Preparing for translocations of a Critically Endangered petrel through targeted monitoring of nest survival and breeding biology J OHANNES H. FISCHER,HEIKO U. WITTMER,GRAEME A. TAYLOR I GOR D EBSKI and D OUG P. ARMSTRONG Abstract The population of the recently-described Whenua Keywords Aotearoa New Zealand, Bayesian inference, Hou diving petrel Pelecanoides whenuahouensis comprises conservation, Pelecanoides whenuahouensis, phenology, c. adults that all breed in a single . km colony in Procellariiformes, restoration, Whenua Hou diving petrel a dune system vulnerable to erosion. The species would Supplementary material for this article is available at therefore benefit from the establishment of a second breed- doi.org/./S ing population through a translocation. However, given the small size of the source population, it is essential that trans- locations are informed by carefully targeted monitoring data. We therefore modelled nest survival at the remaining Introduction population in relation to potential drivers (distance to sea and burrow density of conspecifics and a competitor) across eabirds, and petrels in particular, are among the most three breeding seasons with varying climatic conditions as a Sthreatened taxa (Croxall et al., ; Dias et al., ). result of the southern oscillation cycle. We also documented Nearly half of all petrel species (i.e. families Procellari- breeding phenology and burrow attendance, and measured idae, Oceanitidae, Hydrobatidae and Pelecanoididae) are chicks, to generate growth curves. We estimated egg survival threatened with extinction. Petrel species are affected by a at . , chick survival at . , overall nest survival wide range of threats (Dias et al., ). On land, petrels at . , and found no indication that nest survival was are threatened by invasive predators (Jones et al., ; affected by distance to sea or burrow density. Whenua Dias et al., ), extreme weather events (Cole, ; Rodrí- Hou diving petrels laid eggs in mid October, eggs hatched guez et al., ) and light pollution (Rodríguez et al., ). in late November, and chicks fledged in mid January at At-sea threats include changes in oceanic productivity, c. % of adult weight. Burrow attendance (i.e. feeds) climate patterns, and fisheries impacts such as bycatch decreased from . to . visits per night as chicks and competition (Anderson et al., ; Zydelis et al., ; approached fledging. Nest survival and breeding biology Grémillet et al., ). Various life-history traits render pet- were largely consistent among years despite variation in rels disproportionally vulnerable: they are extremely wide- climate. Nest survival estimates will facilitate predictions ranging (i.e. they utilize entire ocean basins; Shaffer et al., about future population trends and suitability of prospective ), K-strategists (i.e. low fecundity, delayed sexual ma- translocation sites. Knowledge of breeding phenology will turity, high longevity; Rodríguez et al., ) and placed at inform the timing of collection of live chicks for transloca- high trophic levels (i.e. they are top predators; Einoder, tion, and patterns of burrow attendance combined with ). As petrels provide important ecosystem services growth curves will structure hand-rearing protocols. A tuhin- (e.g. nutrient cycling, bioturbation and seed dispersal; Ellis, ā ā ga whakar popoto (te reo M ori abstract) can be found in the ; Orwin et al., ; Otero et al., ), their conserva- Supplementary material. tion is a priority. Translocations are an increasingly common conserva- tion management strategy (Seddon et al., , ), including for petrels (Miskelly et al., ). A conservation JOHANNES H. FISCHER (Corresponding author, orcid.org/0000-0003-3527- translocation entails the intentional movement of individ- 1671) School of Biological Sciences, Victoria University of Wellington, PO uals for species recovery or ecosystem restoration (Seddon Box 600, Wellington, 6140, New Zealand. E-mail [email protected] et al., ). Translocations may be effective conservation HEIKO U. WITTMER School of Biological Sciences, Victoria University of interventions if habitat is available outside a species’ current Wellington, Wellington, New Zealand range, if the species is unlikely to naturally colonize that GRAEME A. TAYLOR and IGOR DEBSKI Aquatic Unit, Department of Conservation, Wellington, New Zealand habitat, and if the translocation is unlikely to cause undesir- able impacts. Translocations may involve supporting exist- DOUG P. ARMSTRONG Wildlife Ecology Group, Massey University, Palmerston North, New Zealand ing populations (i.e. reinforcement), reinstating populations ’ Received April . Revision requested June . within the species indigenous range (i.e. reintroduction), or Accepted July . creating new populations outside of the species’ indigenous This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, Downloadeddistribution, from https://www.cambridge.org/core and reproduction in any medium,. IP address: provided 202.89.140.187 the original work, on is 29 properly Apr 2021 cited. at 05:53:28, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/termsOryx, Page 1 of 9 © The Author(s),. https://doi.org/10.1017/S0030605320000794 2021. