Whooping Cranes had bad year
""Whooping Crane Census Flight
March 15, 2009
The ninth aerial census of the 2008-09 crane season at Aransas was
conducted March 15, 2009 with USFWS observer Tom Stehn in a Cessna 210
piloted by Gary Ritchey of Air Transit Solutions of Castroville,
Texas. ......
Whooping Crane Numbers
With estimated losses that has occurred at Aransas this winter, the current
flock size is estimated at 226 adults + 23 juveniles = 249. The estimated
peak winter flock size was 232 adults + 38 juveniles = 270 total.
Mortality
Today's flight provided evidence of 3 additional mortalities, with total
winter mortality now estimated for the winter at 6 adults and 15 chicks
totaling 21 whooping cranes, a loss of 7.8% 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 (21
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, 55 whooping cranes
have died in the last 12 months, or 20.7% of the flock of 266 present at
Aransas in the spring, 2008.
Four dead whooping cranes have been picked up this winter; at least two
were emaciated, and the virus IBD (infectious bursal disease) has been
isolated from one of the juveniles by Dr. Hon Ip at the National Wildlife
Health Center in Madison, Wisconsin. It is not yet known if this strain of
IBD is pathogenic to whooping cranes, but it seems probable. The 4th
carcass discovered this winter was an old pile of white-plumaged feathers
discovered March 2nd during a blue crab count conducted by volunteer
Katherine Cullen and two Chinese biologists. The two Chinese that have
cranes on their refuges in China expertly identified the feathers. On
today's flight, observations confirmed that one additional adult is
missing, leaving a one-adult family just south of Panther Point on
Matagorda. Also, the refuge's Pipeline and Matagorda's Airport juveniles
are missing and listed as dead. These last 3 mortalities had presumably
all occurred prior to the February 25th flight, with observations on
today's flight confirming the losses.
Migration
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. It was still
present on the Platte through March 9 and presumably is still there.
I have been asked how the current poor conditions of the cranes may affect
the migration. I have no idea how that may affect the timing of the
migration which seems to vary by only about one week from year to
year. Low numbers of whooping cranes start leaving Aransas the last week
in March, with the majority of the cranes departing the first 2 weeks in
April. The last of the breeding pairs have all gone by April 21st; a few
subadults occasionally stay into May. I expect the migration to proceed
normally, with birds making it all the way to Wood Buffalo National Park in
Canada. However, mortality in the migration could increase. My next
census flight is scheduled for the week of April 6th to see how the
migration is progressing.
.......
Habitat use
Management practices are aiding the cranes this winter. Crane locations on
the flight included 7 observed at man-made fresh water sources, 17 on
burned uplands, 33 on unburned uplands mostly foraging for tubers where
feral hogs have rooted up the earth, 4 at game feeders, 1 on a well pad,
and 23 in open bay habitat. Two cranes were on a recent burn on Matagorda
Island conducted March 10th. Tides have risen somewhat since the previous
flight on February 25th. Salinities remain high, measured recently 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. However, rain received in
south Texas on March 14-15 has helped a little.
Blue crabs are still scarce due to the drought. These are the worst
conditions I have ever observed for the cranes at Aransas, with some birds
looking thin and with disheveled plumage. I wish I had better news to
report. The refuge is continuing its program of supplemental feeding with
corn. A moderate response by the whooping cranes has been observed with 76
photographs taken by remote motion-activated cameras in the past week of
whooping cranes at refuge feeders. ....
......
By Tom Stehn - Aransas National Wildlife Refuge
Tom Stehn, Whooping Crane Coordinator
U.S. Fish and Wildlife Service
Aransas NWR" (read full report at http://www.birdrockport.com/tom_stehn_whooping_crane_report.htm )
March 15, 2009
The ninth aerial census of the 2008-09 crane season at Aransas was
conducted March 15, 2009 with USFWS observer Tom Stehn in a Cessna 210
piloted by Gary Ritchey of Air Transit Solutions of Castroville,
Texas. ......
Whooping Crane Numbers
With estimated losses that has occurred at Aransas this winter, the current
flock size is estimated at 226 adults + 23 juveniles = 249. The estimated
peak winter flock size was 232 adults + 38 juveniles = 270 total.
Mortality
Today's flight provided evidence of 3 additional mortalities, with total
winter mortality now estimated for the winter at 6 adults and 15 chicks
totaling 21 whooping cranes, a loss of 7.8% 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 (21
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, 55 whooping cranes
have died in the last 12 months, or 20.7% of the flock of 266 present at
Aransas in the spring, 2008.
Four dead whooping cranes have been picked up this winter; at least two
were emaciated, and the virus IBD (infectious bursal disease) has been
isolated from one of the juveniles by Dr. Hon Ip at the National Wildlife
Health Center in Madison, Wisconsin. It is not yet known if this strain of
IBD is pathogenic to whooping cranes, but it seems probable. The 4th
carcass discovered this winter was an old pile of white-plumaged feathers
discovered March 2nd during a blue crab count conducted by volunteer
Katherine Cullen and two Chinese biologists. The two Chinese that have
cranes on their refuges in China expertly identified the feathers. On
today's flight, observations confirmed that one additional adult is
missing, leaving a one-adult family just south of Panther Point on
Matagorda. Also, the refuge's Pipeline and Matagorda's Airport juveniles
are missing and listed as dead. These last 3 mortalities had presumably
all occurred prior to the February 25th flight, with observations on
today's flight confirming the losses.
Migration
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. It was still
present on the Platte through March 9 and presumably is still there.
I have been asked how the current poor conditions of the cranes may affect
the migration. I have no idea how that may affect the timing of the
migration which seems to vary by only about one week from year to
year. Low numbers of whooping cranes start leaving Aransas the last week
in March, with the majority of the cranes departing the first 2 weeks in
April. The last of the breeding pairs have all gone by April 21st; a few
subadults occasionally stay into May. I expect the migration to proceed
normally, with birds making it all the way to Wood Buffalo National Park in
Canada. However, mortality in the migration could increase. My next
census flight is scheduled for the week of April 6th to see how the
migration is progressing.
.......
Habitat use
Management practices are aiding the cranes this winter. Crane locations on
the flight included 7 observed at man-made fresh water sources, 17 on
burned uplands, 33 on unburned uplands mostly foraging for tubers where
feral hogs have rooted up the earth, 4 at game feeders, 1 on a well pad,
and 23 in open bay habitat. Two cranes were on a recent burn on Matagorda
Island conducted March 10th. Tides have risen somewhat since the previous
flight on February 25th. Salinities remain high, measured recently 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. However, rain received in
south Texas on March 14-15 has helped a little.
Blue crabs are still scarce due to the drought. These are the worst
conditions I have ever observed for the cranes at Aransas, with some birds
looking thin and with disheveled plumage. I wish I had better news to
report. The refuge is continuing its program of supplemental feeding with
corn. A moderate response by the whooping cranes has been observed with 76
photographs taken by remote motion-activated cameras in the past week of
whooping cranes at refuge feeders. ....
......
By Tom Stehn - Aransas National Wildlife Refuge
Tom Stehn, Whooping Crane Coordinator
U.S. Fish and Wildlife Service
Aransas NWR" (read full report at http://www.birdrockport.com/tom_stehn_whooping_crane_report.htm )
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