Wildlife Monographs
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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