The document discusses aerial surveys conducted at Aransas National Wildlife Refuge to monitor the endangered whooping crane population. The surveys employ distance sampling techniques from fixed-wing aircraft to estimate the total number of cranes in the survey area, number of breeding pairs, and reproduction rates. Test flights using decoys validated the accuracy of the distance sampling methodology. Recent survey results found an estimated 254 cranes with 75 pairs and 25 pairs successfully fledging young. Ongoing challenges include surveying areas cranes move to outside the standard survey boundary.

1. Tracking Whooping Crane
Recovery with Aerial Surveys
U.S. Fish and Wildlife Service
Aransas National Wildlife Refuge

3. • Long Lived, >20 years
• 1 – 2 Chicks per Year
• Prairie & Wetlands
• 2,500 mile migration
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4. Aransas & Whooping Cranes
• Winter Aerial Surveys
• Monitor Crane Foods
 Blue Crab
 Wolfberry
• Freshwater
• Prescribed Burning
• Research
• Education

5. Why Monitor Cranes?
• Inform
Conservation &
Management
Decisions
 # of Cranes
 # of Breeding Pairs
 Reproduction Rate

6. How Do We Monitor Cranes?
• ≈140,000 acres to survey
• Fixed-winged Aircraft
 ≈ 200 feet altitude
 ≈ 100 miles per hour
• Mark locations of cranes on a map

7. How Did You Survey Before?
• Observer’s long-term
knowledge
• Identified each bird’s
territory
• Tried to count the
entire population

8. Why Change the Methods?
There’s
• Population grew an app
 Larger area for that
• Observers change
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• Apply the best
1
available science 9
8
• Improved 1
technology
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9. Where Do
We Look?

10. Where Do
We Look?

11. Where Do
We Look?

12. Where Do
We Look?

13. Where Do
We Look?

14. Where Do
We Look?

15. Did We Count Them All?
• Distance Sampling
– Well established method
– Far birds are hard to see
• Test drive

16. Did We Count Them All?
?

17. Distance Sampling: Example
Number of Birds Detected
Distance from the Airplane

18. Distance Sampling: Example
90%
Percent Detected
30%
Distance from the Airplane

19. Good…but Good Enough?
• 4 “test drive” flights
• Decoys were moved
between flights
• 104 decoys per flight
• Results of 3 analyses
 111 decoys (106%)
 104 decoys (100%)
 96 decoys (93%)
• Why are the birds
where they are?

21. Saltmarsh
Anyone?

24. The redder…
the better

25. 2011-2012 Results
• Estimated 254 cranes in the survey area
• Why so few?
 Drought conditions
 Many were not in the survey area
• Estimated 75 crane pairs
• Estimated 25 of those pairs had young
• Saltmarsh is important to cranes

26. What’s Next?
• We need you!
• What do we do
when cranes are not
in the survey area?
• Think like a crane!
• Stay one step ahead

27. Today

28. Tomorrow

29. The Future

30. Questions?
Thanks For the Help
• Volunteers
• Friends of Aransas
and Matagorda Island
• T. Stehn
• Survey Pilots

31. Survey Timing

32. Survey Frequency

33. Reproduction Rate