. Bulletin of the British Ornithologists' Club. Vol. 88 82 Bulletin at the same islands as the equally uniform white-breasted Georgian Diving- petrel P. georgicus in a circumpolar zone around the Antarctic Conver- gence, including the Antipodes and Auckland Islands, possibly Macquarie, Heard Island and Kerguelen, the Crozets and Marion Island, and as reported here. South Georgia, both of them laying fairly close together in November and December, P. georgicus possibly averaging a little later though there is much overlap. Several white-breasted birds taken at sea off southern South Amer
. Bulletin of the British Ornithologists' Club. Vol. 88 82 Bulletin at the same islands as the equally uniform white-breasted Georgian Diving- petrel P. georgicus in a circumpolar zone around the Antarctic Conver- gence, including the Antipodes and Auckland Islands, possibly Macquarie, Heard Island and Kerguelen, the Crozets and Marion Island, and as reported here. South Georgia, both of them laying fairly close together in November and December, P. georgicus possibly averaging a little later though there is much overlap. Several white-breasted birds taken at sea off southern South America have been described as a distinct race P. (w.) coppingeri, but they are close to exsul in size and may perhaps best be referred to that form, though their breeding place and season is still un- known. The precise zonal surface water preferences of P. (u.) exsul and P. georgicus also still require to be worked out; they might feed on opposite sides of the Antarctic Convergence, P. georgicus, if it really nests later, presumably to the south over colder antarctic water because it is not found further north while P. (u.) exsul is, but this is merely speculation, and there may be other ecological differences between them at sea as there are at the breeding stations (Downes, et al., 1959). If this analysis is correct, the urinatrix group of diving-petrels can be broken down into three representatives feeding over distinct subtropical, subantarctic and possibly (?) antarctic zones of surface water in the Southern Ocean, with an intermediate population in a region of water-mixing around the Falkland Islands, in much the same way that the other three species in the family can be arranged in a sequence of three zonal representatives south down the west coast of South America from subtropical P. garnoti through subantarctic P. magellani to P. georgicus with a circumpolar range at the Antarctic Convergence overlapping that of P. (u.) exsul, (Figure 1). It is tempting to speculate that
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