SIMULATION OF REPRODUCTIVE STAGES LIMITING PRODUCTIVITY OF THE ENDANGERED ATTWATERS PRAIRIE CHICKEN

Particularly where ground-nesting birds are concerned, conservation bi ologists require simulation models that explicitly represent populatio n parameters affecting the first year of life. For this reason, we dev eloped and evaluated a computerized model that explicitly represents p rairie chicken (Tympanuchus cupido) clutch size, egg hatchability, nes ting success, brood survival, survivorship of chicks within successful broods, and juvenile and adult survival. Sensitivity analyses of thes e variables suggest that the proportion of hens losing their entire br ood would have the greatest influence on the number of prairie chicken s in the subsequent spring breeding population. We then used the model to compare the relative importance of three reproductive parameters o f endangered Attwater's prairie chicken (T. c. attwateri) populations that are known to be significantly less productive than those of the g reater prairie chicken (T. c. pinnatus). When long-term nesting succes s, brood survival, and number of chicks per brood prior to brood break up were individually increased, values for each parameter had to be su bstantially greater than typically seen in greater prairie chicken pop ulations before the decline in Attwater's prairie chicken numbers was reversed. When these three variables were increased simultaneously, ap proximate to 90% of the difference between Attwater's and greater prai rie chicken values had to be closed before the decline in number was r eversed. (C) 1998 Elsevier Science B.V. All rights reserved.