Whooping Crane Census Flight - February 11, 2009
 
The seventh aerial census of the 2008-09 crane season was conducted February 11, 2009 with USFWS observers Tom Stehn and Carey Strobel in a Cessna 210 piloted by Gary Ritchey of Air Transit Solutions of Castroville, Texas.  Weather conditions were good for the census, although winds aloft made surface conditions somewhat choppy.
 
We only found 229 whooping cranes, but time limitations required us to make wider transects in some areas which as expected resulted in overlooking some of the cranes.

Whooping Crane Numbers
 
The estimated peak winter flock size remains at 232 adults + 38 juveniles = 270 total.  Due to mortality that has occurred at Aransas, I estimate the current flock size to be 229 adults + 30 juveniles = 259, but this figure may change depending on future flight observations.

Mortality

Although no single flight is conclusive, I estimate 11 whooping cranes have died this winter (8 chicks and 3 adults).  That is a loss so far of 4.1% of the wintering population (11 out of 270).

The all-time worst winter on record was 1990 when 11 out of 146 (7.5%) whooping cranes died at Aransas.  The winter of 1993 showed a 4.9% loss at Aransas (7 out of 143).  In the last 20 years, the current winter ranks as the third worst in terms of mortality, but we still have two months to go. Two dead whooping cranes have been picked up this winter - both were emaciated.

Signs of the harsh conditions and/or mortality included:

        The North Dunham Bay chick has separated from its parents.

        The Panther Point chick is missing and presumably has died since the last flight 2 weeks ago.

       One adult with one chick was observed for the second straight flight on the south end of Matagorda Island, indicative of the loss of one adult.

        The Mustang Slough chick that separated from its parents in early January is missing and suspected dead.

        The chick of the Pipeline pair is missing and suspected dead.

        The chick of the West Welder pair is missing and suspected dead.

Habitat use
 
Surveys of whooping crane foods and foraging behavior done by Dr. Felipe Chavez-Ramirez the week of February 2nd confirmed the current scarcity of natural foods for the whooping crane.  At present, it takes additional effort for whooping cranes to find blue crabs; some of the cranes are foraging on clams which are much less nutritious.

Management practices are definitely aiding the cranes this winter.  Cranes on the flight included 27 observed at man-made fresh water sources, 36 on burned uplands, 15 on unburned uplands mostly foraging for tubers where feral hogs have rooted up the earth, 23 at game feeders, and 13 in open bay habitat.  Much of the marsh is still notably dry due to recent low wind-driven tides, though tides started to rise over the past week.  Salinities remain high, measured at 30 ppt in the refuge boat canal.

On January 29th, the refuge conducted two more prescribed burns totaling 2,417 acres (Units C10 and C11).  A total of 5 cranes were observed on this burn during the census flight.  The refuge also continued its program of supplemental feeding using corn.  A moderate response by the whooping cranes has been observed with 20 different whooping cranes documented at feeders the first week in February.  Other animals eating the corn include deer, feral hogs, raccoons, grackles and sandhill cranes.

Sightings near Aransas

Three whooping crane subadults continue to use farm fields south of Austwell.  They were seen in a shallow-flooded portion of an agricultural field since the water where they had been roosting is greatly diminished and can no longer provide safe roosting habitat.   The drought shows no sign of ending in central and south Texas.  Many counties have imposed prescribed burn bans due to the fire danger.

By Tom Stehn - Aransas National Wildlife Refuge