Allison S. Cox

Reevaluating the Cost of Natal Dispersal: Post-Fledging Survival of Red-Bellied Woodpeckers

Abstract. Accurate estimates of juvenile survival are critical to understanding population processes. However, information about post-fledging vital rates is lacking for most avian species because of the difficulty of following individuals after they leave the nest. We radio-tagged 43 Red-bellied Woodpeckers (Melanerpes carolinus) as nestlings. We tracked the birds for 5 months after fledging, during exploratory forays and after natal dispersal. We modeled the influence of intrinsic, temporal, social, and landscape factors with the potential to affect survival during the post-fledging period. Estimates of post-fledging survival were best explained by fledgling age. Predictions of weekly survival rates were 0.94 for birds 1 week after fledging, then quickly increased to over 0.99 for birds 7–22 weeks after fledging. We calculated period survival for the entire 5 months as 0.80 (95% CI: 0.65–0.90). We observed no mortalities after the birds departed natal territories, suggesting that exploratory and dispersal behaviors are not costly in this species.

Translocation of Tuamotu Kingfishers, Postrelease Exploratory Behavior, and Harvest Effects on the Donor Population

Abstract: Conservationists previously described the need for research into using translocation to rescue threatened populations. We conducted an experimental translocation of Tuamotu kingfishers (Todiramphus gambieri gertrudae) to provide foundational information about movement ecology and inform conservation planning for the critically endangered bird. We captured and radio-marked mated pairs of kingfishers on Niau Atoll, French Polynesia, where approximately 125 individuals compose the last remaining population of Tuamotu kingfishers. One bird from each pair was translocated to a reintroduction site on the opposite side of the island, and the other pair member was released back onto the home territory. Home-ranging pair members remained on territories and used habitats disproportional to availability, as determined by Brownian bridge analysis. Translocated individuals made multiple forays from the release site to explore the surrounding landscape, during which habitats were used in proportions similar to availability. The exploratory behavior resembled that of dispersing juvenile birds, which suggested that adults retain the ability to explore, and that dispersal theory may be a useful basis for planning translocations. Vacancies on donor territories were filled within 1–10 days. Our results indicated that translocation was not effective for range expansion on Niau because birds readily returned to donor areas; however, translocation to other islands remains a potential conservation strategy for Tuamotu kingfishers.