Ecological segregation of burrowing petrels (Procellariidae) at Marion Island

• Main Author: Schramm, Michael
• Other Authors: Siegfried, W R
• Format: Master Thesis
• Language: English
• Published: University of Cape Town 1984
• Subjects: Ornithology; Burrows; Kerguelen; Antarc*; Antarctica; Marion Island
• Online Access: http://hdl.handle.net/11427/21886; https://open.uct.ac.za/bitstream/11427/21886/1/thesis_sci_1984_schramm_michael.pdf

1. Eight burrowing petrel species were found nesting within the area studied in north-eastern Marion Island during April 1979 to May 1980. These were Salvin's Prion Pachyptila vittata salvini, Blue Petrel Halobaena caerulea, Greatwinged Petrel Pterodroma macroptera, Kerguelen Petrel Pterodroma brevirostris, Softplumaged Petrel Pterodroma mollis, Whitechinned Petrel Procellaria aequinoctialis, Grey Petrel Procellaria cinerea and South Georgian Divingpetrel Pelecanoides georgicus. Eighty-one percent of burrows found belonged to Salvin's Prions. 2. The nest site preferences of Salvin's Prion, Blue Petrel, Greatwinged Petrel, Kerguelen Petrel, Softplumaged Petrel and Whitechinned Petrel were investigated. These species had individual preferences with respect to soil depth, soil moisture content, slope angle or slope aspect. 3. The Kerguelen breeding biologies and diets of Greatwinged Petrels, Petrels and Softplumaged Petrels were studied. The species bred at different times of the year with non-overlapping chick-rearing periods. Incubation periods were similar but, relative to adult size, Kerguelen Petrel chicks grew fastest. All three species took mainly cephalopods although Kerguelen Petrels took the most crustaceans and fish. 4. Subantarctic Skuas Catharacta antarctica were important predators of petrels. They preyed upon whatever petrel species were most abundant in an area, although large petrels (Whitechinned Petrel) and those breeding in winter (Greatwinged Petrel) were seldom taken. 5. Similar petrel species had the bulk of their breeding populations spread over different habitats thus reducing any competition for nest space. At the same time, staggered timing of breeding, and particularly the non-overlapping chick-rearing periods of the three Pterodroma petrels, helped to minimize competition for food.