Exploring the implications of recreational disturbance on an endangered butterfly using a novel modelling approach

Site and wildlife managers globally are under increasing pressure to implement management strategies that address the negative implications of outdoor recreational activities on wildlife. For many rare and isolated species any anthropogenic activities that cause disturbance could potentially be detrimental to existing populations. Understanding how non-consumptive recreation can influence a species may therefore be critical to its preservation. We developed a novel approach to specifically address this need. Using a combination of field surveys and simulation modelling exercises, we (1) explored the responses of endangered Karner blue butterflies (Lycaeides melissa samuelis) to recreation, (2) assessed whether such responses influenced oviposition rate and/or host plant choice and (3) tested alternative management strategies that could alleviate the negative impacts of recreation. Our field surveys confirmed that Karner blues were sensitive to recreational disturbance. Butterflies flushed at similar speeds and distances from recreationists (2.2 m at 0.17 m/s), as they would from natural threats, such as predators (2.2 m at 0.19 m/s). Incorporating female response parameters into a simulation model revealed that regular disturbance could reduce egg laying potential and significantly restrict host plant choice, which in turn, could impact the butterfly’s population dynamics. However, we established that it was possible to effectively offset the implications of recreational disturbance using our simulation modelling approach. For example, extending Karner blue breeding habitat from trails and other public rights of way has the potential to alleviate such disturbance. Our study demonstrates that the potential impact of recreation on species of conservation concern should not be overlooked.     

Effects of military activity on breeding birds

United States military bases provide habitat for a diverse suite of wildlife species despite intense anthropogenic disturbance inherent in training activities. Little research has examined how military activity affects wildlife reproduction. We compared parental investment, reproductive success, offspring and adult quality, and stress hormone concentrations of northern cardinals (Cardinalis cardinalis) breeding in areas that differed 10-fold in levels of on-ground military activity. We found no evidence of direct impacts of military activity on cardinals, nor did the reproductive success of several other passerine species appear to be affected. However, we observed American crows (Corvus brachyrhynchos) much less frequently in areas of high military activity, and cardinals nesting in those areas were less responsive to crow models. The apparent displacement of this nest predator suggests that military activity could indirectly benefit some wildlife. Although these results are promising for the conservation of birds that depend on military bases for breeding habitat, further assessment of direct and indirect effects of military training on a wider array of species is required before concluding that such activity is benign. © 2012 The Wildlife Society.     

Island accessibility and distance from beach influence nesting success of Sooty Falcons Falco concolor in Oman

Colonial island‐breeding birds can be particularly vulnerable to anthropogenic disturbance, which can adversely affect their nesting success. We studied Sooty Falcons Falco concolor breeding on 10 ground‐predator‐free islands in the Sea of Oman during 2007–2014 and evaluated spatio‐temporal trends in the number of breeding pairs occurring on the islands and the factors influencing nesting success. The number of breeding pairs on the islands declined during the study, due mostly to the decline on accessible islands; the rate of decline on islands accessible to humans was double that on inaccessible ones. The number of nests with one or more eggs declined during the study period, and the percentage of nests with eggs that produced one or more chicks showed an increasing trend over time. Sooty Falcon nests located farther away from beaches experienced a significantly higher probability of nesting success than those located closer to beaches. Our results suggest that the number of breeding Sooty Falcons on the islands of northern Oman is declining and that human disturbance may be a contributing factor; this probably mirrors the situation in other parts of the breeding range of this species.     

Anthropogenic impacts on Costa Rican bat parasitism are sex specific

While anthropogenic impacts on parasitism of wildlife are receiving growing attention, whether these impacts vary in a sex‐specific manner remains little explored. Differences between the sexes in the effect of parasites, linked to anthropogenic activity, could lead to uneven sex ratios and higher population endangerment. We sampled 1108 individual bats in 18 different sites across an agricultural mosaic landscape in southern Costa Rica to investigate the relationships between anthropogenic impacts (deforestation and reductions in host species richness) and bat fly ectoparasitism of 35 species of Neotropical bats. Although female and male bat assemblages were similar across the deforestation gradient, bat fly assemblages tracked their hosts closely only on female bats. We found that in female hosts, parasite abundance per bat decreased with increasing bat species richness, while in male hosts, parasite abundance increased. We hypothesize the differences in the parasite–disturbance relationship are due to differences in roosting behavior between the sexes. We report a sex‐specific parasite–disturbance relationship and argue that sex differences in anthropogenic impacts on wildlife parasitism could impact long‐term population health and survival.     

