236 SNODGRASS AND HELLER 



are suspended at the sides, but held a little away from the body so 

 that from a distance one can see between the wings and the body. 

 When sitting in a horizontal attitude, as they do when evidently taking 

 their ease, generally on the top of some rock, the same hump is con- 

 spicuous at the middle of the back, the wings are held downward at 

 right angles to the body, clasping the sides of the rock as if to help 

 retain the position there. The wings are never held back against the 

 sides of the body in ordinary bird fashion. The bill is nearly always 

 directed upward at a small angle. During progression on land they 

 hop with both feet together, keeping the body erect, and present a 

 very awkward and clumsy appearance ; but in the water they are ex- 

 ceedingly graceful. When quietly floating the bill is inclined a little 

 upward as when they sit on the rocks. They swim entirely by means 

 of the wings, the feet being held close together and extended straight 

 behind the body, acting apparently as a rudder. On the surface they 

 swim rather slowly, and an up-and-down bobbing motion is imparted 

 to the body. Beneath the surface they go in any direction with great 

 rapidity, having then more the appearance of a fish or seal than of a 

 bird. They also leap from beneath the water into the air and dive 

 back again just as does a seal or porpoise when breaching. 



Occasionally they make a sort of grunt, and also utter deep elon- 

 gated sounds resembling ha-a-S-dh, the stress gradually declining 

 toward the end. This latter note seems to be a call from one bird to 

 another, but when uttered no obvious reason appears why they should 

 thus call to one another. We did not find them nesting and did not 

 see any of them mated. 



Family STERCORARIIDiE. 



Genus Stercorarius Brisson. 

 Stercorarius Brisson, Ornithologist, vi, pp. 149, 150, 1760. 



Range. — Breeding in arctic and subarctic regions, migrating in 

 winter south into the tropics. 



2. STERCORARIUS POMARINUS (Temminck). 



Lestris pomarina T^TAumcv:., Manuel d'Ornithologie, p. 514, 1815. 

 Stercorarius pomarinus 'R.OTHSCmt.D and Hartert, Novit. Zool., vi, p. 192, 

 1899 (Galapagos). 



Range. — Nearctic and palaearctic, south in winter to Africa, Aus- 

 tralia and South America. Galapagos Archipelego (accidental) . 



One immature female reported by Rothschild and Hartert, taken by 

 the Harris expedition in December. 



