Rearing of young has long been considered the energetically most demanding phase of the avian breeding cycle. Arctic-breeding shorebirds expend large amounts of energy during breeding. Because they are too small to carry sufficient stores to sit out the incubation period, they regularly interrupt incubation to feed and still can run short of energy, particularly in species in which one adult takes care of the eggs and chicks alone (uniparental). We measured daily energy expenditure (DEE) and time budgets during incubation and chick rearing in the smallest uniparental Arctic shorebird, the Little Stint (Calidris minuta). Daily energy expenditure decreased with increasing temperature but did not differ between the incubation and chick-rearing periods. Because of the increase in potential foraging time from incubation to the chick-rearing phase, the foraging intake rate required to balance the budget dropped by two-thirds. To evaluate the effect of uniparental care on energy budgets, we also measured DEE in the Dunlin (C. alpina), a sympatric congener in which both parents incubate but the female deserts the brood after hatching. Daily energy expenditure decreased with temperature, was the same during incubation and chick rearing, and was higher in males. Our results are discussed in relation to the timing of breeding of Arctic shorebirds with different systems of parental care.
Energy expenditure of terrestrial locomotion on a linear treadmill was measured in five wader species: Turnstone Arenaria interpres, Knot Calidris canutus, Grey Plover Pluvialis squatarola, Oystercatcher Haematopus ostralegus and Bar-tailed Godwit Limosa lapponica. Additional data on Redshank Tringa totanus were taken from the literature. The cost of running in these waders, measured as the slope of the regression line of energy expenditure against speed of locomotion, is significantly less than an allometrically calculated slope for all bird species (Taylor et al. 1982). It is also less than in grouse species which, like waders, must walk to gather their food. Cost of running for a 100 g wader is 22% below the cost of a grouse, and 68% below the cost of a hypothetical penguin of similar mass. Intraindividual cost of running in relation to body mass of a Turnstone and interindividual cost of running in Knots reveal much stronger increases of running costs with increasing body mass than interspecific allometric relations would predict, and this elevated activity cost probably importantly influences the set point for body mass regulation in birds.
1. In precocial birds, where the young feed themselves, the costs and benefits of brood size are still poorly understood. An experimental manipulation of brood size was employed to examine the effects of brood size on both parents and young in a wild population of barnacle geese [ Branta leucopsis (Bechstein)] during brood‐rearing on Svalbard. 2. Social dominance of the family unit, the amount of vigilance behaviour of the parents, the growth of the goslings in the family unit and an index of body condition for female parents during moult were all positively correlated with brood size. 3. When brood size changed as a result of natural events (i.e. predation or adoption) or experimental manipulation, rates of dominance, parental vigilance, gosling growth and female parent condition changed in a similar direction to the observed relation between the variable and brood size in unchanged broods. 4. After fledging, the fast‐growing goslings in large broods survived better during autumn migration, while there was no apparent net cost in survival or next‐year breeding for the parents. 5. Via a direct effect of brood size on dominance of the family unit, large broods were beneficial for both parent and young in a situation where there was strong intraspecific competition for the available food resources. 6. This study provides a clear demonstration of a causal relationship between brood size and various components of both gosling and adult fitness and is of direct relevance to the phenomenon of adoption and the evolution of brood size in this species.
Golden plovers and Grey Plovers Pluvialis spp. all have very distinct breeding plumage rich in contrast, with a conspicuous black belly and breast bordered by a bright white fringe. Eurasian Golden Plovers are known partly to replace their breeding plumage with striped yellow feathers during incubation, different from both breeding and non‐breeding plumages. In this study a similar partial breeding moult was observed in Pacific Golden Plovers and American Golden Plovers caught on the nest or collected during incubation, although the feathers did not differ clearly from those of non‐breeders. This moult starts during incubation and precedes the post‐breeding moult into non‐breeding plumage. Because the lighter feathers reduce the contrast between the black belly and the white flanks, we suggest that during incubation the plumage characteristic that plays an important role in mate choice is no longer important; at this stage it is better for the bird to be inconspicuous. Additional information on museum skins of golden plovers and of Grey Plovers indicated that only the three golden plovers undergo this partial moult, but that Grey Plovers in general retain full breeding plumage throughout incubation. The three golden plovers also resemble each other in their generally very passive nest defence strategies. In contrast, the larger Grey Plovers actively chase and attack aerial and ground predators. Thus, a reduced conspicuousness of the body plumage during incubation is likely to benefit the golden plovers more than the Grey Plover. We suggest that nest defence behaviour, plumage characteristics and perhaps size have co‐evolved as a response to different selection pressures in golden plovers and Grey Plover, but alternative hypotheses are also discussed.
Cumming, G. S., P. A. R. Hockey, L. W. Bruinzeel, and M. A. Du Plessis. 2008. Wild bird movements and avian influenza risk mapping in southern Africa. Ecology and Society 13(2): 26. https://doi.org/10.5751/ES-02536-130226
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