Neotropical Birds Research Articles

Ecological correlates of the threat of extinction in Neotropical bird species

AbstractPredicting the threat of extinction aids efficient distribution of conservation resources. This paper utilises a comparative macroecological approach to investigate the threat of extinction in Neotropical birds. Data on ecological variables for 1708 species are analysed using stepwise regression to produce minimum adequate models, first using raw species values and then using independent contrasts (to control for phylogenetic effects). The models differ, suggesting phylogeny has significant effects. The raw species analysis reveals that number of zoogeographical regions occupied, elevational range and utilisation of specialised microhabitats were negatively associated with threat, while minimum elevation and body mass were positively associated, whereas the independent contrasts analysis only identifies zoogeographical regions as important. Confining the analysis to the 582 species restricted to a single zoogeographical region reveals elevational range and number of habitats occupied to be negatively correlated with threat whether the analysis is based on the raw data or on independent contrasts. Analysis of four contrasting zoogeographical regions highlights regional variation in the models. In two Andean regions the threat of extinction declines as the elevation range across which the species occurs increases. In the presence of substantial human populations on high Andean plateaus, a species with a greater elevational range may be more likely to persist at some (relatively) unsettled altitudes. In Central South America, the strongest predictor of threat is minimum elevation of occurrence: species with a lower minimum are less threatened. The minimum elevation result suggests that lowland species experiencing an ecological limit to their minimum elevation (min. elevation >0 m) may be more at risk than those not experiencing such a limit (min. elevation = 0 m). Finally, in southern Amazonia, where there is little altitudinal variation, the only weak predictors of threat are body size, larger species being more threatened, and number of habitats, species occupying more habitats being less threatened. These contrasting results emphasise the importance of undertaking extinction risk analyses at an appropriate geographical scale. Since the models explained only a low percentage of total variance in the data, the effects of human‐mediated habitat disturbance across a wide range of habitats may be important.

Veery Nest Sites in a Mid-Atlantic Piedmont Forest: Vegetative Physiognomy and Use of Alien Shrubs

Veery (Catharus fuscescens) nest sites were compared to unused sites in a Middle-Atlantic Piedmont forest to determine if nest placement was random or biased with respect to forest structure and alien vegetation. Thus far, available data shows alien plants have a detrimental or neutral effect on the ecology of forest birds; however, empirical data regarding the proximate influence of invasive alien shrubs on avian nest placement in North American forests is lacking. Nest sites were distributed non-randomly in relation to vegetation density and were characterized by dense foliage below 1.5 m with sparse overstory at 2.5 to 3 m. Sites occurred within moist forest in floodplains and on south- and east-facing slopes. All nest sites contained alien shrubs, and alien vegetation supported 84% of nests. Shrub diversity did not differ between nest sites and unused sites yet more alien shrub species were found at nest sites. The density of native shrub-layer foliage did not differ between the two treatments; however, the density of alien shrub foliage was greater at nest sites. In this forest there was no relationship between the density of alien vegetation and the density of native vegetation. These data suggest that alien shrubs have replaced native shrub species and exerted a largely additive effect on foliage density providing the proximate cues for nest placement. The high success rate (70%) of nests within sites used in analyses suggests that the alien shrubs providing these cues are not substantially elevating nest failure rates. Thus, some temperate-breeding Neotropical forest-interior birds may react positively to a change in forest structure resulting from the invasion of alien shrubs. Ecological release resulting from the increase in available nest sites created by alien shrubs may explain the recent regional spread of the Veery. Region-specific studies are needed to determine the forest breeding birds that are affected, either positively or negatively, by the altered spatial heterogeneity created by alien shrubs.

USE OF OAK HAMMOCKS BY NEOTROPICAL MIGRANT SONGBIRDS: THE ROLE OF AREA AND HABITAT

Abstract Many species of Neotropical migrant songbirds have declined in recent decades, due in part to loss and fragmentation of stopover habitat. To properly manage forested landscapes for migrating songbirds, information is needed on how size and habitat structure of forest patches influence their use by migrants during stopover. We conducted surveys of Neotropical migrant birds in eight oak hammocks of varying size (0.32–3.08 ha) at the Savannah National Wildlife Refuge, Jasper County, South Carolina during spring migration 1999 and 2000 and fall migration 1999. Hammock size was the most important factor related to number of total species, species per day, individuals per day, and density of migrants. Differences in vegetation structure and patchiness among hammocks did not explain differences in migrant abundance. Density of migrants tended to be higher in smaller hammocks, particularly during spring. Hammock use was generally similar between seasons and years. Two forest-interior breeding species occ...

