Archive for February, 2012
By Chester McConnell, WCCA
Aransas National Wildlife Refuge biologists now estimate the population of whooping cranes to be approximately 245 individuals within their survey area. This number does not include whoopers known to be in at least five other Texas counties and other states. Some of the birds are moving around off the refuge for reasons not fully understood. It is believed that the whoopers may be seeking additional food sources. The refuge’s January 2012 survey consisted of three flights conducted on January 26, 27, and 29th. Survey biologists searched Matagorda Island, San Jose Island, Blackjack Peninsula, Lamar Peninsula, Dewberry Island and Welder Flats. A second round of survey flights will take place in mid to late February.
Biologists are receiving many reports of whooping cranes outside the survey area in the following Texas counties: Matagorda, Refugio, Calhoun, Aransas, Williamson, San Patricio, Maverick, and Caldwell. Whooping cranes of the Aransas-Wood Buffalo population are also currently residing in other states as far north as Nebraska. These cranes are naturally supplementing their own food sources by wintering around freshwater lakes and other marshes.
Refuge personnel continue to help alleviate low food resources by doing more prescribed burns. This winter they have burned 8,095 acres of habitat. Whooping cranes have been observed eating the roasted acorns and other food sources in burned areas. An additional 6,129 acres are planned to be burned while whooping crane remain on their winter habitat
- Whooping crane with sandhill cranes in Texas rice field. Photo by Leanne Sliva
Fortunately some rains have fallen of Aransas Refuge recently. The first two weeks of February produced a total of 1.89 inches of rain. Water salinity levels have dropped due to recent freshwater inflows from rain in Central Texas, as well as localized rainfall. Salinity levels in San Antonio Bay are currently recorded as 19.9 parts per thousand. Salinity levels in surrounding bays still remain higher than normal which forces whooping cranes to expend more energy flying to fresh water sources.
Methods of counting whooping cranes on Aransas Refuge have been modified. Refuge official, Vicki Muller explained: “In previous years, the refuge gauged the whooping crane population by counting individual birds within the survey area. The aerial surveys objective was focused on counting every individual bird regardless of where they were located within the survey area. This technique is no longer feasible because the population is increasing. Biologists are flying along a transect, straight lines set at specific distances within the survey area. Previously each survey consisted of a single flight; now one survey includes three flights on three separate days (weather permitting) within a preset timeframe. The birds counted represent an estimate of the population within the surveyed area. It is expected that some birds will be not be included in the count, but this method (known as Distance Sampling) is commonly used to determine rare and endangered wildlife populations, including fin whales, Karner blue butterflies, and raptors.”
Aransas officials explain that, “Over the years the whooping crane population has been growing, the habitat changing, and the birds naturally dispersing. The primary goal is to ensure the recovery of the species and to do that the refuge and its partners must adjust with the ever-changing conditions. In 2009, biologists began putting radio telemetry bands on the cranes. Using leg snares, and other trapping techniques, the birds are captured and equipped with GPS leg bands. This technology records birds locations and allows biologists to learn which habitats they are using, where they stop during their migration, and much more. This technology is extremely valuable but it will be several years before sufficient data from the individual birds can be collected and fully analyzed. It will take a considerable more amount of time before the data will reflect patterns of the population as a whole. To date, the refuge and its partners are tracking approximately 30 whooping cranes with leg bands.”
Aransas National Wildlife Refuge reports that a new census technique is being used to estimate whooping crane numbers on the refuge. The estimated number of birds, based on three aerial flights within the survey area is 245. This does not include birds known to be in 5 Texas counties and other states. Recent rain fall has helped lower the salinity levels in area bays where the whooping cranes feed. Click on link to read full report: wc update 2_16_12
Aransas National Wildlife Refuge provides its Whooping Crane Update, February 2, 2012. The report contains current numbers of whooping cranes counted by an aerial survey, habitat conditions on the refuge and rain fall updates.
by Whooping Crane Conservation Association based on Aransas NWR report
Aerial surveys of the whooping crane population wintering on the Aransas National Wildlife Refuge were performed by U.S. Fish and Wildlife Service biologists last week. Refuge biologists have just completed their analysis of the census data and made their findings available. Three aerial surveys were conducted. A survey on January 26th was cut short due to high winds. Surveys conducted on January 27th and 29th were approximately 4 1/2 hours and each systematically searched Matagorda Island, San Jose Island, Blackjack Peninsula, Lamar Peninsula, Dewberry Island, and Welder Flats. Conditions for surveying were most favorable on January 29th, when observers detected 193 whooping cranes. Of the 193 cranes, 125 were white plumage birds, 23 were juvenile birds, and 3 were undistinguished.
The numbers do not represent a complete “census” of birds in the surveyed area, but will provide biologists a means to estimate the whooping crane population size. It is possible that some of the whoopers on the refuge were not detected by the observers. Analysis of these data is ongoing.
At least 16 additional Aransas-Wood Buffalo population of whooping cranes are currently residing outside of the typical wintering area, as far away as Nebraska. Based on the available data, 209 whoopers have been accounted for. The next survey flight will be scheduled for mid-February.
Approximately 5% of whooping cranes detected on the 27th and 29th were found using man-made freshwater sources, such as stock ponds and windmills. Cranes were using both upland and marsh communities. They are naturally supplementing their own food sources by wintering around freshwater lakes.
Refuge personnel continue to help alleviate the low food resources by adding to the prescribed burn totals. This winter the refuge has burned 8,095 acres of habitat that have recorded whooping crane usage. Biologists observed the whooping cranes eating roasted acorns and are seeing continued use. There are still an additional 6,129 acres planned to be burn for the remaining whooping crane season.
Many people have inquired whether the refuge plans to implement a supplemental feeding program for whooping cranes this winter. At this time, refuge officials are concerned about the negative impacts of supplemental feeding. Previous efforts to supplemental feed were not considered successful as only a small portion of the birds actually fed on the shelled corn.
Whooping cranes are territorial and do not naturally gather together to feed. Encouraging them to do so changes their natural behavior; it also creates greater opportunities to transmit diseases, parasites, and makes them more vulnerable to predators. Furthermore, when left out in warm and moist environments, like coastal marsh areas, corn can grow Aspergillis molds. Aflatoxins, which are produced by the molds, can be lethal to whooping cranes and other wildlife. Where whooping cranes may be present, landowners should be aware of the risks that aflatoxins pose. If corn is being be used for feeding other wildlife in areas where whooping cranes may be present, U.S. Fish and Wildlife Service scientists highly recommend purchasing aflatoxin-free corn.
Aransas National Wildlife Refuge has received 0.84 inches of precipitation for the month of January. Central Texas has been fortunate to receive some much needed rainfall recently and the water has raised the Guadalupe River to above flood stage levels from Jan 28th- Jan 31st. This river flows into the San Antonio Bay and the flush of freshwater is expected to further decrease salinity levels. Currently, salinity levels are reported to be 23.2 parts per thousand (ppt) compared to 35.3ppt on December 14, 2011.
January 24th data from Texas Parks and Wildlife Department indicates that samples taken in the San Antonio, East Matagorda, and Espiritu bays were free of red tide. It
is still persisting in some of the surrounding bays but in very low concentrations.
Aransas Refuge officials reported that a second radioed whooping crane chick has died this winter since their last report. The carcass has been sent off for testing and we are awaiting results.