Energetic Costs Of Incubation Research Articles

Brood desertion by female shorebirds: a test of the differential parental capacity hypothesis on Kentish plovers.

The aim of this study was to examine whether the energetic costs of reproduction explain offspring desertion by female shorebirds, as is suggested by the differential parental capacity hypothesis. A prediction of the hypothesis is that, in species with biparental incubation in which females desert from brood care after hatching, the body condition of females should decline after laying to a point at which their body reserves are too low for continuing parental care. We tested this prediction on Kentish plovers (Charadrius alexandrinus) in which both sexes incubate but the females desert from brood care before the chicks fledge. We found no changes in either the body masses or body compositions of both individual male and female plovers from early incubation and throughout early chick rearing. Furthermore, the timing of brood desertion by females was not affected by their body condition. Neither did we find gender differences in the energetic costs of incubation. There were no differences in the timing of brood desertion between experimental and control females in an experiment in which we lengthened or shortened the duration of incubation by one week. These results indicate that energetic costs do not explain offspring desertion by female Kentish plovers and that the needs of chicks for parental care rather than cumulative investment by females is what determines the timing of brood desertion.

Factors Affecting Timing of Brood Desertion By Female Kentish Plovers Charadrius Alexandrinus

[We investigated the factors affecting timing of female desertion in the Kentish plover Charadrius alexandrinus, in relation to a number of previously proposed hypotheses. Females deserted their broods on average 5.9 ± 1.4 (SE) days after hatching. Although timing of desertion was highly variable (0-30d), females deserted on the day of hatching in 9 out of 33 broods (median = 2.3 d). Timing of desertion was not related to mass or condition of the female at hatching, suggesting that energetic costs of incubation were not involved in determining desertion time. Similarly, there was no significant relationship between timing of desertion and the quality of the female's mate, either in terms of his mass, condition, or relative contribution to parental care prior to desertion. Desertion time was also unrelated to brood quality measured by weight, size or number of chicks at hatching. However, timing of desertion was negatively related to hatching date. We conclude that the strategy of desertion is time-constrained: females with early-hatching broods can afford to spend more time with their first brood (perhaps enhancing their expected gain from this brood) and still have sufficient time to desert, remate and rear a second brood. Females with later-hatching broods must desert this brood earlier in order to have time to rear a second brood successfully., We investigated the factors affecting timing of female desertion in the Kentish plover Charadrius alexandrinus, in relation to a number of previously proposed hypotheses. Females deserted their broods on average 5.9 ± 1.4 (SE) days after hatching. Although timing of desertion was highly variable (0-30d), females deserted on the day of hatching in 9 out of 33 broods (median = 2.3 d). Timing of desertion was not related to mass or condition of the female at hatching, suggesting that energetic costs of incubation were not involved in determining desertion time. Similarly, there was no significant relationship between timing of desertion and the quality of the female's mate, either in terms of his mass, condition, or relative contribution to parental care prior to desertion. Desertion time was also unrelated to brood quality measured by weight, size or number of chicks at hatching. However, timing of desertion was negatively related to hatching date. We conclude that the strategy of desertion is time-constrained: females with early-hatching broods can afford to spend more time with their first brood (perhaps enhancing their expected gain from this brood) and still have sufficient time to desert, remate and rear a second brood. Females with later-hatching broods must desert this brood earlier in order to have time to rear a second brood successfully.]

Resting metabolic rate and energetic cost of incubation in macaroni penguins Eudyptes chrysolophus and rockhopper penguins E. chrysocome

1. 1. Oxygen consumption of resting and incubating Macaroni Penguins ( Eudyptes chrysolophus) and Rockhopper Penguins ( E. chrysocome) was measured at Marion Island in the sub-Antarctic. 2. 2. Resting metabolic rate of Macaroni Penguins of mean mass 3779 g averaged 1160.7 kJ/day and that of Rockhopper Penguins of mean mass 2506 g averaged 862.8 kJ/day. 3. 3. Incubating metabolic rates were 1031.8 kJ/day for Macaroni Penguins of mean mass 4839 g and 7014 kJ/day for Rockhopper Penguins of mean mass 2767 g. 4. 4. Energetic cost of incubation was significantly lower than resting metabolic rate in both species but was close to predicted values of basal metabolic rate for birds of equivalent masses. 5. 5. Incubation may not be energetically expensive for small penguins, and incubating metabolic rate may represent a better indication of basal metabolic rate than does resting metabolic rate.