Distribution and Abundance of the Western Grebe (Aechmophorus Occidentalis) in Alberta: an Update
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Distribution and Abundance of the Western Grebe (Aechmophorus occidentalis) in Alberta: An Update Alberta Species at Risk Report No. 160 Distribution and Abundance of the Western Grebe (Aechmophorus occidentalis) in Alberta: An Update Prepared for: Alberta Environment and Parks Prepared by: David R. C. Prescott, Jason Unruh, Samantha Morris-Yasinski and Michelle Wells Alberta Species at Risk Report No. 160 January 2018 ISBN: 978-1-4601-3763-5 (Online Edition) ISSN: 1496-7146 (Online Edition) Cover Photo: Dave Prescott For copies of this report, contact: Information Centre – Publications Alberta Environment and Parks Main Floor, Great West Life Building 9920 108 Street Edmonton, Alberta, Canada T5K 2M4 Telephone: (780) 422-2079 OR Visit our website at: http://aep.alberta.ca/fish-wildlife/species-at-risk/species-at-risk-publications-web-resources/ This publication has been released under the Open Government Licence: https://open.alberta.ca/licence. This publication may be cited as: Prescott, D. R. C., J. Unruh, S. Morris-Yasinski and M. Wells. 2018. Distribution and Abundance of the Western Grebe (Aechmophorus occidentalis) in Alberta: An Update. Alberta Environment and Sustainable Resource Development, Fish and Wildlife Policy Branch, Alberta Species at Risk Report No. 160, Edmonton, AB. 23 pp. ii EXECUTIVE SUMMARY The western grebe (Aechmophorus occidentalis) was listed as a Threatened species in Alberta in 2014. This listing was based on an updated provincial status report (AESRD and ACA 2013), in which 80 lakes were reported to have supported western grebes during the breeding season in the province. Since that time, new sources of data have become available. In this report, we update the known distribution of the western grebe in Alberta using these additional sources and observations. An initial data compilation exercise was conducted in early 2015 using records from the most recent provincial status report as a starting point. We then added all available breeding season records through the end of 2014 from new sources, which included records contained in Fisheries and Wildlife Management Information System (FWMIS), observations gleaned from published and unpublished reports, records solicited from professional biologists and the naturalists’ community, and the online eBird database. In 2015/2016 we visited as many of these lakes as possible, including additional lakes not previously known to support western grebes, and re-checked the eBird database for records from 2015/2016. The initial compilation of records through 2014 resulted in a list of 249 waterbodies known to have supported western grebes in Alberta during the breeding season, with 55 lakes having confirmed breeding records. In 2015/2016, 162 of these lakes were visited to determine occupancy and current habitat condition. Western grebes were recorded on 9 new waterbodies, and breeding was observed on 28 lakes, including 11 lakes where no breeding was previously reported. Recent eBird records (from 2015/2016) also yielded reports of grebes on an additional 21 new lakes. We compiled a total of 318 occupied lakes, with 67 lakes supporting breeding western grebes at some point in their past. Twenty-two lakes supported populations of ≥100 birds in the past 10 years, and 25 additional lakes have supported ≥100 birds at any point in the past, but not in the past decade. Combining high population and habitat scores resulted in a list of 35 priority lakes for population surveys and management actions to be implemented under the provincial recovery plan. This greatly expanded list of lakes suggests there is much more western grebe habitat in Alberta than previously thought, and the species undoubtedly occurs, or has occurred, on additional lakes that are not yet documented. The discovery of new historical records and new lakes with recent breeding evidence, along with the discovery of many smaller waterbodies that support small numbers of western grebes, suggests a highly dynamic system of lake occupancy by western grebes in Alberta, and the possibility that provincial populations are higher than previously thought. iii ACKNOWLEDGEMENTS We thank the numerous people who have contributed records of western grebes in Alberta over many years, including the many birders and naturalists who have contributed data to eBird that are not individually acknowledged here. We are grateful to the following staff and volunteers who responded to our call for assistance, and visited lakes to check for western grebes in 2015 and 2016: Aaron Foss, Adam Collingwood, Adam Moltzahn, Alain Richard, Alison Cole, Amanda Rezansoff, Amelia Orich, Amy Flasko, Anne Hubbs, Brandy Downey, Brendan Ganton, Brian