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TOM
STEHN'S WHOOPING CRANE REPORT
Update: July 3, 2009
Tom Stehn, Whooping Crane Coordinator
U.S. Fish and Wildlife Service
Aransas NWR
P.O. Box 100
Austwell, TX 77950
(361) 286-3559 Ext. 221
fax (361) 286-3722
E-mail:
tom_stehn@fws.gov
FOUR WHOOPERS STILL AT ARANSAS
NWR!
Four whooping cranes were seen by experienced staff this
afternoon (May 28, 09) at Aransas NWR along the Intracoastal Canal that runs
through the refuge. The were grouped as a duo, and then about 5 miles away were
two singles separated by 100+ yards. I presume all 4 are subadults.
I have not done a census flight since April 21st , and probably will not do so
until July to see if these 4 decide to spend the summer and whether any others
are still around. These 4 cranes could still migrate, but they also could spend
the summer at Aransas.
Whooping Crane Census Flight
April 21, 2009
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.
PRIOR REPORTS:
SUMMARY: An estimated 21 whooping cranes have
died this winter at Aransas.
The current flock totals 249 whooping cranes.
Whooping Crane Census Flight
March 15, 2009
Whooping Crane Census Flight
April 7, 2009
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.
Migration
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.
Tom Stehn
Aransas National Wildlife Refuge
birdRockport.com
would like to express great appreciation to Tom
Stehn at the
Aransas National
Wildlife Refuge and for his insightful reports.
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