OF THE NETHERLANDS. 



133 



COLYMBIDAE. 



6. Cohjmbus imber Gunnerus. [IJsduiker]. 



This species is the rarest of the genus in Holland. Spe- 

 cimens in full dress are extremely rare and I believe that 

 the male, killed 15 May 1856 on the island of Wieringen 

 in the Zuiderzee, in the possession of our Museum (Coll. 

 van Wickevoort Crommelin, 301 — 1) is the only specimen 

 in full dress having been killed in the Netherlands. The 

 two specimens mentioned in SchlegeFs Catalogue (Cat. 

 Urinatores, Colymbus glacialis, n° s . 1 and 2) have not been 

 killed with certainty on our shore. 



7. Colymbus arcticus L. [Parelduiker]. 



This diver is less rare than the foregoing, although 

 examples in full plumage are far from common. We received 

 since 1904 four specimens in winter dress, one of them, a 

 male from Leiderdorp, province Zuid-Holland, 12 January 

 1905, with some feathers of the summer plumage on the back. 

 In the collection of the late van Wickevoort Crommelin 

 are two specimens in full summer plumage (300 — 1 and 4) 

 and in our old collection one (Schlegel, Cat. Urinatores, 

 Colymbus arcticus, n°. 2). 



8. Colymbus stellutus Brünnich. [Roodkeelzeeduiker]. 



Young specimens of this species are every winter tolerably 

 common, adult ones are rarer. 



Since 1904 we received 16 specimens in winter plumage, 

 only one specimen showing traces of the red throat. One 

 specimen, a male in winter dress, was shot on Texel, 29 

 May 1906. Only one specimen in the collection van Wicke- 

 voort Crommelin (299 — 7) is in perfect summer plumage, 

 while in the Museum's old collection there are two speci- 

 mens in this dress from our country (Schlegel, Cat. Uri- 

 natores, Colymbus septentrionalis, n os . 1 and 2). 



Notes from the Ley den Museum, Vol. XXX. 



