222 THE BIRDS OF THE BRITISH ISLES. 



the eyes rimmed with red, and above and below the eye is a 

 small white streak. The distribution of brown and grey on 

 the white head in winter, and the mottles on the wings and 

 streaky head of the immature bird, closely correspond with the 

 seasonal and age changes of our Black-headed Gull. Length, 

 15-5 ins. Wing, 1175 ins. Tarsus, rg ins. 



Bonaparte's Gull. Zar?is Philadelphia (Ord). 



Bonaparte's Gull breeds in northern America and migrates 

 so far south as the Gulf of Mexico ; it has occurred six or seven 

 times in Ireland, Scotland, and England, apparently as a 

 wanderer rather than a migrant out of its course, since it 

 has appeared at various seasons. Its flight is light and tern- 

 like, so much so that Ord first classed it with the terns ; it 

 swoops towards the water to catch insects, and flutters after 

 them in the air. Its voice, according to American writers, 

 differs from that of other gulls, being faint, shrill, and often 

 repeated. 



Its size is between that of the Black-head and the Little Gull. 

 The hood is slate-black in summer, but in winter the head is 

 nearly white ; the first primary is white with a black outer 

 margin and tip in mature birds, and dusky-brown margins, on 

 either side of the shaft, in the young, but the white inner web 

 of the first two primaries is a good diagnostic character. The 

 bill is black, the legs are red, and the irides brown. Young 

 birds, except in the primaries, resemble young Black-heads. 

 Length, 14 ins. Wing, 1025 ins. Tarsus, 1-4 ins. 



Black-headed Gull. Lams ridibundiis Linn. 



The range of the Black-headed Gull (Plate 98) extends over 

 Europe and most of Asia, and in winter includes northern 

 Africa. In all parts of the British Isles it is resident and 



