Restoration of scaled quail to historic ranges in the Rolling Plains ecoregion of Texas

Abstract

Scaled quail (Callipepla squamata) are a gallinaceous game bird native to the grasslands and deserts of the southwestern United States and northcentral Mexico experiencing range contraction and population decline due to habitat fragmentation and degradation. Once abundant in the Rolling Plains ecoregion of Texas dating back to the 1880's, scaled quail were locally extinct throughout most of the ecoregion by the late 1980's primarily due to brush encroachment and spatial aggregation of row crop agriculture. Despite state and federal landowner habitat restoration programs (e.g., Landowner Incentive Program, Environmental Quality Incentives Program) scaled quail populations in the Rolling Plains ecoregion failed to respond, likely because the same fragmentation that contributed to decline also prevented effective natural recolonization to restored habitats. Translocation of wild-caught quails to reestablish self-sustaining populations gained popularity during the 2000's, particularly due to success reestablishing northern bobwhites (Colinus virginianus) in fragmented habitats of the southeastern United States. However, many translocations in arid, western climates were either poorly documented or failed outright. Understanding factors that influence translocation outcomes and form best practices is critical for translocation to be used effectively as a management tool. I examined long-term, seasonal survival in a population of scaled quail successfully reestablished on the Rolling Plains Quail Research Ranch in Fisher County, Texas in the context of drought and demographics (Chapter 1). Competing hypotheses predict that scaled quail populations are either resistant to drought or that annual survival is negatively correlated with precipitation amounts. My findings supported the hypothesis that scaled quail are drought sensitive. Additionally, I found survival was lower during non-breeding season, for females, and adults. Scaled quail survival estimates reported here are the most comprehensive for the species and the longest-term study of a translocated scaled quail population to date. I conducted a field experiment to test the effects of source population and variation in delayed release strategy (1–9 weeks) on mortality, dispersal, nest initiation, renesting rate, and nest survival of wild-caught, translocated scaled quail (Chapters 2 and 3). I trapped and translocated quail over 2 years (2016–2017) from source populations in the Edwards Plateau and Rolling Plains ecoregions to a large (>40,000 ha), contiguous release site in Knox County, Texas. Data were analyzed using two multi-state mark-recapture models with state uncertainty to incorporate uncertainty in the process of observing location and nest initiation in radio-marked birds. The framework I used to model reproductive processes is a novel method for obtaining estimates of nest initiation and renesting rate (Chapter 3). I found that scaled quail translocated within the Rolling Plains were more likely to exhibit philopatry to the release site, but that source population did not influence reproduction. Quail with longer holding times had higher mortality, but lower dispersal rates. Additionally, increased length of holding time decreased renesting effort. Yearlings were more likely to initiate nests than adults and the probability of renesting was lower during drought conditions. Finally, I compiled estimated demographics from chapters 1–3 to inform a matrix population model (MPM) that compared asymptotic and transient dynamics under wet and drought conditions (Chapter 4). While traditional MPM analyses focus on asymptotic dynamics, transient dynamics are more relevant for modeling short-term dynamics in translocated or unstable populations. My findings showed divergence between transient and asymptotic dynamics, with asymptotic projections potentially overestimating population growth by 14%. Asymptotic growth rates were most sensitive to renesting rate changes, while transient growth rates were affected by changes in hatchability and renesting rates. The results from my research will inform management decisions and I summarize my recommendations in Chapter 5. I suggest managers avoid initiating translocations in years projected to have drought conditions. Improved accuracy of El Nino–Southern Oscillation cycle-based long-range forecasts has made predictions a useful tool for managers considering translocation. Even so, translocated populations can persist long-term in drought conditions despite the negative impacts to survival and reproduction. Longer holding times for translocated scaled quail result in lower dispersal but higher mortality and lower renesting rates, presenting a decision tradeoff for managers. Managers can hold scaled quail on the release site (up to 9 weeks) when limiting dispersal is a priority (e.g., when in habitats surrounded by a high degree of fragmentation) or holding birds makes the translocation more feasible. However, when considering all factors a holding time of 2–3 weeks is ideal (Chapter 5). The Edwards Plateau is a suitable source site for translocations in the Rolling Plains. Managers should consider transient dynamics when modeling populations where short-term outcomes are relevant such as translocation. By doing so, I show that prioritizing the translocation of yearlings, the stage class with the highest reproductive value, can result in a 16% larger population after one year compared to translocating only adults.