Investigator activities reduce nest predation in blackbirds Turdus merula

The effect of investigator perturbance has been traditionally considered detrimental for avian nesting success in terms of enhanced nest predation. This conclusion was however based on a taxonomically biased group of species and, thus, the study of that effect in additional species was essential for reaching a more firm conclusion. Furthermore, although it has been suggested that the effect of nest visiting could also depend on nest predator community, no study has so far tested this hypothesis yet. Trying to detect possible influence of nest‐visiting rates and predator community on nesting success we visited European blackbird Turdus merula nests at two different experimental rates in two populations that considerably differ in the composition of their nest predator communities and natural nest predation rates. Contrary to the traditional ideas, our results not only show that investigator disturbance significantly reduces nest predation, but also that this reduction is maintained in both populations despite the difference in the community of nest predators. We discuss these findings and suggest that predators, especially mammals, might avoid places disturbed by investigators.     

Egg coloration and selection for crypsis in open-nesting blackbirds

High variation in egg coloration among birds has traditionally been explained as adaptation for camouflage. We tested this hypothesis by conducting reciprocal clutch exchanges (n=301) among Brewer's blackbirds Euphagous cyanocephalus , red-winged blackbirds Agelaius phoeniceus , and yellow-headed blackbirds Xanthocephalus xanthocephalus . We predicted that clutches placed against their natural nest backgrounds would have higher survival rates than heterospecific clutches. Intraspecific clutch exchanges were used as a control. Clutch survival was monitored for a 9-d period at all nests, during which time incubation rhythm and nest defense were quantified. Intraspecific clutch exchanges did not influence incubation or nest defense. For two of the species, intraspecific clutch exchanges did not influence clutch survival; in red-winged blackbirds, however, intraspecifically exchanged clutches had somewhat depressed survival curves relative to control clutches (P=0.08). The effect of interspecific clutch exchanges differed by host species. In Brewer's nests, eggs of the yellow-headed blackbird had lower survival than Brewer's eggs (P=0.02), but survival of red-winged blackbird eggs did not differ from Brewer's eggs (P=0.50). In nests of red-winged blackbirds, all three clutch types had approximately equal survival. In yellow-headed blackbird nests, eggs of the red-winged blackbird had lower survival than yellow-headed blackbird eggs (P=0.06), and survival of Brewer's eggs did not differ from yellow-headed blackbird eggs (P=0.31). These findings support a role for egg coloration as camouflage in two of the three species studied.     

Variation in behavioral traits of two frugivorous mammals may lead to differential responses to human disturbance

Human activities can lead to a shift in wildlife species’ spatial distribution. Understanding the specific effects of human activities on ranging behavior can improve conservation management of wildlife populations in human‐dominated landscapes. This study evaluated the effects of forest use by humans on the spatial distribution of mammal species with different behavioral adaptations, using sympatric western lowland gorilla and central chimpanzee as focal species. We collected data on great ape nest locations, ecological and physical variables (habitat distribution, permanent rivers, and topographic data), and anthropogenic variables (distance to trails, villages, and a permanent research site). Here, we show that anthropogenic variables are important predictors of the distribution of wild animals. In the resource model, the distribution of gorilla nests was predicted by nesting habitat distribution, while chimpanzee nests were predicted first by elevation followed by nesting habitat distribution. In the anthropogenic model, the major predictors of gorilla nesting changed to human features, while the major predictors of chimpanzee nesting remained elevation and the availability of their preferred nesting habitats. Animal behavioral traits (body size, terrestrial/arboreal, level of specialization/generalization, and competitive inferiority/superiority) may influence the response of mammals to human activities. Our results suggest that chimpanzees may survive in human‐encroached areas whenever the availability of their nesting habitat and preferred fruits can support their population, while a certain level of human activities may threaten gorillas. Consequently, the survival of gorillas in human‐dominated landscapes is more at risk than that of chimpanzees. Replicating our research in other sites should permit a systematic evaluation of the influence of human activity on the distribution of mammal populations. As wild animals are increasingly exposed to human disturbance, understanding the resulting consequences of shifting species distributions due to human disturbance on animal population abundance and their long‐term survival will be of growing conservation importance.     

