Japanese Honeysuckle (Lonicera japonica) as an Invasive Species; History,Ecology, and Context

Japanese honeysuckle (Lonicera japonica) was introduced outside of Asia in the early 19th century and is now invasive to varying degrees on every continent, except Anarctica, and many archipelagos. The basic ecology and life history of Japanese honeysuckle are well known and described here; however, research needs on the underlying causes of the voracity and subsequent ecological impacts of this species are many. Virtually all ecological experimentation with Japanese honeysuckle has been conducted in the southeastern U.S., thus more data are needed in other regions, particularly South America and Africa. Although Japanese honeysuckle is naturalized in many areas where it has been introduced, there still may be hope for the control of local infestations and its further spread in areas that have a fairly recent introduction history. Japanese honeysuckle may be secure throughout much of its introduced range, but land management principles that discourage its use and public education to prevent further dispersal are recommended strongly.     

Removal of invasive shrubs reduces exotic earthworm populations

Invasive species are a leading threat to native ecosystems, and research regarding their effective control is at the forefront of applied ecology. Exotic facilitation has been credited with advancing the success of several aggressive invasive species. Here, we suggest using the knowledge of exotic facilitations to control invasive earthworm populations. In northern hardwood forests, the invasive shrubs Rhamnus cathartica (buckthorn) and Lonicera x bella (honeysuckle) produce high quality leaf litter, and their abundance is positively correlated with exotic earthworms, which increase nutrient cycling rates. We performed an invasive plant removal experiment in two northern hardwood forest stands, one dominated by buckthorn and the other by honeysuckle. Removal of invasive shrubs reduced exotic earthworm populations by roughly 50% for the following 3 years. By targeting invasive species that are part of positive feedback loops, land managers can multiply the positive effects of invasive species removal.     

Fruit quantity of invasive shrubs predicts the abundance of common native avian frugivores in central Pennsylvania

Aim Biological invasions pose one of the most severe threats to global biodiversity. Still, invasions can create positive ecological relationships and services, which can sometimes result in challenges for conservation efforts. A case in point is the invasion of alien plants that form mutualisms with native frugivorous birds. Here, we examined the correlation between honeysuckles (Lonicera spp.) and the bird communities in a landscape of central Pennsylvania during the fall months. Location State College area in central Pennsylvania, USA. Methods We conducted point counts to quantify the abundance of birds and fleshy‐fruited plant species within a 187.5 km² landscape that included forested, urban and agricultural lands. We also compared fruit‐removal rates for a native fruiting plant under low and high Lonicera densities. Results The abundance of birds showed a strong positive association with Lonicera fruits, with the abundance of Turdus migratorius and Dumetella carolinensis showing the strongest correlations. We also found that fruit‐removal rates were 30% larger for a native plant species in areas of high Lonicera density compared to a site with low density of Lonicera. Main conclusions Our results suggest that Lonicera may currently serve as a main axis for the organization of bird communities and the networks of frugivore–plant interactions in central Pennsylvania. Since populations of key bird frugivores may be currently depending on Lonicera resources, we argue that control measures should account for the negative effects that the loss of this fruit resource could have on populations of native consumers in highly invaded regions.     

Large-Scale Removal of Invasive Honeysuckle Decreases Mosquito and Avian Host Abundance

Invasive species rank second only to habitat destruction as a threat to native biodiversity. One consequence of biological invasions is altered risk of exposure to infectious diseases in human and animal populations. The distribution and prevalence of mosquito-borne diseases depend on the complex interactions between the vector, the pathogen, and the human or wildlife reservoir host. These interactions are highly susceptible to disturbance by invasive species, including terrestrial plants. We conducted a 2-year field experiment using a Before–After/Control–Impact design to examine how removal of invasive Amur honeysuckle (Lonicera maackii) in a forest fragment embedded within a residential neighborhood affects the abundance of mosquitoes, including two of the most important vectors of West Nile virus, Culex pipiens and Cx. restuans. We also assessed any potential changes in avian communities and local microclimate associated with Amur honeysuckle removal. We found that (1) removal of Amur honeysuckle reduces the abundance of both vector and non-vector mosquito species that commonly feed on human hosts, (2) the abundance and composition of avian hosts is altered by honeysuckle removal, and (3) areas invaded with honeysuckle support local microclimates that are favorable to mosquito survival. Collectively, our investigations demonstrate the role of a highly invasive understory shrub in determining the abundance and distribution of mosquitoes and suggest potential mechanisms underlying this pattern. Our results also give rise to additional questions regarding the general impact of invasive plants on vector-borne diseases and the spatial scale at which removal of invasive plants may be utilized to effect disease control.     

