Assemblage structure and dynamics of terrestrial birds in the southwest Amazon: a camera‐trap case study

Habitat spatial distribution, seasonal variation, and activity patterns influence changes in vertebrate assemblages over time. Terrestrial birds play major roles in the dynamics of tropical forests, but there are few effective methods to study these species due to their cryptic coloration and elusive behavior. We used camera‐trap data collected during 16 mo (February 2017–June 2018) to describe the terrestrial avifauna in southeastern Peru, assess to what extent the composition of terrestrial avifauna changes among seasons and across two major habitats (terra firme and floodplain forests), and determine daily activity patterns of terrestrial birds. We used overlap analyses to examine temporal co‐occurrence between ecologically similar and sympatric species. Camera traps recorded 16 species, including eight species in the family Tinamidae. Capture rates were highest for Pale‐winged Trumpeters (Psophia leucoptera; Psophiidae) and Gray‐fronted Doves (Leptolila rufaxilla; Columbidae). Species composition did not differ between habitats or seasons, and capture rates between habitats only differed for White‐throated Tinamous (Tinamus guttatus). Overlaps of activity patterns were high between ecologically similar species and species found in terra firme habitats (White‐throated Tinamous and Cinereous Tinamous, Crypturellus cinereus) and in both habitat types (Pale‐winged Trumpeters and Gray‐fronted Doves). Low numbers of captures of possibly locally rare or less abundant species hindered a complete analysis of spatial and seasonal patterns of terrestrial bird assemblages. We suggest a greater sampling effort and greater spatial replication to better understand the spatial and seasonal dynamics of the terrestrial avifauna. Further studies that assess the mechanisms that allow the coexistence of sympatric tinamous would be valuable, both in our study area and elsewhere. The use of camera traps in long‐term monitoring projects proved to be an effective tool for monitoring terrestrial birds, identifying cryptic and often rare animals to species level, and providing valuable ecological information at species and community levels.     

Selection based on the size of the black tie of the great tit may be reversed in urban habitats

A standard approach to model how selection shapes phenotypic traits is the analysis of capture–recapture data relating trait variation to survival. Divergent selection, however, has never been analyzed by the capture–recapture approach. Most reported examples of differences between urban and nonurban animals reflect behavioral plasticity rather than divergent selection. The aim of this paper was to use a capture–recapture approach to test the hypothesis that divergent selection can also drive local adaptation in urban habitats. We focused on the size of the black breast stripe (i.e., tie width) of the great tit (Parus major), a sexual ornament used in mate choice. Urban great tits display smaller tie sizes than forest birds. Because tie size is mostly genetically determined, it could potentially respond to selection. We analyzed capture/recapture data of male great tits in Barcelona city (N = 171) and in a nearby (7 km) forest (N = 324) from 1992 to 2008 using MARK. When modelling recapture rate, we found it to be strongly influenced by tie width, so that both for urban and forest habitats, birds with smaller ties were more trap‐shy and more cautious than their larger tied counterparts. When modelling survival, we found that survival prospects in forest great tits increased the larger their tie width (i.e., directional positive selection), but the reverse was found for urban birds, with individuals displaying smaller ties showing higher survival (i.e., directional negative selection). As melanin‐based tie size seems to be related to personality, and both are heritable, results may be explained by cautious personalities being favored in urban environments. More importantly, our results show that divergent selection can be an important mechanism in local adaptation to urban habitats and that capture–recapture is a powerful tool to test it.     

Studying the quantity component of seed dispersal effectiveness from exclosure treatments and camera trapping

The quantity component of effectiveness of seed dispersal by animals is determined by two events: fruit removal (intensity of the interaction) and animal visitation to the plant (frequency of interactions). Considering dispersal of Prosopis flexuosa seeds as case study, this work aimed at investigating the strengths and weaknesses of the two methods for assessing the quantity component of seed dispersal effectiveness: exclosures and camera traps. Prosopis fruits were offered for 48 hr. Exclosure treatments were performed using two types of wire‐screen cages, allowing access to ants (“closed exclosure”) and to small mammals up to 100 g (“open to small mammals”), and a treatment without exclosure (“open to all removers”). The camera trapping experiment was carried out using vertically oriented cameras placed at approximately 1.80 m height and focused on the fruits. The cameras were set in “motion detect mode,” taking series of three consecutive photographs. The exclosures largely allowed estimation of fruit removal by size‐based groups of animals, but did not provide information on species identity. In contrast, camera traps were able to identify all visitors to species level and could not only determine the number of visits by each species but also the proportion of visits, which resulted in removal of fruits. Camera trapping allowed discriminating among small mammals playing different roles, without underestimating fruit removal by scatter‐hoarding species. The quality of estimation of the quantity component of seed dispersal is remarkably better when the camera trapping method is applied. Additional information obtained, such as activity patterns of visitors, can contribute to a better understanding of the seed dispersal process.     

