ARANSAS NATIONAL WILDLIFE REFUGE

The fifth aerial census of the 2010-11 whooping crane season

Feb 23, 2011 | Aransas National Wildlife Refuge by Tom Stehn | Related Press

The fifth aerial census of the 2010-11 whooping crane season was conducted February 23, 2011 in a Cessna 210 piloted by Gary Ritchey of Air Transit Solutions, Castroville, Texas with USFWS observer Tom Stehn.  Search conditions were difficult with mild turbulence, multiple vultures to dodge, and changing light conditions.  Only portions of the crane range were covered in the 3-hour flight since morning fog prevented us from doing a complete census.

Sighted on the flight were 126 adults and 28 juveniles = 154 total whooping cranes.
Adults + Young
San Jose   19 +   4  =   23*
Refuge  79 + 14  =    93
Lamar  11 +   4  =   15
Matagorda       not flown
Welder Flats   17 +   6  =   23*
Total 126 + 28  =  154
*  Incomplete coverage.

Observations on today’s flight confirmed the loss of two whooping cranes sometime after the December 9th flight.  Two groups of 1 adult with 1 chick were observed for the second flight in a row, indicating the loss of one adult from the refuge and one adult from Welder Flats.  There were no other cranes around either of these groupings for the missing adults to have been nearby.  There is also a possibility that the East Spalding Lake pair on San Jose Island has lost their chick (not seen 2 flights in a row), but it is also possible the whole family has moved to a different part of the wintering area.

The two missing adults were not present when the flock size of 281 was derived on our February flight.  Thus, the peak size of the Aransas flock this winter was 283.  With this mortality, the current flock size is estimated at 281.

Crane habitat use observed on the census flight (n=154):
81 of the cranes observed were in salt marsh habitat
22 were on prescribed burns
41 were in shallow open bay habitat
4 were on uplands areas
3 were at fresh water sources
0 were at game feeders

The continuing heavy use of prescribed burns and open bay habitat is notable, although cranes are finding low numbers of blue crabs in the marsh.  Low tides are continuing with over 60% of San Jose Island consisting of dry mudflats.  The prescribed burning of upland Unit C12 on the southwest side of the refuge has changed the distribution of the refuge cranes a bit, with 9 cranes observed on that burn and 14 cranes adjacent to the burn in St. Charles Bay.

Burn Location Unit Number # of Cranes Observed
Matagorda Island       G1                             0
Matagorda Island       G4                             0*
*  7 cranes seen on the burn by refuge staff prior to the flight
Aransas Refuge         C4/C5                        3
Aransas Refuge         C8/C9                       10
Aransas Refuge         C12                             9

Tom Stehn, Aransas National Wildlife Refuge

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