nor 



STERCORARIID.E — THE SKUAS AND JAEGERS — STERCORARIUS. 331 



wliich they have swallowed. As soon as the; fish has been disgorged, the Skua swoops 

 down upon it with so rapid a movement and so sure an aim as frequently to seize 

 tlie prize before it reaches the water. This bird is on this account known to some as 

 the " Parasitic Gull." It is supposed to be a bird of great longevity. Yarrell states 

 tliat a specimen brought alive to Dr. Neill in the sununer of 1820 — then a nestling 

 — was alive at the Cannon-mills in October, 1843. Its plumage in its twenty -fourth 

 yi'ar had become very pale, and its head was grayish white. Another bird was kept 

 alive by Mr. G. T. Fox for ten years, undergoing no change of color at any of its 

 nioultings. 



This bird lays two or three eggs, olive-brown in color, blotched with darker brown, 

 2.75 inches in length and 2.00 in breadth. An egg in the Smithsonian Collection, 

 from Greenland (No. 2G58), measures 2.90 by 1.95 inches, has a ground-color of a 

 dark grayish drab, with irregular spots of raw-umber and sepia. Another specimen, 

 measuring 2.55 by 1.95 inches, has markings much deeper in color and more distinct. 



ll 



111! 



) in 



Genus STERCORARIUS, Brisson. 



Stercorariiis, Bnis.s. Orii. V. 1760, 149 (type, Lurits parasiticus, Lin'N.), 

 Lestris, Illic. Prod. 1811, 272 (same type). 



The difference between tliis genus ami Megalcstris consists chiefly in the srnnllcr size and more 

 sk'uder, <,'raceful form of Stircorarius, the increu.seil slenderness extending (b all parts of the organ- 

 ization. One of the three known species dilfers considerably in form frwu the other two, wLiuU 

 are so much alike that they are sometimes with dilHculty distinguished from each other. 



•f bcin;,' 



Eagli'. 



of tlie 



,a*s Hill. 



ng their 



it tho 



or more 



Fraiv'. 

 redatoiy 



the ti>li 

 nions til'' 



S. parasiliats. 



Synopsis of Species. 



A. Middle rectriccR broad and rounded at ends. 



1. S. pomarlnuB. Wing, about IS.no-U.lKl inches; middle tail-feathers, 8.00-9.00; culmen, 



1.45-1. ."55; tarsus, 2.10; middle t(w (without claw), l.G()-1.76. 



B. Middle reotricos attenuated and ])(iintod at ends. 



2. S. parasitioiM. Wing, 11.80-i:i 15 inches (average, 12.07) ; central rectrices, 7.70-10.25 



(8.66) ; cidmen, 1.15-1.40 (1.27); tarsus, 1.50-1.85 (1.70) ; middle toe, 1.20-1.45 (1.34). 

 Tarsi black in adult ; nasal shield longer than the distance from the anterior edge of the 

 nostril to the tip of the bill. 



