| Population Demography
of Lark Buntings (Calamospiza melanocorys)
Graduate Student: Amy A. Yackel Adams
Project Start Date: 09/04/01
Introduction: Grassland bird species have experienced the largest population declines of any terrestrial avian group in the past four decades in North America. Lark buntings (Calamospiza melanocorys), endemic to the grasslands of North America, have declined by 2.5% per year in Colorado and 2.1% per year in the High Plains physiographic region between 1966 and 2003. Although reasons for these declines have yet to be elucidated, factors influencing reproductive productivity and juvenile survival on the breeding are grounds are among the possibilities. To assess population declines, direct and reliable estimates of survival, fecundity, and dispersal are required. Consequently, we estimated demographic parameters (i.e., post-fledging survival and fecundity) for lark buntings, in a relatively intact (62% grassland remaining) tract of native shortgrass on the Pawnee National Grassland, Weld County, Colorado.
Objectives: 1) Estimate post-fledgling survival and evaluate factors that influence this estimate (viz., drought condition, time in season, age, nestling condition, mark type, and sex of attending parent). Compare the performance of my post-fledging survival estimates and a popular indirect estimate used in population modeling. 2) Examine breeding season decisions, nest survival, and annual fecundity of female lark buntings. Determine a range of adult survival values necessary to maintain a stable population (? = 1) based on our estimates for juvenile survival and female fecundity.Progress: Two manuscripts have been prepared. The first manuscript (Modeling avian post-fledging survival in response to drought) was submitted to Ecology on 17 December 2004.
Plans: The second manuscript (Fecundity and breeding decisions of prairie birds: implications for population declines) will be submitted to a journal by 31 March, 2005.
Yackel Adams, A.A., S.K. Skagen, and J.A. Savidge. In review. Modeling
avian post-fledging survival in
Skagen, S.K., A.A. Yackel Adams, and R.D. Adams. In press. Nest survival relative to patch size in a highly fragmented shortgrass prairie. Wilson Bulletin 117.
Jehle, G., A.A. Yackel Adams, J.A. Savidge, and S.K. Skagen. 2004. Nest survival estimation: A review of alternatives to the Mayfield estimator. Condor 106:472-484.
Yackel Adams, A.A., S.K. Skagen, and R.D. Adams. 2001. Movements and survival of lark bunting fledglings. Condor 103:643-647.
Yackel Adams A.A., S.K. Skagen, and J.A. Savidge. Poster presentation: Are breeding grounds contributing to population declines of prairie birds? Great Plains Grassland Conference, Fort Collins, Colorado, February 23-25, 2005.
Yackel Adams, A.A., S.K. Skagen, and J.A. Savidge. Poster presentation: Modeling post-fledging survival of a grassland bird in response to drought. Shortgrass Steppe Symposium, "Key issues for management, research, and conservation". Fort Collins, Colorado, January 14, 2005.
Yackel Adams, A.A. Invited presentation. Post-fledgling survival of Lark Buntings. Shortgrass Steppe-Long Term Ecological Research brown bag series. Colorado State University, Fort Collins, Colorado, April 21, 2004.