Understanding the factors infl uencing nesting success is a primary goal of many studies. To do this effectively, more advanced tools than Mayfi eld’s ad hoc estimator are needed. The recent development of a nest-survival model in program MARK provides a powerful and fl exible tool for the study of avian nest survival that can incorporate seasonal variation in survival and nest-specifi c covariates. We briefl y review the model and its development, illustrate how to include the effects of daily nest age and observer visits to nests, and conclude with an example analysis of Red-winged Blackbird (Agelaius phoeniceus) nest survival in Iowa. In this example, we found evidence for stagespecifi c differences in nest survival, seasonal patterns in nest survival that were best explained by a quadratic-time trend, and that survival differed between years. An exploration of several nestspecifi c covariates revealed that blackbird nest survival was positively affected by nest height, weakly affected by nest placement (nests placed in living vegetation may have experienced slightly higher survival), and unaffected by clutch size and within- and between-cell nest placement.