NOTES ON BIRDS FROM EASTER ISLAND 21 



This latter characteristic is especially noteworthy, because Mathews 

 (Birds of Australia, Vol. 2, p. 426) says about P. caerulea cinerea (with a 

 distribution from Northeastern Australia to the Kermadec Islands): »under tail- 

 coverts ash-grey like the upper surface*. This latter characteristic together 

 with the great length of its wings (207 mm. according to Mathews) makes 

 P. c. cinerea easily distinct from the Easter Island birds. 



Another of the light- coloured Procelsternas has been named P. caerulea 

 irnitatrix by Mathews. It is from San Ambrosio Island off the coast of Chile, 

 thus geographically not so very far distant from Easter Island. It is, however, 

 much larger (culmen 30,5, wing 215, tarsus 28 mm.) and thus easily distingu- 

 ished from the present form. 



The remaining three subspecies of Procelsterna differ strongly from the 

 Easter Island bird by their much darker colour. Thus P. c. caerulea from 

 Christmas Island, Hawaiian group, is grey on the crown and the under parts 

 of the body; P. c. teretirostris Lafresnaye is »subtus tota cinerea» and »supra 

 brunnescenti-schistacea alls caudaque nigro-schistaceis, capite colloque cinereis», 

 &ca. It is from the Paumotu, Marquesas and Society groups (fide Mathews). 

 The third dark subspecies Mathews named P. c. nebouxi; it is from the EUice, 

 Phoenix and Samoa groups, and has »grey inner wing-coverts», and is said to 

 be » obviously darker than teretirostris and caerulea^). 



It is thus evident that the Easter Island bird has developed into a separate 

 geographical subspecies, which I take the pleasure of naming for the director 

 of the expedition. 



According to Mr. Backstrom this species nested on the main island 

 (Rano Raraku) as well as on Motu Nui. In the former place the eggs were 

 laid on the bare rock, in the latter among grass about 15 cm. high. 



Gygis alba royana Mathews 

 Native name: Quia-Quia. 

 Rano Raraku: i J*, i ? ^"/s 1917- 



These two birds have blackish shafts to the quills and the distance 

 between the feathering of the forehead and the nostril about twice as large as 

 the length of the nostril. 



Length of wing 245 mm. in male, 244 in female. 

 » » culmen 42 » » » , 40 » » 



In these dry specimens the web is yellow (rather pale), but the toes and 

 tarsi dark; it is possible that the latter have been greenish or bluish during 

 Ufe. The length of the tarsi is about 13 mm. 



In his great work »The birds of Australia* Mathews discusses the dif- 

 ferent forms of Gygis and expresses the opinion that the type of Sparrman's 

 »Sterna alba» was from the Atlantic. This view he bases on Sparrman's 

 figure to this name in »Museum Carlsonianum», which displays white shafts to 

 the quills. Fortunately Sparrman's type specimen is still kept in this museum, 



