Forest fragments have biodiversity value that may be enhanced through management such as control of non-native predators. However, such efforts may be ineffective, and research is needed to ensure that predator control is done strategically. We used Bayesian hierarchical modeling to estimate fragment-specific effects of experimental rat control on a native species targeted for recovery in a New Zealand pastoral landscape. The experiment was a modified BACI (before-after-control-impact) design conducted over 6 years in 19 forest fragments with low-density subpopulations of North Island Robins (Petroica longipes). The aim was to identify individual fragments that not only showed clear benefits of rat control, but also would have a high probability of subpopulation growth even if they were the only fragment managed. We collected data on fecundity, adult and juvenile survival, and juvenile emigration, and modeled the data in an integrated framework to estimate the expected annual growth rate (λ) of each subpopulation with and without rat control. Without emigration, subpopulation growth was estimated as marginal (λ = 0.95-1.05) or negative (λ = 0.74-0.90) without rat control, but it was estimated as positive in all fragments (λ = 1.4-2.1) if rats were controlled. This reflected a 150% average increase in fecundity and 45% average increase in adult female survival. The probability of a juvenile remaining in its natal fragment was 0.37 on average, but varied with fragment connectivity. With juvenile emigration added, 6 fragments were estimated to have a high (>0.8) probability of being self-sustaining (λ > 1) with rat control. The key factors affecting subpopulation growth rates under rat control were low connectivity and stock fencing because these factors were associated with lower juvenile emigration and higher fecundity, respectively. However, there was also substantial random variation in adult survival among fragments, illustrating the importance of hierarchical modeling for fragmentation studies.
Efficient decision-making integrates previous experience with new information. Tactical use of misinformation can alter choice in humans. Whether misinformation affects decision-making in other free-living species, including problem species, is unknown. Here, we show that sensory misinformation tactics can reduce the impacts of predators on vulnerable bird populations as effectively as lethal control. We repeatedly exposed invasive mammalian predators to unprofitable bird odors for 5 weeks before native shorebirds arrived for nesting and for 8 weeks thereafter. Chick production increased 1.7-fold at odor-treated sites over 25 to 35 days, with doubled or tripled odds of successful hatching, resulting in a 127% increase in modeled population size in 25 years. We demonstrate that decision-making processes that respond to changes in information reliability are vulnerable to tactical manipulation by misinformation. Altering perceptions of prey availability offers an innovative, nonlethal approach to managing problem predators and improving conservation outcomes for threatened species.
Experimental reintroductions are essential for testing rapid inferences about effects of isolation and habitat quality on patch occupancy.
Managed pine plantations now constitute a large portion of mainland New Zealand. Despite many native birds inhabiting these exotic habitats, their value for biodiversity conservation is unclear. Although numerous studies have quantified densities of native bird species in pine plantations, it is unknown whether these individuals constitute self-sustaining populations. Here we address this question for North Island robins (Petroica longipes) in a Pinus radiata plantation in the central North Island. We compare survival and reproduction data of robins collected in three different compartments of the plantation from 2003-2005 to similar data collected from 20 unmanaged native forest fragments from 2002-2014. We used the data to derive estimates of finite rate of increase (λ) using a Bayesian hierarchical modelling framework that accounted for site-to-site and temporal variation. The mean reproduction rate was much lower in the pine plantation, with females producing 0.34 (SE 0.15) independent juveniles per year, in comparison to 1.02 (SE 0.21) in fenced native fragments and 0.83 (SE 0.21) in grazed native fragments. These differences are attributable to lower nest survival, as nests in the pines had a 0.09 (SE 0.05) probability of surviving to fledging, compared to 0.33 (SE 0.04) for fenced native fragments and 0.28 (SE 0.06) for grazed native fragments. In contrast, the mean adult female survival probability was 0.64 (SE 0.13) in the pines in comparison to 0.55 (SE 0.04) in the native fragments. The λ estimate for the pine plantation was 0.76 (SE 0.14), meaning λ was unlikely to be >1 as is required for a self-sustaining population. The mean λ was estimated to be 0.89 (SE 0.09) for fenced native fragments and 0.83 (SE 0.09) for unfenced native fragments, but varied among fragments with estimates close to 1 for some fenced fragments. Therefore, the pine plantation probably constituted sink habitat that retained robins due to immigration from the surrounding landscape, whereas at least some of the native fragments could potentially be self-sustaining.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.