A systematic review of the effects of recreational activities on nesting birds of prey

Human disturbance to wildlife is a growing topic of concern owing to increasing human access to the countryside. Here we use systematic review methodology to specifically synthesize available information on the impact of recreational activities on raptor breeding parameters. Presently there is insufficient information to quantitatively meta-analyze this topic. The most frequent effect turned out to be decreased time for nest attendance but information on effects on breeding parameters was inconclusive. The only outcome susceptible to quantitative meta-analysis was the influence on nest location of a number of anthropic structures. Out of these we chose distance to the closest paved road, because it was the metric recorded in the largest number of studies, and because it can be taken as a surrogate of recreational access to the countryside. We detected an overall statistically significant impact on the displacement of nests from roads from a total of 25 studies, compared to random points in unoccupied areas suitable for breeding. The magnitude of the displacement was probably a biologically relevant magnitude (back-transformed ln response ratio 1.28; 1.07–1.57 bootstrap 95% CI). Importantly, statistical modelling of effect sizes as a function of raptor body size and nesting site substrate (tree nesting vs. cliff nesting) identified an effect of both nesting habitat and body size on nest placement by raptors in relation to roads. Big raptors nesting in trees exhibited greater displacement distances from nests to roads than big raptors nesting in cliffs, and hence we suggest that conservation efforts should take special attention to this vulnerable raptor group which includes some threatened species.     

Evaluating methods to quantify anthropogenic stressors on wild animals

Humans have a variety of direct and indirect impacts on wildlife and a number of methods have been proposed to identify and quantify anthropogenic stressors that negatively impact wildlife. The ideal method would ultimately help predict the presence, absence, or population viability of animals living with a particular stressor. We critically review seven methods that have been used, or are potentially useful, to identify anthropogenic stressors on animals. We rank them from fitness indicators to disturbance indicators: breeding success, mate choice, fluctuating asymmetry, flight initiation distance, immunocompetence, glucocorticoids, and cardiac response. We describe each method's ease of use, precision in quantifying the stressor, accuracy in predicting the presence, absence, or population viability of a species experiencing a given stressor, and the repeatability of the results across populations and species. From this analysis, we conclude that there is no single optimal method to quantify anthropogenic stressors; method selection will depend on precise goals and fiscal constraints.     

How anthropogenic noise affects foraging

The influence of human activity on the biosphere is increasing. While direct damage (e.g. habitat destruction) is relatively well understood, many activities affect wildlife in less apparent ways. Here, we investigate how anthropogenic noise impairs foraging, which has direct consequences for animal survival and reproductive success. Noise can disturb foraging via several mechanisms that may operate simultaneously, and thus, their effects could not be disentangled hitherto. We developed a diagnostic framework that can be applied to identify the potential mechanisms of disturbance in any species capable of detecting the noise. We tested this framework using Daubenton's bats, which find prey by echolocation. We found that traffic noise reduced foraging efficiency in most bats. Unexpectedly, this effect was present even if the playback noise did not overlap in frequency with the prey echoes. Neither overlapping noise nor nonoverlapping noise influenced the search effort required for a successful prey capture. Hence, noise did not mask prey echoes or reduce the attention of bats. Instead, noise acted as an aversive stimulus that caused avoidance response, thereby reducing foraging efficiency. We conclude that conservation policies may seriously underestimate numbers of species affected and the multilevel effects on animal fitness, if the mechanisms of disturbance are not considered.     