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605320000794 2 J. H. Fischer et al. range (i.e. assisted colonization; IUCN, ). As petrels are ), but additional threats may still be inhibiting pop- often threatened and facilitate ecosystem functioning, their ulation recovery (Fischer et al., a). Unlike other petrels, translocation can be motivated by both species recovery and the species breeds exclusively in fragile foredunes , m restoration goals (Miskelly et al., ; Jones & Kress, ). from the springtide line (Fischer et al., c). Storms and For example, Gould’s petrels Pterodroma leucoptera have storm surges, as well as climate change, may thus be the been translocated to Boondelbah Island, Australia, within main threats to this species (Cole, ;Vousdoukasetal., their indigenous range to strengthen the small existing ). Competition with the more aggressive common diving population (reinforcement; Priddel et al., ). Common petrel for burrow sites may also inhibit population recovery diving petrels Pelecanoides urinatrix have been translocated (Fischer et al., ). An unsuccessful hybridization attempt to Mana Island, Aotearoa New Zealand, to reinstate the between a Whenua Hou diving petrel and a common diving ecosystem functions they once provided (reintroduction; petrel has been recorded (Fischer et al., c), suggesting Miskelly et al., ). additional pressures from this closely related species. As Poor understanding of the agents of decline can cause common diving petrels appear to be also attracted to Whenua translocation failure, including for petrels (Jones & Kress, Hou diving petrel calls, acoustic attraction systems may not ; Osborne & Seddon, ). Insights into the drivers be an option to establish new Whenua Hou diving petrel of nest survival are key for translocations. Many seabirds, colonies (Fischer et al., b). Therefore, a translocation including most petrels, are wide-ranging (e.g. Shaffer et al., of Whenua Hou diving petrels to a more suitable site ). Because of these wide foraging ranges, associated could help ensure long-term viability. Detailed information threats at sea are unlikely to be affected by translocation, on the factors affecting nest survival and breeding biology is as has been shown for short-tailed albatrosses Phoebastria required to meaningfully assess site suitability and design albatrus (Deguchi et al., ; Orben et al., ). Under- translocation protocols. Such information was previously standing drivers of nest survival at source sites may thus unavailable. be key to predicting nest survival at potential translocation To inform future translocations, we monitored Whenua sites and, consequently, translocation success (Osborne & Hou diving petrel burrows across three breeding seasons Seddon, ). As nest survival in seabirds can be subject (–) with a burrowscope, stick palisades, and nest to interannual fluctuations driven by climatic conditions boxes. We aimed to quantify nest survival and its underly- (Chastel et al., ; Quillfeldt et al., ), multi-year stud- ing drivers. In addition, we documented breeding phenology ies of nest survival are critical. and patterns of burrow attendance (as a proxy for feeding Poor understanding of the breeding biology of the target regimes), and measured chicks, to generate growth curves. species is also a potential cause of translocation failure (Jones & Kress, ). Petrels exhibit high philopatry and Study area their semi-precocial chicks are believed to imprint on their natal colonies prior to fledging (Priddel et al., ; The entire Whenua Hou diving petrel colony is restricted Miskelly et al., ). Thus, the use of chicks, – weeks to a . km strip of coastal sand dunes on Whenua Hou prior to fledging, is required to successfully translocate (Codfish Island; Fig. ), km off the west coast of Rakiura these species (Miskelly et al., ; Jones & Kress, ). (Stewart Island), Aotearoa New Zealand. This area holds As these chicks then need to be hand-reared at the trans- c. Whenua Hou diving petrel burrows (Fischer et al., location site, detailed information on the breeding biology a). A small number of common diving petrels