RECIPROCAL INTROGRESSION BETWEEN GOLDEN-WINGED WARBLERS (VERMIVORA CHRYSOPTERA) AND BLUE-WINGED WARBLERS (V. PINUS) IN EASTERN NORTH AMERICA

Abstract Golden-winged Warblers (Vermivora chrysoptera) and Blue-winged Warblers (V. pinus) are small, brightly colored Neotropical migrant birds that breed in eastern North America. Wherever the two species occur together, they hybridize to a limited degree, producing distinctive hybrid phenotypes. In recent decades, chrysoptera has experienced dramatic population declines across much of its range. Those declines have often been correlated with establishment and increase of pinus in the same areas, but it remains uncertain what, if any, role pinus has played in driving the decline of chrysoptera. In a first attempt at molecular genetic analysis of chrysoptera-pinus population dynamics, Gill (1997) reported cryptic, completely asymmetric, and possibly very rapid introgression of pinus mitochondrial DNA (mtDNA) into chrysoptera, causing what he termed “local cytonuclear extinction” of chrysoptera. As Gill (1997) noted, however, those results were based on relatively small samples from a single area in Penn...

Population structure and mitochondrial DNA variation in sedentary Neotropical birds isolated by forest fragmentation

The current worldwide concern about tropical deforestation raises questions about the sustainability of avian populations in isolated forest fragments. One of the most important issues concerns the sizes of forest fragments necessary to maintain populations and the genetic variation within them. We address this by: (1) using mtDNA sequence variation to infer aspects of the population structure of four species of understory birds from four sites in southern Costa Rican rainforest; and (2) determining whether forest fragmentation that has occurred in the last 50 years has had an effect on the amount of within-population variation for the species in question. High levels of between-population differentiation (D xy ) were found over a relatively small geographic scale (<130 km) for white-breasted wood-wren (Henicorhina leucosticta), bicolored antbird (Gymnopithys leucaspis), and gray-headed tanager (Eucometis penicillata), suggesting that these species are highly sedentary and exhibit strong female philopatry. No mtDNA variation was found in Plain Antvireo (Dysithamnus mentalis). In all three of the polymorphic species there was a significant decrease in mtDNA nucleotide diversity in populations isolated by forest fragmentation as compared to populations in contiguous primary forest. Even in relatively large (250–1000 ha) forest reserves, sedentary avian species have lost roughly half (range 43–85) of the nucleotide diversity in mtDNA over a relatively short period of time. Our results indicate that sedentary avian species in forest fragments isolated by clearing have undergone severe reductions in effective population size due to population bottlenecks perpetuated by prolonged isolation and potential edge effects.

VICARIANT SPECIATION OF CURASSOWS (AVES, CRACIDAE): A HYPOTHESIS BASED ON MITOCHONDRIAL DNA PHYLOGENY

Abstract The curassows comprise 14 species of sedentary Neotropical birds classified in four genera (Crax, Nothocrax, Mitu, and Pauxi) in the family Cracidae. Congeneric species have a striking pattern of allopatric distributions that might be attributable to vicariance, dispersal, or a combination of the two. To test those biogeographic hypotheses, a strongly supported phylogeny was needed, so that existing problems of taxonomic rank could be solved and a better understanding of the group's evolutionary history attained. We therefore estimated the phylogenetic relationships of all 14 species, on the basis of 6,929 sites of six different mitochondrial DNA regions, and reassessed the status of the four genera. Sequences from the ND4 gene favored a tree that was highly incongruent with the tree recovered using the other five gene regions. However, when the ND4 sequences were concatenated with the sequences of the other genes, the optimal phylogeny was unchanged from that derived for the other genes. That co...

Efficiency, bias, and consistency of visual and aural surveys of curassows (Cracidae) in tropical forests

Curassows are among the most threatened Neotropical birds, so reliable methods for estimating their abundance are needed to discern distribution patterns and manage populations. Based on the assumptions that the distance to booming curassows cannot be determined reliably and that curassow calling is unpredictable, it has been suggested that curassow abundance should be estimated only through surveys using visual cues. Based on line-transect surveys of Great Curassows (Crax rubra) conducted in a lowland tropical forest in Costa Rica, we show that distance to booming curassows can be measured accurately in the field. We also show that line-transect aural surveys sample curassows over large areas across all forest vertical strata and provide precise estimates of their abundance, but are biased towards detecting males. In contrast, line-transect visual surveys sample only small areas of forest understory and are imprecise, but appear not to be biased towards any sex or age class. We argue that the assumption that curassow calling is unpredictable is not well supported, and we recommend the use of surveys using aural cues to estimate curassow abundance efficiently.

