Improving supplementary feeding in species conservation

Supplementary feeding is often a knee-jerk reaction to population declines, and its application is not critically evaluated, leading to polarized views among managers on its usefulness. Here, we advocate a more strategic approach to supplementary feeding so that the choice to use it is clearly justified over, or in combination with, other management actions and the predicted consequences are then critically assessed following implementation. We propose combining methods from a set of specialist disciplines that will allow critical evaluation of the need, benefit, and risks of food supplementation. Through the use of nutritional ecology, population ecology, and structured decision making, conservation managers can make better choices about what and how to feed by estimating consequences on population recovery across a range of possible actions. This structured approach also informs targeted monitoring and more clearly allows supplementary feeding to be integrated in recovery plans and reduces the risk of inefficient decisions. In New Zealand, managers of the endangered Hihi (Notiomystis cincta) often rely on supplementary feeding to support reintroduced populations. On Kapiti island the reintroduced Hihi population has responded well to food supplementation, but the logistics of providing an increasing demand recently outstretched management capacity. To decide whether and how the feeding regime should be revised, managers used a structured decision making approach informed by population responses to alternative feeding regimes. The decision was made to reduce the spatial distribution of feeders and invest saved time in increasing volume of food delivered into a smaller core area. The approach used allowed a transparent and defendable management decision in regard to supplementary feeding, reflecting the multiple objectives of managers and their priorities

Making structured decisions for reintroduced populations in the face of uncertainty

Structured decision‐making (SDM) has become popular in natural resource management but has been underused in reintroduction programs. We illustrate how conservation managers can use SDM to guide management decisions after initial reintroduction, when data are still limited and uncertainty around vital rates estimates is high. In 2013, the hihi (Notiomystis cincta), an endangered New Zealand forest bird, was reintroduced to Bushy Park (BP), a managed conservation reserve. High post‐release mortality in females led to the population remaining small after 2 years, raising the question of whether more females should be released. We built a model to evaluate three management alternatives, including no further translocation and translocations of 15 additional females (from the only possible source population) in either 2015 or 2016. The fundamental objectives identified were to maximize the number and persistence of female hihi in BP, minimize the impact on the source population, and minimize costs. Our decision analysis incorporated uncertainties in parameter estimation, model selection, and demographic stochasticity. It produced distributions of final scores for each management alternative based on population projections for both the BP population and source population, and objective weights assigned by stakeholders. Although the distributions of final scores overlapped greatly, the “no translocation” alternative was largely stochastically dominant over other management options, that is, it was clearly the best choice in most projections and the choice was ambiguous in the remaining projections. The decision was also unaffected by variation in stakeholder values. Although the underlying modeling was complex, the output provided a simple visualization of outcomes that allowed the recovery group to make an informed decision (no further translocation) that fully considered the uncertainties

Effect of supplementary feeding on reproductive success of hihi (stitchbird, Notiomystis cincta) at a mature forest reintroduction site

Supplementary feeding has proven to be a successful conservation tool for many species, including New Zealand’s hihi (stitchbird, Notiomystis cincta). Previous research has shown supplementary feeding to substantially increase hihi reproductive success at regenerating forest sites, but suggested that it would have reduced benefit in mature forest habitat. Here we report the first direct test of the effect of supplementary feeding on hihi reproductive success in mature forest, using data from the recently reintroduced population at Maungatautari Ecological Island. Eight feeder-using females and nine non-feeder-using females were monitored during the 2012/13 breeding season at Maungatautari to determine how feeder use affected reproductive success (nest success, number of first-clutch fledglings per female and total number of fledglings per female). Feeder-using females fledged 3.7 times as many fledglings as non-feeder-using females in their first-clutch attempts (95% CI 1.6–8.8), and 1.8 times as many fledglings in total (95% CI 1.0–3.5). No feeder-using female experienced nest failure, whereas 7 of the 16 nest attempts of non-feeder-using females failed to fledge any young. The results suggest that, counter to expectations, supplementary feeder use has a significant impact on reproductive success in mature forest habitat. At least for Maungatautari, providing supplementary food in mature forest habitat appears to greatly reduce the probability of hihi nest failure, and increases the number of young a female can fledge

Determinants of male floating behaviour and floater reproduction in a threatened population of the hihi (Notiomystis cincta)

