Thursday, September 23, 2021

Census of the three shag species in the Chatham Islands

TitleCensus of the three shag species in the Chatham Islands
Publication TypeJournal Article
Year of Publication2000
AuthorsBell, M, Bell, D
Type of Articlepaper
Keywordsblack shag: Phalacrocorax carbo, Chatham Island shag, distribution, Leucocarbo onslowi, Pitt Island shag, status, Stictocarbo featherstoni

During the 1997/98 breeding season we counted the breeding populations of Chatham Island shag (Leucocarbo onslowi), Pitt Island shag (Stictocarbo featherstoni) and black shag (Phalacrocorax carbo). Surveys, on foot or from kayaks and fishing boats, of all potential shag nesting habitat within the Chatham Islands provided the first complete census for shags breeding there. The breeding population of Chatham Island shag was 842 pairs in 10 discrete colonies, while there were 729 breeding pairs of Pitt Island shag at 63 locations throughout the group. Given that the counts of the endemic shags are for the total world populations. these species are extremely rare. The black shag breeding population was 233 pairs, in 5 locations on Chatham Island only. Comparisons with counts made during the 1960s and 1970s by visiting ornithologists suggest that the populations of Chatham Island shag and black shag have remained relatively stable, although the distribution of colonies of both species has changed significantly. Too few previous counts of Pin Island shag colonies were available to determine a population trend. All 3 species are threatened in the Chatham Islands by destruction of nesting habitat, disturbance of nesting colonies, human persecution, and predation by introduced mammals.

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