ARTIFICIAL NEST PREDATION ACROSS RIPARIAN-UPLAND FOREST ECOTONES

Abstract On the central Appalachian Plateau, evergreen trees and shrubs often dominate riparian vegetation. In contrast, deciduous trees dominate upland forests. To evaluate an important aspect of habitat suitability for Neotropical migratory birds, we placed artificial nests baited with a Japanese quail (Corturnix coturnix japonica) egg at regular intervals along successively upland transects paralleling Poplar Lick Run and Little Savage River, Garrett County, Maryland. Nests were alternated between 0–0.5 m and 1–2 m heights and were exposed for 12 days during each of four trials in 1990, and 12 days during each of six trials in 1991. Egg predation was typically higher within 50 m of these streams than farther from them. Although artificial nests may not truly represent natural nests and the losses incurred by nesting birds, our results should alert land managers and conservationists to a potential problem and stimulate further research into the suitability of existing, evergreen riparian zones for nesti...

The influence of sampling scheme and interpolation method on the power to detect spatial effects of forest birds in Ontario (Canada)

Spatial ecology is becoming an increasingly important component of resource management, and the general monitoring of how human activities affect the distribution and abundance of wildlife. Yet most work on the reliability of sampling strategies is based on a non-spatial analysis of variance paradigm, and little work has been done assessing the power of alternative spatial methods for creating reliable maps of animal abundance. Such a map forms a critical response variable for multiple scale studies relating landscape structure to biotic function. The power to reconstruct patterns of distribution and abundance is influenced by sample placement strategy and density, the nature of spatial auto-correlation among points, and by the technique used to extrapolate points into an animal abundance map. Faced with uncertainty concerning the influence of these factors, we chose to first synthesize a model reference system of known properties and then evaluate the relative performance of alternative sampling and mapping procedures using it. We used published habitat associations of tree nesting boreal neo-tropical birds, a classified habitat map from the Manitou Lakes area of northwestern Ontario, and point count means and variances determined from field studies in boreal Canada to create 4 simulated models of avian abundance to function as reference maps. Four point sampling strategies were evaluated by 4 spatial mapping methods. We found mixed-cluster sampling to be an effective point sampling strategy, particularly when high habitat fragmentation was avoided by restricting samples to habitat patches >10 ha in size. We also found that of the 4 mapping methods, only stratified ordinary point kriging (OPK) was able to generate maps that reproduced an embedded landscape-scale spatial effect that reduced nesting bird abundance in areas of higher forest age-class fragmentation. Global OPK was effective only for detecting broader, regional-scale differences.

PREHISTORIC EXPLOITATION OF BIRDS ON THE PACIFIC COAST OF CHIAPAS, MEXICO

Abstract We report bones of 60 species of birds from the Paso de la Amada archaeological site (ca. 3600 to 3150 years old) in the Soconusco region of Chiapas, Mexico. Among 36 species of landbirds and 24 marine, estuarine, and aquatic species, four landbirds (Harpia harpyja, Ortalis vetula, Cyrtonyx ocellatus, and Ara militaris) have not been recorded previously from coastal Chiapas. Their nearest populations are characteristic of foothill or montane forest. The families of birds most commonly exploited at Paso de la Amada were Columbidae (pigeons, doves), Phasianidae (quail), Falconidae (caracaras), Ardeidae (herons), and Cracidae (chachalacas). Because of human interactions with birds and their habitats over the millennia, it is difficult or impossible to determine the precise species-level composition for any Neotropical bird community under conditions free of human influence. Prehistoric data thus improve our understanding of how these communities have changed over long time scales, whether or not the...