Floating males are usually thought of as nonbreeders. However, some floating individuals are able to reproduce through extra-pair copulations. Floater reproductive success can impact breeders’ sex ratio, reproductive variance, multiple paternity and inbreeding, particularly in small populations. Changes in reproductive variance alter the rate of genetic drift and loss of genetic diversity. Therefore, genetic management of threatened species requires an understanding of floater reproduction and determinants of floating behaviour to effectively conserve species. Here, we used a pedigreed, free-living population of the endangered New Zealand hihi (Notiomystis cincta) to assess variance in male reproductive success and test the genetic (inbreeding and heritability) and conditional (age and size) factors that influence floater behaviour and reproduction. Floater reproduction is common in this species. However, floater individuals have lower reproductive success and variance in reproductive success than territorial males (total and extra-pair fledglings), so their relative impact on the population's reproductive performance is low. Whether an individual becomes a floater, and if so then how successful they are, is determined mainly by individual age (young and old) and to lesser extents male size (small) and inbreeding level (inbred). Floating males have a small, but important role in population reproduction and persistence of threatened populations

Targeted management buffers negative impacts of climate change on the hihi, a threatened New Zealand passerine

In order to buffer the risks climate change poses to biodiversity, managers need to develop new strategies to cope with an increasingly dynamic environment. Supplementary Feeding (SF) is a commonly-used form of conservation management that may help buffer the impacts of climate change. However, the role of SF as an adaptation tool is yet to be fully understood. Here we used the program MARK to quantify the relationship between weather (average temperature and total precipitation) and vital rates (survival and recruitment) of an island bird population, the hihi Notiomystis cincta, for which long term demographic data are available under periods of little and ad libitum SF. We then used predictive population modelling to project this population’s dynamics under each management strategy and several climate change scenarios in accordance with the Intergovernmental Panel on Climate Change predictions. Our stochastic population projections revealed that ad libitum SF likely buffer the population against heavier rainfall and more stochastic precipitation patterns; no buffering effect on temperature was detected. While the current SF approach is unlikely to prevent local extinction of the population under increasing temperatures, SF still presents itself as a valuable climate change adaptation tool by delaying extinction. To the best of our knowledge, this is the first study to quantify the interaction between climate and SF intensity of a threatened population. We call for on-going critical evaluation of management measures, and suggest that novel adaptation solutions that combine current approaches are required for conserving species with limited opportunity for dispersal

Minutes matter: brief hatching asynchrony adversely affects late-hatched hihi nestlings, but not life beyond the nest

Size hierarchies are often seen when nestlings hatch asynchronously over a period of days. Shorter hatch periods are common across passerines, however, and while these may also give rise to asymmetries, their effects are rarely considered. Regardless of hatch period, the long-term consequences for later hatched nestlings that survive to fledge is unknown for wild birds. Here we explored the timing of hatch order in a free-living population of hihi nestlings, Notiomystis cincta, and followed any effects in and out of the nest. We found that while hatching time from first- to last-hatched nestlings was often less than 24 h, last-hatched individuals grew more slowly and were lighter and smaller at fledging than older siblings. Last-hatched nestlings were also less likely to fledge. These effects were greater in larger broods. Adult body size is correlated with fledging size in hihi; however, we found no evidence that hatch order affected longevity postfledging, or lifetime reproductive success. We then explored whether carotenoid availability might buffer these stressful rearing conditions (through food supplementation of parents) but found no evidence that increased access to carotenoids for mothers and/or growing nestlings influenced incubation schedules, or the effects of hatching late. Together these results suggest that while even a very short hatch period can influence adult phenotype, hatching asynchrony is not maladaptive for hihi: when last-hatched nestlings survive to fledge they can contribute as much to their mothers' fitness as first-hatched siblings

Habitat selection in a reintroduced population: social effects differ between natal and post-release dispersal

Animal translocations are human-induced colonizations that can represent opportunities to contribute to the knowledge on the behavioral and demographic processes involved in the establishment of animal populations. Habitat selection behaviors, such as social cueing, have strong implications on dispersal and affect the establishment success of translocations. Using modeling simulations with a two-population network model (a translocated population and a remnant population), we investigated the consequences of four habitat selection strategies on post-translocation establishment probabilities in short- and long-lived species. Two dispersal strategies using social cues (conspecific attraction and habitat copying) were compared to random and quality-based strategies. We measured the sensitivity of local extinctions to dispersal strategies, life cycles, release frequencies, remnant population and release group sizes, the proportion of breeders and the connectivity between populations. Our results indicate that social behaviors can compromise establishment as a result of post-release dispersal, particularly in long-lived species. This behavioral mechanism, the “vacuum effect”, arises from increased emigration in populations that are small relative to neighboring populations, reducing their rate of population growth. The vacuum effect can drive small remnant populations to extinction when a translocated group is large. In addition, the magnitude of the vacuum effect varies non-linearly with connectivity. The vacuum effect represents a novel form of the behaviorally mediated Allee effect that can cause unexpected establishment failures or population extinctions in response to social cueing. Accounting for establishment probabilities as a conditional step to the persistence of populations would improve the accuracy of predicting the fates of translocated or natural (meta)populations

