Whooping Crane Conservation Association

The eleventh aerial census of the 2008-09 crane season at Aransas was conducted April 21, 2009 with USFWS observer Tom Stehn in a Cessna 210 piloted by Gary Ritchey of Air Transit Solutions of Castroville, Texas. Viewing conditions were ideal with clear skies and moderate winds. Nearly all parts of the crane range were flown.

Migration
Today’s flight tallied 20 adults plus 1 juvenile = 21 total. BLACKJACK! Thirteen of the cranes were located on the BLACKJACK Peninsula (Aransas NWR), 6 were on Matagorda Island, and 2 at Welder Flats. Thus, 91.5% of the flock has started the migration (226 birds out of 247), including all known adult pairs. Eighty-eight cranes have started the migration since the last flight on April 7th when 109 cranes were estimated present. Whooping cranes in migration have recently been reported as far north as Saskatchewan. Some cranes not tallied above presumably headed north today since conditions were very good for migration with sunny skies and mostly southwest and south winds after several days of unfavorable migration weather.

Eight of the 21 cranes located on today’s flight were singles. The one juvenile present was closely associated in a group with 3 white-plumaged cranes, the largest group observed on today’s flight. The juvenile’s parents have presumably started the migration and left “junior” behind. This juvenile crane will be fine and has the knowledge to make the return migration to Wood Buffalo National Park on its own or with other subadult cranes.

Whooping Crane Numbers
With estimated losses that have occurred at Aransas this winter, the current flock size is estimated at 225 adults + 22 juveniles = 247. The estimated peak winter flock size was 232 adults + 38 juveniles = 270 total.

Habitat use
For the first time all winter, all the whooping cranes on today’s flight were found in salt marsh. The cranes are believed to be feeding on fiddler crabs since blue crabs in the marsh ponds are still scarce due to the continuing drought. A blue crab count done on April 1st found zero crabs in the marsh. The refuge has discontinued its program of supplemental feeding with corn since most of the cranes have migrated.

A lightning-caused wildfire that started April 18th on Matagorda Island burned approximately 10,000+ acres of upland prairie lands. The fire, located between Pringle Lake and Power Lake, was contained on April 20th and allowed to burn out. The burn will benefit the prairie habitat by recycling nutrients and controlling brush.
– By Tom Stehn – Aransas National Wildlife Refuge

Marty Folk, Florida Fish and Wildlife Conservation Commission reports that “One whooping crane chick hatched from the nest described in my first update. Today the chick is 24 days old. A second nest was initiated in Lake County on 4 March. This 2nd nest was incubated longer than necessary (something that never happens in Wisconsin!) and on Friday we collected 2 non-viable eggs for necropsy. We video-taped both nests this year with surveillance equipment that recorded the activity at the nest during all daylight hours. We will be analyzing this pool of video, along with other footage previously recorded through the years, to determine if incubation behavior by the birds may have been associated with nest success.”

Marty advises, “We’ve not witnessed any other nesting activity this spring. Because of drought, there is little suitable habitat available.Beginning in March we began intensively monitoring the flock in order to collect more data to help us understand what happens to the birds when they go missing. In March, 3 field people drove 9660 miles, flew 28.6 hours, and spent long days monitoring the flock. So far we’ve recovered no dead birds (we need birds to die so we can find them and necropsy them). What we have documented is substantial movements by much of the flock. Some birds have dispersed beyond where we could find them (beyond the central FL peninsula), only to return later. Several are still missing. Dispersal is a suspected reason why birds have “disappeared” in the past. So even if we don’t document mortality with our intensive monitoring, we are documenting this extreme rate of movements/dispersal. We suspect the birds are moving in response to drought, perhaps looking for wetter/greener pastures.”

Since the beginning of the year one pair has been bouncing between 4 points in north and central Florida (see attached figure). The minimum distance traveled by the whoopers this past quarter was 470 miles. This much traveling of course increases the odds of travel-related mortality such as collisions with power lines, etc.

