NON-INDIGENOUS BRITISH BIRDS. 307 



India — but is more generally amongst the coarse vegeta- 

 tion of the marsh. The actions of this Tern when 

 disturbed at the nest are similar to those of allied 

 species. 



Range of egg colouration and measurement : 

 The eggs of the Whiskered Tern are two or three in 

 number. They vary in ground colour from pale buff to 

 pale grayish-green, blotched and spotted with various 

 shades of reddish-brown and blackish-brown, and with 

 underlying markings of pale brown and gray. The 

 markings are neither very numerous nor very large, and 

 as a rule pretty evenly distributed over the surface of the 

 Qgg. On some eggs the markings are elongated into 

 short streaks intermixed with faint scratches and scrawls. 

 Average measurement, r55 inch in length, by ri5 inch 

 in breadth. Incubation is apparently performed by both 

 sexes, but the duration of the period is undetermined. 



Diagnostic characters : The eggs of this Tern are 

 readily separated from those of the two following species 

 by their larger size, smaller markings, and paler and 

 greener ground colour. Some eggs of the Arctic Tern 

 approach them in colour, but are generally more heavily 

 marked and larger. 



