Influence du moment de diffusion d'enregistrements de chant pendant un point d'écoute et de la durée du point d'écoute sur la probabilité de détection d'oiseaux de marais nicheurs

Translated title of the contribution: Influence of call broadcast timing within point counts and survey duration on detection probability of marsh breeding birds

Douglas C. Tozer, C. Myles Falconer, Annie M. Bracey, Erin E. Gnass Giese, Gerald J. Niemi, Robert W. Howe, Thomas M. Gehring, Christopher J. Norment

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


The Standardized North American Marsh Bird Monitoring Protocol recommends point counts consisting of a 5-min passive observation period, meant to be free of broadcast bias, followed by call broadcasts to entice elusive species to reveal their presence. Prior to this protocol, some monitoring programs used point counts with broadcasts during the first 5 min of 10-min counts, and have since used 15-min counts with an initial 5-min passive period (P1) followed by 5 min of broadcasts (B) and a second 5-min passive period (P2) to ensure consistency across years and programs. Influence of timing of broadcasts within point counts and point count duration, however, have rarely been assessed. Using data from 23,973 broadcast-assisted 15-min point counts conducted throughout the Great Lakes–St. Lawrence region between 2008 and 2016 by Bird Studies Canada’s Marsh Monitoring Program and Central Michigan University’s Great Lakes Coastal Wetland Monitoring Program, we estimated detection probabilities of individuals for 14 marsh breeding bird species during P1B compared to BP2, P1 compared to P2, and P1B compared to P1BP2. For six broadcast species and American Bittern (Botaurus lentiginosus), we found no significant difference in detection during P1B compared to BP2, and no significant difference in four of the same seven species during P1 compared to P2. We observed small but significant differences in detection for 7 of 14 species during P1B compared to P1BP2. We conclude that differences in timing of broadcasts causes no bias based on counts from entire 10-minute surveys, although P1B should be favored over BP2 because the same amount of effort in P1B avoids broadcast bias in all broadcast species, and 10-min surveys are superior to 15-min surveys because modest gains in detection of some species does not warrant the additional effort. We recommend point counts consisting of 5 min of passive observation followed by broadcasts, consistent with the standardized marsh bird protocol, for surveying marsh breeding birds.

Translated title of the contributionInfluence of call broadcast timing within point counts and survey duration on detection probability of marsh breeding birds
Original languageFrench
Article number8
JournalAvian Conservation and Ecology
Issue number2
StatePublished - Dec 2017

Bibliographical note

Funding Information:
We are very grateful for the dedication of hundreds of volunteer MMP participants, whose collective effort contributed a substantial portion of the large number of point counts analyzed in this study. We are also grateful for the coordination and promotion of the Great Lakes and Québec MMPs by Kathy Jones, Andrew Coughlan, and a large team of regional coordinators throughout the Great Lakes basin; and for past coordination of the programs by Russ Weeber, Steve Timmermans, and Ryan Archer in the Great Lakes, and Catherine Poussart in Québec. We extend a debt of gratitude to hundreds of landowners who granted access to private property. Bird Studies Canada is grateful for the support of its MMPs by the Government of Canada through the federal Department of the Environment, Brant Waterways Foundation, Ducks Unlimited Canada, Great Lakes Commission, Great Lakes Protection Fund, Great Lakes Restoration Initiative, Great Lakes Sustainability Fund, Great Lakes United, Government of Ontario, John and Pat McCutcheon Charitable Foundation, Kenneth M. Molson Foundation, National Audubon Society, Ontario Eastern Habitat Joint Venture, Ontario Trillium Foundation, Service Canada Summer Jobs Program, Science Horizons Program, TD Friends of the Environment Foundation, United States Environmental Protection Agency, Wetland Habitat Fund, and Wildlife Habitat Canada. We are grateful for the generous support of the CWMP by the Great Lakes National Program Office of the U.S. Environmental Protection Agency, under grant number GL-00E00612-0. Although the research described in this work has been partly funded by the U.S. Environmental Protection Agency, it has not been subjected to the agency’s required peer and policy review and therefore does not necessarily reflect the views of the agency and no official endorsement should be inferred. The project was supported by Bird Studies Canada’s Long Point Waterfowl and Wetlands Research Program, S. C. Johnson, The Bluff’s Hunting Club, and the Great Lakes Restoration Initiative. And finally, we thank Ryan Norris, Erik Blomberg, and two anonymous reviewers for improving the manuscript.

Publisher Copyright:
© 2017 by the author(s).


  • Audio lures
  • Bird studies Canada’s marsh monitoring program
  • Call broadcasts
  • Central Michigan University’s great lakes coastal wetland monitoring program
  • Standardized North American marsh bird monitoring protocol


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