Breeding performance of black-legged kittiwakes on Great Island, Newfoundland, during periods of reduced food availability

Regehr, Heidi (1994) Breeding performance of black-legged kittiwakes on Great Island, Newfoundland, during periods of reduced food availability. Masters thesis, Memorial University of Newfoundland.

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Abstract

The breeding success of Black-legged Kittiwakes (Rissa tridactyla) was investigated on Great Island, Witless Bay, Newfoundland, in 1992 and 1993, following two years of breeding failure. Egg production was low in both years. High egg mortalities (90% and 89%) and high chick mortality in 1992 (93%), but not in 1993 (32%), resulted in a breeding success of 1% in 1992 and 7% in 1993. Timing of breeding was later than in previous years and clutches and eggs were smaller. Failure was extensive throughout the colony. The degree of failure varied consistently among regions between years which was probably related to cliff structure and therefore to nest predation. Comparison of egg shape indices among years suggested that a higher proportion of older individuals were breeding in years of poor productivity. This is consistent with the hypothesis that older breeders are more able and willing to expend effort and incur cost. -- Egg predation, primarily by Great Black-backed Gulls (Larus marinus), accounted for most egg mortality. Results suggest that egg predation in both years and poor chick survival in 1992 were related to food shortage. Capelin (Mallotus villosus) arrived inshore for spawning up to 1 month later than normal, which, in conjunction with a lack of fish offal, was associated with food shortage in kittiwakes and in other gulls. Kittiwake incubation and chick-rearing shifts were shorter and survival time of chicks was longer after capelin arrival than before in 1992, indicating increased food availability. Observations and growth measurements indicated that chicks hatching before capelin arrival were starving. The effect of hatchdate on chick survival was less pronounced in 1993 than in 1992. Unattended eggs and chicks were uncommon and adults endured long nest shifts, probably in response to high predation risk. Incubation and chick-rearing shifts were shorter and feeding rates were greater in 1993 than in 1992, suggesting greater food availability in 1993. The seasonal migration of capelin into inshore waters in Witless Bay provides an important resource to kittiwakes, affecting their time budgets and survival of their chicks.

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