Wilson's petrel. - 417 



QCEANITES OCEANICUS 



335. Oceanites oceanicus (Kuhl)— WILSON'S PETREL. 



Proceixaria oceanica Kuhl, Beitrage z. Zool., p. 136, pi. 10, fig. 1 

 (1820 — Southern Oceans ; no locality stated. Typical locality S. Atlantic 

 Ocean east of La Plata, ex Solander's MS.). 

 Oceanites oceanica (Kuhl), Yarrell, iv, p. 48 ; Saunders, p. 733. 



Description. — Adult male and female. Winter and summer. — 

 Coloration much as in 0. leucorrhoa but slate -grey tinge not so 

 marked as is often case in 0. leucorrhoa ; immediately in front of 

 eye a varying number of feathers partially white or whitish 

 mostly concealed and amount of whitish varying considerably ; 

 all upper tail-coverts entirely white (but feathers of lower -rump 

 brown-black tipped white) ; greater wing-coverts when fresh with 

 rather wide tips and fringes ; lower scapulars when fresh faintly 



Wilson's Petrel {Oceanites oceanicus). 



tipped pale brown but not white ; white patch on lower -flanks 

 large and lateral under tail -coverts with some white as in 0. castro ; 

 white at base of tail-feathers confined to inner webs and extending 

 as a streak (on outer pair for about two-thirds of length). N.B. — 

 When fresh, feathers of belly have very faint, and under tail -coverts 

 rather wider, white tips, which are soon worn off as are white fringes 

 and tips of greater wing-coverts and these latter become browner 

 and less grey-brown than when fresh. This plumage is acquired 

 by complete moult May-Sept, (two near Aden, Nov., and one 

 Massachusetts, Jan., in full moult may be birds in their first 

 year). 



Nestling. — (Not examined.) Uniform greyish -black (R. Hall). 



Juvenile. Male and female. — Plumage immediately succeeding 

 nestling down is like adult but with longer white fringes to feathers 

 of belly.* Complete moult takes place apparently Nov.-Jan. 



Measurements and structure. — $ wing 140-152 mm., tail : 

 central pair 58-65, outermost 62-71, depth of " fork " 2-9, tarsus 

 33-39, middle toe with claw 27-30, bill from feathers 12-13 (12 

 measured). $ wing 135-158. Primaries : 1st minute, pointed and 

 concealed by primary-coverts, 3rd longest, 2nd 4r-8 mm. shorter, 



* R. C. Murphy {Bull. Amer. Mus. N.H., xxxviii, p. 118) states that 

 young birds have a whitish spot on the lores. I have not examined any very 

 young birds but cannot find that there is any constant difference in this 

 concealed whitish spot in adults or young birds, the variation in the amount 

 ,of white being individual. — H.F.W. 



VOL. II. 2 E 



