Whoopers Doing Well at Aransas

The sixth aerial census of the 2009-10 whooping crane season was conducted February 16, 2010 in a Cessna 210 piloted by Gary Ritchey of Air Transit Solutions of Castroville, Texas with USFWS observer Tom Stehn. Sighted on the flight were 237 adults and 19 juveniles = 256 total whooping cranes. No evidence of mortality was noted on the flight other than the one juvenile that had died earlier in the winter. The radioed family on Lamar Peninsula was overlooked on the flight, but GPS data indicates it was on Lamar before and after the census flight. Since it has not been documented leaving Lamar since being tagged in December, it is considered very unlikely that they had moved over to San Jose to account for the extra family found there during the census. The flight provided a firm tally of the 20 family groups currently at Aransas. With one juvenile last seen in Oklahoma December 25th that apparently separated from its parents during migration and is presumably okay and wintering in an unknown location, and the S. Sundown Island chick that has died at Aransas, this accounts for 22 of the 22 juveniles found in Canada during the mid-August fledging surveys. This is one more juvenile accounted for than on previous survey flights this winter. With the one documented mortality this winter, the current flock size is estimated at 242 + 21=263.

February 16th – Recap of whooping cranes (256) found at Aransas:


* One family group was overlooked.
** Ties record high for Matagorda Island set during the 2008-09 winter.

The territories of adult cranes remain difficult to figure out as many of the crane pairs have left their marsh and are searching for food on the uplands. Upland areas on the barrier islands are flooded, with numerous wet swales on the uplands up to the beach dunes. Three cranes on Matagorda Island were in one of these flooded swales next to the dunes. Overall habitat use documented included an unusually high 67 cranes (26%) on unburned uplands, 16 in open bays, two at a game feeder south of the Big Tree on Lamar, 0 on prescribed burns, and 171 (67%) in salt marsh. Blue crabs are at low levels and the cranes are having to look for other sources of food, although some cranes continue to catch a few crabs. This is a stressful time of winter for the whooping cranes as evidenced by all the cranes on uplands.

No whooping cranes have been reported up the coast at Smith Marsh in Matagorda County located west of the Nature Conservancy’s Mad Island Marsh Preserve since 1/17/10. Two whooping cranes are continuing to winter northwest of Austwell on the Guadalupe Delta Wildlife Management Area managed by the Texas Parks and Wildlife Department.

I noted one thing on the flight that I had never observed previously. Twenty sandhill cranes on the southern end of the crane range on San Jose Island flushed from the census aircraft and flew a very short distance to stand in open bay habitat. I had never seen sandhill cranes before in open bay habitat.

Flight Conditions: Visibility was excellent throughout the flight, though the sun angle on late afternoon transects made for difficult viewing conditions when heading into the sun at Welder Flats. Winds were light and flight conditions were smooth until mid-afternoon, enabling us to travel at approximately 130 knots for most of the flight. Due to reported crane movements, the search area was expanded further out into upland areas. This paid off, as cranes were found near the beach dunes on Matagorda Island, inland in a pasture at Welder Flats and on Aransas National Wildlife Refuge uplands. The largest group size observed was 9 birds seen on the uplands on San Jose and in the marsh on Matagorda Island.

Post-Flight Update
Food availability improved for the cranes during the last week in February with more cranes observed feeding on 2-3-inch blue crabs. Upland swales remain very wet and bay salinities remain moderate < 10 ppt.

Spring Migration, 2010
A single white-plumaged whooping crane was confirmed present at Salt Plains NWR in northern Oklahoma on February 24th and 26th. Since we did not know of any other white-plumaged whooping cranes in the Flyway this winter, this must be a case of a whooper on the Texas coast getting influenced by sandhill cranes and starting the journey ahead of the normal time for whooping cranes. Except for birds that had a history of separating from their parents as juveniles, I think it would be the earliest migration start on record.

– Tom Stehn, Aransas National Wildlife Refuge