An improved night-lighting technique for the selective capture of sandgrouse and other steppe birds

The night-lighting technique is routinely used to catch birds. We improved this technique using a thermal infrared camera to catch steppe birds such as the sandgrouse. Target birds were located by an observer using the thermal camera, and approached and dazzled by another observer carrying a spotlight attached to a helmet and a hand-held net together with a playback noise to camouflage the footsteps of the observer. Using this improved technique, we caught on average 1.14 individuals per 3-h capture session (N = 81) and a total of 92 sandgrouse in 2007–2010 (86 pin-tailed sandgrouse Pterocles alchata and six black-bellied sandgrouse Pterocles orientalis). Capture rate and success were negatively influenced by moonlight (lowest during full moon nights). Our night-lighting technique is a highly selective and harmless method to capture sandgrouse and can be used for other small/medium-sized open-land birds or mammals.     

Dodging the moon: The moon effect on activity allocation of prey in the presence of predators

Animals can adapt their activity patterns throughout the circadian cycle. Prey may use moonlight as a predation risk cue and allocate their activity to lower risk periods. Here, we assessed moon transit influence on the activity allocation of nocturnal mammalian prey, in the presence of a predator (pumas, Puma concolor), during different moon phases, through camera trapping in Central Amazon. Thirty camera traps were installed 2 km apart from each other in each of our three study sites. Prey record distributions were assessed across the moon cycle, and their daily activity patterns were described in each moon phase. The record distributions of pacas (Cuniculus paca) (N = 262) and armadillos (Dasypus sp.) (N = 244) were concentrated in darker nights, contrasting with red brocket deer (Mazama americana) (N = 123) and pumas (N = 31), whose records were evenly distributed through the moon cycle. Yet, every prey was found to avoid the brighter times of the night regardless of the moon phase. These findings suggest prey can shift the temporal distribution of their activities under different moon phases when predators are present, perhaps in response to predation risk variations.     

Host‐seeking activity and avian host preferences of mosquitoes associated with West Nile virus transmission in the northeastern U.S.A.

Mosquito host‐seeking activity was studied using a custom‐designed trap to explore: (1) at which time interval of the night adult mosquito abatement would be most effective, and (2) if there exists an avian‐specific host‐seeking preference. Overnight trials using traps baited with dry ice showed that Aedes taeniorhynchus (Wiedemann) was most active at dusk and was then captured throughout the night. In contrast, Culex spp. (Cx. pipiens (Linnaeus) and Cx. restuans (Theobald) delayed most activity until about two h after dusk and were then captured through the night. This pattern suggests that management activities directed at adult Culex spp. would be most effective if initiated well after sunset. Mosquito capture rates in traps baited with birds in net bags were significantly greater than those with empty net bags, indicating that mosquitoes were attracted to the birds and not incidentally being sucked in by the custom trap's strong fan motor (Wilcoxon matched‐pairs signed‐ranks test, n= 24, t= 30, p < 0.05). Regression analysis showed that bird weight influenced mosquito attraction (r²= 0.21, p= 0.02). Trials with paired traps that contained different native bird species showed that Gray Catbirds, Dumatella carolinensis, attracted more mosquitoes than the heavier Northern Cardinals, Cardinalis cardinalis (paired samples t‐test, t= 2.58, df= 7, p= 0.04). However, attractiveness did not differ substantially among bird species, and Gray Catbirds did not attract more mosquitoes than all other birds combined as a group. American Robins, Turdus migratorius (n = 4) were comparable in attractiveness to other bird species, but not enough American Robins were captured for a comprehensive study of mosquito avian preference.     