Living with Aliens: Effects of Invasive Shrub Honeysuckles on Avian Nesting

Invasive species have come to the forefront of conservation biology as a major threat to native biodiversity. Habitats dominated by shrub honeysuckles (Lonicera spp.) in the United States have been characterized as “ecological traps” by ecologists. Here we tested this hypothesis by investigating the effects of shrub honeysuckles on the nesting ecology of native birds in seven study sites in central Pennsylvania, USA. We examined how the abundance of shrub honeysuckles influenced the selection of nesting substrates and habitat for a community of common songbirds, and the parental-care behavior and nestling development of gray catbirds (Dumetella carolinensis). We found that birds had a strong bias towards nesting in honeysuckle shrubs, but not necessarily for nesting in honeysuckle-dominated habitats. Nest predation rates were affected by the density of nests in a habitat, but not by the overall abundance of honeysuckles in such habitats. Honeysuckle abundance in the habitat did show significant effects on some parental-care behavioral parameters: catbirds had higher nest visitation rates and shorter visit lengths in areas of high honeysuckle density. On average, Gray catbirds fed fruit 12%±0.31 s.e. of their nestling-feeding bouts, mostly fruits of shrub honeysuckles. Nestlings in sites with high honeysuckle density also showed higher mass:tarsus ratios, suggesting a good (possibly better) physiological condition of catbird nestlings at the time of fledging. Our study shows that honeysuckle-dominated habitats could have equivocal effects on nesting parameters of common species of native birds. We advise more caution in the widespread denomination of novel plant communities with high densities of honeysuckle as “ecological traps” as effects can be null or positive on native birds in certain localities.     

Effects of invasive seaweeds on feeding preference and performance of a keystone Mediterranean herbivore

The consequences of invasive species on ecosystem processes and ecological interactions remain poorly understood. Predator–prey interactions are fundamental in shaping species evolution and community structure and can be strongly modified by species introductions. To fully understand the ecological effects of invasive species on trophic linkages it is important to characterize novel interactions between native predators and exotic prey and to identify the impacts of invasive species on the performance of native predators. Although seaweed invasions are a growing global concern, our understanding of invasive algae—herbivore interactions is still very limited. We used a series of feeding experiments between a native herbivore and four invasive algae in the Mediterranean Sea to examine the potential of native sea urchins to consume invasive seaweeds and the impacts of invasive seaweed on herbivore performance. We found that three of the four invasive species examined are avoided by native herbivores, and that feeding behaviour in sea urchins is not driven by plant nutritional quality. On the other hand, Caulerpa racemosa is readily consumed by sea urchins, but may escape enemy control by reducing their performance. Recognizing the negative impacts of C. racemosa on herbivore performance has highlighted an enemy escape mechanism that contributes to explaining how this widespread invasive alga, which is preferred and consumed by herbivores, is not eradicated by grazing in the field. Furthermore, given the ecological and economic importance of sea urchins, negative impacts of invasive seaweeds on their performance could have dramatic effects on ecosystem function and services, and should be accounted for in sea urchin population management strategies.     

