The eradication of invasive predators from islands is a successful technique to safeguard seabird populations, but adequate post-eradication monitoring of native species is often lacking. The Whenua Hou Diving Petrel (Pelecanoides whenuahouensis; WHDP) is a recently-described and 'Critically Endangered' seabird, restricted to Codfish Island (Whenua Hou), New Zealand. Invasive predators, considered the major threat to WHDP, were eradicated on Codfish Island in 2000. However, estimates of WHDP population size and trends remain unknown, hindering assessments of the success of the eradications. We collated intermittent burrow counts (n = 20 seasons) conducted between 1978 and 2018. To estimate the population growth rate (k) before and after predator eradications, we used log-linear models in a Bayesian hierarchical framework while retrospectively accounting for differences in detection probabilities among burrow counts, due to differences in effort, marking and timing. The number of WHDP burrows was estimated at 40 (36-46) in 1978 and 100 (97-104) in 2018. The pre-eradication k was estimated at 1.023 (0.959-1.088), while the post-eradications k was estimated at 1.017 (1.006-1.029). The WHDP population appears to be increasing, yet the rate of increase is low compared to other Procellariiformes following predator eradications. The comparatively low post-eradication k, combined with an apparent lack of change between pre-and post-eradication k, indicates that additional threats might be limiting WHDP population growth and that further conservation management is required. The continuation of affordable and simple, albeit imperfect, monitoring methods with retrospective corrections facilitated the assessment of invasive predator eradications outcomes and should guide future management decisions. An abstract in Te Reo M aori (the M aori language) can be found in Appendix S1.Animal Conservation 23 (2020) 94-103 ª
Harvesting individuals for translocations can negatively impact source populations, a critical challenge for species reduced to small populations. Consequently, translocation cohorts often remain small, reducing the establishment probability at the destination. Balancing the potential benefits and risks of such translocations is further complicated by philopatry and natural metapopulation dynamics if the target species is highly mobile. These challenges highlight the importance of translocation feasibility assessments, but such assessments often remain qualitative to date. The critically endangered Kuaka (Whenua Hou Diving Petrel; Pelecanoides whenuahouensis) is a philopatric, highly mobile seabird that could benefit from conservation translocations, but only one small population remains. Through expert elicitations with a user‐friendly Shiny app, we developed a novel metapopulation extension to an integrated population model fitted to long‐term data, allowing us to simultaneously project harvest impact on the source and establishment of destination populations under alternative translocation scenarios, while accounting for philopatry and metapopulation dynamics. Establishment of a destination population without excessive impact on the source was possible, but subject to uncertainty about philopatry and metapopulation dynamics. Accounting for juveniles returning to the source post‐translocations reduced impact on the source, but also decreased establishment at the destination. Natural movements of adults and juveniles between source and destination populations were predicted to modulate effects of different harvest intensities. Synthesis and application. Using state‐of‐the art integrated population models and expert elicitations, we illustrate how translocation feasibility can be evaluated transparently and quantitatively, even when targeting endangered, philopatric and highly mobile species. Our approach is a considerable improvement on current qualitative feasibility assessments. However, we also illustrate that, ultimately, the favoured translocation strategy depends on balancing biological and other fundamental objectives inherent to translocations. Therefore, the ideal strategy cannot be determined solely mathematically, and feasibility assessments should incorporate explicit value statements. Our methodology is applicable to any future translocation scenario.
Lightweight capillary tube depth gauges were attached to eight petrel species breeding at New Zealand colonies during the period 1998-2008. This paper presents the first information on the diving ability of Pterodroma petrels. Grey-faced Petrels, Pterodroma macroptera gouldi, re corded maximum dives down to 23 m. Males (6.3 ± 6.3 m SD) dived deeper on average than females (3.6 ± 2.5 m) during the incubation period but not significantly so (P�0.06). Breeding birds dived significantly deeper on average than non-breeders, and breeding males dived significantly deeper on average than non-breeding males. The two small Pterodroma species sampled, Pterodroma pycrofti and Pterodroma nigripennis, only exhibited shallow dives down to 2 m but sample sizes were small. Sooty Shearwaters, Pujfinus griseus, had mean maximum dive depths of 42.7 ± 23.7 m, with males (53.0 ± 17.3 m) diving significantly deeper on average than females (20.1 ± 20.4 m) during the incubation period. One male Sooty Shearwarer dived to nearly 93 m, the deepest dive so far recorded in the order Procellariiformes.Flesh-footed Shearwaters, Pujfinus carneipes, dived to 28 m, with a mean maximum dive depth of 13.6 ± 7.9 m. Hutton' s Shearwaters, Pujfinus huttoni, had a mean maximum dive depth of 23.0 ± 8.5 m (range 11.1-36.6 m). A single Fluttering Shearwater, Pujfinus gavia, recovered with a dive gauge had dived to 29 m. Mean maximum dives made by Common Diving-Petrels, Pelecanoides urinatrix, of 10.9 ± 6.1 m (range 6.9-22.2 m) were shallower than results reported from other sites but may have been biased by gauge failures. Capillary gauges provide the best means we have at present to understand the diving capability of small seabirds. While studies elsewhere have shown these gauges may overestimate diving performance by about 10-15%, other factors identified in this study indicate rhat sometimes diving performance will be underestimated using this simple technique.
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