Stochastic dominance to account for uncertainty and risk in conservation decisions

Practical conservation normally requires making decisions in the face of uncertainty. Our attitude toward that uncertainty, and the risks it entails, shape the way conservation decisions are made. Stochastic dominance (SD), a method more commonly used in economics, can be used to rank alternative conservation actions by comparing the probability distributions of their outcomes, making progressive simplified assumptions about the preferences of decision makers. Here, we illustrate the application of SD to conservation decisions using the recovery plan for an endangered frog species in Australia as a case study. Stochastic dominance is simple and intuitively appealing for conservation decisions; its broader application may encourage conservation decision makers to consider probabilistic uncertainty in light of their preferences, which may otherwise be difficult to recognize and assess transparently. A better treatment of attitudes towards uncertainty and risk may help ensure rational decision making in conservation and remove potential causes of stakeholder conflict

Genomic data of different resolutions reveal consistent inbreeding estimates but contrasting homozygosity landscapes for the threatened Aotearoa New Zealand hihi

Inbreeding can lead to a loss of heterozygosity in a population and when combined with genetic drift may reduce the adaptive potential of a species. However, there is uncertainty about whether resequencing data can provide accurate and consistent inbreeding estimates. Here, we performed an in-depth inbreeding analysis for hihi (Notiomystis cincta), an endemic and nationally vulnerable passerine bird of Aotearoa New Zealand. We first focused on subsampling variants from a reference genome male, and found that low-density data sets tend to miss runs of homozygosity (ROH) in some places and overestimate ROH length in others, resulting in contrasting homozygosity landscapes. Low-coverage resequencing and 50 K SNP array densities can yield comparable inbreeding results to high-coverage resequencing approaches, but the results for all data sets are highly dependent on the software settings employed. Second, we extended our analysis to 10 hihi where low-coverage whole genome resequencing, RAD-seq and SNP array genotypes are available. We inferred ROH and individual inbreeding to evaluate the relative effects of sequencing depth versus SNP density on estimating inbreeding coefficients and found that high rates of missingness downwardly bias both the number and length of ROH. In summary, when using genomic data to evaluate inbreeding, studies must consider that ROH estimates are heavily dependent on analysis parameters, data set density and individual sequencing depth

A Comparison of Disease Risk Analysis Tools for Conservation Translocations

Conservation translocations are increasingly used to manage threatened species and restore ecosystems. Translocations increase the risk of disease outbreaks in the translocated and recipient populations. Qualitative disease risk analyses have been used as a means of assessing the magnitude of any effect of disease and the probability of the disease occurring associated with a translocation. Currently multiple alternative qualitative disease risk analysis packages are available to practitioners. Here we compare the ease of use, expertise required, transparency, and results from, three different qualitative disease risk analyses using a translocation of the endangered New Zealand passerine, the hihi (Notiomystis cincta), as a model. We show that the three methods use fundamentally different approaches to define hazards. Different methods are used to produce estimations of the risk from disease, and the estimations are different for the same hazards. Transparency of the process varies between methods from no referencing, or explanations of evidence to justify decisions, through to full documentation of resources, decisions and assumptions made. Evidence to support decisions on estimation of risk from disease is important, to enable knowledge acquired in the future, for example from translocation outcome, to be used to improve the risk estimation for future translocations. Information documenting each disease risk analysis differs along with variation in emphasis of the questions asked within each package. The expertise required to commence a disease risk analysis varies and an action flow chart tailored for the non-wildlife health specialist are included in one method but completion of the disease risk analysis requires wildlife health specialists with epidemiological and pathological knowledge in all three methods. We show that disease risk analysis package choice may play a greater role in the overall risk estimation of the effect of disease on animal populations involved in a translocation than might previously have been realised