Patterns and mechanisms of invasive plant impacts on North American birds: a systematic review

Understanding how invasive plants affect biodiversity is a crucial conservation need. Numerous studies examine impacts of invasions on birds, but trends in these effects have not been synthesized. We reviewed 128 studies from North America to quantify the frequency of positive, negative, and neutral (non-significant) effects of invasive plants on avian ecology, and then evaluated support for proposed mechanisms of impacts. Our frequency-based approach enabled us to draw value from the full breadth of available literature, including articles that do not provide information necessary for meta-analyses and articles examining understudied phenomena. Total avian abundance and prevalence of individual bird species were usually unaffected by invasion, with 48.9 and 57.2% of tests showing neutral results, respectively. Avian richness decreased with invasion in 41.3% of tests. Although birds often preferred nesting in invasive vegetation (45.0% of tests), effects on nest survival were typically neutral (57.9%). Multiple metrics (e.g. body condition, fledgling survival) have received scant attention. Some of the patterns we highlight differ across ecological contexts, emphasizing the need to understand impact mechanisms. Several studies have directly linked invasion impacts to altered nest-site availability, habitat heterogeneity, and food supplies. There is mixed evidence that plant architecture impacts nest-site selection and nest predation. Our review highlights the nonuniform consequences of biological invasions. The high frequency of reported neutral effects suggests that invasions often have minimal impacts on birds, but positive and negative impacts certainly can arise. Managers considering eradicating invasive plants for avian conservation should monitor impacts locally to determine whether eradication will be beneficial.     

Habitat use and seed removal by invasive rats (Rattus rattus) in disturbed and undisturbed rain forest,Puerto Rico

Despite frequent occurrences of invasive rats (Rattus spp.) on islands, their known effects on forests are limited. Where invasive rats have been studied, they generally have significant negative impacts on native plants, birds, and other animals. This study aimed to determine invasive rat distribution and effects on native plant populations via short‐term seed removal trials in tropical rain forest habitats in the Luquillo Experimental Forest, Puerto Rico. To address the first objective, we used tracking tunnels (inked and baited cards inside tunnels enabling animal visitors’ footprints to be identified) placed on the ground and in the lower canopy within disturbed (treefall gaps, hurricane plots, stream edges) and undisturbed (continuous forest) habitats. We found that rats are present in all habitats tested. Secondly, we compared seed removal of four native tree species (Guarea guidonia, Buchenavia capitata, Tetragastris balsamifera, and Prestoea acuminata) between vertebrate‐excluded and free‐access treatments in the same disturbed and undisturbed habitats. Trail cameras were used to identify animals responsible for seed contact and removal. Black rats (Rattus rattus) were responsible for 65.1% of the interactions with seeds, of which 28.6% were confirmed seed removals. Two plant species had significantly more seeds removed in disturbed (gaps) than undisturbed forest. Prestoea acuminata had the lowest seed removal (9% in 10 days), whereas all other species had >30% removal. Black rats are likely influencing fates of seeds on the forest floor, and possibly forest community composition, through dispersal or predation. Further understanding of rat–plant interactions may be useful for formulating conservation strategies.     

Effect of Hydrologic Restoration and Lonicera maackii Removal on Herbaceous Understory Vegetation in a Bottomland Hardwood Forest

Amur honeysuckle (Lonicera maackii (Rupr.) Herder), a large deciduous shrub from China, has invaded many forests in eastern/central United States. The species was removed by cutting and herbicide application from a recently hydrologically restored section of a bottomland hardwood forest in central Ohio, and the response of understory plants, especially herbaceous species, was measured. Plots were established in uncleared and cleared sections, and percent cover of each herbaceous understory species was estimated monthly. One season after several years of Lonicera removal efforts, no significant association was discovered between percentage of Lonicera cover and total understory species abundance. There was, however, a direct correlation between elevation and honeysuckle abundance; L. maackii abundance was negatively associated with low elevations, likely due to hydrologic factors. Plant species diversity (H) and richness (s) increased with elevation but were not significantly different on plots with honeysuckle removal (H = 0.86 ± 0.08 vs. 0.78 ± 0.09 and s = 4.4 ± 0.19 vs. 4.2 ± 0.2 species/m², respectively) despite the fact that understory light levels measured by densiometer were significantly higher (α= 0.003) in cleared versus uncleared sections. Native and invasive species were found in similar proportions in the two sections, and significant sprouting and regrowth of L. maackii were observed throughout the cleared section. Although the removal of L. maackii altered the characteristics of the plant species assemblage, the value of this management remains questionable in the years immediately following treatment.     

