Wednesday, September 26, 2012

impact of cats on birds, bird mortality estimates > Loss Marra Will

In early April 2012 I saw that Peter Marra of the Smithsonian (he is opposed to freeroaming cats and Trap Neuter Return and was Nico Dauphine's former boss) was to be a plenary speaker on annual cycle of birds at this August 2012 NAOC conference. Abstracts became available recently; below is a different but related presentation (which I've posted about previously.)

The University of British Columbia, and the city of Vancouver, hosted the 5th North American Ornithological Conference (NAOC-V) in Vancouver, British Columbia, Canada, 14 - 18 August 2012

The total of 1478 attendees at NAOC-V was the largest ornithological meeting ever held in Canada or the United States,

W12.6 Loss, Scott, (Migratory Bird Center, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, United States); Marra, Peter (Migratory Bird Center, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC, United States); Blancher, Peter (Environment Canada, Ottawa, ON, Canada); Will, Tom (U.S. Fish and Wildlife Service, Division of Migratory Birds, Bloomington, MN, United States)


Direct anthropogenic mortality sources, including collisions with man-made obstacles, poisoning, and cat predation, combine to kill large numbers of North American birds annually, but there is great uncertainty about the magnitude of this mortality and the relative importance of different mortality sources. Previous estimates of annual mortality from cat predation in the U.S. range from hundreds of millions to greater than one billion birds, but no study to date has taken a systematic data-driven approach. We reviewed temperate-zone cat predation studies and defined inclusion criteria to remove studies with methodological limitations that could substantially bias mortality estimates. From the remaining studies, we defined a distribution range of predation rates and incorporated this range in a calculation that included ranges for population sizes of cats, the proportion of house cats allowed outdoors and of outdoors cats that hunt, and a correction factor for imperfect prey detection. Repeated random draws from these distributions produced mortality estimates that range from 250 million to 1.5 billion birds for free-ranging house cats and from 890 million to 2.7 billion birds for feral/semi-feral cats. These estimates are the first to systematically consider results from multiple cat predation studies and are greater than previous U.S. estimates. Major knowledge gaps still exist, and more study is needed to assess variation in predation vulnerability among bird species, age classes, seasons, habitats, and regions, and to estimate U.S. population sizes of feral and semi-feral cats. Greater data availability will allow more rigorous statistical analyses to be conducted, including hierarchical models to quantify mortality, and full-life cycle models to assess population impacts. These approaches can also be used to improve quantification of other sources of direct anthropogenic mortality.

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The title of the above presentation is similar to several previous cat opposition papers including Dauphine's 2009 paper, presented in 2008 at Partners in Flight. Unfortunately, any "research" "study" "report" "science" "facts" etc. presented by the bird, wildlife, conservation opponents of feral or freeroaming cats and Trap Neuter Return who continue to disseminate misinformation needs critical analysis.

Selected previous related Feral Cat Blog! posts:

Direct human-caused mortality of birds
Tuesday, June 19, 2012

Partners in Flight Action Plan > Cats
scroll down to the partial list of recent opponent research including bird life cycle, impact of cats on grassland birds, etc.