February 7, 2013

Whooping Crane Update

Wade Harrell, U.S. Whooping Crane Recovery Coordinator

On the morning of Feb. 7, 2013, Aransas Refuge staff retrieved the remains of an adult whooping crane on Matagorda Island. The remains will be sent to a lab for analysis and those results will be shared with the public as soon as they are available.

Surveys & Monitoring 

The data on the winter whooping crane population estimate is being processed. We are applying sound science to calculate this estimate and will share it with the public as soon as the estimate is complete.

Whooping Cranes:
On the Aransas National Wildlife Refuge:
• A family group of whooping cranes has been seen using the refuge’s Heron Flats area. The newly renovated observation deck provides some excellent views of the birds, which have been seen relatively close (within a couple of hundred yards).
• A pair of whooping cranes has an established territory that is visible from the Observation Tower.
• Whooping cranes continue to be seen using the prescribed burn areas throughout the refuge.
• When you visit the refuge keep your eyes to the sky as we have whooping cranes flying over the visitor center on occasion!

From Texas Whooper Watch and other observers:
• On Feb. 4, 10 whooping cranes were spotted at Granger Lake. The 10 birds were photographed, including in a field with a couple of hundred sandhill cranes. Previous reports confirmed eight birds.
• One of the whooping cranes at Granger Lake is part of the tracking study and has a GPS leg band. Last year, the juvenile bird spent the entire winter at Granger Lake with its parents. Data collected from the bird’s GPS leg band documents that this year the bird migrated to Aransas Refuge arriving at the end of October and returning to Granger Lake in late January.
• A confirmed pair of whooping cranes was documented in Matagorda County, the Mad Island Marsh, which is on the coast about 30 miles northeast of Aransas National Wildlife Refuge. We had 2 confirmed pairs in the area earlier this winter, but they were not spotted during late December through mid-January. Since these birds are not marked, we don’t know if they have moved around this winter or simply were overlooked for a period of time.

Tracking the Whooping Cranes
In 2009, biologists began putting radio telemetry bands on the Aransas-Wood Buffalo whooping crane population. The opportunity to mark the wild birds with Global Positioning System (GPS) technology represents the best opportunity to enhance understanding of the birds and assess the risks they face.

The technology records bird’s locations and allows biologists to learn which habitats they are using, where they stop during their migration, and more. It captures data from the breeding sites at Wood Buffalo National Park, wintering sites along the Texas coast near and at Aransas National Wildlife Refuge, and stopover locations between. Near completion, the project calls for the tracking of up to 30 juvenile and 30 adult birds.

The reasons for doing this project are to: 1) learn more about the whooping crane’s breeding, wintering, and migratory ecology, including threats to survival and population; 2) provide reliable scientific data to support decisions affecting conservation, management and recovery efforts; and 3) minimize the negative effects of research activities on the birds.

The whooping cranes are primarily captured using leg snares, a common trapping technique used on larger birds. Capture teams consist of individuals experienced at handling cranes, including a licensed veterinarian. A veterinarian performs a health check on each crane, which includes a general external examination; blood collection to determine pathogen, toxin, and genetic screening; and fecal collections to check for parasites.

The GPS band is attached as a leg band. The bands have solar panels that maximize the battery life giving them a potential lifespan of 3–5 years. The transmitters on the leg bands are programmed to record four GPS locations daily, including daytime and nighttime locations. This data collection schedule allows for detailed information on daytime and roosting sites and general flight paths. Transmitters upload new data approximately every two and a half days allowing researchers to monitor survival of the banded birds. As of this winter, 42 transmitters have been put on wild whooping cranes.

Data collected during the winter of 2011 showed the birds used a variety of distinct areas while over-wintering in Texas, including coastal salt and brackish marsh, agricultural and ranching areas and the inland freshwater wetlands. GPS-marked cranes provided more than 11,000 locations. Approximately 65% of the recorded locations were within the boundaries of the Aransas National Wildlife Refuge and 22% were recorded on nearby, privately owned lands -- areas the whooping cranes have often used in the past. Nearly 13% of the locations were in areas not known to be frequented by whooping cranes previously.

The 2012 data shows that total time spent migrating between wintering and summering areas ranged from 15 to 46 days and averaged 27 days. For comparison, researchers estimated the average migration time during spring 2011 to be 31 days. The study has documented the whooping cranes using 266 stopover locations -- areas where the birds stayed for one night or more during their migration -- in every state and province in the Great Plains region.

Trapping efforts for the 2012 winter have been completed with researchers able to put tracking bands on 12 birds. While this technology is already proven to be extremely valuable, it will be several years before sufficient data from the individual birds can be collected and fully analyzed. It will take a considerable amount of time before the information gathered will reflect patterns of the population as a whole.

This project is conducted by a partnership of agencies and organizations, which includes the Canadian Wildlife Service, Crane Trust, U.S. Fish and Wildlife Service, Platte River Recovery Implementation Program, and U.S. Geological Survey, with support from the Gulf Coast Bird Observatory, International Crane Foundation, and Parks Canada.

As this is being written, the refuge is getting much-needed rainfall. As of Feb. 6, the salinity levels in San Antonio Bay are currently 24 ppt.

Food Abundance:
The current winter prescribed burn total is more than 8,000 acres. We have approximately 2,000 acres more planned for the winter. Our prescribed burning program is an important part of how we manage whooping crane habitat on the Aransas Refuge. We are seeing continued whooping crane use in the prescribed burned areas throughout the refuge. It opens up new habitat for the birds to forage in and provides food resources such as live oak acorns that would not typically be available. The satellite tracking study is providing insight into how the whooping cranes use the recently burned areas.