G38 mr. ii. saunders on the sternin^;. [June 20, 



(Plate LXI.) 



Having recently had opportunities of examining some interesting 

 types of various real and supposed species of the subfamily Sternince, 

 I propose to anticipate to a certain extent the monograph of the 

 Laridce upon which I have been for some time engaged, and to give 

 the result of my observations in the following review of the species 

 at present known to me, with general remarks upon their geo- 

 graphical distribution. 



The principal writers who have hitherto treated of the Ster- 

 nince are : — Prof. Schlegel, in the Mus. d'Hist. Nat. Pays-Bas, 

 Sternce, 1863 ; Prof. Blasius, in Journ. fur Orn. 1866, p. 73 ; Dr. 

 Elliott Coues, in Proc. Phil. Acad. 1862, and monographically, as re- 

 gards the North-American species, in his ' Birds of the North West ' 

 18/4 ; and Messrs. Sclater and Salvin (Neotropical Laridse, P. Z. S. 

 18/1). And from the works of these able authors I have derived 

 much assistance, especially from the last, owing to the care with 

 which the synonymy and the geographical distribution have been 

 worked out. Indeed as regards America I might well have been 

 content to wait until the completion of my monograph; but as there 

 are a good many species in other parts of the globe which have not 

 been so recently noticed, there may be room for a few remarks. 



It is almost needless to say that, owing to the general similarity in 

 colour, the StemincB area troublesome subfamily to handle, the ques- 

 tion of what constitutes specific distinctness being here more than 

 usually perplexing. The individual differences in size of bill, length 

 of wing, &c. are often considerable ; added to which there are subtile 

 gradations in the various shades of plumage, which render it impos- 

 sible to accord specific rank to forms which, when judged by their 

 extremes alone, seem totally distinct. Under these circumstances it is 

 not surprising that a species should sometimes be based upon what 

 may appear at the first glance to be a very slight distinction ; for the 

 alternative is to unite under one head some forms which are clearly 

 different ; and considering the general tendency that there is towards 

 blending, the systematist must be glad to avail himself of the smallest 

 permanent characteristic. The young are often very much alike ; and 

 indeed in several cases they are as yet undistinguishable with the 

 limited material at present available ; but larger series of authentic 

 specimens will doubtless clear up several points. The coloration 

 of the soft parts presents considerable difficulties, owing to the 

 changes which take place at different ages and seasons, it frequently 

 happening that the bill and legs in quite young birds increase in 

 intensity of colour up to a certain time in autumn, and then become 

 dark, the brighter colour not being resumed until the following 

 spring : this is notably the case with the Common and the Arctic 

 Terns, in which the bills become dark very suddenly between the 

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