no. 3605 SEABIRDS — GILL / 



ents, plankton abundance, and primary productivity) were being 

 taken by other members of the Anton Bruun's scientific party. These 

 data and the methods used in their determination are presented in 

 detail in the "Final cruise report, Anton Bruun cruise #5" (Woods 

 Hole Oceanographic Institution, March 1965), and will be summarized 

 only briefly here. The values obtained for surface salinity (36.0- 

 36.35%o), nutrient concentrations (P0 4 , .46-.49jug A/1.; N0 2 -N, .35- 

 .60Mg A/1.), and primary productivity (18-44/zg C/l./d) 3 in the western 

 Arabian Sea near the Gulf of Aden and Socotra (sta. 282-287) were 

 consistently higher than most other locations visited. Although nutri- 

 ent concentrations at a few of our southernmost stations (308-310) were 

 comparable to or higher than Arabian Sea values, primary productivity 

 levels were much lower (6-7/xg C/l./d.). Unfortunately, the results 

 of analyses of plankton samples are not yet available. Surface water 

 temperatures in the western Arabian Sea were several degrees lower 

 than in the seas immediately to the south. This decrease in tempera- 

 ture and concomitant increase in the nutrient concentrations and 

 productivity are indicative of strong local upwelling which is known 

 to occur in that region and which is believed to be the major deter- 

 minant of the composition and density of the seabird community there 

 (Bourne, 1963; Bailey, 1966). Between the Arabian Sea and the 

 Mascarene Islands on the 55° E transect, surface temperatures ranged 

 from 26° to 29.2° C. At comparable latitudes on the 75° E transect 

 they ranged from 27° to 30.1° C. A progressive decrease in temper- 

 ature was noted south of the Mascarenes, but the drop (from 19° to 

 15° C) was especially pronounced from 35° to 40° S, the region of the 

 subtropical convergence. It was also in this region that the numbers 

 of seabirds increased markedly. 



Species Accounts 

 Eudyptes crestatus Rockhopper Penguin 



Common at St. Paul Island on Apr. 7, where they were breeding in 

 colonies on the steep grassy slopes though they were not nearly as 

 abundant as Jeannel found them on these same slopes in February 

 1939 (Jeannel, 1941, pi. x). Many full-size young, which had lost 

 most of the down tips on their juvenal feathers, were present, but no 

 small young or eggs were found. The soft part colors recorded from 

 five specimens were as follows: hides orange; bill dull orange; feet 

 dark grey below, white above. Weights ranged from 1915 to 

 2475 grams (mean 2205 grams). The measurements (in mm) 4 of 



1 Average of combined values to depths of 25 percent incident light. 

 * Made by George E. Watson, Division of Birds, U.S. National Museum, 

 Washington, D.C. 