Dyadic associations reveal clan size and social network structure in the fission–fusion society of spotted hyaenas

Estimating the size and dynamics of populations is of paramount importance in ecology. In species with uniquely marked individuals, capture–recapture methods can be used to establish population size and to explore associations between individuals. However, very few studies have used cameras traps to focus on group composition in social carnivores, despite being of particular interest in species characterised by “fission–fusion” formation of sub-groups. Here, we provide estimates of (a) population size, (b) density, (c) clan size, (d) association patterns and (e) social network structure in spotted hyaenas (Crocuta crocuta) based on images from camera traps deployed at waterholes on Ongava Game Reserve (northern Namibia). In a 15 week study period, we identified 32 individuals. Dyadic associations and the resulting social network showed that all but two hyaenas associated directly or indirectly with each other, indicating the presence of one clan of at least 30 individuals, resulting in a density of 8.1 hyaenas/100 km². We found a very high variability in the tendency of individuals to associate with others. This study confirms a highly dynamic fission–fusion society in spotted hyaenas. We argue that camera traps can provide relevant insights into large carnivore social network structure where associations between individuals are difficult to observe directly.     

Non-intrusive systematic study reveals mutualistic interactions between threatened island endemic species and points to more impactful conservation

Oceanic islands harbour a disproportionately large share of extinct and endangered birds worldwide and up to about 6,800 highly threatened plants, stressing the urgency for conservation efforts there. However, effective conservation action can only be as sound as the ecological understanding on which it is based. Knowledge about the ecology of threatened birds and plants can be relatively sketchy even in well-studied oceanic islands and this can potentially misdirect or erode conservation actions’ effectiveness. We used camera traps to document vertebrate flower visitors of a threatened, mono-specific endemic oceanic island plant (Roussea simplex) that produces much nectar and which was abundant until the 1930s before declining severely despite its presence mostly within protected areas. We determined proportions of native and alien flower visitors in four populations and characterised their ecological role (e.g. florivore, nectar robber, pollinator) through observations and exclusion experiments alongside experiments to determine seed sets by agamospermy, autogamy, geitonogamy and xenogamy. Five native and three alien vertebrate species visited flowers (N = 5,085 camera trap-hours), 96.6% of visits being from birds. Among endemics, 74–96% of visits were by the Mauritius Bulbul (Hypsipetes olivaceus), a threatened bird able to effect pollination contrary to the other endemic birds. Roussea simplex is primarily xenogamous, producing 2,657 ± 480 seeds, and seed set dropped markedly when the bird was excluded (861.8 ± 91.0 SE, Kruskal-Wallis χ² = 14.2, p < 0.001). Natural seed set was very low (410.0 ± 85.3 SE) where the bird was locally extinct or very rare. Invasive alien rats (Rattus rattus) and long-tailed macaques (Macaca fascicularis) were important florivores or nectar robbers. Systematic non-intrusive study using camera traps combined with manipulative experiments revealed a mutualism between two relatively well-studied threatened endemic species as well as new threats from alien vertebrates acting as nectar robbers and florivores. Roussea simplex’s major decline within protected areas and its abundant and year round flowering and nectar production point to a major hitherto unrecorded drop in floral resource previously available to at least five endemic species, and particularly to its commonest flower visitor and principal pollinator, the threatened Mauritius Bulbul. These findings exemplify how systematic non-intrusive study of threatened species may radically change conservation managers’ priorities which in the current case should focus primarily on controlling alien rats and macaques and re-instating or reinforcing Bulbul-Roussea mutualism as each would be more impactful than addressing gecko-Roussea mutualism disruption by alien ants which so far was the only recorded threat thought to drive the rapid decline of Roussea simplex. Our study underscores that current conservation efforts should also pay particular attention to medium to longer-term changes in habitat or community composition which may not be obvious from merely considering extent and composition of current habitats.     

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.     

