Family STERNIDAE. 



Sterna macrura Naumann ') — Arctic Tern. 



(Folates 177-178, fig. n-li). 

 (Snouckaert: Avifauna Neerlaiidica, p. 116, No. 275). 



Colour of surface of shell: like that of the preceding species. 

 Colour of spots: „ „ „ „ „ „ 



Average dimensions: 40.5 . \ 29 millimetres. 



Average weight of shell: about 1 gram. 



Texture of shell: like that of the preceding species. 

 Shape : „ , .i „ „ „ 



Nest and its site: „ „ „ „ „ „ 



Number of eggs: usually 2. 



Breeding season: end of May, June. 



Duration of incubation: about 18 days. 



') See also the general review of the XLI. and XLll. Families, under: 

 S. fluviatitis and S. macrura. 



