Juvenile at Feeding Station
most recent aerial Whooping Crane Census flight census took place
on March 15th. Just short of 4 hours,
we stopped the flight due to overcast skies and light rain, leaving
parts of the crane range not flown. The estimated
peak number of Whooping cranes in the 2009 winter flock was 270
38 juveniles). This flight provided evidence of 3 more
mortalities since my last census. An
estimated 21 whooping cranes have died this winter at Aransas.
The current flock totals 249 Whooping cranes (226 adults and 23
juveniles). This brings
the total winter mortality to
an estimated 21 birds: 6 adults and 15 chicks, or a loss of 7.8%
of last fall’s record sized flock of 270.
Worst Winter for Crane Losses
Out of the last 20 years, the current winter ranks as the worst
in terms of mortality. It's more than in 1990 when 7.5% of
the Whooping cranes (11 out of 146) died at Aransas. The 21
deaths this winter 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
in the last 12 months, or 20.7% of the flock of 266 present
at Aransas in the spring, 2008.
Problems With the Food Supply
Blue crabs are still scarce due to
the record-setting 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. Meanwhile,
the refuge is continuing supplemental feeding with
Remote motion-activated cameras let us monitor how many cranes
are feeding at all refuge feeders.
feeding has its pros and cons. See what you think. We are
carefully monitoring as many of the "cons" as we can,
in places with minimal risk of predation, making sure cranes continue to eat
natural foods, making sure aggressive interactions aren't occurring,
making sure the corn stays dry, moving the feeders as needed
to prevent diseases from building up in the soil. So far we don't
see much in the way of negative aspects of providing supplemental
food. However, only a limited
number of cranes are using the feeders, and we currently are not measuring how
much corn the cranes may be eating, making it hard to measure the impact of the
Will Migration Be Affected?
I have no idea how the poor habitat conditions due to the record-setting drought
may affect the timing of the migration, which seems to vary by only about one
cranes start leaving Aransas the last week in March, with the majority of the
cranes departing the first two weeks in April. The last of the breeding pairs
are usually all gone by April 21st, while a few sub-adults occasionally stay
into May. One juvenile Whooping crane was confirmed on the Platte River in
Nebraska on February 20th. We think this is the juvenile that over-wintered
in Oklahoma and likely moved north to the Platte with Sandhill cranes.
My next census flight is scheduled for the week of
April 6th. I should have some good migration news to report!
Aransas National Wildlife Refuge