SEASONAL EFFECTS OF TIMING AND REPRODUCTION IN THE KING PENGUIN - A UNIQUE BREEDING CYCLE

There was a seasonal biomodality in the distribution of breeding activ ities of King Penguins Aptenodytes patagonicus, studied from 1991 to 1 994 at South Georgia, with peaks of courtship and egg-laying 2-3 month s apart. The late peak was of birds that bred successfully the previou s year, whereas the early peak was of birds that had failed. Successfu l birds were delayed because the median time for a complete breeding c ycle, including moult, was > 14 month. Although most birds made a bree ding attempt each year, none bred successfully in two consecutive seas ons. Hence, in practice the cycle was biennial. The egg-laying period spanned four months but only pairs that laid within the first quarter of this period were successful. Parental quality, rather than laying d ate, strongly influenced the outcome of first quarter breeding attempt s. No late breeding attempt was successful and why they are undertaken is unclear. At least they posed no measurable cost, either by delayin g subsequent breeding or by increasing mortality; this may be importan t for balancing the low benefit. After the over-wintering fast the chi ck could be fledged by a single parent; but no sex-specific difference in invested time in the chick near to fledge was observed.