Recent literature

1. Notes on the at-sea identification of some Pacific gadfly petrels (genus: Pterodroma). L. B. Spear, S. N. G. Howell, and D. G. Ainley. 1992. Colon. Waterbirds 15:202218.--This paper presents new criteria, and analyzes previously published criteria, on the visual identification, at sea, of 14 species (11 to some workers) of Pterodroma petrels which regularly occur in the eastern Pacific area. Comparisons are presented of five groups of similar appearing species which are difficult to separate in the field and which have largely overlapping ranges: (1) Juan Fernandez (P. externa) and White-necked (P. cervicalis), (2) Collared (P. brevipes) and White-winged (P. leucoptera), (3) Black-winged (P. nigripenn•s), Pycroft's (P. pycrofti), Stejneger's (P. lor•g•rostrzs), Cook's (P. cook•), and Defilippe's (P. defil•pp•ana), (4) Kermadec (P. neglecta), Murphy's (P. ultima), and Herald (P. armmjomana heraldlea), and (5) Tahiti (P. rootrata) and Phoenix (P. alba) petrels. The information presented is based on 6731 hours of observation on 19 cruises from 1983-1992, supported by examination of 692 freshly collected specimens (pertinent measurements reported). Range maps for the eastern Pacific are presented for all groups. Salient features in identification are illustrated by photographs of specimens, including photographs of dorsal and ventral surfaces of extended wings, and three at-sea flight photographs. Pterodroma petrels are difficult to identify because they usually pass rapidly through the field of view, are similar in appearance and flight pattern, change in appearance with varying lighting conditions, and observation is often hindered by shipboard motion. The authors emphasize the importance of experience in recognizing key features for separating Pterodroma species, and urge caution in identification at sea.