APPARENT SURVIVAL OF SNOWY PLOVERS (CHARADRIUS NIVOSUS) VARIES WITH REPRODUCTIVE EFFORT AND YEAR AND BETWEEN SEXES

Life history theory predicts a tradeoff between reproductive effort and survival, which suggests that some management practices aimed at increasing productivity may compromise population growth. We analyzed a 10-year data set of 225 individually marked Snowy Plovers (Charadrius nivosus), a threatened shorebird, to determine whether individual reproductive effort was correlated with low apparent survival. Most adults resided in the population an average of 2 years (range: 1-10 years), during which females laid 3-60 eggs, and both males and females invested considerable time in incubation and brooding. Apparent survival varied annually and was higher for males than for females. Contrary to theory, we found no evidence that increased reproductive effort, either current or cumulative, compromised survival. Instead, apparent survival was correlated positively with incubation time, which may be related to either high-quality individuals having high reproductive rates and high survival or permanent emigration of failed breeders (who incubated for shorter intervals). Although our results suggest that some predator management practices (e.g., nest exclosures) aimed at increasing productivity will not compromise survival in a subsequent year, we caution that these same practices may have serious negative consequences for population growth if (1) reproductive effort does not translate into higher per capita fledging success and (2) direct mortality of adults results from the practice.