Tom Stehn, USFWS biologist, Aransas National Wildlife Refuge and assocates recently completed another census of whooping cranes at Aransas. Stehn reports that, “The eighth aerial census of the 2008-09 crane season at Aransas was conducted February 24-25, 2009 with USFWS observer Tom Stehn in a Cessna 210 piloted by Gary Ritchey of Air Transit Solutions of Castroville, Texas. Viewing conditions were very good for the survey, although strong winds made for a very choppy ride.”
Stehn advised that, “We found 238 whooping cranes, but time limitations required us to fly at
greater speeds making it likely a few whooping cranes were overlooked. Strong tail winds and full power gave us at one point a maximum recorded speed of 198 mph on our GPS.”
Whooping Crane Numbers
The estimated peak winter flock size remains at 232 adults + 38 juveniles = 270 total. However, the last two census flights have documented additional mortality that has occurred at Aransas. I estimate the current flock size to be 228 adults + 25 juveniles = 253, but this figure may change depending on future observations.
Mortality this winter is currently estimated at 4 adults/subadults and 13 juveniles totaling 17 whooping cranes. This is a loss so far of 6.3% of the wintering population (17 out of 270). The all-time worst winter on record was 1990 when 11 out of 146 (7.5%) whooping cranes died at Aransas. In the last 20 years, the current winter ranks as the second worst in terms of mortality, but we still have one month to go. The 3rd worst winter in 1993 showed a 4.9% loss at Aransas (7 out of 143). Mortality in the 2008-09 winter (17 birds) must be added to the 34 whooping cranes that left Aransas in the spring of 2008 and failed to return in the fall. Thus, 51 whooping cranes have died in the last 12 months, or 19.2% of the flock of 266 present at Aransas in the spring, 2008.
Three dead whooping cranes have been picked up this winter; two were emaciated. The wing from a juvenile whooping crane was picked up by refuge staff in the North Pt. Pasture on February 13th. The remainder of the carcass was in the mouth of an alligator at a freshwater dugout. This chick from the North Dunham Point family had separated from its parents as observed by staff on January 29th and February 11th. It presumably was sick and/or emaciated, a factor that contributed to its separation and made the juvenile vulnerable to predation.
One juvenile whooping crane was confirmed on the Platte River in Nebraska on February 20th. This is presumably the juvenile that had over-wintered in Oklahoma and probably moved north with sandhill cranes.
Sightings near Aransas
Three whooping crane subadults continue to use farm fields south of Austwell. They were seen in a pond next to an agricultural field.
Management practices are aiding the cranes this winter. Cranes on the flight included 28 observed at man-made fresh water sources, 9 on burned uplands, 13 on unburned uplands mostly foraging for tubers where feral hogs have rooted up the earth, 18 at game feeders, 1 on a shell road, and 20 in open bay habitat. Some water is starting to move back into the coastal salt marshes, although much of San Jose Island remained as dry tidal flats. Salinities remain high, measured at 30 ppt in the refuge boat canal. The drought rated as “exceptional” shows no sign of ending in central and south Texas. Many counties have imposed prescribed burn bans due to the fire danger.
Blue crabs are still scarce due to the drought. The refuge is continuing its program of supplemental feeding using corn. A moderate response by the whooping cranes has been observed with 100 photographs taken by remote motion-activated cameras in the past week of whooping cranes at refuge feeders. Other animals eating the corn include feral hogs, deer, raccoons, grackles and sandhill cranes.
The USFWS used up to 2 airboats the week of February 23rd to pick up abandoned crab traps in the crane area. This was done in conjunction with a program organized by Texas Parks and Wildlife Department to pick up traps all along the Texas coast. Volunteers running private boats picked up many traps on February 21st.