Does localized control of invasive eastern gambusia (Poeciliidae: Gambusia holbrooki) increase population growth of generalist wetland fishes?

While invasive fish management is heavily focussed on containment measures when introductions occur, examples from invasive species management in terrestrial systems suggest that there may also be considerable conservation benefits in implementing localized control programmes. We conducted a field‐based experiment to assess the effectiveness of removing a globally significant invasive fish, eastern gambusia Gambusia holbrooki, from natural wetland habitats of south‐eastern Australia. With recent work suggesting the impacts of eastern gambusia may be minimal for species with generalist life‐history strategies, we hypothesized that the removal of eastern gambusia will reduce localized population growth of the invasive species, but will have little influence on the population growth of more generalist sympatric wetland fish species. We used a predictive modelling approach to investigate changes in eastern gambusia populations following removal activities, and how sympatric fish species responded to such changes. Although eastern gambusia rapidly populated habitats, we demonstrated that control actions substantially reduced the rate of population increase over the four‐month study period. This suggests that control may be an effective localized strategy to suppress eastern gambusia densities. There was however, no evidence of any response to the removal actions by any of the three sympatric fish species investigated – carp gudgeon (Hypseleotris spp.), Australian smelt (Retropinna semoni) and the invasive common carp (Cyprinus carpio). These results support previous work which suggests that the flexible life‐history strategies and behavioural traits of all three species allow co‐existence with eastern gambusia. The study highlights the importance of understanding the potential outcomes of control options which is particularly pertinent for established aquatic invasive species where information on control effectiveness, population dynamics and/or ecosystem response is currently lacking.     

How bad are invaders in coastal waters? The case of the American slipper limpet Crepidula fornicata in western Europe

Introduced species are assumed to exert a variety of negative ecological effects in their new environments. However, rigid studies on such effects are still rare. Using a case study we exemplify pitfalls and obstacles for research on ecological effects of invaders and highlight the need for a concise framework. The suspension feeding gastropod Crepidula fornicata was accidentally introduced with American oysters to Europe and was soon after defamed as an ‘oyster pest’ although no evidence was provided in justification. Recently, small-scale experiments with C. fornicata and the Pacific oyster Crassostrea gigas failed to prove competition. As an epizootic, however, C. fornicata is impeding native mussels Mytilus edulis but at the same time provides protection against starfish predation. It also may serve as a sink for infectious trematode parasites and hence be beneficial for bivalve basibionts. Another positive effect of C. fornicata, especially at the coast of France where it is superabundant, may be that it causes a shift of phytoplankton blooms from toxic flagellates to diatoms. The multiple interactions with recipient coastal ecosystems result in a complex interplay of negative as well as positive effects of the invader on native biota. Positive effects of invaders might occur with the same frequency as negative ones, and the general prejudice that introduced species exert per se a negative effect may dictate the outcome of research. We argue that considering both, negative as well as positive effects of an introduced species is needed to eventually enable us to evaluate the overall effect of an invasion on recipient ecosystems. Besides pointing to the importance of positive effects, this case study also shows that research on effects of introduced species should (1) be species specific, (2) consider different spatial scales, (3) clarify which stage of an invasive process is under observation and (4) clearly distinguish between ecological effects, human-relevant impacts and the ethical judgment of both. A concise framework for research on ecological effects of introduced species – which still has to be developed – should incorporate these aspects.     

Invasive plant species alters consumer behavior by providing refuge from predation

Understanding the effects of invasive plants on native consumers is important because consumer-mediated indirect effects have the potential to alter the dynamics of coexistence in native communities. Invasive plants may promote changes in consumer pressure due to changes in protective cover (i.e., the architectural complexity of the invaded habitat) and in food availability (i.e., subsidies of fruits and seeds). No experimental studies have evaluated the relative interplay of these two effects. In a factorial experiment, we manipulated cover and food provided by the invasive shrub Amur honeysuckle (Lonicera maackii) to evaluate whether this plant alters the foraging activity of native mammals. Using tracking plates to quantify mammalian foraging activity, we found that removal of honeysuckle cover, rather than changes in the fruit resources it provides, reduced the activity of important seed consumers, mice in the genus Peromyscus. Two mesopredators, Procyon lotor and Didelphis virginiana, were also affected. Moreover, we found rodents used L. maackii for cover only on cloudless nights, indicating that the effect of honeysuckle was weather-dependent. Our work provides experimental evidence that this invasive plant species changes habitat characteristics, and in so doing alters the behavior of small- and medium-sized mammals. Changes in seed predator behavior may lead to cascading effects on the seeds that mice consume.     