Seasonal abundance and habitat use of bird species in and around Wondo Genet Forest,south‐central Ethiopia

The habitat use and seasonal migratory pattern of birds in Ethiopia is less explored as compared to diversity studies. To this end, this study aimed at investigating the patterns of distribution related to seasonality and the effect of habitat characteristics (elevation, slope, and average vegetation height) on habitat use of birds of Wondo Genet Forest Patch. A stratified random sampling design was used to assess the avian fauna across the four dominant habitat types found in the study area: natural forest, wooded grassland, grassland, and agroforestry land. A point transect count was employed to investigate avian species richness and abundance per habitat type per season. Ancillary data, such as elevation above sea level, latitude and longitude, average vegetation height, and percent slope inclination, were recorded with a GPS and clinometers per plot. A total of 33 migratory bird species were recorded from the area, of which 20 species were northern (Palearctic) migrants while 13 were inter‐African migrants. There was a significant difference in the mean abundance of migratory bird species between dry and wet seasons (t = 2.13, p = .038, df = 44). The variation in mean abundance per plot between the dry and wet seasons in the grassland habitat was significant (t = 2.35, p = .051, df = 7). In most habitat types during both dry and wet seasons, omnivore birds were the most abundant. While slope was a good predictor for bird species abundance in the dry season, altitude and average vegetation height accounted more in the wet season. The patch of forest and its surrounding is an important bird area for migratory, endemic, and global threatened species. Hence, it is conservation priority area, and the study suggests that conservation coupled with ecotourism development is needed for its sustainability.     

Determining the efficacy of camera traps,live capture traps,and detection dogs for locating cryptic small mammal species

Metal box (e.g., Elliott, Sherman) traps and remote cameras are two of the most commonly employed methods presently used to survey terrestrial mammals. However, their relative efficacy at accurately detecting cryptic small mammals has not been adequately assessed. The present study therefore compared the effectiveness of metal box (Elliott) traps and vertically oriented, close range, white flash camera traps in detecting small mammals occurring in the Scenic Rim of eastern Australia. We also conducted a preliminary survey to determine effectiveness of a conservation detection dog (CDD) for identifying presence of a threatened carnivorous marsupial, Antechinus arktos, in present‐day and historical locations, using camera traps to corroborate detections. 200 Elliott traps and 20 white flash camera traps were set for four deployments per method, across a site where the target small mammals, including A. arktos, are known to occur. Camera traps produced higher detection probabilities than Elliott traps for all four species. Thus, vertically mounted white flash cameras were preferable for detecting the presence of cryptic small mammals in our survey. The CDD, which had been trained to detect A. arktos scat, indicated in total 31 times when deployed in the field survey area, with subsequent camera trap deployments specifically corroborating A. arktos presence at 100% (3) indication locations. Importantly, the dog indicated twice within Border Ranges National Park, where historical (1980s–1990s) specimen‐based records indicate the species was present, but extensive Elliott and camera trapping over the last 5–10 years have resulted in zero A. arktos captures. Camera traps subsequently corroborated A. arktos presence at these sites. This demonstrates that detection dogs can be a highly effective means of locating threatened, cryptic species, especially when traditional methods are unable to detect low‐density mammal populations.     

Avian species diversity in different habitat types in and around North Nandi Forest,Kenya

Forest fragmentation and degradation leads to formation of modified habitats whose ability to support existing avifaunal diversity is still largely unknown. Bird diversity in indigenous forest, disturbed forest, plantation forest and farmlands adjacent to North Nandi Forest reserve was studied between January 2015 and June 2015. The distribution of bird feeding guilds in these habitat patches was also evaluated. Birds were surveyed using point counts, timed species counts and line transects and classified into six feeding guilds. A total of 3,232 individual birds of 151 species were recorded in the four habitats. Significant difference on bird abundance across the four habitats (F = 15.141, P ≤ 0.05, df = 3, 1121) was noted. Shannon–Weiner diversity index H′ for bird community ranged from 3.06 for plantation forest to 4.05 for disturbed forest showing a relatively diverse bird community. Insectivores (F = 3.090, P ≤ 0.05, df = 3, 297) dominated the foraging species assemblage in all the habitats significantly. Linear regression analysis revealed a strong linear relationship on bird species richness and abundance with vegetation variables (P < 0.01 in all cases). The results indicate that disturbed forest and indigenous forest support high bird species richness than plantation forest and farmlands. However, high bird abundance was observed in farmlands and plantation forest as opposed to indigenous forest and disturbed forest as they provide dispersal routes over a short distance and are important for creating corridors between primary forests.     

