Bats are Not Birds – Different Responses to Human Land‐use on a Tropical Mountain

Land‐use intensification has consequences for biodiversity and ecosystem functioning, with various taxonomic groups differing widely in their sensitivity. As land‐use intensification alters habitat structure and resource availability, both factors may contribute to explaining differences in animal species diversity. Within the local animal assemblages the flying vertebrates, bats and birds, provide important and partly complementary ecosystem functions. We tested how bats and birds respond to land‐use intensification and compared abundance, species richness, and community composition across a land‐use gradient including forest, traditional agroforests (home garden), coffee plantations and grasslands on Mount Kilimanjaro, Tanzania. Furthermore, we asked how sensitive different habitat and feeding guilds of bats and birds react to land‐use intensification and the associated alterations in vegetation structure and food resource availability. In contrast to our expectations, land‐use intensification had no negative effect on species richness and abundance of all birds and bats. However, some habitat and feeding guilds, in particular forest specialist and frugivorous birds, were highly sensitive to land‐use intensification. Although the habitat guilds of both, birds and bats, depended on a certain degree of vegetation structure, total bat and bird abundance was mediated primarily by the availability of the respective food resources. Even though the highly structured southern slopes of Mount Kilimanjaro are able to maintain diverse bat and bird assemblages, the sensitivity of avian forest specialists against land‐use intensification and the dependence of the bat and bird habitat guilds on a certain vegetation structure demonstrate that conservation plans should place special emphasis on these guilds.     

Temporal variation in the organization of a Neotropical assemblage of leaf-nosed bats (Chiroptera: Phyllostomidae)

In the present study, I described the organization of a Neotropical bat assemblage, and tested whether this organization was variable in time. In an Atlantic Forest reserve in southeastern Brazil bats were captured monthly with mist nets over 4 years, and individuals were classified into guilds. I analyzed only leaf-nosed bats, and observed that guilds of fruit-eating bats dominated the assemblage. This pattern was repeated across months and years. However, among frugivores, canopy and understory guilds peaked during different months, but in both cases during the rainy season, while variation among habitat-opportunistic species was not explained by rainfall. The most reliable ecological service delivered by phyllostomid bats in the area is seed dispersal, although other services may be also important in particular seasons. My results suggest that the observed patterns of temporal species turnover are related to the abundance of preferred food items.     

Conserving long unburnt vegetation is important for bird species,guilds and diversity

Landscape-level wildfires have a major role in structuring faunal assemblages, particularly in fire-prone landscapes. These effects are mediated by changes to vegetation structure and composition that directly influence the availability of shelter, feeding and breeding resources. We investigated the response of a semi-arid shrubland bird community in Western Australia to the prevailing fire regime by examining the abundance, diversity and guild structure in relation to time since fire. We also examined vegetation structural attributes in relation to time since fire. We surveyed 32 sites ranging in age from 12 to 84 years since last fire. A total of 845 birds from 40 species were recorded. Vegetation structure varied with fire history with old and very old sites characterised by less bare ground, more leaf litter cover and greater canopy cover. Bird community composition varied with time since fire, driven by increased bird species richness and abundance of insectivores, granivores/frugivores, golden whistlers, grey shrike-thrush and red-capped robins with time since fire. Frequent, intense landscape-scale fires transform the landscape into homogeneous young shrublands, which may render vegetation unsuitable for several species and guilds.     

The relative influence of competition and prey defences on the trophic structure of animalivorous bat ensembles

Deterministic filters such as competition and prey defences should have a strong influence on the community structure of animals like animalivorous bats which have life histories characterized by low fecundity, low predation risk, long life expectancy and stable populations. We investigated the relative influence of these two deterministic filters on the trophic structure of animalivorous bat assemblages in South Africa. We used null models to test if patterns of dietary overlap were significantly different from patterns expected by chance and multivariate analyses to test the correlations between diet and phenotype (body size, wing morphology and echolocation). We found little evidence that competition structured the trophic niche of coexisting bats. Contrary to predictions from competition, dietary overlap between bats of ensembles and functional groups (open-air, clutter-edge, and clutter foragers) were significantly higher than expected by chance. Instead, we found support for the predictions of the allotonic frequency hypothesis: there were significant relationships between peak echolocation frequency and the proportion of moths in the diets of bats at local and regional scales, and peak echolocation frequency was the best predictor of diet even after we controlled for the influence of body size and phylogeny. These results suggest that echolocation frequency and prey hearing exert more influence on the trophic structure of sympatric animalivorous bats than competition. Nonetheless, differential habitat use and sensory bias may also be major determinants of trophic structure because these are also correlated with frequencies of bat calls.     

