TAP Concerned About Whooping Crane Survey Methodology Changes

by Ron Outen,

The Aransas Project (TAP) leaders announced their concerns about the U.S. Fish and Wildlife Service’s proposed new whooping crane survey methodology. TAP is urging its members to attend a critical public meeting being hosted by the Aransas National Wildlife Refuge to address the changes being made in the survey methods used to count the endangered whooping cranes that winter at the Refuge. Beginning in the winter of 2011-2012, U.S. Fish & Wildlife Service (USFWS) altered its methodology for tracking how many cranes are in the flock and this will be the first public meeting providing any insight or explanation of their methods. In July 2012, TAP released our State of the Flock 2011-2012 report, documenting concerns with the methodology as well as how the flock fared in Winter 2011-2012.

TAP members are strongly encouraged to attend to remain informed on this critical issue:

Thursday, October 4, 2012
6 PM to 8 PM
Paws and Taws Convention Center
402 North Fulton Beach Road Fulton, TX 78358

According to a USFWS news release, the presentation “will investigate and define aerial survey methods used historically and currently to count the Aransas-Wood Buffalo flock of whooping cranes.” Refuge Biologist Brad Strobel will lead the presentation, and there will be a Q&A session following the presentation.

October 3, 2012: USFWS Posts Report 

On October 3, the eve of their public meeting in Fulton, the USFWS has posted to their website a report that they titled,“Aransas-Wood Buffalo Whooping Crane Abundance Survey (2011-2012)”. The report states that its first objective is “to share information in a timely manner;” however, the report was promised by August and was posted October 3, one day in advance of the public meeting noted above.

The report primarily focuses on criticizing the previous census method and introducing their new statistical modeling method of estimating peak flock size. The previous census method was used since 1982 by USFWS’s own prior Crane Coordinator, Tom Stehn. Stehn’s work led the recovery and survey of this species until he retired in September 2011.

Given the timing of the release of this report, TAP’s review has identified, at a minimum, a number of issues of concern:

Territoriality: The report states that, “[the] assumption of territoriality is unnecessary and untenable given recent data.” This conclusion is stunning, and flies in the face of the established scientific literature, decades worth of banding data, and earlier GPS tracking data. This conclusion appears to be based solely on one year’s GPS tracking data that was collected in a year when the cranes were clearly dispersed due to severe drought.

The End of Crane Counting?: Because the new method is designed to statistically estimate only peak flock size, it appears that USFWS no longer intends to track or tell the public how many cranes are in the flock, or how many cranes die at Aransas in any given year.

Basis and Data for New Peak Count Unclear: In contrast to the previous method that clearly counted and reported the number of cranes, the new statistical style instead counts some cranes and then estimates the peak flock count, a number that is buried in pages of complex statistical lingo. Additionally, because USFWS does not share the underlying raw data, it is difficult to determine how a new peak flock estimate of 254 birds was derived.

These are only a few of the questions that are prompted by this report, and TAP is concerned that the report was not provided further in advance of this public meeting to allow full analysis by researchers and the public. We hope that USFWS will be able to shed additional light on the reasoning and conclusions reached in the report in light of the concerns expressed above.