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Nutritional Constraints on Egg Formation in the Lesser Black-Backed Gull: An Experimental Study

Mark Bolton, David Houston and Pat Monaghan
Journal of Animal Ecology
Vol. 61, No. 3 (Oct., 1992), pp. 521-532
DOI: 10.2307/5607
Stable URL: http://www.jstor.org/stable/5607
Page Count: 12
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Nutritional Constraints on Egg Formation in the Lesser Black-Backed Gull: An Experimental Study
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Abstract

1. The use of supplementary feeding experiments to investigate the relationship between food supply and clutch and egg size in birds has yielded disparate results, some authors showing an advancement in laying and/or increased clutch size in response to additional food whereas other studies have found no effect. 2. Here we investigate the nutritional requirements of egg formation in lesser blackbacked gulls Larus fuscus L., through a series of feeding experiments providing additional food of different quality. 3. Provision of additional food on the nesting territories did not result in a decrease in the amount of time spent away from the colony by females, although fish-fed males did spend more time on territory during the early part of the pre-laying period in a year of normal food supply. 4. Courtship feeding rates were very low in comparison with other studies and were not influenced by provision of additional food. 5. Providing either supplementary fish or fat during the pre-laying period demonstrated that in a year of apparent low food availability, clutch size was depressed by protein, but not energy, limitation. A second experiment, supplying either fish or cooked egg to pre-laying birds, suggested that in addition to these general protein requirements, egg production may further be limited by the supply of specific nutrients, contained in the egg, but not present in sufficient quantity in the fish supplement. The possible identity of these specific nutrients is discussed. 6. There was no advancement in laying dates of fed birds compared with controls in the same year. This contrasts with studies on other species and suggests that clutch size may not be primarily determined by laying date in lesser black-backed gulls. 7. Chicks hatching from the eggs laid by females receiving an egg supplement prior to laying tended to be skeletally larger and heavier on hatching, but any potential advantages of hatching from larger eggs were short-lived. There was no difference in subsequent growth or survival of chicks of egg-fed parents compared with controls.

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