Sunday, March 22, 2009

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.


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.


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 )

Birds buffer against virus


North American scientists studying West Nile virus have shown that more diverse
bird populations can help to buffer people against infection. Since the virus
first spread to North America it has reached epidemic proportions and claimed
over 1,100 human lives. “This is an important example of the links between
biodiversity and human health”, commented Dr Stuart Butchart, BirdLife's
Global Research and Indicators Coordinator.

Biodiversity is increasingly being recognised as socially and economically
important because of the valuable services it provides. The authors of this
latest research - John Swaddle and Stavros Calos - highlighted the
“increasing evidence for economically valuable ecosystem services provided by
biodiversity”. "


"Scientists studying the virus looked at US counties east of the Mississippi River and compared their avian diversity with the number of human cases. They found that high bird diversity was linked with low incidence of the virus in humans. They reported that about half of the human incidences of West Nile virus could be explained by the differences in local bird populations. The study’s results also suggest that bird communities lowered human case numbers even when the epidemic was underway.

The way in which biodiversity and disease rates are linked has been dubbed the ‘dilution effect’. Although the exact mechanisms aren’t currently clear, scientists believe that increased diversity within an ecosystem reduces - or dilutes - the proportion of suitable hosts for a disease, and therefore reduces transmission rates. It has previously been studied through another infection, Lyme disease, but this new research suggests that it may be more widely applicable. If so, it could be a valuable tool for public health and safety plans" Read the full article. SeEtta