Point count offsets for estimating population sizes of north American landbirds

Brandon P.M. Edwards, Adam C. Smith, Teegan D.S. Docherty, Marcel A. Gahbauer, Caitlyn R. Gillespie, Alexis R. Grinde, Taylor Harmer, David T. Iles, Steven M. Matsuoka, Nicole L. Michel, Andrew Murray, Gerald J. Niemi, Jon Pasher, David C. Pavlacky, Barry G. Robinson, Thomas B. Ryder, Péter Sólymos, Diana Stralberg, Edmund J. Zlonis

Research output: Contribution to journalArticlepeer-review


Bird monitoring in North America over several decades has generated many open databases, housing millions of structured and semi-structured bird observations. These provide the opportunity to estimate bird densities and population sizes, once variation in factors such as underlying field methods, timing, land cover, proximity to roads, and uneven spatial coverage are accounted for. To facilitate integration across databases, we introduce NA-POPS: Point Count Offsets for Population Sizes of North American Landbirds. NA-POPS is a large-scale, multi-agency project providing an open-source database of detectability functions for all North American landbirds. These detectability functions allow the integration of data from across disparate survey methods using the QPAD approach, which considers the probability of detection (q) and availability (p) of birds in relation to area (a) and density (d). To date, NA-POPS has compiled over 7.1 million data points spanning 292 projects from across North America, and produced detectability functions for 338 landbird species. Here, we describe the methods used to curate these data and generate these detectability functions, as well as the open-access nature of the resulting database.

Original languageEnglish (US)
Pages (from-to)482-503
Number of pages22
Issue number2
StatePublished - Apr 2023

Bibliographical note

Funding Information:
Natural Sciences and Engineering Research Council of Canada We thank the hundreds of skilled observers across North America who have collected point count data for the projects used here. NA-POPS curated data from several projects across North America, and we have listed and acknowledged the data owners at https://na-pops.org. We thank the members of the Partners in Flight Population Estimates working group and the Boreal Avian Modelling project for their crucial feedback throughout this study. We thank all constructive reviewers for their extremely valuable feedback to improve the manuscript. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Publisher Copyright:
© 2022 His Majesty the King in Right of Canada and The Authors. Ibis published by John Wiley & Sons Ltd on behalf of British Ornithologists' Union. Reproduced with the permission of the Minister of Environment and Climate Change. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.


  • QPAD
  • availability
  • data integration
  • detectability
  • distance sampling
  • perceptibility
  • removal sampling
  • roadside effects
  • sound attenuation


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