Aransas: December 9th, 2010
Tom Stehn, Aransas National Wildlife Refuge reports: “The second aerial census of the 2010-11 whooping crane season was conducted December 9, 2010 in a Cessna 210 piloted by Gary Ritchey of Air Transit Solutions, Castroville, Texas with USFWS observers Tom Stehn and Brad Strobel.”
Sighted on the flight were 223 adults and 45 juveniles = 268 total whooping cranes.
|Adults + Young|
|San Jose||52 + 11 = 63|
|Refuge||62 + 10 = 72|
|Lamar||15 + 4 = 19|
|Matagorda||68 + 14 = 82|
|Welder Flats||26 + 6 = 32|
|123 + 45 = 268|
This was an increase of 31 cranes since the previous flight conducted December 1st. Flight conditions and visibility were excellent throughout the flight. A low pressure system that had brought howling north winds on December 8th had moved off the coast, followed by clear skies and moderate southeast winds. With nearly complete flight coverage of the crane area, the 268 cranes counted represents an accurate estimate of the number of cranes present.
One additional whooping crane is known present near Cherokee in northern Oklahoma. Thus, flock size is at least 269. Although there have been no additional recent migration reports, as many as 15-20 more whooping cranes are hoped to still be in migration. Recent reports of whooping cranes at Aransas possibly not located on today’s flight include a group of 9 seen flying over the refuge’s back gate road on December 7, and a single that was observed roosting at Heron Flats Marsh on December 1 and 6 and followed sandhills to forage on pasture land and/or farm fields north of the refuge.
To date, 45 of the 46 juveniles found in mid-August on the nesting grounds have made it safely to Aransas. The 45 chicks at Aransas include five sets of “twin” chicks, (adult pairs that have brought two chicks each). Five pairs with two chicks each had been sighted in Canada in August. This is the second highest total of “twin” families at Aransas, exceeded only by the 7 sets of “twins” present at Aransas in the 2006 winter. The two new twin families found on today’s flight were located on Matagorda Island and Welder Flats.
Crane habitat use observed on the census flight:
- 209 of the 268 cranes observed were in salt marsh habitat.
- 10 were in shallow open bay habitat.
- 8 were on uplands in areas rooted up by feral hogs on Matagorda Island.
- 26 were on uplands with no sign of hog rooting.
- 4 were at a game feeder at Welder Flats.
- 11 were at fresh water sources.
Habitat use by the whooping cranes has changed some over the past week. A total of 78.0% of the cranes were in salt marsh, whereas the previous week it had been 89.0%. Upland use observed totaled 34 cranes compared to eight last week, and freshwater use is starting to occur (11 cranes compared to zero last week). The salinity at a gauge in San Antonio Bay north of Mustang Lake is currently 14.5 parts per thousand (ppt). Refuge salinities measured on December 6 ranged from 17 to 20 ppt, levels where crane use of fresh water sources starts to be observed. Blue crabs are still readily available, with 101 crabs counted on a 1,000 meter transect on December 6. However, the wolfberry crop is nearing an end with only 7 berries and no flowers observed on transects run on December 6. Tides were also considerably lower this week with exposed mud flats observed on San Jose. A string of about 100 commercial blue crab traps were noted in the bay edge off of Matagorda Island between Twin lakes and Power Lake.
Tom Stehn, Aransas National Wildlife Refuge
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