Dataset Information

Movement patterns in a partial migrant: a multi-event capture-recapture approach.

ABSTRACT: Partial migration is a pervasive albeit poorly studied phenomenon by which some individuals of a population migrate while others are residents. It has tremendous consequences on seasonal variations of population size/structure and therefore management. Using a multi-event capture-mark-recapture/recovery (CMR) approach, we assessed seasonal site occupancy, survival and site fidelity of a partially migratory diving duck, the Common pochard (Aythya ferina), in an area potentially including both local breeders and winter visitors. The modelling exercise indeed discriminated two different categories of individuals. First, locally breeding females which had a probability of being present in our study area during winter of 0.41. Females of this category were found to be more faithful to their breeding site than males (breeding site fidelity probabilities of 1 and 0.11, respectively). The second category of birds were winter visitors, which included adults of both sexes, whose probability of being present in the study area during the breeding season was nil, and young of both sexes with a 0.11 probability of being present in the area during the breeding season. All wintering individuals, among which there was virtually no locally breeding male, displayed a high fidelity to our study area from one winter to the next (0.41-0.43). Estimated annual survival rates differed according to age (adults 0.69, young 0.56). For both age classes mortality was higher during late winter/early spring than during summer/early winter. Our study is among the first to show how and under which conditions the multi-event approach can be employed for investigating complex movement patterns encountered in partial migrants, providing a convenient tool for overcoming state uncertainty. It also shows why studying patterns of probability of individual presence/movements in partial migrants is a key towards understanding seasonal variations in numbers.

SUBMITTER: Gourlay-Larour ML

PROVIDER: S-EPMC4011787 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Movement patterns in a partial migrant: a multi-event capture-recapture approach.

Gourlay-Larour Marie-Lucile ML Pradel Roger R Guillemain Matthieu M Guitton Jean-Sébastien JS L'Hostis Monique M Santin-Janin Hugues H Caizergues Alain A

PloS one 20140506 5

Partial migration is a pervasive albeit poorly studied phenomenon by which some individuals of a population migrate while others are residents. It has tremendous consequences on seasonal variations of population size/structure and therefore management. Using a multi-event capture-mark-recapture/recovery (CMR) approach, we assessed seasonal site occupancy, survival and site fidelity of a partially migratory diving duck, the Common pochard (Aythya ferina), in an area potentially including both loc ...[more]

PMID: 24802936

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Project description:Over the last decade, spatial capture-recapture (SCR) models have become widespread for estimating demographic parameters in ecological studies. However, the underlying assumptions about animal movement and space use are often not realistic. This is a missed opportunity because interesting ecological questions related to animal space use, habitat selection, and behavior cannot be addressed with most SCR models, despite the fact that the data collected in SCR studies - individual animals observed at specific locations and times - can provide a rich source of information about these processes and how they relate to demographic rates. We developed SCR models that integrated more complex movement processes that are typically inferred from telemetry data, including a simple random walk, correlated random walk (i.e., short-term directional persistence), and habitat-driven Langevin diffusion. We demonstrated how to formulate, simulate from, and fit these models with standard SCR data using data-augmented Bayesian analysis methods. We evaluated their performance through a simulation study, in which we varied the detection, movement, and resource selection parameters. We also examined different numbers of sampling occasions and assessed performance gains when including auxiliary location data collected from telemetered individuals. Across all scenarios, the integrated SCR movement models performed well in terms of abundance, detection, and movement parameter estimation. We found little difference in bias for the simple random walk model when reducing the number of sampling occasions from T = 25 to T = 15. We found some bias in movement parameter estimates under several of the correlated random walk scenarios, but incorporating auxiliary location data improved parameter estimates and significantly improved mixing during model fitting. The Langevin movement model was able to recover resource selection parameters from standard SCR data, which is particularly appealing because it explicitly links the individual-level movement process with habitat selection and population density. We focused on closed population models, but the movement models developed here can be extended to open SCR models. The movement process models could also be easily extended to accommodate additional "building blocks" of random walks, such as central tendency (e.g., territoriality) or multiple movement behavior states, thereby providing a flexible and coherent framework for linking animal movement behavior to population dynamics, density, and distribution.

Project description:Spatial capture-recapture (SCR) models are powerful analytical tools that have become the standard for estimating abundance and density of wild animal populations. When sampling populations to implement SCR, the number of unique individuals detected, total recaptures, and unique spatial relocations can be highly variable. These sample sizes influence the precision and accuracy of model parameter estimates. Testing the performance of SCR models with sparse empirical data sets typical of low-density, wide-ranging species can inform the threshold at which a more integrated modeling approach with additional data sources or additional years of monitoring may be required to achieve reliable, precise parameter estimates. Using a multi-site, multi-year Utah black bear (Ursus americanus) capture-recapture data set, we evaluated factors influencing the uncertainty of SCR structural parameter estimates, specifically density, detection, and the spatial scale parameter, sigma. We also provided some of the first SCR density estimates for Utah black bear populations, which ranged from 3.85 to 74.33 bears/100 km2 . Increasing total detections decreased the uncertainty of density estimates, whereas an increasing number of total recaptures and individuals with recaptures decreased the uncertainty of detection and sigma estimates, respectively. In most cases, multiple years of data were required for precise density estimates (<0.2 coefficient of variation [CV]). Across study areas there was an average decline in CV of 0.07 with the addition of another year of data. One sampled population with very high estimated bear density had an atypically low number of spatial recaptures relative to total recaptures, apparently inflating density estimates. A complementary simulation study used to assess estimate bias suggested that when <30% of recaptured individuals were spatially recaptured, density estimates were unreliable and ranged widely, in some cases to >3 times the simulated density. Additional research could evaluate these requirements for other density scenarios. Large numbers of individuals detected, numbers of spatial recaptures, and precision alone may not be sufficient indicators of parameter estimate reliability. We provide an evaluation of simple summary statistics of capture-recapture data sets that can provide an early signal of the need to alter sampling design or collect auxiliary data before model implementation to improve estimate precision and accuracy.

Dataset Information

Movement patterns in a partial migrant: a multi-event capture-recapture approach.

Publications

Movement patterns in a partial migrant: a multi-event capture-recapture approach.

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