Some aspects of the breeding biology of the diving petrels Pelecanoides georgicus and P. urinatrix exsul at Bird Island, South Georgia
Roby, DD.; Ricklefs, RE.
British Antarctic Survey Bulletin 59: 29-34
Aspects of the reproductive biology of the diving petrels P. georgicus and P. urinatrix exsul were studied at Bird Island, South Georgia, during Jan. and Feb., 1982. Average mass of P. georgicus adults near the end of the incubation period was 122.6 g (n = 49, SE = 1.20) and average wing length was 118.3 mm (n = 49, SE = 0.47). Incubating adults lost 4% of their mass each day. The length of P. georgicus eggs increased in direct proportion to width. The estimated average fresh mass of P. u. exsul eggs was 22.2 g. The estimated median hatching date for P. u. exsul (Dec. 24th) was 28 days earlier than the median hatching date for P. georgicus (Jan. 22nd). The length of the incubation spell in P. georgicus was normally 2 or 3 days while the length of the brooding spell was usually 1 day. Length of the brooding period averaged 6.7 days for P. georgicus and was estimated to be 11-12 days for P. u. exsul.