Tom Stehn, Aransas National Wildlife Refuge completed the first 2009 fall whooping crane census recently. Tom reports, “The first aerial census of the 2009-10 whooping crane season was conducted 12 November, 2009 in a Cessna 210 piloted by Gary Ritchey of Air Transit Solutions of Castroville, Texas with USFWS observer Tom Stehn.
Weather conditions were ideal during the 4-hour flight with sunshine and light east winds. Sighted were 87 adults and 4 juveniles = 91 total. Based on August fledging surveys done on the nesting grounds by CWS, I am expecting up to 22 juveniles. With that number of juvenile produced, the flock may experience a break-even year with a flock total around 247 expected.”
November 12th – Recap of cranes (91) found at Aransas on the aerial:
Migration Update: The first whooping crane arrival at Aransas was reported the morning of October 17th by refuge staff going over to Matagorda Island that saw a pair. This sighting was just one day after the average first whooping crane arrival date of October 16th. A cold front that reached Aransas early on 10/16 brought great migration conditions through 10/17 that aided the arrival of the first migrants. The next strong cold front at Aransas on the afternoon of 10/26 brought multiple reports of sandhill cranes moving through Texas and I had my first sighting of 125 sandhills in the farm fields north of the refuge on November 27th. A cold front October 30th brought favorable migration conditions lasting through November 5th. The next front on November 9th brought favorable migration conditions through November 12th.
Minimum # of Cranes
From this and weather records, it appears that a low number of whooping cranes reached Aransas in the second half of October and the first week in November, but quite a few cranes arrived between November 7-12. These later than average arrivals were simply due to birds not moving down the flyway. The migration appears to be about a week later this year than average. Last year, we flew on November 14th and tallied 239 cranes, quite
a difference from the 91 counted on today’s flight. Numerous whooping cranes have been reported November 2-11 in Kansas and Oklahoma, including 39 at Quivira NWR in central Kansas on November 10. Quivira at one point had 36 cranes together, a record flock size for whooping cranes in migration. A flock of 32 was seen the following day by Salt Plains NWR in Oklahoma. The next strong pacific cold front is forecast to reach Aransas on November 16th, which I think will allow a large number of additional whooping cranes to reach Aransas.
Habitat Use: Tides were an estimated 1 foot above what I consider to be high water levels for the crane area. The high water levels were a result of Hurricane Ida that crossed the Gulf and reached Alabama as a tropical storm on November 10th. Ida raised tides 2.5 feet along the central Texas beaches. The cranes responded to the high water by being mostly in vegetated marsh, with 19 cranes on uplands next to the marsh. The distribution seen on today’s flight looked like the cranes were mostly responding to wolfberries that seems to have had a good crop this year.
Not a single commercial blue crab trap was seen in the crane area, including in the shallow bays edges next to the crane marshes. This is unusual and indicative of the poor harvest that has been ongoing all summer caused by the drought and insufficient inflows reaching the crane area.
Marsh salinities are approximately 24 ppt and continue above the threshold when whooping cranes must seek out fresh water to drink. Two cranes were observed on today’s flight at a fresh water dugout. Two cranes were observed at a private game feeder. The largest group size observed was 5 birds seen on a high salt prairie at Welder Flats.
– Tom Stehn, Aransas National Wildlife Refuge