TIME-ENERGY USE AND LIFE HISTORY STRATEGIES 



157 



MALE'S 



FORAGING RANGE 



FEMALE S 

 FORAGING RANGE 



10.0 12.0 14.0 16.0 



Fig. 14. Percentage observations of foraging sea- 

 birds at different distances from the nest site. 

 After Cody (1973). Each vertical bar represents 

 5% of total observations. Note nonlinear hori- 

 zontal scale. 



cids, and shags (Snow 1963; Vermeer 1963; 

 Drury and Smith 1968; Ashmole and Tovar S. 

 1968; Potts 1968; Ashmole 1971; LeCroy 

 1972). 



Fig. 13. Foraging ranges of a pair of mew gulls dur- 

 ing the breeding season, on a Barents Sea colony. 

 From Belopol'skii (1961). 



between geographical regions. For example, 

 rhinoceros auklets are nocturnal in the far 

 north (where the summer night is particularly 

 short), crepuscular in the Olympic Peninsula, 

 and mainly diurnal in the Farallon Islands 

 (Manuwal 1974a). 



Food demands of nestlings have a great in- 

 fluence on the time and energy allocation of 

 breeding over nonbreeding seabirds. Because 

 food is particularly abundant in the reproduc- 

 tive season, however, one cannot ascertain 

 whether the vulnerability of breeding birds to 

 time or energy crises is far different from that 

 at other times of the year. 



Postfledging Care 



Little is known about the amount of care 

 provided by adults to young after they are 

 fully grown. At least some species, such as 

 gannets and procellariformes (Ashmole 1971), 

 are known to desert their young, whereas 

 others are known to feed their young, at least 

 occasionally, for some weeks or months after 

 they can fly e.g., terns and gulls, many al- 



Annual Time and 

 Energy Budgets 



The discussion of time and energy alloca- 

 tion during reproduction was complex and de- 

 tailed because so much more is known about 

 the influences altering budgeting during this 

 period than during other times of the year. It 

 is likely that influences on molt and migration 

 will prove to be equally complicated, once 

 more is learned about them. 



If all data on time and energy allocation for 

 a single species were known, it would be pos- 

 sible to make up detailed budgets for birds of 

 different age, sex, and experience throughout 

 the year. However, such detailed data have 

 not been collected for any species. An annual 

 time budget for male and female yellow-billed 

 magpie, Pica nuttalli (Verbeek 1972), points 

 out the great amount of difference between 

 the sexes (Fig. 15). A time and energy budget 

 for the reproductive season only (Fig. 16) 

 shows large differences between two closely 

 related species, as well as between sexes; it 

 also indicates the wide difference between the 

 budgeting of energy as opposed to budgeting 

 of time. All other time-energy budgets to date 

 are for nonseabird species and for only a por- 

 tion of the annual cycle (Verbeek 1964; Verner 