Effects of capture and video‐recording on the behavior and breeding success of Great Tits in urban and forest habitats

Behavioral research often involves capturing and video‐recording birds, but these procedures may have undesired effects on the behavior of birds that have rarely been quantified. In addition, birds in urban and more natural areas may differ in their sensitivity to disturbance. We examined the possible effects of both capturing, weighing and measuring, and taking a blood sample, and the presence of video‐cameras on the behavior of male and female Great Tits (Parus major) breeding in urban and forest habitats. Using a 2 × 2 block design, we compared the behavior and breeding success of parents that either were or were not captured on their nests a few days before behavioral observations, and of parents that either were or were not habituated to the presence of a concealed video‐recorder mounted on nest boxes. We found no significant effects of habituation to the camera on bird behavior, but males captured in their nest boxes were more vigilant and hesitated longer before entering nest boxes, and also had slightly lower provisioning rates than males that had not been captured. Captured females also tended to be more vigilant than females that had not been captured, but their provisioning rates were not affected. Capturing males also influenced the behavior of their non‐captured mates, but capturing females had no effect on the behavior of their non‐captured mates. We found no difference in the effects of capture on Great Tits in urban and forest habitats, and our treatments also had no effect on the mass, size, and survival of nestlings until fledging. Our results suggest that, for Great Tits, being captured results in sex‐dependent behavioral effects that can last for at least several days. As such, we suggest that the possibility of similar effects in other species of birds should be considered in behavioral studies where birds must be captured, and recommend either that behavioral data be collected before capturing birds or that all birds in a study should be captured and handled in a standardized way.     

Home‐range size of an Andean bird: Assessing the role of physical condition

Because space‐use patterns are a key aspect of the ecology and distribution of species, identifying factors associated with variation in size of territories and home ranges has been central to studies on population ecology. Space use might vary in response to extrinsic factors like habitat quality and to intrinsic factors like physical condition and individual aggressiveness. However, the role of these factors has been poorly documented in the tropics, particularly in high‐elevation bird species. We report the home‐range size of a Neotropical Andean bird, the gray‐browed brush finch (Arremon assimilis), and evaluate the role of physical condition in explaining variation in home‐range size among individuals. We performed spot mapping to estimate the home ranges of 14 territorial males in Bogotá, Colombia, using minimum convex polygons (MCP) and 95% kernel density estimators (KDE). The mean home‐range size estimated for the 100% MCP was 0.522 ± 0.305 ha (range = 0.15–1.18 ha), whereas the 95% KDE estimation was 0.504 ± 0.471 ha (range = 0.13–1.88). We calculated the real mass index of each bird as a proxy of physical condition to assess whether individuals in better physical condition had larger home ranges. Because we found no relation between our estimations of physical condition and home‐range size, we conclude that space use in this species might depend more on ecological factors such as habitat quality or neighbor density than on individual traits. Abstract in French is available with online material.     

Commensal association of the common kingfisher with foraging Eurasian otters

Positive interactions between birds and mammals are a fascinating aspect of animal behaviour. Feeding associations may consist of local enhancement or facilitation, and in the latter case, of commensalism or mutualism depending on the benefits received by the facilitator. We report here on a previously undescribed feeding association between piscivorous birds and Eurasian otters Lutra lutra. In Spain, common kingfisher Alcedo atthis and grey heron Ardea cinerea were observed closely following foraging otters and benefited from feeding opportunities provided by these. Behavioural observations of otters in central Spain (28.4 hr; 19 days) revealed that an association with kingfishers occurred in 33% of otter foraging events (n = 92). Simultaneous observations in northern Spain (14.2 hr; 16 days) showed an association between otters and kingfishers or grey herons in 41.6% and 11.7% of otter foraging events (n = 77), respectively. The association probability between kingfishers and otters increased significantly when otters foraged closer to the shore and on small fish rather than other prey (crayfish or large fish). Birds fed on prey remain left by the feeding otters, on small fish captured by otters when these were satiated and playing, or on prey displaced by otters. Our observations are consistent with facilitation and commensalism: piscivorous birds gained feeding opportunities provided by the otters, with no apparent costs or benefits to the latter. Similar feeding associations have been described between other species of otters and piscivorous birds (kingfishers, herons, egrets, storks) in Asia, South America and Southern Africa, but had not yet been described in Europe. The occurrence of piscivorous bird–otter associations in different species and regions suggests that this commensalism may be often overlooked but widespread. We have shown that the association can be frequent and is context‐dependent, with benefits for associating birds depending on otters´ behaviour and targeted prey.     