Reproductive interactions of the Shiny Cowbird Molothrus bonariensis and the Yellow-hooded Blackbird Agelaius icterocephalus in Trinidad

The reproductive interactions of the Shiny Cowbird Molothrus bonariensis , a brood parasite, and the Yellow-hooded Blackbird Agelaius icterocephalus , a host of the cowbird, were studied In Trinidad, West Indies. We gathered information on the breeding biology of the Shiny Cowbird and the Yellow-hooded Blackbird, the frequency of use of the host species, and the effects of brood parasitism on host breeding success. Yellow-hooded Blackbirds are polygynous for the most part; males build nests and attempt to attract females to lay in them by means of song and visual displays directed towards the nests. This behaviour probably makes it easy for cowbirds to locate breeding birds and their nests. Cowbird eggs were found in 153 of 377 (40–3 %) blackbird nests located before the nestling stage. Shiny Cowbird parasitism of the Yellow-hooded Blackbird had little negative impact on host reproductive success, whereas predation accounted for the majority of nest failures. Vigilant nest defense by male blackbirds combined with colonial breeding apparently also minimized the extent of host egg damage and removal by cowbirds, and the parasitized and unparasitized nests were equally successful at producing blackbirds. Cowbirds most frequently parasitized the first or only nesting attempts in blackbird territories, and first or only nests were also successful more frequently than subsequent nests.     

Long-billed curlew nest site selection and success in the Intermountain West

Grassland birds have experienced steeper population declines between 1966 and 2015 than any other bird group on the North American continent, and migratory grassland birds may face threats in all stages of their annual cycle. The grassland-associated long-billed curlew (Numenius americanus) is experiencing population declines in regional and local portions of their North American breeding range. The nesting period is an important portion of the annual cycle when curlews may face demographic rate limitations from a suite of threats including predators and anthropogenic disturbance. We compared nest sites to random sites within breeding territories to examine nest site selection, and modeled correlates of nesting success for 128 curlew nests at 5 Intermountain West sites. Nest sites were 6 times more likely than random sites to be situated adjacent to existing cowpies. Additionally, curlews selected nest sites with shorter vegetation, and less bare ground, grass, and shrub cover than at random sites within their territories. Nest success varied widely among sites and ranged from 12% to 40% in a season with a mean of 27% for all nests during the 2015 and 2016 seasons. Higher nest success probability was associated with higher curlew densities in the area, greater percent cover of conspicuous objects (cowpies, rocks) near the nest, and higher densities of black-billed magpies (Pica hudsonia) and American crows (Corvus brachyrhynchos) at the site. We also found increased probability of nesting success with increased distance from a nest to the nearest potential perch in that territory. Given the central role of working lands to curlews in much of the Intermountain West, understanding limitations to nesting success in these diverse landscapes is necessary to guide adaptive management strategies in increasingly human-modified habitats. We suggest some grazing and irrigation practices already provide suitable nesting conditions for curlews, and others may require only minor temporal shifts to improve compatibility. © 2019 The Wildlife Society.     

Sociality influences thermoregulation and roost switching in a forest bat using ephemeral roosts

In summer, many temperate bat species use daytime torpor, but breeding females do so less to avoid interferences with reproduction. In forest‐roosting bats, deep tree cavities buffer roost microclimate from abrupt temperature oscillations and facilitate thermoregulation. Forest bats also switch roosts frequently, so thermally suitable cavities may be limiting. We tested how barbastelle bats (Barbastella barbastellus), often roosting beneath flaking bark in snags, may thermoregulate successfully despite the unstable microclimate of their preferred cavities. We assessed thermoregulation patterns of bats roosting in trees in a beech forest of central Italy. Although all bats used torpor, females were more often normothermic. Cavities were poorly insulated, but social thermoregulation probably overcomes this problem. A model incorporating the presence of roost mates and group size explained thermoregulation patterns better than others based, respectively, on the location and structural characteristics of tree roosts and cavities, weather, or sex, reproductive or body condition. Homeothermy was recorded for all subjects, including nonreproductive females: This probably ensures availability of a warm roosting environment for nonvolant juveniles. Homeothermy may also represent a lifesaver for bats roosting beneath loose bark, very exposed to predators, because homeothermic bats may react quickly in case of emergency. We also found that barbastelle bats maintain group cohesion when switching roosts: This may accelerate roost occupation at the end of a night, quickly securing a stable microclimate in the newly occupied cavity. Overall, both thermoregulation and roost‐switching patterns were satisfactorily explained as adaptations to a structurally and thermally labile roosting environment.     