Marty stated, “We continue to monitor 4 migratory whoopers in Polk County and the 1 on Paynes Prairie near Gainesville. We will keep you posted.”

The tenth aerial census of the 2008-09 crane season at Aransas was conducted April 7, 2009 with USFWS observer Tom Stehn in a Cessna 210 piloted by Gary Ritchey of Air Transit Solutions of Castroville, Texas. Viewing conditions were ideal with clear skies and light winds, although turbulence made the ride uncomfortable most of the time. Nearly all parts of the crane range were flown.

Migraton
Today’s flight tallied 103 adults + 6 juveniles = 109 total. Thus, 56% of the flock has started the migration. Whooping cranes have been confirmed on April 2nd as far north as Nebraska. I expect a considerable number of cranes will start the migration in the next week. Conditions should be ideal for departure with very strong southeast winds forecast for Aransas April 8-9.

Whooping Crane Numbers
With estimated losses that have occurred at Aransas this winter, the current flock size is estimated at 225 adults + 22 juveniles = 247. The estimated peak winter flock size was 232 adults + 38 juveniles = 270 total.

Mortality
Today’s flight provided evidence of 2 additional mortalities, with total winter mortality now estimated for the winter at 7 adults and 16 chicks totaling 23 whooping cranes, a loss of 8.5% of the flock that was a record 270 in the fall. In the last 20 years, the current winter ranks as the worst in terms of mortality, ahead of 1990 when 7.5% of the whooping cranes (11 out of 146) died at Aransas. The 3rd worst winter in 1993 showed a 4.9% loss at Aransas (7 out of 143). Mortality in the 2008-09 winter (23 birds) can be added to the 34 whooping cranes that left Aransas in the spring of 2008 and failed to return in the fall. Thus, 57 whooping cranes have died in the last 12 months, or 21.4% of the flock of 266 present at Aransas in the spring, 2008.

The 2 additional mortalities confirmed on today’s flight that had been reported earlier by volunteers and staff are as follows:

Tour Boat Naturalist Ray Kirkwood had seen March 19-29 the Rattlesnake Island juvenile with a very bad limp, using its wings when it moved to try to reduce the weight put on its injured leg. The bird retained flight ability but was lethargic and may have stopped eating. The chick was not observed on April 1st when I looked for it from a boat and had presumably died. The pair believed to be its parents was observed on their territory on today’s flight with no sign of the juvenile.

The second mortality involved a grouping of 1 adult with 1 chick observed twice about 4 hours apart on April 1st in the marsh west of the airstrip on the south end of Matagorda Island. This same grouping of 1+1 was observed on their East Bray territory on today’s flight, providing confirmation that one adult has died.

Sightings near Aransas
Three whooping crane subadults that used the farm fields south of Austwell for much of the winter were last reported present on March 14th. They have either returned to the salt marsh or have started the migration.

Habitat use
For the first time all winter, nearly all the whooping cranes were found in the salt marsh on today’s flight. The cranes are believed to be feeding on fiddler crabs since blue crabs in the marsh ponds are still scarce due to the continuing drought. A blue crab count done on April 1st found zero crabs in the marsh.

Whooping crane locations on the flight included 2 observed at man-made fresh water sources, 2 at a game feeder, and 9 in open bay habitat. No cranes were on burned or unburned uplands. Tides were low caused by a very strong “norther” that had brought northwest winds on April 6th. Salinities remain high, measured recently at 29 ppt in the refuge boat canal and 39 in the adjacent marsh. One monitoring station in San Antonio Bay has a salinity of 25 ppt. 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. Corpus Christi, Texas is 4.5 inches below normal rainfall starting January 1st.

Overall, these continue to be some of the worst conditions I have ever observed for the cranes at Aransas, with some birds looking thin and with disheveled plumage. The refuge is continuing its program of supplemental feeding with corn. A moderate response by the whooping cranes has continued. The cranes are getting somewhat of an energy boost by catching fiddler crabs just prior to migration.
– By Tom Stehn – Aransas National Wildlife Refuge