Morphological diversity at different spatial scales in a Neotropical bat assemblage

The morphology of species can be used to represent their ecological position and infer potential processes determining the structure of species assemblages. This ecomorphological approach has been widely applied to the study of bat assemblages which mainly focuses on a single spatial scale and particular guilds. We extended such an ecomorphological approach to a multi-scale analysis of a Neotropical bat assemblage and its constituent guilds (aerial and gleaning insectivores, frugivores, and nectarivores) to describe their structure at different spatial scales and determine the relative importance of inter-specific competition, habitat filtering, or stochastic processes shaping such structures. We measured the occupied morphological space (size) defined by wing and skull morphology independently and the nearest-neighbour distance (structure) among species within these spaces at each spatial scale. Observed patterns were compared with random expectations derived from null models for statistical inference. When controlling for species richness and regional sampling effects in the null models, we did not find a significant effect of spatial scale in the morphological structure of the studied bat assemblage and guilds. Morphological structure followed the same patterns across scales as those expected from random drawings of sample size alone. Similar results were obtained regardless of morphological complex (wing and skull) and guilds. At both the assemblage and guild levels, bat morphological structure seems to be determined by regional, abiotic processes (e.g. habitat filtering) shaping the composition and organization of the species pool.     

Vertical stratification of an avian community in New Guinean tropical rainforest

Vertical stratification of avian communities has been studied in both temperate and tropical forests; however, the majority of studies used ground-based methods. In this study we used ground-to-canopy mist nets to collect detailed data on vertical bird distribution in primary rain forest in Wanang Conservation Area in Papua New Guinea (Madang Province). In total 850 birds from 86 species were caught. Bird abundance was highest in the canopy followed by the understory and lowest in the midstory. Overall bird diversity increased towards the canopy zone. Insectivorous birds represented the most abundant and species-rich trophic guild and their abundances decreased from the ground to canopy. The highest diversity of frugivorous and omnivorous birds was confined to higher vertical strata. Insectivorous birds did not show any pattern of diversity along the vertical gradient. Further, insectivores preferred strata with thick vegetation, while abundance and diversity of frugivores increased with decreasing foliage density. Our ground-to-canopy (0–27 m) mist netting, when compared to standard ground mist netting (0–3 m), greatly improved bird diversity assessment and revealed interesting patterns of avian community stratification along vertical forest strata.     

How Does Restoration of Native Canopy Affect Understory Vegetation Composition? Evidence from Riparian Communities of the Hunter Valley Australia

Restoration of native vegetation often focuses on the canopy layer species, with the assumption that regeneration of the understory elements will occur as a consequence. The goal of this study was to assess the influence of canopy restoration on the composition and abundance of understory plant species assemblages along riparian margins in the Hunter Valley, NSW, Australia. We compared the floristic composition (richness, abundance, and diversity) of understory species between nonrevegetated (open) and canopy revegetated plots across five sites. A number of other factors that may also influence understory vegetation, including soil nutrients, proximity to main channel, and light availability, were also measured. We found that sites where the canopy had been restored had lower exotic species richness and abundance, as well as higher native species cover, but not native species richness, compared with open sites. Multivariate analysis of plots based on plant community composition showed that revegetated sites were associated with lower total species diversity, light availability, and exotic cover. This study has found that the restoration of the canopy layer does result in lower exotic species richness and cover, and higher native species cover and diversity in the understory, a desirable restoration outcome. Our results provide evidence that restoration of native canopy species may facilitate restoration of native understory species; however, other interventions to increase native species richness of the understory should also be considered as part of management practice.     

