130 BULLETIN 133, UNITED STATES NATIONAL MUSEUM 



The first species given above, the pomarine jaeger, has in recent 

 usage been recognized as a monotypic genus Coprotheres^ a distinc- 

 tion proposed first by Reichenbach in 1850. The second species 

 farasiticus is the type of the genus Stercorarius of Schaeffer 1789, 

 while Mathews" has proposed Atalolestris as a subgenus for longi- 

 caudus. After consideration of the differences indicated it has 

 seemed that the three small jaegers may be placed in one genus 

 Stercorarius. In case any further degree of superspecific difference 

 is desired it may be indicated by the use of subgeneric terms. 



On November 4, south of Cabo San Antonio, two parasitic jaegers 

 came beating down the sea beach from the northward, pausing at 

 intervals for an agile pursuit of some tern, or to investigate some 

 other source of food. I secured one and later saw another. On 

 November 7 several more were seen and two were taken. Though 

 less abundant than the long-tailed species the parasitic jaeger was 

 well represented in the migration passing southward at this time, 

 so that I estimated that they were present in a ratio of 1 to 15 among 

 the bands of longicaudus. The notes made on the habits of the long- 

 tailed jaeger apply equally well to the present species. 



The female secured in light phase had the tip of the bill and the 

 gape dull black, the remainder deep mouse gray; iris natal brown; 

 tarsus and toes black. 



STERCOKARIUS LONGICAUDUS Vieillot 



Stercorarius longicaudus Vieillot, Nouv. Diet. Hist. Nat., vol. 32, 1819, 

 p. 157. (Northern Regions.) 



Four females and two males were taken on the beaL-h 25 kilometers 

 south of Cape San Antonio, eastern Buenos Aires, on November 4, 

 6, and 7, 1920. Of these birds one is a nearly adult male, as it has 

 only scattering feathers of the immature plumage on the white 

 upper breast and on the flanks. The remaining five are immature 

 but seem to be more than 1 year old. The feathers of the upper 

 surface are more or less margined with white. All are light under- 

 neath, but vary from deep mouse gray on the throat to white streaked 

 with deep mouse gray. The wing quills show more or less wear. 

 A female had the tip of the bill and the gape dull black, the re- 

 mainder of the bill deep mouse gray; crus, toes, and webs black; 

 tarsal joint pale green-blue gray; tarsus pale olive gray, with the 

 dark and light areas on tarsus and toes sharply delimited. The 

 blotching of light and dark was conspicuous, so that it attracted 

 attention in handling the birds. The extent of the light patches 

 varied considerably, as in some individuals it covered the entire 

 tarsus and the hind toe with its nail, while in others part of the 



" Birds of Australia, vol. 2, pt. 5, .Tan. 81, 1913, p. 500. 