Divergent movement patterns of adult and juvenile ‘Akohekohe,an endangered Hawaiian Honeycreeper

The movement patterns of birds across a landscape are often highly variable and influenced by complex interactions between individuals and environments. Because periods of movement can be marked by high mortality, especially among juvenile birds, understanding these patterns may be vital for the conservation of many bird species. However, these patterns can be challenging to quantify. We used radio-telemetry to document the movement patterns of ‘Akohekohe (Palmeria dolei), an endangered Hawaiian Honeycreeper endemic to Maui Island, Hawai'i. This species is believed to be highly susceptible to mosquito-transmitted avian malaria (Plasmodium relictum) and only breeds in high-elevation wet forests on the windward side of east Maui (> 1715 m) that serve as mosquito-free refugia. Over a 2-yr period (2013–2014), we used radio-telemetry and resightings of color-banded birds to track the movements of juveniles (N = 11) and adults (N = 24) and quantified home ranges with minimum convex polygons (MCP) and 95% fixed kernels (KHR). Movement patterns and home range sizes of adult and juvenile ‘Akohekohe were significantly different, with adults having relatively small home ranges (0.57 ha, MCP; 1.09 ha, KHR) and juveniles moving greater distances and having larger home ranges (25.02 ha, MCP; 90.56 ha, KHR). Only juveniles moved into lower-elevation forests that can support mosquito populations, at least seasonally. The absence of adults in this transitional malaria zone suggests that adult ‘Akohekohe cannot maintain long-term home ranges in areas with an increased risk of malaria infection. In addition, the long-distance movements of juveniles during the post-fledging, pre-breeding period likely increases their risk of contracting avian malaria and could be a key factor limiting the population of this species.     

Birds nesting survival in disturbed and protected Neotropical savannas

Fragmentation and other habitat disturbances are long known to negatively affect birds, in large part by decreasing nest success due to high nest predation rates. The factors, however, that cause this decrease in nest success are still poorly understood and may vary among regions or species. Here, we show that nest survival is also lower in a disturbed landscape versus a protected cerrado (savanna-like) Neotropical landscape. Also, we tested the importance of garbage in the nest, brood parasitism, microhabitat and bird family in nest survival, controlling for temporal effects. We monitored 144 birds’ nests in a disturbed landscape and 150 nests in a natural reserve of cerrado vegetation in central Brazil, between September and December 2006. We used Program MARK to estimate nest survival probabilities and evaluate the effect of covariates in nest success in the disturbed area. Nest daily survival rate (DSR) was higher in the reserve (survival probability = 29.4%) than in the disturbed landscape (survival probability = 16.6%). Nest daily survival rate (DSR) was smaller in nests with garbage (survival probability = 9.3%) than in nests without garbage (survival probability = 19.5%) in the disturbed landscape. Effects of habitat disturbance on nest survival differed among bird families, with finches and tanagers being more affected mostly due to high nest predation rates. Conservation and management of birds in disturbed landscapes should include actions to decrease nest predation. In poor rural or suburban areas in developing countries, such as Brazil, actions like better garbage treatment may help conserve birds in disturbed landscapes.     

Unveiling the environmental drivers of intraspecific body size variation in terrestrial vertebrates

Aim

Whether intraspecific spatial patterns in body size are generalizable across species remains contentious, as well as the mechanisms underlying these patterns. Here we test several hypotheses explaining within-species body size variation in terrestrial vertebrates including the heat balance, seasonality, resource availability and water conservation hypotheses for ectotherms, and the heat conservation, heat dissipation, starvation resistance and resource availability hypotheses for endotherms.

Location

Global.

Time period

1970–2016.

Major taxa studied

Amphibians, reptiles, birds and mammals.

