Aspects of the behaviour and ecology of black-legged kittiwakes, Rissa tridactyla, breeding at two sites in Newfoundland, 1990-1991

Neuman, Josephine Ann (1993) Aspects of the behaviour and ecology of black-legged kittiwakes, Rissa tridactyla, breeding at two sites in Newfoundland, 1990-1991. Masters thesis, Memorial University of Newfoundland.

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Abstract

An examination of variability in the breeding success of Black- legged Kittiwakes, Rissa tridactyla, was the focus of this research. An attempt was made to relate this variability to ecological conditions, in particular food availability. Apparent food shortages in 1991 provided a natural experiment as data were collected from two Newfoundland colonies, Cape St* Mary's and Gull Island in Witless Bay, in 1990 and 1991, comparisons were also made with previous Newfoundland studies. -- At both colonies, timing of breeding was later, there was a greater amount of non-breeding, and clutch sizes were smaller in 1991, the year with the most apparent food shortages. Observer access to the nests was only possible on Gull Island and there egg volumes were smaller, and chick survivorship and growth rates were lower in 1991. The behavioural evidence for food shortages on Gull Island in 1991 was also compelling. Chicks begged more intensely and had fewer successful begging bouts in 1991, but chick feeding rates in the two years were similar. As the few chick growth rates obtained in 1991 clearly showed that chicks were starving, future studies should incorporate estimates of bolus size and food type in addition to determining feeding rates. Chicks were seldom left unattended in 1990 (for all ages combined, less than 3% of the time), and in 1991 they were not seen left alone at all. Adults may have been responding to increased predation by Herring Gulls, Larus arqentatus. -- Courtship feeding, a significant event in the pre-laying period, was the subject of special emphasis at Cape St. Mary's in 1990. One of the hypothesized functions of courtship feeding is its nutritional significance, providing the female with extra food prior to egg laying. The phenology of courtship feeding in relation to egg laying, and the substantial amount fed (at the peak, 8 boluses per pair per day) circumstantially confirmed the nutritional importance of courtship feeding. Courtship feeding rate was not significantly correlated with timing of breeding, clutch size, hatching success or fledging success. -- An examination of inter-observer reliability was made in the context of the courtship feeding study. Two of the seven variables were scored reliably, while the remaining variables were affected by either systematic error or random error and influenced conclusions differently depending on the questions asked. The difficulties inherent in obtaining adequate observer agreement in field studies of animal behaviour indicate that an assessment of inter-observer reliability should be a part of every behavioural study. -- In general, seabirds represent extreme “K-selected” species and this pattern was clearly exemplified by Black-legged Kittiwakes in a year of apparent food shortages, as they attempted to maximize adult survival rates by reducing their investment in reproduction.

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