January 8, 2009
Whooping Crane Census Flight - January 8, 2009The fifth aerial census of the 2008-09 crane season was conducted January 8, 2009 in a Cessna 210 piloted by Gary Ritchey of Air Transit Solutions of Castroville, Texas with USFWS observers Tom Stehn and Felipe Prieto. Weather conditions were excellent for the census. However, a complete census was not conducted due to smoke from a prescribed burn on San Jose Island and limitations on allowable flight time.Whooping Crane NumbersThe estimated peak flock size remains at 232 adults + 38 juveniles = 270 total. One subadult crane has died at Aransas, and the South Sundown Island juvenile has been missing on two consecutive flights and is considered dead, leaving the flock at an estimated 268. With every crane sighted on the flight plus 33 cranes known to be wintering in a part of San Jose Island not flown, we tallied 267 cranes. However, eight cranes may have been counted twice due to movements. Numerous crane movements to upland areas and water holes made it very difficult to determine exact numbers. Future flights will continue to attempt to pin down the exact number of family groups wintering on Matagorda Island.Sightings near AransasWhooping cranes are showing up in unusual places presumably related to food shortages and the need to seek fresh water to drink. On today's flight, 2 adults were in a former fish farm impoundment on the Bauer property south of Austwell along FM 774. The subadult and juvenile seen at that location on the December 29th flight were not located on today's flight and presumably were overlooked, but could possibly have been on Lamar in a group of 14 cranes. However, tourists reported the juvenile again in the farm fields on Jan. 10th.Habitat useWith food shortages continuing in the salt marsh, crane use of uplands as well as a notable shift to open bay habitat has cranes staying off their territories. This makes it very difficult to determine the identity of pairs and family groups and leads to much uncertainty during the census count. Cranes on the flight included 27 observed at fresh water sources, 6 on burned uplands, 25 on unburned uplands including shell roads, and 79 in open bay habitat. On the flight, 6 whooping cranes were next to wild game feeders on the Lamar Peninsula. Food sources for whooping cranes continue to be very low this winter, primarily due to the summer drought. Although the Tour Boat Captains occasionally see cranes catching a crab, many of the birds have switched to eating razor clams in open bay habitat. The increased amount of crane use in open bay habitat on the flight (n=79) is indicative of the food stress the population is facing. Twenty-one of the 79 were foraging along the edges of the Gulf Intracoastal Waterway. On last week's flight, 24 were in open bay habitat. Although the whooping cranes will fill up on clams, previous research shows they are actually using up fat reserves when feeding on a food so low in protein.
Items of interestOn December 29th, Aransas staff sighted a solitary whooping crane juvenile at the refuge boat ramp. This single juvenile was photographed by tourists on the V3 burn on 1-31-08. It has continued to feed daily along the edge of the paved road as well as on the V3 burn and in the upper end of Redfish Slough. It is not afraid of cars and people can drive to within 15 yards of it. However, it is alert and flies normally. This is not the solitary juvenile that has been in the farm fields south of Austwell. It is also not the lone juvenile seen in migration in Nebraska since that juvenile would not know how to find Aransas. On the census flight, the Mustang Slough family was confirmed for the second flight in a row without their chick. One possibility is that the lone juvenile utilizing the refuge tour loop is the Mustang Slough juvenile.
On December 31st, a family group of 2 adults and 2 chicks was photographed on the refuge tour loop by a visitor. I have no explanation or confirmation of this potential second twin family at Aransas this winter. This grouping was not located on today's census flight. Did it arrive from migration in late December? If so, where was it on January 8th? Was it a twin family, or had the solitary juvenile on the refuge tour loop temporarily joined up with a family group?The search area has been expanded this winter since the cranes are showing up in unusual places. A group of 12 adults and 2 juveniles was sighted in the interior of the Lamar Peninsula in a location I have never flown over before. The group was in a large clearing near a waterhole and windmill west of the Big Tree Marsh. This sighting put 4 chicks on the Lamar Peninsula instead of the usual distribution of 3. Where had this extra family come from? Could it be connected with the solitary juvenile that has been in the farm fields north of Aransas, or somehow related to the twin family group sighted January 31st? The total of 20 cranes observed on the Lamar peninsula set an all-time record.
Tom Stehn, Whooping Crane Coordinator
U.S. Fish and Wildlife Service
P.O. Box 100
Austwell, TX 77950
(361) 286-3559 Ext. 221
fax (361) 286-3722