Estimating the Nest-Success Rate and the Number of Nests Initiated by Radiomarked Mallards

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Allen Press is collaborating with JSTOR to digitize, preserve and extend access to The Journal of Wildlife Management.Abstract: 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. JOURNAL OF WILDLIFE MANAGEMENT 67(4):843-851

Costs of Reproduction in Breeding Female Mallards: Predation Risk during Incubation Drives Annual Mortality

“…We considered two metrics of previous nesting effort: total eggs laid and total days spent incubating, each tallied over all previous nesting attempts. On average, we discovered nests on the day the fifth egg was laid (X = 4.6, SD = 2.9) and we discovered 94.5% of all nests before clutch completion (assuming a 9-egg clutch), but because of high nest failure rates during laying, we estimate that approximately 28% of nests (range: 9%-47% among sites) failed before they were discovered (McPherson et al 2003;D. Howerter and L. Armstrong, unpublished data).…”

“…1), and mortality risk of postnesters peaked 5-15 days following clutch failure, similar to when females would have been initiating renests . We hypothesize three potentially complementary explanations for these patterns of increased mortality risk: (1) our samples included some birds that had started nesting, but whose nests we had not yet discovered, and the elevated predation risk was due to unrecognized nesting behavior (McPherson et al 2003), (2) these females had not yet started nesting, but they were engaged in nest prospecting behaviors, which placed them at elevated risk to terrestrial predators (McKinney et al 1990), or (3) concurrent peaks in mortality risk may have been due to prey switching behavior by predators, and once predators had experience capturing vulnerable nesting females they were more likely to attack non-nesting females as well.…”

“…Females were captured between arrival and just prior to or concurrent with the earliest recorded nesting attempts at each site (4 April to 5 May, depending on site). On average, females were captured 24.3 days (SD = 12.9, range 0 -79 days, n = 2783) before their first observed nesting attempt, although we suspect that most of the longer values were due to failure to discover earlier nesting attempts (McPherson et al 2003). Captured females were banded, weighed (± 10g), radio-marked, and released back to the capture site, usually within two hours of capture.…”

Survival and Selection of Migrating Salmon From Capture–recapture Models With Individual Traits

“…Further, there is a trend in capture-recapture studies toward selecting a suite of well-performing models (Johnson and Omland 2004) as opposed to choosing a single ''best'' model. Model averaging (Burnham and Anderson 2002) is then used where all the selected models contribute to the final parameter estimates (for ecological examples, see MacKenzie and Kendall 2002, Mazerolle 2003, McPherson et al 2003). An advantage of model averaging is that model uncertainty is incorporated into the estimation of model parameters (MacKenzie andKendall 2002, Johnson andOmland 2004).…”

A review of designs for capture–mark–recapture studies in discrete time

“…Of particularly concern is the inference scope for left censored data, which may not include nests that fail early (McPherson et al 2003) and may reduce the interpretation of random effects (Williams et al 2002;Heisey et al 2007). Temporal and spatially stratified sampling schemes may be useful for maximizing the inference scope for these studies by increasing the probability of detecting nests that fail early and therefore reducing heterogeneity in the sample (Rotella et al 2007).…”