1896.] WarrKN. — The Terns of Killala Bay. 149 



Common Tkrn {Sterna fltiviatilis). — A summer visitor, 

 generally appearing in the bay and estuary about the first 

 week in May, and sometimes delaying its visit if the weather 

 is cold and stormj^ It is an abundant species and widely dis- 

 tributed during the breeding season amongst the freshwater 

 lakes and sea-shores. Large numbers breed on a low gravelly 

 island near Brrew Abbey in I^ough Conn, and on another 

 island at the Pontoon end of the lake, while lesser numbers are 

 scattered about the lake, solitary pairs breeding on the stony 

 points of many of the smaller islands. They also breed on 

 islands in Troughs Mask and Carra, also in Mayo, while I have 

 seen a small colony on an island in Lough Gill, near Sligo. 

 Of their marine breeding-haunts the principal one on the 

 North Mayo coast is that of the Inch, a low gravelly island in 

 Killala Pool, where they breed in company of the Lesser and 

 Arctic Terns ; a few pairs also breed on Horse Island, near 

 Raughly, Sligo Ba}^ amongst the crowd of Arctic Terns. 



Arctic Tern {Sterna macrura) is not so numerous in the 

 bay and estuary as the Common Tern, and although I had 

 occasionally shot specimens in company of the Common Tern 

 it was not until the past summer that I ascertained that they 

 bred in this locality, when I found them breeding on the Inch 

 with the Common and Lesser Terns. I had in previous years 

 shot birds at the Inch, that from the darkness of their under 

 plumage when seen in flight I took to^be Arctic Terns, but in 

 every instance they proved to be the Common ; so that I find 

 it impossible to identify an Arctic Tern on the wing by the 

 colours of its plumage. Indeed my experience is, that unless 

 seen close enough to discern the lake-coloured bill, the 

 colours of plumage will not distinguish this bird from the 

 Common Tern. Other means of distinguishing between the 

 two species when flying are the much sharper cry, when 

 alarmed, than that of the Common Tern, and the greater length 

 of the tail feathers, but these are not always perceptible to 

 the observer. 



When visiting the Inch on 14th June, 1895, I remarked that 

 several of the Terns emitted the same sharp cries that I had 

 heard previously at breeding-haunts of the Arctic Terns, at 

 other plaees, but still I could not perceive any difierence in 

 appearance between any of the large numbers of birds flying 

 about, until walking over to some nests of the Lesser Terns, 



