The study was conducted from early May to early August 1975-77 on a 1.6 ha island in north-central Minnesota. All breeding spotted sandpipers were colour-ringed. Time budgets were determined for 10 females and 23 males by instantaneous sampling (at 15-second intervals) of 10 predetermined behaviours. A total of 1,899 30-minute samples (2 birds each) yielded 308,817 data points when birds were visible. Terrestrial arthropod abundance was sampled by cylindrical sticky traps at 12 locations for 48 hours per week. Temperature, wind direction and velocity, and cloud cover were recorded at the time instantaneous samples were conducted. Basal metabolic rates were calculated separately for each sex as a function of body weight. Energy budgets were estimated by extrapolation from time budgets. Caloric and calcium content of principal food items and sandpiper eggs was determined with a Parr adiabatic oxygen calorimeter and a Perkin-Elmer atomic absorption spectrophotometer. During prelaying, females foraged more than males, preened less and flew less. During laying, females foraged, rested, and engaged in agonistic activity more than males. Males spent more time preening, flying, nest building and incubating than their mates. All behaviours differed between sexes during incubation as females spent more time than males in all activities except nest building and incubation. Sex differences were the result of differential strategies to maximize reproductive success and differing energy requirements due to size dimorphism and the energy costs of egg production. Time spent in all behaviours varied among stages of the breeding cycle due primarily to changes in foraging and incubation requirements. Foraging varied by time of day but the pattern of this variation changed among stages of the breeding cycle due principally to diurnal variation in incubation and brooding time. With the exception of the incubation period when only courtship and agonistic behaviour did not vary diurnally, most behaviours did not show diurnal variation. When females helped their mates, nests were incubated a greater proportion of the time than when males incubated alone. Terrestrial arthropod abundance exhibited 2 major peaks each year about 4 weeks apart. Each year a different territory produced the most food over the season as a whole. Time budgets varied among clutches, among territories, and among years but these dif ferences were largely explicable by changes in food abundance. Food abundance consistently influenced foraging time for both sexes. Other activities correlated less consistently with food abundance. Decreases in foraging time, due to higher food levels, were compensated for primarily by increasing time spent in maintenance activities. Temperature, wind, and cloud cover had less influence on time budgets than food abundance, especially for females. Eggs averaged 5.6 Kcal/g dry weight and 1.3 Kcal/g fresh weight. Each egg cost a female 17.8 Kcal to produce. On days of peak egg formation costs, this represented an increase of 94 % (prelaying) to 102 % (laying) in the daily energy expenditure (DEE) of females. For activities other than egg formation, foraging received the most energy expenditure during all stages of the breeding cycle except for males during incubation. Both sexes had minimal DEE's during the incubation period. A clutch of 4 eggs totaled 1.7 times a female's total body calcium. Analysis of principal food items indicated that it was unlikely that females totally relied on these organisms as a calcium source. Energy expended in foraging was typically lower during periods of food abundance than periods of food scarcity. DEE usually increased as food changed from abundant to scarce. Required foraging efficiencies (RFE) decreased as food abundance decreased, indicating that birds had to expend greater amounts of energy to obtain a given quantity of food as food levels dropped. For polyandry to evolve, males must assume most or all of the parental duties. Data of the present study support the hypothesis of EMLEN & ORING (1977) that a male increases his individual fitness by conducting most parental care because the low success rate of individual nesting attempts (due to factors such as high predation rates) places a high priority on the female's ability to provide replacement clutches for the male. A female can produce replacement clutches faster if freed from incubation duties, as this allows her more time to forage. Once male parental care has evolved, sequential polyandry can readily evolve where fewer replacement clutches are required (e.g., where predation rates are less than average) and "surplus" males are available.

15 radio-marked female ruffed grouse (Bonasa umbellus) were monitored with an automatic radiotracking system. The largest mean home range was during the prelaying period. Movements decreased during laying and reached a minimum during incubation. Mean weekly postincubation home ranges as well as postincubation cumulative home ranges were larger for brood hens than broodless hens. Habitat use varied among individuals and stages of the breeding season. Alder, mixed hardwoods, white birch, oak and tamarack habitats received substantial use by 1 or more hens. Alder and mixed hardwoods were used most consistently. Seventeen of 22 nests were in mixed hardwood or oak habitats. Nests in mixed hardwoods were more successful than those in oaks. During incubation hens fed almost exclusively on trembling aspen. Both male and female trees were used. Hens with broods had different activity patterns, used larger home ranges, occupied different habitats, and suffered higher mortality rates than hens without broods.

Spotted Sandpipers are unusual among animals in that a female's annual reproductive effort is regulated primarily by her ability to obtain mates. Males provide most of the parental care in this species. We recorded data on the abundance of food, and on the timing, number, and size of eggs laid by marked females over a 9—yr period on an island in central Minnesota, USA. The onset of egg—laying varied from year to year in association with the abundance of flying insects early in the season. After laying began, there was no relationship between food abundance and the number of size of eggs laid, the time taken to produce a clutch, or the intervals between clutches. The rate of egg—laying per female was affected, however, by rates of nest predation and by the operational sex ratio, which became increasingly female—biased over the season. Females ceased laying eggs in early July, even in years when food and mates were still available. We conclude that nutrient availability acts as a proximate factor in determining the onset of breeding, and that it may have been ultimate factor causing cessation of egg—laying. Within the season, however, the reproductive rate of individual females is primarily determined by competitive interactions with other females for males. Thus both intra and intersexual selection have important effects on fitness in this species.

A color-banded population of Spotted Sandpipers (Actitis macularia) was studied over a 10-yr period on Little Pelican Island, Leech Lake, Minnesota. A total of 75 females and 107 males bred for 144 ♀ ♀ yr and 200 ♂ ♂ yr. The observed skew in the population sex ratio was due primarily to behavioral exclusion of inexperienced females. Density appeared to limit population size and productivity. Locally hatched chicks accounted for 31% and 40% of the breeding females in the final 2 yr. Females laid eggs for 1.35-2.06 males per year. Experienced females had significantly more mates, eggs, chicks, and fledglings than did inexperienced females. Locally hatched chicks accounted for 21% and 19% of the breeding males in the final 2 yr. Males mated with 1.0-1.4 females per year. Experienced males had more mates and received more replacement eggs than did inexperienced males; in contrast to females, however, inexperienced males had no less hatching or fledging success than did experienced males. Thirty-eight marked females and 16 marked males tried unsuccessfully to enter the population, and 6 females and no males were observed to be nonbreeders all season long. Of 1,142 eggs, 442 hatched and 256 fledged. Experienced birds returned to breed more often in subsequent years than did inexperienced ones (61% vs. 50%). Return rates of successful birds were consistently higher than those of unsuccessful birds, the difference decreasing with age. Young males appeared to be less site-faithful than were females and older males. Successfully breeding females lived an average of 3.7 yr. Relative to other scolopacids with multipurpose territories, the Spotted Sandpiper is considered a pioneering species that quickly and frequently colonizes new sites, emigrates in response to reproductive failure, breeds first at an early age, lives a relatively short time, lays many eggs per female per year, and has relatively low nest success.

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