Estimating the nest-success rate and the number of nests initiated by radiomarked mallards

We developed a methodology for estimating the nest-success rate, the total number of nests initiated, and the average number of nests initiated per breeding pair by a group of radiomarked mallard (Anas platyrhynchos) females. Our methodology allows incomplete observation of all nests initiated and is related to current nest-success models. However, our method relaxes the assumption of equal daily survival rates made by the Mayfield method, and it incorporates the detection probabilities of newly encountered nests, which are ignored by the Mayfield method. Model selection and model averaging using Akaike's Information Criterion (AIC) are used so that estimates are no longer conditional upon the best-fitting model. Estimated daily nest-survival rates in our example were 0.94 (SE = 0.005), which gives an estimated nest-success rate over 25 days of 0.20 (SE = 0.03). We estimated that our sample of 124 resident females initiated 237 (SE = 15) nests for an estimated 1.91 (SE = 0.12) nests initiated per female. This was substantially larger than the observed (uncorrected) 1.41 nests per female, despite the high sampling effort and the fact that the nests were located at an average of 5 days of age. Our estimate of nests initiated was substantially more precise than similar estimates derived using the Mayfield method. We estimate an approximate 6-fold reduction in the sample size required by our method compared to the Mayfield method to obtain comparable precision for this parameter.