Age-specific costs of first-time breeding

摘要: -We investigated the cost of first-time breeding in a population Lesser Snow Geese (Anser caerulescens caerulescens) nesting at La Perouse Bay, Manitoba, Canada. We estimated local survival and capture probabilities female geese by capture-recapture analysis. first found that birds were less likely to be recaptured one year after their successful than on later occasions. Since only successfully are captured, this suggests affects ability next year. then show effect is much more severe for age 2 (the youngest which can breed) starting breed an older age. Finally, we compare mean expected lifetime reproductive success time as two-year-olds or three-year-olds, conditionally until 4. On average, produce similar numbers offspring 3. Received 28 July 1993, accepted 11 January 1994. ASSESSING THE COSTS reproduction key challenges applying life-history theory natural populations. There two major questions: (1) Does present effort have adverse future life history (survival performance)? (2) Do relative costs vary among different segments population? Empirical answers question extremely difficult obtain field. Although predicts some genotypic trade-offs between early late (Williams 1966), negative phenotypic not necessarily expected, since environmental factors induce positive covariation individuals several components fitness (Reznick 1985, Van Noordwijk de Jong 1986). As consequence, whereas covariance traits evidence such trade-offs, results showing no against (Nur 1990). Many researchers, therefore, concluded experimentation necessary investigate (e.g. Gustafsson However, differences overall groups within population, there substitute detailed measures under field conditions. Such studies essential bet1 Present address: Department Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, ter understanding selective pressures In highly philopatric species, often absent from area following observed (Wooller Coulson 1977, Ollason Dunnet 1988, Weimerskirch This experience costly those subsequent years. If case, might expect with breeding. A second whether function per se event itself (i.e. do fail frequently attempt because they young, bred same did breed?). Newton (1988) Sparrowhawks (Accipiter nisus) had one, two, three years He reasoned that, risk mortality, it advantageous begin possible, even if performance poor. attributed variation quality individuals, good-quality would able ages. delayed maturation was result conditions "constraint" hypothesis) rather "restraint" hypothesis; Curio 1983). lifetime-reproductive-success calculations used valid resighting close 100%.