(A special request: if anyone along the migration route has any information of the disposition of any whooping crane losses (power line strikes, predator attacks, etc.), please get in touch with Tom Stehn or contact me off-list immediately, especially if you know of any locations of any possible remains. Information on crane losses is always harder to come by during migration due to flight paths over non-monitored areas, but is an extremely valuable and necessary part of the recovery program. Thank you. - Patty)
The following report is forwarded with permission from Tom Stehn, USFWS biologist and US Whooping Crane Coordinator.
Where applicable, CWS stands for Canadian Wildlife Service; USFWS is US Fish and Wildlife Service. Crane monitoring involves cooperative efforts and support by both countries, plus many volunteers and non-profit organizations along the way.
Anyone wanting to contact Tom about the report or the whooping crane projects can reach him via email at: email@example.com. Other information, including archived copies of these reports, can be found at the Texas Whooping Crane web site at http://tiercel.cbi.tamucc.edu/nature/falcon/twc/index.html.
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An aerial census of the Aransas NWR and surrounding areas made 29 November,
2001 estimated the number of whooping cranes present at 154 adults + 15
young = 169.
Recap of cranes observed: (169)
San Jose 28+2
Welder Flats 23+1
Total 154 + 15 = 169
Remarks: Clear skies with west winds and temperatures in the 40's provided very good viewing conditions. A complete census effort was made with 8.0
hours of flight time.
An estimated 9 cranes that completed the migration since the previous flight on November 21 were aided by cold fronts that reached the Texas Coast on November 24 and 27. This latter storm brought snow to north Texas and temperatures in the 40's to the coast with strong northwest winds aiding the migration. Many more sandhill cranes were sighted on upland pastures on today's flight. Whooping cranes known to have arrived included the South Matagorda Island family (2+1), the Big Tree Family (1+1), another single adult family (1+1) at Mustang Lake, and the Allyn's Bight (2) and Pat's Bay pair (2). Although these new arrivals account for 11 new cranes, I only actually tallied 9 additional cranes. I also cannot account for having 13 juveniles present last flight, adding three more, and yet finding only 15 on today's flight. A family group that last week was located just south of the Pump Canal was not located this week, leaving the possibility that 16 chicks had arrived. However, there were enough changes in the locations of families and much uncertainty so that the estimate remains at 15 families. The only certainty on a census flight is that new puzzles always arise that can only be sorted out on future flights. Perhaps there are actually between 171 and 174 cranes present.
The most disturbing discovery was the loss of one of the Big Tree adults. This family was seen in Canada as late as November 29th with bands read on
both adults. When first sighted this winter at Aransas, the Big Tree male was present, (nil-hs, originally banded as Y-R in 1986), but there was no sign of the female hs-nil (former B-o/y also hatched in 1986). Instead, the Big Tree male and chick were with adult female YbY-RwR (1987). The two adults and chick looked harmonious and were spaced close together. Last winter, YbY-RwR had lost her mate. Although YbY-RwR had re-paired and nested in Canada at nest 11/01, this pair had not hatched a chick. When first seen at Aransas this winter, YbY-RwR was seen with another single adult family group on the refuge. The following week, YbY-RwR was on her traditional territory located next to the Big Tree Marsh, with an unbanded bird, presumably her mate. With the arrival of the Big Tree male, perhaps he has already taken YbY-RwR as his new mate. We know from other instances that a male will sometimes re-pair with an adult female from another pair, thus breaking up an existing pair. Only with observations in the coming weeks can we better figure out this situation. Two single cranes, very widely spaced apart, were in the vicinity of the Big Tree family. When the Big Tree family flew, one of the single cranes shortly thereafter took flight, following the family but landing short about 300 yards away. This single bird could be the male mate of YbY-RwR. Perhaps it has been driven off by the Big Tree male and knows to keep his distance, yet doesn't want to desert his former mate YbY-RwR.
On November 24th, a single unbanded adult with chick arrived in front of the Mustang Lake observation tower. This marsh had been vacant since the territorial Mustang Lake pair is staying about 5 miles to the south, a totally unexpected move. On November 20, a 1+1 family group was sighted at Quivira NWR in Kansas that could have been this group at Mustang Lake. Earlier this winter, the S. Sundown Bay family arrived as 1+1. The apparent arrival of three single-adult families this winter is most alarming. If 3 of the 15 family groups that arrived all lost one adult since mid-August, this indicates a 10 % loss of adults that presumably occurred during the fall migration. Although the small sample size must overestimate the rate of loss, losses during the spring and fall migration are the largest source of mortality in the Aransas-Wood Buffalo flock. Collisions with power lines is the predominate cause of these losses. Although the number of chicks that have made it to Aransas so far (15) is better than expected, the presence of 3 single-adult families is an indication that losses between spring and fall were significant, so that the population is expected not to increase much above last year's spring total of 174. The record size of the flock was 188 in the 1998-99 winter.
Pairs still not present at Aransas include Behind Lakeside, and the R-Y pair north of Power Lake, although the latter could be here but bands just not yet read. Most all cranes usually arrive by mid-December with a few remaining stragglers possible in late December.
Habitat: Tides were similar to last week, measured at 2.7 mlt on November 26th. However, heavy rains on the refuge received November 27-28 flooded some upland pastures and raised water levels in coastal marshes, particularly notable on the refuge and on San Jose. Other recent rains in the Texas Hill Country brought vital inflows to whooping crane critical habitat. Bay salinities in the crane area were measured at 10 ppt on November 26, a drop from 15 ppt the previous week.
On today's flight, most cranes were in habitat supporting blue crabs, and about half a dozen cranes were observed holding blue crabs in their beaks. This indicates the cranes are at present foraging primarily on crabs. No cranes were at fresh water sources or prescribed burns. Five cranes were on upland areas, including a family group on the refuge's Burn Unit 38 in a flooded pasture recently roller chopped to reduce brush height. The refuge fire program has made great progress the last three years renovating upland pastures that had become overrun with brush. Management tools used were
roller chopping and conducting summer prescribed burns.
- Tom Stehn
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Special thanks to Texas A&M University's Conrad Blucher Institute server and Dr. Robert Benson for providing server space for the Texas Whooping Crane web site.
Patty Waits Beasley
Corpus Christi, Texas
Web site: http://tiercel.cbi.tamucc.edu/nature/falcon/twc/index.html