Simulation of reproductive stages limiting productivity of the endangered Attwater's prairie chicken
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abstract
Particularly where ground-nesting birds are concerned, conservation biologists require simulation models that explicitly represent population parameters affecting the first year of life. For this reason, we developed and evaluated a computerized model that explicitly represents prairie chicken (Tympanuchus cupido) clutch size, egg hatchability, nesting success, brood survival, survivorship of chicks within successful broods, and juvenile and adult survival. Sensitivity analyses of these variables suggest that the proportion of hens losing their entire brood would have the greatest influence on the number of prairie chickens in the subsequent spring breeding population. We then used the model to compare the relative importance of three reproductive parameters of endangered Attwater's prairie chicken (T. c. attwateri) populations that are known to be significantly less productive than those of the greater prairie chicken (T. c. pinnatus). When long-term nesting success, brood survival, and number of chicks per brood prior to brood breakup were individually increased, values for each parameter had to be substantially greater than typically seen in greater prairie chicken populations before the decline in Attwater's prairie chicken numbers was reversed. When these three variables were increased simultaneously, 90% of the difference between Attwater's and greater prairie chicken values had to be closed before the decline in number was reversed.
