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Determinants of Breeding Distributions of Ducks

Results


Relations with Life History Characteristics

Values of the 2 indices of life history characteristics and their average are presented in Table 5. As predicted, the negative of the first index and the other index varied together (r = 0.683, P = 0.03). Because these indices covary, it is reasonable to combine them into a single measure corresponding to the r- and K-continuum. Average indices indicate that the pintail mallard, blue-winged teal, and shoveler show the most features associated with unpredictable environments (i.e., are the most r - selected). Gadwall, American wigeon and green-winged teal are intermediate, and the diving ducks are most associated with predictable environments (i.e., are toward the K-selected end of the continuum).


Table 5. Indices to life history characteristics: average permanence values of ponds used by species, median correlation coefficient with pond densities, and average index.

Species Pond
permanence
indexa
Median
correlation
with ponds
Average
Northern pintail -0.296 0.547 0.126
Mallard -0.310 0.417 0.053
Blue-winged teal -0.325 0.390 0.032
Northern shoveler -0.340 0.388 0.024
Gadwall -0.336 0.228 -0.054
Green-winged teal -0.310 0.199 -0.056
American wigeon -0.334 0.143 -0.100
Canvasback -0.393 0.192 -0.100
Redhead -0.384 0.154 -0.115
Lesser scaup -0.389 0.145 -0.122

aFrom Stewart and Kantrud (1973); average permanence (cropland ponds = 2, seasonal ponds = 3, semipermanent ponds and reservoirs = 4) times -0.1.


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