Methods

We collected 235,905 body size records for 2,229 species (amphibians = 36; reptiles = 81; birds = 1,545; mammals = 567) and performed a phylogenetic meta-analysis of intraspecific correlations between body size and environmental variables. We further tested whether correlations differ between migratory and non-migratory bird and mammal species, and between thermoregulating and thermoconforming ectotherms.

Results

For bird species, smaller intraspecific body size was associated with higher mean and maximum temperatures and lower resource seasonality. Size–environment relationships followed a similar pattern in resident and migratory birds, but the effect of resource availability on body size was slightly positive only for non-migratory birds. For mammals, we found that intraspecific body size was smaller with lower resource availability and seasonality, with this pattern being more evident in sedentary than migratory species. No clear size–environment relationships were found for reptiles and amphibians.

Main conclusions

Within-species body size variation across endotherms is explained by disparate underlying mechanisms for birds and mammals. Heat conservation (Bergmann's rule) and heat dissipation are the dominant processes explaining biogeographic intraspecific body size variation in birds, whereas in mammals, body size clines are mostly explained by the starvation resistance and resource availability hypotheses. Our findings contribute to a better understanding of the mechanisms behind species adaptations to the environment across their geographic distributions.     

红外相机技术与其他几种森林鸟类多样性调查方法的比较

为了探讨红外相机技术、网捕法、固定距离样线法和固定半径样点法对森林鸟类多样性调查的有效性和实用性, 我们于2011-2016年, 用这几种方法调查了广东南岭国家级自然保护区和车八岭国家级自然保护区的鸟类多样性。在南岭, 固定距离样线法和固定半径样点法记录鸟类222种, 网捕鸟类43种, 红外相机拍到鸟类47种; 其中1种鸟仅网捕到, 6种鸟仅被红外相机拍到, 164种鸟仅被固定距离样线法和固定半径样点法记录到。在车八岭, 固定距离样线法和固定半径样点法记录鸟类109种, 网捕鸟类42种, 红外相机拍到鸟类27种, 其中9种鸟仅网捕到, 3种鸟仅被红外相机拍到, 97种鸟仅被固定距离样线法和固定半径样点法记录到。随着鸟类的体重、体长、翅长和跗蹠增加, 网捕到的鸟类个体数量减少, 鸟类身体大小与网捕到的鸟类数量呈显著负相关; 而红外相机拍到的鸟类数量随鸟类的身体大小增大而增加, 并且呈显著的正相关。本文的结果显示, 网捕法和红外相机技术针对不同类群的鸟类调查效力不同, 但都是固定距离样线法和固定半径样点法的有效补充。建议今后开展森林鸟类多样性调查与监测时, 尽量采用多种研究方法相结合, 以求达到最优的效果。     

Diversity and composition of epigeal arthropods using pitfall trapping method in different habitat types of Abu Dhabi Emirate,UAE

Pitfall trapping is an efficient self-sampling method for capturing epigeal arthropods for ecological and faunistic studies. During the present study, conducted between March 2009 and March 2015, pitfall trapping was undertaken in five study sites of different habitats in Abu Dhabi Emirate. During the study period a total of 94 monitoring visits were made to collect data from the pitfall traps at five sites in Abu Dhabi. A total of 36,238 individuals of ground-dwelling arthropods of 121 different species belonging to 14 orders and 46 families were recorded from all the study sites using pitfall traps. The order Coleoptera (beetles) was recorded to be the most dominant order with 46 species followed by Hymenoptera (ants, bees & wasps) with 24 species. On average 37.5 ± 3 (mean ± SE) species were recorded every month from all the study sites and number of species did not vary significantly across the months (df = 11, F = 0.48, p = 0.91 one-way – ANOVA). The arthropod fauna was recorded to be highly diversified in different habitat types, but the number of individuals were not evenly distributed across the study sites (H) 1.10, (E) 0.53, Shannon Diversity Index). The highest diversity of arthropods was recorded from a site Wadi Tarabat, followed by Al Wathba Wetland Reserve (AWWR) and Abu Al Abyed. Our findings indicate that to study ground dwelling invertebrate species, pitfall trapping is an efficient method. Moreover, capture efficiency of pitfall traps can be affected by climatic factors and habitat types of Abu Dhabi Emirate. The ideal period to encounter the highest number of species is between March to April and September to November across all the habitat types.