Bat frugivory in two subtropical rain forests of Northern Argentina: Testing hypotheses of fruit selection in the Neotropics

Phyllostomid bats are prominent components of mammalian assemblages in the Neotropics. With many species specialized in frugivory, phyllostomids represent major partners of fleshy-fruited plants in the mutualism of seed dispersal. Here we present dietary data from two subtropical rainforests of Argentina, where fruit diversity is low and thus offer unique opportunities to test hypotheses of diet selection originally proposed for species-rich tropical assemblages. Particularly, we tested whether frugivorous phyllostomids exhibit pronounced dietary specialization in core plant taxa where fruit offer is greatly reduced as compared to tropical rainforests. We analyzed dietary overlap and niche breadth of subtropical frugivorous bats on the basis of >1000 dietary records plus >500 samples from a previous study in the region. We show that in the subtropics, frugivores from different genera remain faithful to their respective core plant taxa with few exceptions, rather than shifting toward alternative fruit resources available in the study sites. This supports predictions of specialization, which is confirmed to have a deep historical origin. The response of phyllostomid ensembles to restricted fruit diversity is at the level of species composition: absence of species for which preferred fruits do not occur in the sites. Taken together, these data lend strong support to hypotheses that explain coexistence of frugivorous phyllostomids on the basis of dietary specialization on core plant taxa with chiropterochorous fruits.     

Effects of Agricultural Intensification on the Assemblage of Leaf-Nosed Bats (Phyllostomidae) in a Coffee Landscape in Chiapas,Mexico

The agricultural matrix surrounding forested areas serves critical functions as dispersal corridors and alternate habitat for wildlife. Agricultural intensification, however, can reduce the conservation value of these areas. To evaluate the effects of agroecosystem management on bat assemblages, we studied the abundance and diversity of leaf-nosed bats (family: Phyllostomidae) in southwestern Chiapas, Mexico, a landscape dominated by shade coffee agroforestry. During 2104 mist-net hour (MNH), we captured 3167 bats of 27 phyllostomid species. Total species richness in each land-use type varied from 24 species in forest fragments to 22 species in commercial shade polycultures. Although the cumulative observed species richness showed little change in response to management intensity, the number of bats captured per MNH declined significantly in the more intensively managed (i.e., low-shade monocultures) plantations. Intensively managed coffee plantations had lower phyllostomid diversity and species similarity, and had lower proportions of nectarivorous and animalivorous bats. Among frugivores, the proportion of large (>25 g) frugivores captured increased with management intensity. Recapture frequency was significantly higher than expected in forest fragments, and lower than expected in more intensively managed coffee. Our results suggest that less intensively managed coffee agroforests can serve as valuable feeding and commuting areas for most leaf-nosed bats, and that maintaining forest fragments in agricultural landscapes contributes to bat diversity. Declines in populations of gleaning insectivores, however, could compromise natural suppression of insect pests in these agricultural areas.     

Effects of site and fruit size on the composition of avian frugivore assemblages in a fragmented Afrotropical forest

Factors influencing the interaction between fruiting trees and their frugivorous seed dispersers in fragmented Afrotropical landscapes are poorly known. With the use of Mantel statistics we analysed assemblages of frugivorous birds on 58 individual trees belonging to 11 species growing in seven Kenyan cloud forest fragments. Overall, frugivores showed little specialization on particular trees. Fruit size explained a substantial amount of the variation in frugivore assemblages among different tree species at the same site. In addition, frugivore assemblages on conspecific trees were significantly more similar when the trees occurred at the same site. This location effect was attributable to the different sites and forest fragments (of different sizes and disturbance levels) varying in the densities and composition of their avian frugivores, vegetation composition and tree fruiting phenologies. It was consolidated further by the low mobility of most of these avian frugivores, particularly their reluctance to cross between forest fragments. Habitat disturbance and fragmentation may therefore have affected fruit selection, with implications for both seed dispersal and regeneration.     

Effect of Tree‐Fall Gaps on Fruit‐Feeding Nymphalid Butterfly Assemblages in a Peruvian Rain Forest

One of the main natural disturbances that affects the structure of rain forests is treefalls, frequently resulting in gaps. Tree‐fall gaps can bring drastic changes in environmental conditions compared with the undisturbed understory. We investigated the effect of tree‐fall gaps on fruit‐feeding butterfly (Nymphalidae) species assemblages in an undisturbed lowland rain forest in southeastern Peru. We used fruit‐baited traps suspended 2 m above ground in 15 tree‐fall gaps ranging in area from 100 to 1000 m² and in adjacent undisturbed understory. Our data support the hypothesis that tree‐fall gap and understory habitats are utilized by different butterfly species assemblages. There were morphological differences between gap and understory species, where the understory species had a larger wing area to thoracic volume. Vegetation structure and composition were important factors affecting the butterfly assemblages. Most of the butterfly species showed an avoidance of vines and a strong association with the presence of trees and shrubs in gaps. There were also differences among gap assemblages that increased with gap size. Some of the species that were associated with gaps have been considered as canopy species. Other gap species in the present study, however, are known to feed on fruits and/or use host plants mainly, or only, occurring in gaps, implicating that the gap assemblage is a mix of canopy species and those unique to gaps. This indicates that, in an undisturbed Amazon forest, tree‐fall gaps may contribute to maintain species diversity by creating a mosaic of specific habitats and resources that favors different butterfly assemblages.     