Ecological consequences of invasion across the freshwater–marine transition in a warming world

The freshwater–marine transition that characterizes an estuarine system can provide multiple entry options for invading species, yet the relative importance of this gradient in determining the functional contribution of invading species has received little attention. The ecological consequences of species invasion are routinely evaluated within a freshwater versus marine context, even though many invasive species can inhabit a wide range of salinities. We investigate the functional consequences of different sizes of Corbicula fluminea—an invasive species able to adapt to a wide range of temperatures and salinity—across the freshwater–marine transition in the presence versus absence of warming. Specifically, we characterize how C. fluminea affect fluid and particle transport, important processes in mediating nutrient cycling (NH₄‐N, NO₃‐N, PO₄‐P). Results showed that sediment particle reworking (bioturbation) tends to be influenced by size and to a lesser extent, temperature and salinity; nutrient concentrations are influenced by different interactions between all variables (salinity, temperature, and size class). Our findings demonstrate the highly context‐dependent nature of the ecosystem consequences of invasion and highlight the potential for species to simultaneously occupy multiple components of an ecosystem. Recognizing of this aspect of invasibility is fundamental to management and conservation efforts, particularly as freshwater and marine systems tend to be compartmentalized rather than be treated as a contiguous unit. We conclude that more comprehensive appreciation of the distribution of invasive species across adjacent habitats and different seasons is urgently needed to allow the true extent of biological introductions, and their ecological consequences, to be fully realized.     

Sublethal effects on reproduction in native fauna: are females more vulnerable to biological invasion?

Although invasive species are a major threat to survivorship of native species, we know little about their sublethal effects. In soft-sediment marine systems, mat-forming invasive species often have positive effects, facilitating recruitment and enhancing the diversity and abundance of native invertebrates. However, because mat-forming invasive species change the habitat in which they invade, and benthic invertebrates are sensitive to environmental disturbance, important sublethal effects on native species may exist. Using a model marine system we show that the widespread mat-forming invasive alga Caulerpa taxifolia (Vahl) C. Agardh has strong negative effects on the reproductive traits of a native bivalve Anadara trapezia (Deshayes, 1840) (e.g. timing of reproductive development and spawning, and follicle and gamete production) even though the invader has positive effects on recruitment. Moreover, gender specific responses occurred and indicated that females were more susceptible to invasion than males. Our results indicate that sublethal effects of an invasive species on reproductive traits will have severe consequences for fitness of the native species.     

Foliar production and decomposition rates in urban forests invaded by the exotic invasive shrub, <Emphasis Type="Italic">Lonicera maackii</Emphasis>

Exotic invasive shrubs can form dense monocultures in forest understories, which can have cascading effects on ecosystem structure and function. Amur honeysuckle, an exotic shrub that forms dense canopies in eastern forests, has the potential to alter plant community structure and ecosystem functions, such as primary production and decomposition. The goal of this study was to examine foliar productivity and leaf litter decomposition in forests invaded by Amur honeysuckle (Lonicera maackii) and to determine the extent to which the presence of this dominant exotic species may alter ecosystem function in these forests. We found that forests invaded by Amur honeysuckle had 16 times greater honeysuckle foliar biomass and 1.5 times lower total foliar biomass than forests of equivalent tree basal area, but having few honeysuckle shrubs. This suggests that productivity of native tree and shrub species may be reduced where honeysuckle density is high. Additionally, honeysuckle litter decayed four times faster and released nitrogen more rapidly than sugar maple litter, and sugar maple litter decayed 19% faster in forests invaded by Amur honeysuckle. These findings suggest that forests invaded by Amur honeysuckle may exhibit lower rates of organic matter accrual and less nitrogen retention in the forest floor. Since honeysuckle leaves develop in early spring before those of other shrubs or trees in the area, the rapid release of nitrogen from honeysuckle litter that we measured in early spring is timed to benefit this invasive species. The temporally coincident phenologies of nitrogen release during decomposition with the foliar growth needs of this shrub indicates that a potential positive feedback loop may exist between these processes that promotes continued growth and dominance of honeysuckle shrubs in these forested systems.     