Makowecki, Britt Keeling, Brook Skagen, Cindy Kemper, Cody Nahirniak, Cole Herle, Colin Starkevich, Curtis Stambaugh, Dan Sturgess, Darryl Jarina, Dave Hobson, Dave Moyles, Dave Prescott, David Musto, Delaney Anderson, Don Thacker, Dwayne Latty, Dylan Cummings, Elizabeth Walsh, Emily Herdman, Eric Pybus, Erin Rowlands, Fauve Blanchard, Gavin Berg, Geoff Holroyd, Grant Chapman, Greg Wagner, Gwen Roy, Heather Cuthill, Hugh Wollis, Janelle Sloychuck, Jason Unruh, Jeff Gilham, Jeff Zimmer, Jessica Lockhart, Jim Allen, Jim Castle, Jim McCabe, Julia Wachowski, Julie Landry-DeBoer, Justin Gilligan, Ken Orich, Kevin Downing, Kevin Methuen, Kim Morton, Kim Pearson, Kristen Rumbolt-Miller, Kristin Kline, Lance Engley, Laraine Hess, Lindsay Theissen, Lisa Wilkinson, Lonnie Bilyk, Louise Geldorp, Luke Vander Vennen, Megan Jensen, Melanie deKappel, Melynda Johnson, Michael Geldorp, Michael Sample, Mike Ranger, Monica Ready, Natalka Melnycky, Nick Parayko, Nils Anderson, Patt Dunn, Quentin Isley, Richard Quinlan, Roland Perot, Ron Bjorge, Rose Painter, Samantha Morris-Yasinski, Sam Uhlick, Sandi Robertson, Sarah Rovang, Scott Stevens, Stephanie Fenson, Steve Nadworny, Sue Peters and Tim Schowalter. We also thank Alain Richard and Julienne Morissette (Ducks Unlimited Canada), Jonathan Thompson (Golder Associates Ltd) and Glenn Mack (Alberta Environment and Parks) for retrieving records from previous Ducks Unlimited surveys in Alberta, and Ann McKellar (Environment Canada) and Mike Barr (Alberta NAWMP Partnership) for locating reference material. Mary Duane and Morley Riske provided many years of unpublished records from central Alberta. We thank Cindy Kemper, Fauve Blanchard and Gwen Roy (Alberta Environment and Parks) for comments on a previous draft of this document. The work was supported with funding from the Species at Risk Program of Alberta Environment and Parks. iv TABLE OF CONTENTS EXECUTIVE SUMMARY ............................................................................................... iii ACKNOWLEDGEMENTS ............................................................................................... iv LIST OF FIGURES ........................................................................................................... vi LIST OF TABLES ............................................................................................................. vi INTRODUCTION .............................................................................................................. 1 METHODS ......................................................................................................................... 1 RESULTS ........................................................................................................................... 3 DISCUSSION ..................................................................................................................... 5 LITERATURE CITED ....................................................................................................... 8 APPENDIX ....................................................................................................................... 12 v LIST OF FIGURES Figure 1. Map of lakes known to be occupied by western grebes in Alberta during the breeding season (1 May to 31 August). See Appendix for occupancy history on each lake.................................................................................................................. 4 Figure 2. Number of lakes known to be occupied by western grebes in Alberta, 1970- 2016, from all sources. Data compiled from the Appendix ................................... 6 LIST OF TABLES Table 1. Priority lakes for future surveys and management actions in Alberta. List includes lakes that have supported >100 birds in the past, and currently have “Medium” or “High” habitat suitability (see text). Detailed population information on each of these lakes is provided in the Appendix. ........................... 5 vi INTRODUCTION The western grebe (Aechmophorus occidentalis) was listed as a Threatened species in Alberta in 2014 (Alberta Environment and Parks 2014). This listing was based on a calculated population decline in excess of 30% over 10 years, a small area of occupancy (72 km2), a loss of colonies (particularly large ones), a reduction in number of mature individuals to less than 10 000, and declining extent and quality of habitat. The concern over the status of western grebes is not confined to Alberta. The species is listed as being of Special Concern in Canada by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC 2014), and has appeared on the Red List of Species in British Columbia (B.C. Ministry of Environment, Lands and Parks 1999). In Alberta, the recent listing of Threatened was based on a compilation of occupied lakes and reported population