Snowy Plover Demography in Oregon

A thorough understanding of demographic parameters and their contribution to overall population growth is fundamental to effective conservation of small populations, but this information is often lacking. The Pacific Coast population of the Western Snowy Plover (Charadrius nivosus nivosus) is listed as threatened and has been the target of long-term, multi-pronged management in Oregon. The Oregon coastal population has been intensively monitored since 1990, and over 80% of the population is color banded, but a comprehensive analysis of demographic parameters and the effect of management on vital rates and population growth has been unavailable until now. Here, the author used capture-mark-resight techniques to document survival at each life stage and to explore environmental and management factors that best explained variation in survival over a 25-year study period. The author analyzed the effects of habitat restoration, exclosure use, and lethal predator management on survival at appropriate life stages and evaluated the effects of one management option, lethal predator control, on overall population growth. Chick survival to fledging improved dramatically after the chicks\u27 5th day, was higher in years with lethal predator management, and was highest during the peak of the long brood-rearing season. Cold weather, particularly during the chicks\u27 first 5 days, had a negative effect on survival to fledging. Juvenile survival from fledging to the following spring declined over the study period, but rebounded after implementation of lethal predator management. Adult survival was lower in wetter-than-average winters and higher in years with predator management. The author used the survival analyses and productivity data collected over 25 years in a matrix population model to reveal that population growth is most sensitive to changes in adult survival, and that while predator management is important for continued growth, its use may be scaled back by as much as 50% and still maintain a growing population. My results, encompassing all phases of this species\u27 life cycle, demonstrate that with holistic and thoughtful adaptive management, and with the cooperation of numerous agencies, a balance can be struck between protection and control of native species to bring about recovery of species threatened with (local) extinction

Detection Probability of Least Tern and Piping Plover Chicks in a Large River System

Monitoring the abundance and stability of populations of conservation concern is often complicated by an inability to perfectly detect all members of the population. Mark-recapture offers a flexible framework in which one may identify factors contributing to imperfect detection, while at the same time estimating demographic parameters such as abundance or survival. We individually color-marked, recaptured, and re-sighted 1,635 federally listed interior least tern (Sternula antillarum; endangered) chicks and 1,318 piping plover (Charadrius melodus; threatened) chicks from 2006 to 2009 at 4 study areas along the Missouri River and investigated effects of observer-, subject-, and site-level covariates suspected of influencing detection. Increasing the time spent searching and crew size increased the probability of detecting both species regardless of study area and detection methods were not associated with decreased survival. However, associations between detection probability and the investigated covariates were highly variable by study area and species combinations, indicating that a universal mark-recapture design may not be appropriate