Wintering Whooping Crane Update, April 7, 2017


Wintering Whooping Crane Update
Wade Harrell, – U.S. Whooping Crane Recovery Coordinator

Whooping crane spring migration is in full swing. It has been another tremendous winter season here at Aransas NWR, but the whooping cranes are ready to get back up to Wood Buffalo National Park for another breeding season.

Whooping Crane Update

Whooping crane family flying over Aransas NWR. Photo by Chuck Hardin

As of yesterday, of 7 birds that have active satellite transmitters, 5 have departed Aransas NWR. Quivira NWR (Kansas) and surrounding areas seem to be a hotspot for stopovers this spring, with a group of 14 whooping cranes reported last week and a group of 8 reported this week as well as sightings of smaller groups. There have also been a number of whooping cranes reported in the Platte River in Nebraska and a number that have already made it to the Dakotas. Here in Texas, 2 marked whoopers were spotted on Ft. Hood Army Base this past week. The number of whooping cranes at Aransas will quickly dwindle over the next couple weeks. Spring migration is typically shorter in duration than fall migration, usually only taking about 30 days.

As soon as results from the Annual Whooping Crane Winter Abundance Survey are complete, we will post a summary on the Aransas NWR website.

Whooping Cranes on the Refuge

Whooping crane update

Whooping Cranes over Aransas NWR at sunset. Photo by Kevin Sims

Cranes have recently been seen from the observation tower on the Refuge, but it’s difficult to say how much longer they will remain. But there are many other interesting wildlife species to view at the Refuge now, including many spring migrating songbirds, so don’t hesitate to come out and enjoy other spring wildlife watching opportunities.

Texas Whooper Watch

Please report any whooping cranes you observe in migration in Texas to Texas Whooper Watch. We’ve had a number of people making use of the new Texas Whooper Watch I-Naturalist phone app as well, which is encouraging. The old saying “a photo is worth a thousand words” applies to reporting whooping cranes as well. Just be careful not to disturb or get too close the birds!

Habitat Management on the Refuge

Refuge staff burned 4 Units this winter, totaling 4,871 acres. This year’s winter season was challenging given that our cold weather windows with consistent north winds were limited and the latter part of the winter brought significant rains.

Precipitation/Salinity

The Refuge received 6.16” of rain from January-March 2017. Freshwater levels and food resources remained high throughout most of this winter season.  Salinity levels in San Antonio Bay stayed in the low teens (ppt) most of the winter, but recent rains in the middle portion of the Guadalupe river watershed have dropped salinities significantly this last week. Let’s hope we stay in a wet cycle for a bit longer.

***** FOTWW’s mission is to help preserve and protect the Aransas/Wood Buffalo
population of wild whooping cranes and their habitat. *****

Friends of the Wild Whoopers is a nonprofit 501(c)3 organization.

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Debate about counting Whooping Cranes continues

by Friends of the Wild Whoopers

Not all Whooping Cranes counted

Whooping Cranes

Whooping Cranes over Aransas NWR.  Photo by Kevin Sims ©2105

 

Aransas Wildlife Refuge biologist Tom Stehn conducted Whooping Crane census flights for 29 years at Aransas during which he tried to find every crane.  When Tom Stehn retired from U.S. Fish and Wildlife Service (USFWS) in 2011, the agency changed from doing a weekly Whooping Crane census to conducting a survey that takes place for roughly one week every December.  The change to a survey incorporated a technique called distance sampling where not every crane is counted but estimates of the cranes not seen are based on how far observed cranes were from the aircraft when sighted.  This statistically-derived method provides 95% confidence limits for an estimated Whooping Crane population.  Unfortunately, those confidence limits are quite large, equaling plus or minus 39 cranes out of an estimated flock of 338 during the winter of 2016.

Monitoring Whooping Cranes, Comparison article published

Dr. Bruce Pugesek and Tom Stehn, in January, 2017 published an article in the Proceedings of the 13th North American Crane Workshop entitled “THE UTILITY OF CENSUS OR SURVEY FOR MONITORING WHOOPING CRANES IN WINTER”.  The article compares the survey and census methods of counting Whooping Cranes.  An abstract for this paper is provided below, along with a link to download the entire 10-page article.

Tom Stehn commented to Friends of the Wild Whoopers about the article as follows:

“The article is not an easy read, but that’s the way science sometimes works.  It is a rebuttal of some of the things that USFWS wrote regarding their crane survey method.  In the article, Dr. Pugesek and I point out problems with the survey, including statistics, as well as what we consider as some of the “falsehoods” contained in what was written trying to justify the survey instituted after I retired.  I feel the USFWS was overly critical with unfair and overstated criticism of the census method that USFWS had done for 60 years.  And I firmly believe that with very thorough coverage of the crane area combined with the knowledge I had of individual cranes and their territories accumulated over 29 years of work and over 400 census flights, I could estimate the size of the whooping crane population in a manner much more accurately, and with a justifiable estimate of winter mortality, than what is being done on the current survey method.  The bottom line is that a census is usually stronger scientifically than a survey if the species’ biological parameters allow a census to be conducted.”

Tom continues: “If current USFWS policy requires that a survey with confidence limits be continued, I recommend that after the annual survey is completed, that additional funds be spent doing a census in a manner similar to what I used to do.  Doing some additional flying will allow comparison of the former census method with the current survey results which will provide more information about the crane population as well as better assess the survey methodology currently being employed.  A census would involve thorough coverage of the crane range with transects no more than 500 meters apart.  If there are now more cranes and a bigger area to cover, do the census over 1.5 days if need be.  Also, territories of all family groups should be determined, with a follow-up flight or two in early March to show which juveniles have died during the winter.  This estimate of annual winter mortality is very important, given what is known about drought and reduced inflows related to increased whooper mortality.”

ABSTRACT:

THE UTILITY OF CENSUS OR SURVEY FOR MONITORING WHOOPING CRANES IN WINTER
BRUCE H. PUGESEK,
1 Department of Ecology, Montana State University, Bozeman, MT 59717, USA
THOMAS V. STEHN, 1613 South Saunders Street, Aransas Pass, TX 78336, USA

Abstract: We discuss recent changes in the monitoring program for endangered whooping cranes (Grus americana) on their winter habitat in Texas. A 61-year annual census was replaced in the winter of 2011-2012 with a distance sampling procedure. Justification for the change was, in part, based on criticism of the previous methods of counting cranes and the assessment of crane mortality on the wintering grounds. We argue here that the arguments, methods, and analyses employed to discount the census procedure and mortality estimates were applied incorrectly or with flawed logic and assertions. We provide analysis and logical arguments to show that the census and mortality counts were scientifically valid estimates. The distance sampling protocol currently employed does not provide the accuracy needed to show small annual changes in population size, nor does it provide any estimate of winter mortality. Implications of the relative merit of census and mortality counts versus distance sampling surveys are discussed in the context of management of the whooping crane.

Link to article

***** FOTWW’s mission is to help preserve and protect the Aransas/Wood Buffalo
population of wild whooping cranes and their habitat. *****

Friends of the Wild Whoopers is a nonprofit 501(c)3 organization.

wind farm

friendsofthewildwhoopers.org

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