Do Tropical Frugivores Compete for Food?

In this paper I ask two questions: Is fruit ever limiting tovertebrate frugivores and, if so, do frugivores presently competefor food, either with closely- or distantly-related species?A brief review of the fruiting strategies of tropical plantsindicates that fruit can occasionally be superabundant, butit is often produced at low rates and in low quantities. Variationin fruit abundance results from several biotic selective pressures,including variation in the density, diversity, and reliabilityof potential dispersal agents. To judge from the size structure,dietary similarities, habitat preferences and foraging behaviorsof taxonomically-restricted guilds of frugivorous birds andmammals, members of these guilds have competed for food in thepast and must occasionally do so today. Unusual climatic conditionscan occasionally "upset" phenological patterns and can createfood shortages that promote competition among closely-relatedspecies of frugivores. Avian and mammalian frugivores, however,probably seldom compete with each other for food in present-daytropical ecosystems. A major reason for this is that many tropicalplants have evolved fruits that are attractive to only a limitedsubset of frugivores (e.g., only birds or only bats). Plantsapparently "perceive" qualitative differences in the dispersalservices of birds and mammals and attempt to attract membersof one group but not the other.     

Collpas: Activity Hotspots for Frugivorous Bats (Phyllostomidae) in the Peruvian Amazon

In the SE Peruvian Amazon, large numbers of frugivorous bats regularly visit natural forest clearings known locally as collpas (which are also referred to as clay licks or mineral licks). Bats arrive at collpas to drink water that has accumulated in depressions created by larger geophagous mammals that consume exposed soil. Although collpa visitation is common, little is known about its causes and its ecological implications for the bat community. We compared patterns of use of collpas and non- collpa forest sites by bats in SE Peru. We mist netted bats at collpas and non- collpa sites during the dry season and compared abundance, species richness, species composition, sex ratio, and reproductive condition. More species were captured at collpas than at non- collpa sites, and collpas were visited almost exclusively by frugivores. Overall, bat-capture frequency and combined frugivorous bat-capture frequency were higher at collpas than at non- collpa sites, although some species of frugivorous bats were captured more frequently at non- collpa sites than at collpas ( e.g ., Carollia spp.). Irrespective of capture site, more female bats were pregnant or lactating than not, but there was a distinct female sex bias in bats that visited collpas : 70 percent of bats captured at collpas were female, whereas 44 percent of bats captured away from collpas were female. These patterns suggest that collpas may provide important resources for frugivorous bats in SE Peru, just as they are thought to provide important resources to the vertebrates that consume collpa soils. Accordingly, collpas are important conservation targets in the region.     

Influence of overstory composition on understory colonization by native species in plantations on a degraded tropical site

Abstract. Patterns of understory colonization by native and naturalized trees and shrubs were evaluated in 4.5-year-old plantations of three exotic tree species, Casuarina equisetifolia, Eucalyptus robusta, and Leucaena leucocephala, on a degraded coastal grassland site with reference to overstory composition and understory environmental conditions. 19 secondary forest species were established in the plantation understories (with a total area of 0.52 ha), while no natural regeneration occurred in unplanted, though protected, control areas. The majority of these species (90 %) and the total seedling population (97 %) were zoochorous, indicating the importance of frugivorous bats and particularly birds as facilitators of secondary forest species colonization. Understory species richness and seedling densities were affected significantly by overstory composition, the most abundant regeneration occurring beneath Leucaena and least under Casuarina. Understory colonization rates within mixed-species stands were intermediate between those of single-species stands of the trees comprising their overstories. Significant negative correlations were found between understory species richness and seedling density, and forest floor depth and dry mass, especially for small-seeded ornithochorous species. Higher colonization rates near the peripheries of plantation plots relative to plot interiors were due in part to roosting site preferences by frugivores, particularly bats. The study results indicate that overstory species selection can exert a significant influence on subsequent patterns of colonization by secondary forest species and is an important consideration in the design of plantations for ‘catalyzing’ succession on deforested, degraded sites.     

