The period from arrival of the Wilson's petrel to its breeding grounds to the onset of breeding covered 33 days (November 5 — December 8). The egg-laying period averaged 56 days; the frequency distribution of egg laying in different colonies was close to normal. Incubation took 44 days, on the average, and chicks stayed in nests 59 days. The weight of chicks at hatching was 7.5 g, and the maximum weight was 80 g, that is, 205"o of adult weight. Growth rate of chicks depended on weather conditions, especially on the amount of snowfall, blocking the access to the neast. This caused many-day starvation of chicks and their weight could drop by 46"',.. The diet of chicks and adults consisted of the krill in 96% mostly of Euphausia superba High nesting losses were caused by rainfall and snowfall. Of 129 nesting attempts, 61.2% failed in the stage of eggs and 27.9% in the stage of chicks. Mortality was related to the age and weight of chicks. It has been found that the prolonged egg-laying period, rapid growth rate of chicks in their first days, and their high weight represent adaptations to the climate of Antarctica.
The period of nesting development of Wilson's storm petrels (approx. 60 days) could be divided into three stages: first from hatching to 8th—10th day of development; second, from 10th to approx. 25th day and third from 25th day until nestlings leave the nests. During the first stage hemoglobin concentration in the blood decreases significantly while total surface of erythrocytes and the hematocrit increases. At that time nestlings do not grow very fast. In the second stage of development the values of all studied parameters do not change, while the growth of body weight is very intensive. The last stage is characterized by significantly reduced growth rate accompanied by important changes of all hematological parameters responsible for the respiratory function of blood volume unit.
Thermoregulation is fully developed in 5 day old Wilson's storm petrels Oceanites oceanicus (Kuhl). Resting metabolic rate (RMR) and body temperature (Tb) of unattended 1- and 3-day old chicks continuously decrease at ambient temperature (Ta) of 5°C. After being heated the chicks return to normothermia. Ability to survive temporal deep hypothermia seems to be an adaptation to absence of parents and low temperatures in the nest during first days of life. After snow storm, during two days of starvation, chick RMR decreases by 40% at Ta of 0°C, but chick Tb is stable. This suggest decrease of thermal conductance (Ct). Fall of Ct may suggest beginning of hypohermia.