Ornithology of Corsica. 325 



discover in 1908 was nesting on a small low islet, and a 

 good series of eggs was obtained here in 1908 and 1909. 

 The breeding-habits and distinctions between this species 

 and L. a. cachinnans were fully treated in an article of mine 

 in the ' Ornithologische Jahrbuch/ xx. pp. 139-143 (1909). 

 The alarm-note of Audouin^s Gull is a monotonous 

 " Ek-ek-ek-ek/' frequently repeated as the bird flies close 

 overhead. The nests are composed entirely of a mass of 

 silvery-Avhite ribbon-like alga which is thrown up in pro- 

 fusion on the Corsican coast, and are placed among the 

 luxuriant clumps of low vegetation, so that they are not 

 •particularly easy to see. The eggs are generally two, 

 occasionally three, in number. They are much smaller on 

 average than those of the Herring-Gull, and the yolk is 

 quite differently coloured, being of a very deep red (not 

 unlike that of the Chough), while the yolk of the Herring- 

 Gull's e^^ is yellow. Although the measurements of the eggs 

 of the two birds overlap, they can always be distinguished 

 by their weights. The average weight of sixteen unblown 

 fresh eggs of L. audouini was 64*69 g. (7h to 51 g.) ; four 

 typical fresh eggs of L. a. cachinnans averaged 91*25 g. 

 "When blown fourteen eggs of L. audouini average 4*19 g. 

 (4'82 to 3*7 g.), whereas the average of twenty-eight eggs of 

 L. a. cachinnans from the jNlediterranean is 6*26 g. (7"60 to 

 5*18 g,), so that the heaviest egg of L. audouini is lighter 

 than the lightest egg of L. a. cachinnans. Average size of 

 eighteen Corsican eggs, 63*2 x 44*87 mm.; max. 66*2x46 

 and 63 X 46*2, min. 58*6 x 42*3. The normal time for fresh 

 eggs is about May 7 to 16, and a second clutch is laid 

 soon afterwards if the first is taken. 



214. Larus gelastes Licht. Slender-billed Gull. 



• Giglioli notes this species as seen at Bonifacio on Sep- 

 tember 27. 



215. Stercorarius pomarinus (Temm.). Pomatorhiue 

 Skua. 



Recorded by Giglioli as seen at sea near Aleria on Sep- 

 tember 12. 



