The fourth aerial census of the 2009-10 whooping crane season was conducted January 5, 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 244 adults and 19 juveniles = 263 total. This was an increase of 19 cranes since the previous flight conducted December 10th when some birds had still been in migration and 244 cranes were accounted for. One additional juvenile separated from its parents was sighted near Medford, Oklahoma December 14-25 which brings the current estimated flock size to 264. In addition, the South Sundown Island chick known to be at Aransas was not found on today’s flight, so one chick can be added to the peak flock size for the 2009-10 winter (244+21=265). It is not known if the entire South Sundown Island family group was overlooked on today’s flight, or possibly the chick has died and its parents were sighted off of their territory but not identified as such during the flight.
January 5th – Recap of whooping cranes (264) found at Aransas and Oklahoma:
[TABLE=6]
*The presence of one chick last seen in Oklahoma makes the current estimated flock size 264, including 20 chicks.
The discovery of 19 additional cranes is really good news. If cranes moved around during the flight, I am concerned that perhaps this tally is artificially high by a few birds due to double counting them. Future census flights will attempt to pin this down. The current estimated flock size of 264 is surprisingly high but indicates that survival between spring and fall, 2009 was excellent. The 21 wintering chicks that successfully migrated out of the 22 fledged in Canada added to the estimated flock size of 247 in spring, 2009 meant that a maximum of 268 cranes could have arrived at Aransas this fall. One crane seen injured in Saskatchewan in the fall migration is believed to have perished. The fact that we are accounting for 265 out of the potential 267 is excellent news.
Migration Update: The solitary whooping crane near Medford, Oklahoma was last seen Christmas Day. It apparently has moved further south. Four cranes in the second week in December west of Mad Island Preserve in Matagorda County Texas about 40 miles northeast of Aransas have moved on and presumably were seen on today’s census flight. Two cranes that have been staying east of Tivoli about 15 miles north of Aransas were re-located on today’s flight in the Hynes Bay Unit of the Guadalupe Delta Wildlife Management Area operated by Texas Parks and Wildlife.
Habitat Use and Food Resources: Tides have lowered somewhat with about 30% of the mud flats dry on San Jose Island. However, few observations have been made this winter of cranes feeding in open bay habitat, and only 6 cranes were in open bay habitat on today’s flight. Salinities in San Antonio Bay are currently 14 parts per thousand, low enough that the cranes are drinking directly from the salt marsh. On today’s flight, 65 cranes were located in unburned uplands, 10 were on refuge prescribed burns, 12 were at feeders on private lands, and 2 were on shell roads. The presence of so many cranes in the uplands and cranes traveling longer distances than usual into uplands is indicative of food scarcity. A crab count conducted December 18th found only 1 crab. No commercial crab traps were sighted on today’s flight, another indication that crab populations are at low levels. The cranes since Christmas have not been observed catching blue crabs, whereas before that, some crabs were still being taken. A few wolfberries were still available to the cranes the week before Christmas but have tapered off since then. With blue crabs in very short supply and the wolfberry crop finished for the year, the cranes are entering the period of the winter when food shortages sometimes occur and the cranes end up using up fat reserves to survive.
Flight Conditions: Visibility was excellent for most of the flight. Due to reported crane movements, the search area was expanded much further out into upland areas. This turned out to be very important in finding additional cranes. Eight cranes were found in an area rooted up by hogs in the former farm field enclosure across the refuge’s East Shore Road about 0.7 miles from the salt marsh. Twelve cranes were sighted at feeders at Welder Flats, 8 of them at a location that is rarely searched. Seven cranes were found northwest of the refuge’s Burgentine Lake where cranes had been reported back on December 10th. The largest group size observed was 8 birds seen both on the uplands on San Jose and at a game feeder at Welder Flats. Large groups seen in salt marsh included 7 birds on the south end of Matagorda Island and 6 on Lamar’s Cow Chip Bayou.
– Tom Stehn, Aransas National Wildlife Refuge