Insights Gained From 50 Years of Studying the Evolution of Self-Compatibility in <Emphasis Type="Italic">Leavenworthia</Emphasis> (Brassicaceae)

The shift from outcrossing to selfing is one of the most common evolutionary trends in plants, and there is intense interest in why this is so. The genus Leavenworthia has been the focus of research on this question for half of a century, with particular attention paid to the evolution of self-compatibility from self-incompatibility. In this review, we discuss the last 50 years of research concerning this evolutionary transition in Leavenworthia. Selfing appears to have evolved independently at minimum three times within this genus of eight species. Work on the ecological basis of mating system evolution in Leavenworthia has clarified that selection among individuals is likely a major force behind the recurrent evolution of selfing. Although inadequate pollination is appreciated as a factor favoring selfing, definitive ecological mechanisms that act to favor selfing are still not known and future work on the efficacy of pollinating bees and the effects of climate change is needed. Recent research has likely identified the SRK ortholog at the S-locus controlling self-incompatibility in Leavenworthia alabamica. Analyses of S-locus variation have revealed substantial S-allele diversity in outcrossing populations, with the recurrent fixation of mutations at the S-locus permitting the parallel evolution of selfing in this species. Although we appreciate some of the factors that may explain the evolution of selfing in this group, there is less known about the mechanisms underlying the widespread maintenance of outcrossing at the population and species levels. Studies in Leavenworthia have revealed that genetic diversity is lost over the long-term within selfing populations and leads to elevated population subdivision, but work is needed to determine why these genetic consequences of selfing cause lineages to become evolutionary dead ends.     

Managed livestock grazing for conservation outcomes in a Queensland fragmented landscape

Protecting native biodiversity is a difficult prospect in extremely modified landscapes, especially where high‐impact exotic species are widespread. Using new data and a review of the literature, this paper comments on the use of livestock grazing to manage the invasive and highly combustible pasture grass species, Buffel Grass (Cenchrus ciliaris) and thereby help conserve fire‐sensitive Brigalow (Acacia harpophylla) vegetation in reserves in Queensland, Australia. We cite evidence that shows that grazing is a potentially useful management tool in such cases and its use can be compatible with the protection of both fire‐sensitive vegetation and other native plant species within the understorey. However, there are limitations in implementing grazing within conservation reserves including the lack of a clear understanding of the influence of grazing on biodiversity and resource condition. Importantly, we highlight secondary invasion by the exotic grass Indian Couch (Bothriochloa pertusa) as a key emerging threat that may undermine the biodiversity benefits gained by grazing in reserves. Grazing can be a useful tool for conservation management in particular scenarios, but the associated risks demand accompanying monitoring and reporting of positive and negative impacts to ensure the fundamental aim of biodiversity protection is being achieved.     

Individual and interactive effects of Amur honeysuckle (Lonicera maackii) and white-tailed deer (Odocoileus virginianus) on herbs in a deciduous forest in the eastern United States

