 a flock of several gulls following. A close watch failed 

 to discover any other species of gulls at this sport, and 

 I believe the persecutors are invariably the Larus heer- 

 manni, although the Western gull is much more apt to 

 commit such atrocities. In this locality, however, the 

 Heermann Gulls outnumber the Western three to one. 

 Mr. Grinnell says this is the case also at Los Angeles, 

 while at Monterey Mr. Loomis reports them as varying 

 iu proportion at different times during migration. 



60. BONAPARTE GULL. — Larus Philadelphia. 



Family : The Gulls and Terns. 



Length: 13.00. 



Adults in Summer: Head and throat dark slate, nearly black ; mantle 

 pearly gray ; under jiarts, tail, nape, and sides of head white ; wings 

 wliite, shailing to pearl-gray ; first primary tipped and edged on 

 outer web with blaek ; other iiriinarie.s with broad black transverse 

 S])ots, I'onning a bar ; feet and legs oninge ; bill black. 



Adults in, Winter : Similar, but head and throat white, back and sides 

 of head gray. 



Young: Head white, top and nape wa.'shed with gray; under parts and 

 tail white, the tail bimded with black near en<l ; back and wing- 

 coverts .-ishy ; primiines lihiish gray, narrowly tiiiped with black. 



Geoiirnphical Distribution : Whole of North America. 



Breeding Range: Northern ]iarts of the United States northward. 



Breeding Sea'^on: Approximately, June 1 to August 1. 



A^ent: Of sticks and gra.sses ; lined with fibre ; always elevated from the 

 ground in hushes, trees, or high stumjis. 



Eggs: From greenish to olive-lirown, spotted with brown and light 

 purple, chiefly at larger end. Size 1.9j X 1.34. 



The distinguishing feature of the Bonaparte Gull is 

 its slate-gray hood in summer, all the other Pacific gulls 

 having light-colored or white heads. Its appearance as 



