Causes of high mortality of the second chick from a pair of skua (Catharaeta maccormicki) eggs; egg content and chick weights, feeding rates, parental brooding behaviour, experimental removal and starvation of chicks

The cause/factors of heavy mortality of the second chick hatching from a pair of eggs at a skua nest was investigated. Previous observations found that the second chick is chased away from the nest area by the first hatched chick, most often ending in the death of the second chick. Reasons for this unusual behaviour was investigated. A detailed study of the egg content of the two eggs and the weight of the chicks at hatching was conducted. After hatching, a close watch was maintained on the chicks until fighting began and records were kept of feeding rates of the chicks and of parental brooding routine. A series of experiments in which chicks were shifted to new parents or starved at the nest by disturbing the parents were conducted to determine if hunger might be the stimulant to fighting in the chicks.