464 THE BIRDS OF HELIGOLAND 



land can boast of several interesting strangers, enrolled as ' honorary 

 citizens ' on the list of European birds. These are the North 

 American species, Charailrius virginicus, the Asiatic C fiUvus, 

 and C. caspius, which may also be termed an Asiatic species. Of 

 the first of these species, the example shot in Heligoland is the 

 only one hitherto observed in Europe ; of C. fulvus, three other 

 examples have been killed on European soil, but Heligoland had 

 the start by nearly ten years ; in the case of C caspius, on the 

 other hand, the two examples of this species which have occurred 

 here are the only ones hitherto killed west of the Caspian. A^jart 

 from those above-named, another American species new to Europe, 

 C vocifer, has once been shot in England. 



In the genus of the Plovers, we find brought into striking promi- 

 nence the phenomenon of two or even three species, almost exactly 

 resembling each other in the colour of their plumage, yet exhibiting 

 the most marked diti'erences in the general size of their body, or in 

 the relation of the size of particular jjarts of the body to the total 

 size of the individual. Thus, while the wmgs and tarsi of G. 

 awratus and G. fulviis are, on an average, of the same length, the 

 breast-bone of the former measures 2-52 ins. (64 mm.), that of the 

 latter only 1-96 in. (50 mm.), being thus by nearly a quarter-length 

 shorter than that of G. auratus. It is unnecessary to explain how 

 this must aft'ect the general shape of the one species as comjoared 

 with the other. Similar relations obtain in the case of G. hiaticula 

 and G. minor. 



Among other genera, those of the Geese and Gulls present us 

 with similar phenomena. In the case of the former, the sjiecies 

 concerned are Anser cinereus and A. brachyrhynchus ; and also 

 A. alhifrons and A. minutus. Among the Gulls, we have the 

 phenomenon repeated in Larus marinus and L. fuscus, as well as 

 in L. glaucus and L. leucopterus. In all these cases, so far as I have 

 been able to judge from the material at my command, it is invari- 

 ably the smaller species which is distinguished ft-om the similarly 

 coloured larger form by a more slender form of body, and compara- 

 tively longer wings and feet. 