Noise Pollution Changes Avian Communities and Species Interactions

Humans have drastically changed much of the world's acoustic background with anthropogenic sounds that are markedly different in pitch and amplitude than sounds in most natural habitats [1], [2], [3] and [4]. This novel acoustic background may be detrimental for many species, particularly birds [1]. We evaluated conservation concerns that noise limits bird distributions and reduces nesting success via a natural experiment to isolate the effects of noise from confounding stimuli and to control for the effect of noise on observer detection biases [5]. We show that noise alone reduces nesting species richness and leads to different avian communities. Contrary to expectations, noise indirectly facilitates reproductive success of individuals nesting in noisy areas as a result of the disruption of predator-prey interactions. The higher reproductive success for birds within noisy habitats may be a previously unrecognized factor contributing to the success of urban-adapted species and the loss of birds less tolerant of noise. Additionally, our findings suggest that noise can have cascading consequences for communities through altered species interactions. Given that noise pollution is becoming ubiquitous throughout much of the world, knowledge of species-specific responses to noise and the cumulative effects of these novel acoustics may be crucial to understanding and managing human-altered landscapes.     

Nesting Ecology of Boreal Forest Birds Following a Massive Outbreak of Spruce Beetles

Abstract: We studied breeding dark-eyed juncos (Junco hyemalis), yellow-rumped warblers (Dendroica coronata), and spruce-nesting birds from 1997 to 1998 among forests with different levels of spruce (Picea spp.) mortality following an outbreak of spruce beetles (Dendroctonus rufipennis) in Alaska, USA. We identified species using live and beetle-killed spruce for nest sites and monitored nests to determine how the outbreak influenced avian habitat selection and reproduction. We tested predictions that 1) nesting success of ground-nesting juncos would increase with spruce mortality due to proliferation of understory vegetation available to conceal nests from predators, 2) nesting success of canopy-nesting warblers would decrease with spruce mortality due to fewer live spruce in which to conceal nests, and 3) both species would alter nest-site selection in response to disturbance. Juncos did not benefit from changes in understory vegetation; nesting success in highly disturbed stands (46%) was comparable to that in undisturbed habitats throughout their range. In stands with low spruce mortality, nesting success of juncos was low (5%) and corresponded with high densities of red squirrels (Tamiasciurus hudsonicus). Yellow-rumped warblers nested exclusively in spruce, but success did not vary with spruce mortality. As disturbance increased, nesting warblers switched from selecting forest patches with high densities of live white spruce (Picea glauca) to patches with beetle-killed spruce. Warblers also placed nests in large-diameter live or beetle-killed spruce, depending on which was more abundant in the stand, with no differences in nesting success. Five of the 12 other species of spruce-nesting birds also used beetle-killed spruce as nest sites. Because beetle-killed spruce can remain standing for >50 years, even highly disturbed stands provide an important breeding resource for boreal forest birds. We recommend that boreal forest managers preserve uncut blocks of infested forest within managed forest landscapes and practice partial harvest of beetle-killed spruce rather than commercial clear-cutting of infested stands in order to sustain breeding bird populations until natural reforestation occurs. Because breeding densities do not always reflect fitness, assessing impacts of a massive natural disturbance should include measuring impacts of changes in vegetation on both reproductive success and predator-prey dynamics.     

Characterization of fungi associated with the nasal hairs of Molossid bats

Fungal pathogens have become a serious threat to wildlife, threatening populations of even once common, abundant species. We describe the mycobiota associated with the nasal hairs of three Molossid bat species, Cynomops planirostris, Molossus molossus, and Molossus rufus, in southwest Brazil. Bats were captured in the Cerrado and Pantanal biomes. We cultured 22 fungal isolates from twelve individual bats. Sixteen sequences of the ITS region were obtained, yielding 11 unique sequence types from the genera Aspergillus, Cladosporium, Paecilomyces, and Penicillium. No obvious detrimental effects on the bats from the fungi were observed, although some species or genera that we identified are known pathogens in other species. This is the first report of such fungi associated with the nasal hairs of Molossid bats. Our results indicate the need for further research on the biodiversity, ecological role, and potential effects of this mycobiota on Molossid bats.     

