Sources of variation in estimating breeding success of migratory birds from autumn counts
Abstract Understanding drivers of change in population sizes requires estimation of demographic rates such as survival and productivity. In migratory geese, productivity or breeding success is typically assessed at the autumn staging and wintering grounds by observing the number of young versus adul...
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crwiley:10.1002/2688-8319.12212 2024-03-31T07:55:02+00:00 Sources of variation in estimating breeding success of migratory birds from autumn counts Jensen, Gitte Høj Johnson, Fred A. Madsen, Jesper Aarhus Universitet 2023 http://dx.doi.org/10.1002/2688-8319.12212 https://onlinelibrary.wiley.com/doi/pdf/10.1002/2688-8319.12212 https://onlinelibrary.wiley.com/doi/full-xml/10.1002/2688-8319.12212 https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1002/2688-8319.12212 en eng Wiley http://creativecommons.org/licenses/by/4.0/ Ecological Solutions and Evidence volume 4, issue 1 ISSN 2688-8319 2688-8319 Management, Monitoring, Policy and Law Nature and Landscape Conservation Ecology Global and Planetary Change journal-article 2023 crwiley https://doi.org/10.1002/2688-8319.12212 2024-03-05T05:31:09Z Abstract Understanding drivers of change in population sizes requires estimation of demographic rates such as survival and productivity. In migratory geese, productivity or breeding success is typically assessed at the autumn staging and wintering grounds by observing the number of young versus adults in flocks of geese—also called age counts. Such age counts are, however, likely to be affected by a number of factors as we are compelled to sample from an open population, in which the temporal and spatial age composition can vary due to differential migration, mortality and flocking behaviour. In this study we seek to provide guidance for the design of age counts, by identifying which factors need to be taken into account when collecting data. Identification of these factors will facilitate a more targeted data collection and enable better conservation and management recommendations. We use the long‐term age count dataset for the Svalbard population of the pink‐footed goose and focus on the following factors: May thaw days on Svalbard, region of sampling, flock size, time and cumulative harvest, calculated as the amount of shot individuals up to each observation of juveniles. We find that the temporal trend in goose productivity based on raw data will be affected by variation in how (which flock sizes), where (which region) and when (which Julian day) the data have been collected. The sources of variation in observations of goose productivity confound inference at the population level. Thus, if the goal is to follow changes in annual productivity, pooled totals of age counts are only useful if data are collected following a random design. We recommend adjusting for these effects using a demographic population model, particularly for hunted species where age counts are conducted during the hunting season and where annual population assessment work is used to recommend an optimal harvest strategy and allocation of hunting quotas. These considerations not only apply to geese, but more generally to migratory birds ... Article in Journal/Newspaper Pink-footed Goose Svalbard Wiley Online Library Svalbard Ecological Solutions and Evidence 4 1 |
institution |
Open Polar |
collection |
Wiley Online Library |
op_collection_id |
crwiley |
language |
English |
topic |
Management, Monitoring, Policy and Law Nature and Landscape Conservation Ecology Global and Planetary Change |
spellingShingle |
Management, Monitoring, Policy and Law Nature and Landscape Conservation Ecology Global and Planetary Change Jensen, Gitte Høj Johnson, Fred A. Madsen, Jesper Sources of variation in estimating breeding success of migratory birds from autumn counts |
topic_facet |
Management, Monitoring, Policy and Law Nature and Landscape Conservation Ecology Global and Planetary Change |
description |
Abstract Understanding drivers of change in population sizes requires estimation of demographic rates such as survival and productivity. In migratory geese, productivity or breeding success is typically assessed at the autumn staging and wintering grounds by observing the number of young versus adults in flocks of geese—also called age counts. Such age counts are, however, likely to be affected by a number of factors as we are compelled to sample from an open population, in which the temporal and spatial age composition can vary due to differential migration, mortality and flocking behaviour. In this study we seek to provide guidance for the design of age counts, by identifying which factors need to be taken into account when collecting data. Identification of these factors will facilitate a more targeted data collection and enable better conservation and management recommendations. We use the long‐term age count dataset for the Svalbard population of the pink‐footed goose and focus on the following factors: May thaw days on Svalbard, region of sampling, flock size, time and cumulative harvest, calculated as the amount of shot individuals up to each observation of juveniles. We find that the temporal trend in goose productivity based on raw data will be affected by variation in how (which flock sizes), where (which region) and when (which Julian day) the data have been collected. The sources of variation in observations of goose productivity confound inference at the population level. Thus, if the goal is to follow changes in annual productivity, pooled totals of age counts are only useful if data are collected following a random design. We recommend adjusting for these effects using a demographic population model, particularly for hunted species where age counts are conducted during the hunting season and where annual population assessment work is used to recommend an optimal harvest strategy and allocation of hunting quotas. These considerations not only apply to geese, but more generally to migratory birds ... |
author2 |
Aarhus Universitet |
format |
Article in Journal/Newspaper |
author |
Jensen, Gitte Høj Johnson, Fred A. Madsen, Jesper |
author_facet |
Jensen, Gitte Høj Johnson, Fred A. Madsen, Jesper |
author_sort |
Jensen, Gitte Høj |
title |
Sources of variation in estimating breeding success of migratory birds from autumn counts |
title_short |
Sources of variation in estimating breeding success of migratory birds from autumn counts |
title_full |
Sources of variation in estimating breeding success of migratory birds from autumn counts |
title_fullStr |
Sources of variation in estimating breeding success of migratory birds from autumn counts |
title_full_unstemmed |
Sources of variation in estimating breeding success of migratory birds from autumn counts |
title_sort |
sources of variation in estimating breeding success of migratory birds from autumn counts |
publisher |
Wiley |
publishDate |
2023 |
url |
http://dx.doi.org/10.1002/2688-8319.12212 https://onlinelibrary.wiley.com/doi/pdf/10.1002/2688-8319.12212 https://onlinelibrary.wiley.com/doi/full-xml/10.1002/2688-8319.12212 https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1002/2688-8319.12212 |
geographic |
Svalbard |
geographic_facet |
Svalbard |
genre |
Pink-footed Goose Svalbard |
genre_facet |
Pink-footed Goose Svalbard |
op_source |
Ecological Solutions and Evidence volume 4, issue 1 ISSN 2688-8319 2688-8319 |
op_rights |
http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.1002/2688-8319.12212 |
container_title |
Ecological Solutions and Evidence |
container_volume |
4 |
container_issue |
1 |
_version_ |
1795036412804857856 |