Vertical stratification of feeding guilds and body size in beetle assemblages from an Australian tropical rainforest

Abstract The vertical stratification of insect species assemblages inhabiting tropical rainforests is well established but few have examined whether these patterns are reflected in vertical stratification of body size or feeding guilds. We used Malaise and Flight Interception Traps to sample beetle assemblages from five locations, at both canopy and ground zones of a tropical lowland rainforest site near Cape Tribulation, Australia. Beetles from 4 years of sampling were sorted to Family and morphospecies, and allocated to one of five feeding guilds. Within feeding guilds the number of species and individuals, from canopy‐ and ground‐caught traps were compared. The body lengths of species were measure and compared within feeding guilds and families. Herbivores was the dominant guild but was not the majority of all species or individuals. Most beetle species (69%) were less than 5 mm in length and the mean size of canopy‐caught species was greater than that for ground‐caught species. This was probably due to slightly more species of plant feeders (herbivores and xylophages) present in the canopy, which were significantly larger than saprophages, fungivores and predators. Among feeding guilds, there were few overall canopy–ground differences. These results contrast with species composition results presented elsewhere where strong differences between the canopy and the ground were evident. We suggest that our guild groupings may have been too coarse to detect fine‐scale differences and that resource partitioning may have also masked faunal stratification. We propose that fine‐scale differences in resources between the canopy and the ground, together with strong microclimate gradients, are likely to be important in structuring the vertical stratification of insect assemblages at the level of species, but not with respect to functional groups.     

Subtle changes in elevation shift bat‐assemblage structure in Central Amazonia

The distribution patterns of animal species at local scales have been explained by direct influences of vegetation structure, topography, food distribution, and availability. However, these variables can also interact and operate indirectly on the distribution of species. Here, we examined the direct and indirect effects of food availability (fruits and insects), vegetation clutter, and elevation in structuring phyllostomid bat assemblages in a continuous terra firme forest in Central Amazonia. Bats were captured in 49 plots over 25‐km² of continuous forest. We captured 1138 bats belonging to 52 species with 7056 net*hours of effort. Terrain elevation was the strongest predictor of species and guild compositions, and of bat abundance. However, changes in elevation were associated with changes in vegetation clutter, and availability of fruits and insects consumed by bats, which are likely to have had direct effects on bat assemblages. Frugivorous bat composition was more influenced by availability of food‐providing plants, while gleaning‐animalivore composition was more influenced by the structural complexity of the vegetation. Although probably not causal, terrain elevation may be a reliable predictor of bat‐assemblage structure at local scales in other regions. In situations where it is not possible to collect local variables, terrain elevation can substitute other variables, such as vegetation structure, and availability of fruits and insects.     

Forest plant community as a driver of soil biodiversity: experimental evidence from collembolan assemblages through large‐scale and long‐term removal of oak canopy trees Quercus petraea

Plant–soil interactions are increasingly recognized to play a major role in terrestrial ecosystems functioning. However, few studies to date have focused on slow dynamic ecosystems such as forests. As they are vertically stratified by multiple vegetation strata, canopy tree removal by thinning operations could alter forest plant community through tree canopy opening. Very little is known about cascading effects on soil biodiversity. We conducted a large‐scale, multi‐site assessment of collembolan assemblage response to long‐term canopy tree removal in sessile oak Quercus petraea temperate forests. A total of 33 experimental plots were studied covering a large gradient of canopy tree basal area, stand age and local abiotic contexts. Collembolan abundance strongly declined with canopy tree removal in early forest successional stage and this was mediated by negative effect of understory plant community composition changes, i.e. shift from moss and forb to tree seedling, fern, shrub and grass species. Negative effect of this composition shift on collembolan species richness was largely offset by positive effect of the increase in understory plant species richness. This gives support to both the plant mass‐ratio and functional diversity hypotheses. Collembolan functional groups had contrasting response patterns, which were mediated by different ecological factors. Epedaphic (r‐strategist) abundance and species richness increased with canopy tree removal in relation with the increase in understory plant species richness. In contrast, euedaphic (K‐strategist) abundance and species richness declined with canopy tree removal in early forest successional stage in relation with changes in understory plant community composition and species richness, as well as microclimatic conditions. Overall, our study provides experimental evidence that forest plant community can be a strong driver of collembolan assemblages. It also emphasizes the role of trees as foundation species of forest ecosystems that can shape soil biodiversity through their regulation of understory plant community and ecosystem abiotic conditions.     

