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SUMMARY Parental attentiveness in. the Sooty Shearwater Puffinus griseus was studied on Whero Island, near Stewart Island, New Zealand, in 1951-52 and 1952-53. In the first year 30 chicks were watched from 18 March until they left the burrow, and in the second year 57 chicks from 10 February (i.e. for practically the whole of the chick stage). The chief feature of the pre-desertion period is the irregularity of parental attention (with wide individual variation). Inattentive periods range from 1 to 25 days (mean 4-3), attentive from 1 to 11 days (mean 2–4). From 10 February to 31 March 1953, 13%-65% (mean 37-2%) of the chicks were visited nightly by parents; from 1 April to 18 April, 13%˜46% (mean 27'5%); and from 19 April to 4 May, 0 %–11 % (mean 3%). In the second period 43 chicks (76-8%) were deserted by their parents, and in the third period all the remaining 13 chicks. Of 83 chicks which survived to leave the burrow in the 1951-52 and 1952-53 seasons, 58 (70%) left weighing more than 455 grams and 25 (30%) weighing less. Only the former group of chicks was believed to survive. Parents desert the breeding area in any given season apparently in answer to a migration urge, irrespective of the chick's age. Chicks hatched late therefore have little chance of survival. The length of time a chick remains in the burrow varies from 86 to 106 days (mean 97). The chicks leave the burrow apparently in answer to an internal urge, irrespective of the degree of parental attention. Before finally leaving the burrows, chicks may emerge at night and then return. Chicks more than 455 grams at departure emerged from 0 to 14 nights (mean 5–9 nights). The length of the desertion period is much shorter than we have been led to believe. For 58 normal chicks the period ranged from 0 to 27 days (mean 12 days). Chicks have been known to be fed just before departure and birds assumed to be parents have been known to enter the burrow after the chick has departed. If so, this means that these chicks departed in an inattentive period by the parent. The presence or otherwise of a desertion period in petrels depends on whether or not the species concerned is migratory. For example, as far as is known, migratory shearwaters have a short desertion period, but the non-migratory Royal Albatross and other species have not. |
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