Latitudinal extent and natural history characteristics of birds in Nicaragua

AbstractThis paper assesses the latitudinal extent of terrestrial breeding birds in Nicaragua. In particular, associations among latitudinal midpoint, body mass, and latitudinal extent are examined; significant differences between natural history characteristics (trophic guild, forest dependence, number of forest types) and latitudinal extent are identified; and a test is undertaken of Rapoport's rule for birds at the edge of their northern or southern range in Nicaragua. Birds in Nicaragua were classified into four categories based on latitudinal extent: birds generally restricted to Central America (20%); birds near the edge of their range within Nicaragua (34%); Neotropical birds (42%); and Pan‐American birds (4%). Latitudinal midpoint had a significant negative correlation with latitudinal extent over different taxonomic scales. Natural history characteristics of trophic guild, forest dependence and number of forest types can account for significant differences in species latitudinal extent. Carnivores had greater latitudinal extents than most other trophic guilds, non‐forest birds had greater latitudinal extents than birds that require patchy forest, and birds that occur in four or more forest types had greater latitudinal extents than birds restricted to one or two forest types. Contrary to Rapoport's rule, birds with a northern affinity or latitudinal midpoint north of Nicaragua had significantly smaller latitudinal extents than birds with a southern affinity or latitudinal midpoint south of Nicaragua. A comparison of natural history characteristics of birds with northern and southern affinities found no difference between trophic guild or forest dependence but a significant difference among the number of forest types used by forest birds. Birds with a southern affinity were restricted to fewer forest types than birds with a northern affinity.

Pelecitus helicinus Railliet & Henry, 1910 (Filarioidea, Dirofilariinae) and other nematode parasites of Brazilian birds.

We report Pelecitus helicinus Railliet & Henry, 1910 from 13 species of birds of 2 orders and 7 families, collected from the states of São Paulo and Mato Grosso, Brazil. All 13 constitute new host records for this nematode. In addition, we report the first record of Aprocta golvani Diaz-Ungria, 1963 from Brazil and Monasa nigrifrons (Bucconidae), as well as a number of other nematode records from Neotropical birds.

Jean Dorst (1924–2001)

In addition to his work as a renowned zoologist, whose main interest was in birds and mammals, Professor Jean Dorst will be remembered particularly for his actions as a most celebrated nature conservationist. Indeed, during his long career he had many opportunities to demonstrate what a brilliant naturalist he was. He was born on 7 August 1924 at Mulhouse in Alsace and became interested in natural history early on, when still a schoolboy. After graduating at the Faculty of Sciences in Paris, he joined ORSTOM (now the Institut de Recherches pour le Développement) as a plant pathologist in 1945, but one year later left and entered the Muséum national d’Histoire naturelle. Here he was appointed Assistant at the Laboratoire de Zoologie (Mammifères et Oiseaux), the laboratory in which he was to spend the rest of his scientific life, being its director for 26 years. He was appointed Sous-Directeur there in 1949 and Professor in 1964 holding the chair of mammals and birds until he retired in 1990. To deal with all the subjects on which he wrote would require far more space than is available for this obituary. He leaves an impressive literature, being the author of more than 300 scientific papers and 150 popular articles, and a dozen books (including a three-volume work on the life of birds, published in 1972), some of them with editions in various languages. He published a large number of primary articles in scientific journals and book chapters on mammals, particularly on bats and rodents, but he is also well known for the pioneering field guide on large African mammals, which he published with Pierre Dandelot in 1970. His contribution to Ornithology is also important. He published papers on the anatomy of feathers, particularly of hummingbirds (the subject of his D.Sc. thesis in 1949), and of the tongues of nectarivores. He did much systematic work (e.g. on Corvids, thrushes, vangas) as well as biogeographical studies, particularly on Neotropical birds. He also conducted research on the biological, physiological and ecological adaptations of montane birds, especially of the Andes. He was particularly interested in bird migration, a topic to which he dedicated a thick book first published in French in 1956 and updated in English in 1962. Arguably his most important contributions, however, were to the conservation of habitats and species all over the world, and to the solving of problems posed by the introduction of alien species in natural, and particularly insular, ecosystems. The brightest jewel of his crown will undeniably remain his Before Nature Dies, first published in French in 1965 and then translated into 17 languages. This book had, and still has, a great impact on the general public as well as on politicians. Jean Dorst was President of the XVIth I.O.C. in Canberra in 1974. He was a member of many scientific committees and an honorary member (or fellow) of a number of scientific societies, including the BOU (elected 1976). He had been closely involved in the creation of the Charles Darwin Foundation for the Galapagos Islands for which he served as General Secretary (1959–64) and then President (1964–74). He had also been very active at IUCN and ICPB (later Birdlife International). He was elected to the French Institute (Academy of Sciences) in 1973 and appointed Director of the Muséum national d’Histoire naturelle from 1976 to 1985. In this latter position, he initiated the restoration of the Gallery of Zoology which became the Grande Galerie de l’Evolution in 1994. Jean Dorst died in Paris on 8 August 2001. He will be remembered as a great inspiring naturalist and, for those who knew him well, as a very sensitive man who too often masked his sensitivity behind an elusive, reticent, almost haughty or even gruff exterior. He was in fact a warm, caring, brilliant open-minded man who had a remarkable potential for hard work and a gift for synthesizing and transmitting scientific information, not only to other scientists, but also to the general public, politicians and decision-makers. Nature conservation has lost one of its greatest and most eager upholders.