Importance of the understory stratum to entomofaunal diversity in a temperate deciduous forest

The vertical stratification of lepidopteran and coleopteran communities in a cool-temperate deciduous forest in Japan was examined to evaluate the hypothesis of an expected uniform distribution of mobile flying insects between the canopy and understory of temperate forests. Lepidopteran and coleopteran insects were trapped using light traps at three sites in each of the canopy and understory for three consecutive nights each month from April to October 2001. For Lepidoptera, species richness, abundance, and family richness were significantly higher in the understory than in the canopy. For Coleoptera, only abundance was larger in the canopy relative to the understory; species and family richness did not differ between the strata. The beta diversity of the lepidopteran community was larger between the strata than among sites, but the coleopteran community showed an inverse pattern. These results imply the presence of vertical stratification within the lepidopteran community, but not within the coleopteran community, in the temperate forest. The understory contributes more than the canopy to lepidopteran diversity in the temperate forest, although this stratification may be relatively weak because, in contrast to the situation in tropical forests, the canopy and understory assemblages share many species.     

城市化对杭州市鸟类营巢集团的影响

为了了解城市化对鸟类营巢集团的影响,2007年3月至2007年8月,沿城市化梯度在杭州地区的城区、城乡结合区、农田区、农林交错区和自然林区等类型栖息地内设置3 000 m长、100 m宽的样线各18条,共计90条;并对其鸟类物种与群落营巢集团进行调查。调查共记录到繁殖鸟类96种,根据鸟类营巢位置可将其分为林冠枝干营巢集团、灌草丛营巢集团、林冠枝干/灌草丛营巢集团、自然洞穴营巢集团、人工建筑营巢集团、自然洞穴/人工建筑营巢集团地面营巢集团、水面营巢集团和寄生集团共9种。进一步分析显示,随城市化程度提高,鸟类营巢集团的数目呈整体下降趋势,而各集团的物种数也基本呈下降趋势。但是,不同的营巢集团对城市化的反应存在差异,导致其物种组成在群落中比例的明显变化。城市化程度的提高使树冠筑巢鸟、灌丛筑巢鸟、地面筑巢鸟及自然洞穴筑巢鸟在群落中所占的比例明显下降,其中地面筑巢鸟最为敏感,灌丛筑巢鸟次之。同时,自然洞穴/人工建筑集团的鸟类在群落中的比例却随着城市化程度的提高明显上升。各营巢集团之所以对城市化做出不同反应,是因为它们对筑巢地资源利用方式不同。此外,还发现植被盖度、人工设施面积、至市中心距离以及人为干扰等因素均可对鸟类营巢集团结构产生影响,但不同类型的营巢集团对上述因素的反应各异。     

Canopy bird assemblages are less influenced by habitat age and isolation than understory bird assemblages in Neotropical secondary forest

Secondary forest habitats are increasingly recognized for their potential to conserve biodiversity in the tropics. However, the development of faunal assemblages in secondary forest systems varies according to habitat quality and species‐specific traits. In this study, we predicted that the recovery of bird assemblages is dependent on secondary forest age and level of isolation, the forest stratum examined, and the species’ traits of feeding guild and body mass. This study was undertaken in secondary forests in central Panama; spanning a chronosequence of 60‐, 90‐, and 120‐year‐old forests, and in neighboring old‐growth forest. To give equal attention to all forest strata, we employed a novel method that paired simultaneous surveys in canopy and understory. This survey method provides a more nuanced picture than ground‐based studies, which are biased toward understory assemblages. Bird reassembly varied according to both habitat age and isolation, although it was challenging to separate these effects, as the older sites were also more isolated than the younger sites. In combination, habitat age and isolation impacted understory birds more than canopy‐dwelling birds. Proportions of dietary guilds did not vary with habitat age, but were significantly different between strata. Body mass distributions were similar across forest ages for small‐bodied birds, but older forest supported more large‐bodied birds, probably due to control of poaching at these sites. Canopy assemblages were characterized by higher species richness, and greater variation in both dietary breadth and body mass, relative to understory assemblages. The results highlight that secondary forests may offer critical refugia for many bird species, particularly specialist canopy‐dwellers. However, understory bird species may be less able to adapt to novel and isolated habitats and should be the focus of conservation efforts encouraging bird colonization of secondary forests.