Ardea
Official journal of the Netherlands Ornithologists' Union

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Norstrom R.J., Clark T.P., Kearney J.P. & Gilman A.P. (1986) Herring gull energy requirements and body constituents in the Great Lakes. ARDEA 74 (1): 1-23
1. Estimates of the major components of Herring Gull annual energy requirements are presented with the intention of providing groundwork for an energetics model. Emphasis is placed on reproductive needs and chick growth. The total annual budget is 9.4 x 104 kcal yr- l for a female juvenile in its first year (June-May) and 9.3 x 104 kcal yr- l for an adult female of mean annual weight 1,039 g. 2. Energy requirements of egg-laying are estimated to be about 678 kcal of which 432 kcal is deposited in the eggs. The peak energy demand is 65 kcal day-1, 3 or 4 days prior to laying the first egg, which represents a 20-25% increase in the female's total requirement. 3. A Gompertz equation for chick growth is presented with regressions relating the water index and energy content change during growth with fresh weight and time. 4. Precise understanding of Herring Gull body constituent changes during the year is lacking, however, regressions for juvenile and adult fat and weight change as functions of temperature are presented. Fat deposition is 5% and 1% of juvenile and adult annual energy budget respectively. 5. Energy cost of feather replacement is estimated to have a maximum of 5 kcal day-1. Total cost is less than 1% of the annual budget. Behavioural mitigation of energy requirements during moult, such as reduced flight time, is not estimated. 6. Two equations proposed by Kendeigh et al. (1977) for the existence metabolism of non-passerine species during summer and winter photoperiods are transformed into a single expression. Existence energy is therefore given as a function of body weight, ambient temperature and photo period. Use of this general equation is strongly supported by experimental data for Herring Gull existence metabolism during the first 100 days after hatching. 7. Foraging costs are estimated to be 0.28 0.14 of a Herring Gull's net metabolizable energy requirement based on an analysis of their time budget during chick feeding and an average flying cost of 20 kcal hr- 1. 8. It is estimated that two parents feeding a 3 chick brood each sustain 100 kcal day-l extra foraging cost for chicks around the time of fledging, bringing their energy expenditure near its maximum capability. Total cost of feeding chicks is 5.8 x 103 kcal per adult, 6% of its total annual budget. 9. Courtship feeding is estimated to provide briefly an energy gain for females approximately equivalent to their basal metabolic rate thus reducing their foraging energy requirement. During that time, territorial defence may be the largest energy requirement of males but no information is available. 10. Flight energy requirements during migration are estimated for typical Herring Gulls from the Great Lakes area to have maximums of 106 kcal month-1 during March for adults and 371 kcal month-1 during January for juveniles.


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