Abstract:
Skuas at high latitiudes have high chick mortality shortly after the chicks hatch due to the older chick chasing the younger and smaller chick from the nest area where it starves or becomes predated. Field observations were made on 49 nests with pairs of chicks. Nests were checked routinely each day with nest activity recorded. Two experimental manipulations were attempted: (a) to assess whether
... chick aggression could be tempered by high nutrition levels and (b) whether the real problem was because the second chick left the nest area entirely after dominance was established. To determine if feeding levels influenced chick aggression, skua pairs with 2-egg nests were identified and labelled. As the second chicks hatched, pairs were assigned to experimental (fed each day with dog food) or control groups. Feeding continued until well beyond the age when dominance fighting and mortality naturally occurred. To determine if high mortality occurs due to the second chick leaving the immediate nest area, pairs with 2-egg nests were assigned to either experimental or control groups once the second chick hatched. Experimental groups had the two chicks held in separate enclosures at the nest area once fighting between the chicks was observed. All chicks in both experiments were monitored daily for survival and weight gain and regular observations were made of both chick and parental behaviours. 
