Remarks . --The extent of the post-breeding range in the North Atlantic is 

 unknown. The species is nearly impossible to identify in the field, 



WILSON'S STORM PETREL ( Oceanites oceanicus ) 



Status . --Summer visitant from late April to late September; locally 

 abundant in areas beyond 50 km offshore. Uncommon to common in shallow near- 

 shore areas, but usually absent in waters within 15 km of shore (Fig. 13). 



Earliest record . --23 April 1977. 



Latest record . --26 September 1976; but probably lingers into October. 



Maximum counts . --SPRING: 1,708 in 6 h, 90-120 km E Ocean City, 9 May 

 1976; 3,076 mostly 96 km E Ocean City {38°15'N, 74°00'W), 1 June 1975. 



SUMMER: 310 in 13 h, 112-154 km SE Cape May, New Jersey, 14 August 1975; 425 

 in 10 h, 55-115 km E Ocean City, 3 September 1976. 



Remarks . --From May through early September, Wilson's storm petrels made 

 up 66.6% of the total offshore avifauna. Beyond 50 km from shore, they are 

 almost always in view. I attempted to learn how long individuals remained 

 near the vessel by capturing and color marking the rumps of nine birds with 

 Rhodomine-B pink dye during the extended ocean pollution cruises of August 

 1974 and 1975. Only two of the nine marked storm petrels remained near the 

 boat where they were seen intermittantly throughout the day of release. The 

 experience of being captured may have inhibited the seven other birds from 

 remaining near the vessel. 



Wilson's storm petrels are gregarious when feeding and at rest. Feeding 

 aggregations of at least 3,000 on 1 June 1975, (38°15'N, 74°00'W), and 1,000 

 on 9 May 1976, (38°10'N, 74°24'W), closely attended 20-30 fin whales 

 ( Balaenoptera physalus ), gathering on the slicks or "whale tracks" left after 

 a whale submerged. Concentrations were sometimes so thick as to blacken the 

 surface. Nearfy all of the petrels observed on 1 June 1975 were at the same 

 site, suggesting that the whales attracted birds from a rather large area. 



Chumming with oily substances including ground fish, vegetable oil, and 

 shark liver was generally successful for attracting storm petrels. 



On 13 August 1974, approximately 200 Wilson's storm petrels gathered over 

 a slick created during the dumping of a barge load (1 million gallons) of sul- 

 furic acid-iron sulfate waste at the duPont Acid Waste Dump Site (Fig. 2), 70 

 km E Indian River Inlet (38°33'N, 74°16'W), Delaware. The slick contained 

 "floes" of ferric oxide and phosphate absorbed by clumped plankton and detri- 

 tus which floated on the surface. Although the slick remained visible for up 

 to three days after dumping, the petrels were only seen feeding on portions 

 less than 3 h old. The effects of ferric oxide and phosphate ingestion to 

 storm petrels and other marine organisms may pose a threat to these species. 



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