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PTT STUDY

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Methods
Trapping
Who?
Crane 8725
Crane 8726
Crane 8737
Crane 8746
Crane 8824
Crane 8827

 

 

Who?

WHO ARE THESE CRANES?


MEASUREMENTS

Identification of subspecies of sandhill cranes requires the determination of gender which can not be ascertained from a physical examination. We hope that blood analyses will determine gender. Measurements used for comparison of subspecies are from two sources: Johnson and Stewart (1973) and Schmidt and Hale (1997). However, the birds reported in these studies were from the Mid-Continent Population (Central Flyway - - the migration corridor between the Rocky Mountains and Mississippi River), and those in the Pacific Flyway (west of the Rockies) may differ morphologically. Measurements were plotted on charts for comparisons.

Tarsus

 

 

 

 

The tarsus is the long bone in the lower leg. Length of tarsus (n = 7) measurements were generally shorter than Canadian sandhill cranes, and mostly within the upper limits for lessers.

 

 

 

 

Wing Chord

 

 

 

Wing chord is measured from the bend of the wing to the tip. Measurements (n = 8) overlapped with all 3 subspecies, but 4 of 8 birds were within the standard deviation for Canadians. One crane measured larger than any Canadians reported, but within the range for Greaters. The other 3 cranes were closest to means for lessers.

 

Exposed Culmen

 

 

 

 

This measurement is from the base of the upper mandible to the tip. Four exposed culmen measurements (n = 8) were closest to the ranges reported for Canadian sandhill cranes, while the other four fell between the ranges for Canadians and lessers.



 

Weight

 

 

 

 

Weights of cranes (n = 7) fell within the ranges for greater and Canadian sandhill cranes, with little overlap with reported weights of lessers. Most weights were closest to the means for Canadians, however, weights of two birds were closer to greaters.






 

Middle Toe

 

 

 

Measurements of the middle toe fell mostly within the upper ranges of lesser sandhill cranes with some overlap with female Canadians.






 

 

 



SUBSPECIES DETERMINATION

We believe that the cranes in this study were Canadian sandhill cranes. Most of their measurements were within the ranges reported for this subspecies. Disparities in some measurements may indicate that there are morphological differences between cranes of the Central Flyway and those of the Pacific Flyway. The fact that these cranes migrated to the B.C. and southern Alaska coasts also supports the conclusion that they are Canadians. According to the book The Birds of British Columbia (Campbell et al. 1990), about 1,500 Canadian sandhill cranes nest along the B.C. coast.

For the birds we captured , the head profiles seemed to match those of Canadians, with a flat forehead and medium bill (see photos of birds on the other pages). Lessers have a rounded head and fine, short bill, while Greaters also have a flattened forehead, but a longer bill. We also noted that the legs were shorter than greaters that we had previously handled. The heads of these birds appeared different than lesser sandhill cranes we have observed in California, and eastern Oregon and Washington, and their bills appeared shorter than typical greaters.

References

Campbell, R. W., N. K. Dawe, E. McTaggart-Cowan, J. M. Cooper, G. W. Kaiser, and M. C. E. McNall. 1990. The birds of British Columbia. Royal British Columbia Museum, Victoria, B.C.

Johnson, D. H., and R. E. Stewart. 1973. Racial composition of migrant populations of Sandhill Cranes in the northern plain states. Wilson Bulletin 85:148-162.

Schmidt, G. C., and B. Hale. 1997. Sandhill Crane hunts in the Rio Grande Valley and southwest New Mexico. Proceedings North American Crane Workshop 7:219-231.

 

Click the following items to see detailed results for this study:

Up Methods Trapping Who? Crane 8725 Crane 8726 Crane 8737 Crane 8746 Crane 8824 Crane 8827

 


 

 

 

 

 

 

 

 

 

 
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