Low breeding success of the little egret (Egretta garzetta) near residential areas and in colonies exposed to gales: a comparison of colony in Sichuan,Southwest China,with literature

The breeding biology of the little egret (Egretta garzetta) was studied in 20 nests within the mixed-species breeding colonies at Nanchong, Sichuan, Southwest China, in 2006. By measuring a set of physical characteristics of vegetation at the nests and at a set of 20 randomly chosen sites we showed that birds preferentially used taller trees in areas with fewer shrubs of higher species diversity. Nests at lower locations in trees had marginally lower hatching success due to their destruction by humans; this destruction contributed marginally significantly to lowering of the total nesting success in all studied nests. Although gale winds also had a negative effect on breeding success, the anthropogenic influences were a greater factor in reproductive failure. We found similar effects in our review of literature on breeding success of the little egret from various geographical areas. Our results may be of use by conservation organizations in their actions to protect colonies of the little egret.     

Off-Highway Vehicle Trail Impacts on Breeding Songbirds in Northeastern California

Abstract: Rapid growth in off-highway vehicle (OHV) use in North America leads to concerns about potential impacts on wildlife populations. We studied the relationship between distance to active OHV trail and songbird nesting success and abundance in northeastern California, USA, from 2002 to 2004. We found evidence of greater nest desertion and abandonment and reduced predation on shrub nests <100 m from OHV trails than at nests >100 m from OHV trails. Two of 18 species studied were less abundant at sites on trails than at sites 250 m from trails, and no species were more abundant on trails. Management of OHV trail development should consider possible negative impacts on nesting success and abundance of breeding birds.     

Traffic noise exposure affects telomere length in nestling house sparrows

In a consistently urbanizing world, anthropogenic noise has become almost omnipresent, and there are increasing evidence that high noise levels can have major impacts on wildlife. While the effects of anthropogenic noise exposure on adult animals have been widely studied, surprisingly, there has been little consideration of the effects of noise pollution on developing organisms. Yet, environmental conditions experienced in early life can have dramatic lifelong consequences for fitness. Here, we experimentally manipulated the acoustic environment of free-living house sparrows (Passer domesticus) breeding in nest boxes. We focused on the impact of such disturbance on nestlings’ telomere length and fledging success, as telomeres (the protective ends of chromosomes) appear to be a promising predictor of longevity. We showed that despite the absence of any obvious immediate consequences (growth and fledging success), nestlings reared under traffic noise exposure exhibited reduced telomere lengths compared with their unexposed neighbours. Although the mechanisms responsible for this effect remain to be determined, our results provide the first experimental evidence that noise alone can affect a wild vertebrate''s early-life telomere length. This suggests that noise exposure may entail important costs for developing organisms.     

Large-scale spatial variation in the breeding performance of song thrushes Turdus philomelos and blackbirds T. merula in Britain

1.  Spatial variation in breeding performance is of critical importance in understanding the large-scale distribution and abundance of living species, and in understanding species conservation. We studied the large-scale spatial variation in reproductive output of two species of declining British bird, the song thrush Turdus philomelos and the blackbird Turdus merula .
2.  We developed a method to predict spatial variation in reproductive output. Brood size and nest failure rates during the incubation and nestling periods were related to environmental factors using generalized linear models. Predicted values obtained from these models were combined to give values of number of fledglings produced per nesting attempt for 10-km squares throughout Britain.
3.  We observed substantial spatial variation in reproductive output for both species; the component that varied most was nest failure rate during incubation. We were more successful in relating environmental factors to spatial variation in reproductive output for song thrush than for blackbird.
4.  Reproductive output in both species was affected mainly by factors that vary on a small spatial scale. Nest failure rate during incubation increased significantly where corvids were more abundant, suggesting a role for avian nest predators in determining spatial variation in reproductive output.
5.  Our approach can be extended readily to other species of birds, to other taxonomic groups and to finer spatial scales. Such models could be used to evaluate the implications of current and proposed wider countryside management for spatial variation in breeding performance. Evaluations based on breeding success as well as numbers are likely to be more robust than those based solely on abundance.