Senescence and carryover effects of reproductive performance influence migration, condition, and breeding propensity in a small shorebird

Abstract

Breeding propensity, the probability that an animal will attempt to breed each year, is perhaps the least understood demographic process influencing annual fecundity. Breeding propensity is ecologically complex, as associations among a variety of intrinsic and extrinsic factors may interact to affect an animal's breeding decisions. Individuals that opt not to breed can be more difficult to detect than breeders, which can (1) lead to difficulty in estimation of breeding propensity, and (2) bias other demographic parameters. We studied the effects of sex, age, and population reproductive success on the survival and breeding propensity of a migratory shorebird, the piping plover (Charadrius melodus), nesting on the Missouri River. We used a robust design Barker model to estimate true survival and breeding propensity and found survival decreased as birds aged and did so more quickly for males than females. Monthly survival during the breeding season was lower than during migration or the nonbreeding season. Males were less likely to skip breeding (range: 1–17%) than females (range: 3–26%; βsex = −0.21, 95% CI: −0.38 to −0.21), and both sexes were less likely to return to the breeding grounds following a year of high reproductive success. Birds that returned in a year following relatively high population‐wide reproductive output were in poorer condition than following a year with lower reproductive output. Younger adult birds and females were more likely to migrate from the breeding area earlier than older birds and males; however, all birds stayed on the breeding grounds longer when nest survival was low, presumably because of renesting attempts. Piping plovers used a variety of environmental and demographic cues to inform their reproduction, employing strategies that could maximize fitness on average. Our results support the “disposable soma” theory of aging and follow with predictions from life history theory, exhibiting the intimate connections among the core ecological concepts of senescence, carryover effects, and life history.

Direct and indirect effects of nesting density on survival and breeding propensity of an endangered shorebird

“…A previous study indicated that some non-breeders did not return to the study area (Weithman et al 2017) and thus were not observable, but not all non-breeding plovers were absent from the study area. A previous study indicated that some non-breeders did not return to the study area (Weithman et al 2017) and thus were not observable, but not all non-breeding plovers were absent from the study area.…”

“…We used estimates of population size from a robust design Barker survival model (Kendall et al 2013, Weithman et al 2017) to calculate population density (adult birds/ha nesting habitat). dry or wet sand, <30% ground cover) was estimated from Pan-sharpened multispectral Quick-Bird (satellite) imagery (1 m resolution) that was classified using Definiens Developer Software (C. Huber, USACE, unpublished data).…”

“…Previous studies have indicated that plover reproduction (Hunt et al 2018), immigration, and emigration are density dependent, but key aspects of demography such as adult survival and breeding propensity (Weithman et al 2017) are relatively unstudied with respect to density. The objectives of this study were to evaluate the effect of nesting density on the breeding propensity and survival of second year (one year post-hatch) and adult plovers, and to compare survival rates for breeding and non-breeding birds.…”

Making use of multiple surveys: Estimating breeding probability using a multievent‐robust design capture–recapture model

“…Weithman et al. () additionally interpreted the “availability” parameter ( a ʹ, the probability of being available for capture given that the individual was previously unavailable for capture) as a measure of breeding probability in piping plover ( Charadrius melodus ), a migratory shorebird. The Barker/robust design implemented in program MARK currently lacks multistate and/or multievent extensions, but the multistate extension of the Barker model (Barker, ) allows an alternative, direct means of estimating breeding probability and accommodates uncertain identification of states.…”

“…Robust design in combination with auxiliary resightings of live individuals outside of the primary sampling area or period is a very effective way of reducing terminal bias in survival estimates under Markovian temporary emigration (Peñaloza, Kendall, & Langtimm, 2014). Despite the benefits of increased precision of parameter estimates and user-friendly implementation in program MARK (White & Burnham, 1999), the Barker/robust design approach has only rarely been used in empirical applications to estimate survival and population size or density (as derived parameters) of wild animal populations (Fabrizio, Tuckey, Latour, White, & Norris, 2018;Gómez-Ramírez, Gutiérrez-González, & López-González, 2017;Gutiérrez-González, Gómez-Ramírez, López-González, & Doherty, 2015;Ivan, White, & Shenk, 2014;Weithman et al, 2017). Weithman et al (2017) additionally interpreted the "availability" parameter (aʹ, the probability of being available for capture given that the individual was previously unavailable for capture) as a measure of breeding probability in piping plover (Charadrius melodus), a migratory shorebird.…”