Assessing and modelling abundance from animal count data is a very common task in ecology and management. Detection is arguably never perfect, but modern hierarchical models can incorporate detection probability and yield abundance estimates that are corrected for imperfect detection. Two variants of these models rely on counts of unmarked individuals, or territories, (binomial N\u2010mixture models, or\u00a0binmix) and on detection histories based on territory mapping data (multinomial N\u2010mixture models or\u00a0multimix). However, calibration studies which evaluate these two N\u2010mixture model approaches are needed. We analysed conventional territory mapping data (three surveys in 2014 and four in 2015) using both binmix and multimix models to estimate abundance for two common avian cavity\u2010nesting forest species (Great Tit\u00a0Parus major\u00a0and Eurasian Blue Tit\u00a0Cyanistes caeruleus). In the same study area, we used two benchmarks: (i) occupancy data from a dense nest box scheme; (ii) total number of detected territories. To investigate variance in estimates due to the territory assignment, three independent ornithologists conducted territory assignments. Nest box occupancy yields a minimum number of territories, since some natural cavities may have been used, and binmix model estimates were generally higher than this benchmark. Estimates under the multimix model were slightly more precise than binmix model estimates. Depending on the person assigning the territories, the multimix model estimates became quite different, either overestimating or underestimating the \"truth\". We conclude that N\u2010mixture\u2010models estimated abundance reliably, even for our very small sample sizes. Territory\u2010mapping counts depended on territory assignment and this carried over to estimates under the multimix model. This limitation has to be taken into account when abundance estimates are compared between sites or years. Whenever possible, accounting for such hidden heterogeneity in the raw data of bird surveys, via including a \"territory editor\" factor, is recommended. Distributing the surveys randomly (in time and space) to editors may also alleviate this problem.
", "publication_date": "2019-12-02", "publisher": "Zenodo", "related_identifiers": [ { "identifier": "10.1111/ibi.12802", "relation_type": { "id": "iscitedby", "title": { "de": "Wird zitiert von", "en": "Is cited by" } }, "scheme": "doi" } ], "resource_type": { "id": "dataset", "title": { "de": "Datensatz", "en": "Dataset" } }, "rights": [ { "description": { "en": "CC0 waives copyright interest in a work you've created and dedicates it to the world-wide public domain. Use CC0 to opt out of copyright entirely and ensure your work has the widest reach." }, "icon": "cc-cc0-icon", "id": "cc0-1.0", "props": { "scheme": "spdx", "url": "https://creativecommons.org/publicdomain/zero/1.0/legalcode" }, "title": { "en": "Creative Commons Zero v1.0 Universal" } } ], "subjects": [ { "subject": "abundance estimation" }, { "subject": "cavity nesters" }, { "subject": "detection probability" }, { "subject": "Forest birds" }, { "subject": "territory assignment" } ], "title": "Field evaluation of abundance estimates under binomial and multinomial N\u2010mixture models" }, "parent": { "access": { "owned_by": { "user": "90070" } }, "communities": { "default": "734b6452-1f40-4db0-b218-08ab1d568b7f", "entries": [ { "access": { "member_policy": "open", "members_visibility": "public", "record_submission_policy": "open", "review_policy": "open", "visibility": "public" }, "children": { "allow": false }, "created": "2020-02-04T14:03:17.992421+00:00", "custom_fields": {}, "deletion_status": { "is_deleted": false, "status": "P" }, "id": "734b6452-1f40-4db0-b218-08ab1d568b7f", "links": {}, "metadata": { "curation_policy": "The Dryad collection in Zenodo contains datasets mirrored from the Dryad Digital Repository. If you want your dataset to appear here, submit it through https://datadryad.org. No other datasets will be accepted.
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