Invasive Amur honeysuckle (Lonicera maackii) has reduced diversity, growth, and reproduction of native herbs in the Midwest USA. These effects may be compounded by browsing from overabundant white-tailed deer (Odocoileus virginianus). We used experimental treatments of honeysuckle (present, absent, removed) and deer (present, excluded) to measure their independent and interactive impacts on diversity, richness, and abundance of herbs in a deciduous forest in southwestern Ohio, USA. Species diversity and richness of herbs were not affected by honeysuckle or deer. Honeysuckle reduced abundance of annuals, graminoids, spring perennials, and summer perennials; deer decreased abundance of annuals and spring perennials, but increased abundance of graminoids. A deer × honeysuckle interaction showed that when honeysuckle was absent or removed, browsing by deer kept abundance of annuals and spring perennials low. Effects of honeysuckle and deer also were assessed for the three most abundant herbs: honeysuckle reduced abundance of Carex rosea and Sanicula odorata, and deer reduced abundance of Viola soraria. Herb abundance varied seasonally and annually. Honeysuckle and deer reduced number of leaves/stem of Maianthemum racemosum and a deer × honeysuckle interaction indicated that the negative effect of honeysuckle was released only when deer were excluded. Herb abundance and M. racemosum rebounded to or near to control levels after removal of honeysuckle. Our findings revealed that impacts of invasive honeysuckle or overabundant deer were not the same across all levels of biological organization (i.e., individual species, growth forms, community measures of species diversity/richness). Measuring impacts of these species at multiple levels of biological organization, considering deer × honeysuckle interactions, and collecting data for several years to account for seasonal and annual fluctuations will help guide management plans. The rapid response by herbs to removal of honeysuckle demonstrated the resilience of this community and is a hopeful sign for restoration of native understory herbs.     

Current perspectives in avian nutrition: domestic animal models and their role in conservation management

As biodiversity declines, wildlife conservation focuses on in situ and ex situ management strategies. Zoo-based breeding programmes are often designed to contribute to the conservation of species that are threatened in the wild. Diet contributes to the reproductive success, disease status and longevity of all animals. It is near-impossible to replicate a species' diet in captivity using only the species they consume in the wild, but the nutritional composition of a wild diet, if known, can be closely matched using commercially available foods for which the nutritional composition has been calculated. Ecological research has identified food items of importance in the diet of many species. However, the nutritional composition of these food items is rarely evaluated, even though the composition of wild food items is important in understanding the dietary adaptations and requirements of wildlife. In contrast, the nutritional requirements of domestic species are well researched and can be used to predict a range of plausible nutrient requirements of some wild species, especially those with similar life histories. Access to wild populations provides further opportunities for nutritional science to determine the requirements of individual species. Small-scale dietary experimentation undertaken at conservation institutions may show positive effects on health and welfare but is rarely published in the scientific literature. This review describes current standards in nutritional management of birds and recommends pathways for filling knowledge gaps. Research on mammals has dominated the nutrition literature, so there is a relative lack of nutritional management information for birds. We combine concepts of domestic animal nutrition with recent findings on the nutritional requirements of birds to provide a foundation for further studies of avian nutrition. We call for the broader zoological community to share data and collaborate on nutritional research to support conservation institutions in nutritional management of wild birds.     

Bird demographic responses to predator removal programs

Invasive predators pose a significant risk to bird populations worldwide. Humans have a long history of removing predators from ecosystems; current island restoration actions typically focus on the removal of invasive predators, such as non-native rodents, from seabird breeding islands. While not overly abundant, the results of predator removal studies provide valuable information on the demographic response of birds, and can assist conservation practitioners with prioritizing invasive predator removal projects. We review such studies focusing on observed demographic responses of bird populations to predator removal campaigns and whether ecological factors are useful in predicting those responses. From the 800+ predator removal programs indentified, a small fraction (n = 112) reported demographic responses of bird populations. Change in productivity was the most commonly reported response, which on average increased by 25.3% (2.5 SE) with predator removal. The best supported model for predicting the change in productivity from predator removal incorporated bird body mass, egg mass, predator type, nest type and an interaction term for body mass and nest type (AIC_c weight = 0.457). The predicted percent increase in productivity resulting from hypothetical predator removal ranged from 16.9 to 63.0% (mean = 45.0, 5.6 SE), and was lowest for large, surface nesting birds such as albatrosses. The predicted increase in productivity resulting from predator removal alone was insufficient to reverse the predicted population decline for 30–67% of bird species considered, suggesting that in many cases, removal of predators must be performed in combination with other conservation actions in order to ensure a stable or increasing population.