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AVIFAUNA 



168. Gelochelidon nilotica (Hasselquist). [Lachstern], 



The Museum received four specimens, an old male, two 

 young males and a young female, killed 7 August 1908 

 on the sandbank »Onrust" near Texel. 



The old male is in breeding plumage, the young speci- 

 mens are of different age; the oldest one, a male, has the 

 bill dark grey and the base of the lower mandible olive- 

 brown ; in the two others the bill is dark grey and the 

 base of the lower mandible pale orange. 



We have still another example of this very rare visitor 

 to our country: a male in perfect dress, shot 15 August 

 1838 on the Haarlemmermeer by H. Schlegel. 



169. Sterna fluviatilis Naumann. [Vischdiefje]. 



The Museum received 37 specimens in different plumage. 



It seems that this species does not assume always its full 

 plumage in the second year, for on 12 June 1908 a male 

 and on 24 June 1908 a male and a female in winter 

 plumage were killed near Texel. The dissection showed, 

 that they were young birds of last year, the genitals being 

 very small. The bill in these birds is black with a light 

 horny tip and with some red at the base; the feet are 

 dull dark red. 



170. Sterna macrura Naumann. [Noordsche stern]. 



This species breeds on Texel in an equal number with 

 aS. fluviatilis. In June 1905 and 1906 I collected on Texel 

 three adult males and four adult females and a young in 

 down. As a rule on Texel S. macrura seems to lay two 

 eggs, for all the birds, snared on the nests containing two 

 eggs, belonged to macrura. On 20 October 1906 a young 

 male in first plumage and on 31 July 1907 a young female 

 in first plumage were killed on the coast of Groningen. On 

 the Hoek van Holland, where a large colony of S, fluviatilis 

 is breeding, S, macrura does not breed; I have shot there 

 several terns, but none of this species. 



Notes from, the Leyden ]yiu.seutn, "Vol. XXX. 



