DOI: 10.5061/dryad.6n579
title: Data from: Food availability and predation risk, rather than intrinsic attributes are the main factors shaping the reproductive decisions of a long-lived predator

description: Deciphering the causes of variation in reproductive success is a
 fundamental issue in ecology, as the number of offspring produced is an
 important driver of individual fitness and population dynamics. Little is
 known however, about how different factors interact to drive variation in
 reproduction, such as whether an individual's response to extrinsic
 conditions (e.g. food availability or predation) varies according to its
 intrinsic attributes (e.g. age, previous allocation of resources towards
 reproduction). We used 29 years of reproductive data from marked female
 tawny owls and natural variation in food availability (field vole) and
 predator abundance (northern goshawk) to quantify the extent to which
 extrinsic and intrinsic factors interact to influence owl reproductive
 traits (breeding propensity, clutch size and nest abandonment). Extrinsic
 and intrinsic factors appeared to interact to affect breeding propensity
 (which accounted for 83% of the variation in owl reproductive success).
 Breeding propensity increased with vole density, although increasing
 goshawk abundance reduced the strength of this relationship. Owls became
 slightly more likely to breed as they aged, although this was only
 apparent for individuals who had fledged chicks the year before. Owls laid
 larger clutches when food was more abundant. When owls were breeding in
 territories less exposed to goshawk predation, 99.5% of all breeding
 attempts reached the fledging stage. In contrast, the probability of
 breeding attempts reaching the fledging stage in territories more exposed
 to goshawk predation depended on the amount of resources an owl had
 already allocated towards reproduction (averaging 87.7% for owls with
 clutches of 1-2 eggs compared to 97.5% for owls with clutches of 4-6
 eggs). Overall, our results suggested that changes in extrinsic conditions
 (predominantly food availability, but also predator abundance) had the
 greatest influence on owl reproduction. In response to deteriorating
 extrinsic conditions (fewer voles and more goshawks) owls appeared to
 breed more frequently, but allocated fewer resources per breeding attempt.
 However, intrinsic attributes also appeared to have a relatively small
 influence on how an individual responded to variation in extrinsic
 conditions, which indicates that reproductive decisions were shaped by a
 complex series of extrinsic and intrinsic trade-offs.
description: Juvenile
 surivalThe input file used for
 the juvenile survival analysis first individual covariate is the
 standardized connectivity to goshawk nest sites, and the second individual
 covariate is the standardized distance to the nearest goshawk nest
 sitefempuli8513CI49andngos.txtTemporal covariates for juvenile survival analysisTemporal covariates for juvenile survival analysis. The first covariate is the standardized autumn vole density, The second is the standardized local goshawk abundance. The third is the standardized total goshawk abundance. The 4th is the interaction between the 1st and 2nd covariates. The 5th is the interaction between the 1st and 3rd covariate.8513autvolelocalgostotalgosi.txtbreeding propensity analysis data filebreeding propensity analysis.pdfClutch size and nest abandonment analysis datafileClutch size and nest abandonment analysis.pdf