Vertical stratification and use of vegetation and light habitats by Neotropical forest birds

The vertical stratification of bird species has been intensively studied in both temperate and tropical bird communities. I investigated the vertical stratification of bird species and their use of vegetation structures and light habitats using observation data from 92 rainforest species. Most observations were made from a 40 m high canopy crane situated close to the Surumoni river (65°40′W, 3°10′N) near Esmeralda, Estado Amazonas, southern Venezuela. Further observations were made at several forest sites nearby. Previous analyses had shown that bird species foraged in stratified vertical niches, with wider niches for midstorey birds than for either canopy or understorey birds. In this study, I used across-species as well as phylogenetically-controlled analyses to correlate the vertical position of bird species with variables relating to vegetation structures and the amount of illumination. I found that species which foraged low in the forest were mostly found in small gap and forest shade light habitats, while species that foraged high were mostly found in large gap and woodland shade light habitats. Furthermore it was the lower-foraging species that were more often found in dimmer light conditions inside denser cover. In correspondence with their wider vertical niches, midstorey birds foraged in a wider range of light habitats and illumination than either canopy or understorey birds. While preserving their overall stratification, species actively moved within their preferred stratum, e. g. downwards and into denser vegetation during hours of strong sunlight and around midday when temperatures are highest. Bird activity appeared to be lowest shortly after midday, as I discovered when controlling for the effects of chance encounters with multi-species flocks. These observations are important not only for the determination of foraging niches, but also for the study of crypsis and the conspicuousness of a bird species in relation to its foraging stratum.

Brown-Headed Cowbird Parasitism of Ovenbirds in Suburban Forest Fragments

Abstract Forest fragmentation in North America concerns many biologists because of its effects on wildlife populations. One group that has demonstrated particular sensitivity is Neotropical migrant birds. We studied Ovenbirds (Seiurus aurocapillus) in forest fragments in a suburban landscape in eastern Massachusetts to determine effects of cowbird parasitism on Ovenbird reproductive success. Our three large (120–312 ha) and six small (10–59 ha) forests were all smaller than most of those studied by other researchers, and they were surrounded by wooded suburban lots rather than agricultural land. Twenty-nine percent of nests found were parasitized by cowbirds; that frequency is lower than other investigators have reported for small, isolated fragments. The number of Ovenbirds fledged in successful parasitized (x̄ = 2.4) and unparasitized (x̄ = 3.8) nests was similar to other studies. Cowbirds were found to remain in nests for one to two days after their Ovenbird nestmates fledged. Differences in parasitism rate between this and other Ovenbird studies may be related to landscape characteristics. Ovenbirds nesting in small fragments in relatively wooded landscapes, as was the case in this study, have higher reproductive success than do Ovenbirds nesting in similar-sized fragments within an agricultural landscape. Using Ovenbirds as a model for neotropical migrants, we suggest that small fragments in a landscape with relatively wooded connections between forested areas may allow migrants to attain higher reproductive success than similar sized forests surrounded by agricultural land.

Influence of host ecology and morphology on the diversity of Neotropical bird lice

Host‐parasite systems can be powerful arenas in which to explore factors influencing community structure. We used a comparative approach to examine the influence of host ecology and morphology on the diversity of chewing lice (Insecta: Phthiraptera) among 52 species of Peruvian birds. For each host species we calculated two components of parasite diversity: 1) cumulative species richness, and 2) mean abundance. We tested for correlations between these parasite indices and 13 host ecological and morphological variables. Host ecological variables included geographic range size, local population density, and microhabitat use. Host morphological variables included body mass, plumage depth, and standard dimensions of bill, foot and toenail morphology, all of which could influence the efficiency of anti‐parasite grooming. Data were analysed using statistical and comparative methods that control for sampling effort and host phylogeny. None of the independent host variables correlated with louse species richness when treated as a dependent variable. When richness was treated as an independent variable, however, it was positively correlated with mean louse abundance. Host body mass was also positively correlated with mean louse abundance. When louse richness and host body mass were held constant, mean louse abundance correlated negatively with the degree to which the upper mandible of the host's bill overhangs the lower mandible. This correlation suggests that birds with longer overhangs are better at controlling lice during preening. We propose a specific functional hypothesis in which preening damages lice by exerting a shearing force between the overhang and the tip of the lower mandible. This study is the first to suggest a parasite‐control function of such a detailed component of bill morphology across species. Avian biologists have traditionally focused almost exclusively on bills as tools for feeding. We suggest that the adaptive radiation of bill morphology should be reinterpreted with both preening and feeding in mind.

EFFECT OF NATURAL AND ANTHROPOGENIC LANDSCAPE MATRICES ON THE ABUNDANCE OF SUBANDEAN BIRD SPECIES

The nature of the landscape matrix can control the capacity of forest organisms to move among forest patches. Some matrices may constitute foraging or breeding habitat and, as a result, could influence the local abundance of forest organisms and their persistence in fragmented landscapes. This study represents a first approach to examining the effect of natural vs. anthropogenic landscape matrices on the abundance of neotropical birds in forest sites. The influence of three contrasting matrices on the relative abundance of 113 bird species in a subandean region was evaluated. Species were grouped into categories showing the same response to the matrix, and these groups were then examined to determine whether ecological characteristics or taxonomic affinities were associated with responses to surrounding matrices. The abundance of individual species in forest plots within a continuous forest matrix was compared with their abundance in forest fragments embedded in pastures or exotic-tree plantations. The matrix surrounding forest areas was a major factor influencing bird abundance: 65.5% of the species showed significant differences in abundance among sites surrounded by different matrices. The most important explanatory factors in the variation in abundance within fragments were: abundance within continuous forest, presence in the anthropogenic matrices, migratory strategy, and habitat association. Species with small geographic ranges and species of terrestrial insectivores had low tolerance to fragmentation. Responses were highly species specific and largely independent of foraging strata, trophic group, and taxonomic affinities. Several lines of evidence indicate an increased connectivity among forest remnants surrounded by exotic-tree plantations compared to pastures. Landscape supplementation by the exotic-tree plantation matrix was observed for a hummingbird species. These results suggest that structurally complex anthropogenic matrices have potential as management tools for bird conservation by complementing habitat protection and restoration.

OBSERVATIONS OF PREDATION EVENTS AT BIRD NESTS IN CENTRAL PANAMA

We describe 14 nest predation events witnessed in the Republic of Panama during studies of avian nesting success. Eight predations were by birds, including two species of toucan and one forest-falcon. Four predations were by two species of snake, one was by monkeys, and one near-predation was by army ants (Eciton burchelli). In three cases, a fraction of the nest contents were removed by the predator on one visit before it returned later to consume the remaining items. Our observations, although limited to diurnal encounters, indicate that Neotropical birds are susceptible to a diverse array of potential predators. Detailed investigations using cameras are needed to quantify the potential importance of each predator species and to identify the occurrence and importance of nocturnal predation.

The Survival Value of Flocking in Neotropical Birds: Reality or Fiction?

The Survival Value of Flocking in Neotropical Birds: Reality or Fiction?

The effects of fragmentation on fluctuating asymmetry in passerine birds of Brazilian tropical forests

Summary 1. Fluctuating asymmetry (FA) refers to the difference between the right and left sides in characters that should otherwise be bilaterally symmetrical, but whose expression is affected by epigenetic stress during development. Forest fragmentation may promote an increase in FA in isolated populations, by either genetic or environmental stress. FA may function as a biomonitor index in conservation biology if increased levels were observed in populations from fragmented habitats. 2. We tested the hypothesis that FA is higher in birds from small tropical forest patches than in large forest tracts. We measured wing and tarsus FA on mist‐netted birds from seven fragments and seven continuous areas from south‐eastern Atlantic rain forest in Brazil. We performed FA comparisons between fragments and control groups for the whole community, for individual foraging guilds and for the six most abundant species. 3. Wing and tarsus FA were significantly greater in fragments than continuous areas for the whole community and were both negatively correlated with forest fragment size. Differences in FA varied among foraging guilds, being more evident for insectivorous species, especially those feeding in or near the understorey. 4. FA levels increased significantly in forest fragments in at least one trait for five of the six most abundant species. There was no correlation between tarsus and wing asymmetries for the individuals of any species nor any difference between the degree of asymmetries of these characters. 5. We suggest that FA is a useful tool to assess the effects of fragmentation on forest birds, and may be applied in monitoring neotropical birds. FA indices might be profitably developed, particularly in species most threatened by fragmentation effects and when investigated in different morphological characters.