Tropical Forest Birds Research Articles

Predation behaviour of the bridle snake (Lycodon cf. davisonii) on Asian tropical evergreen forest bird nests

Predation behaviour of the bridle snake (Lycodon cf. davisonii) on Asian tropical evergreen forest bird nests

Effectiveness of protected areas in conserving tropical forest birds

Protected areas (PAs) are the cornerstones of global biodiversity conservation efforts, but to fulfil this role they must be effective at conserving the ecosystems and species that occur within their boundaries. Adequate monitoring datasets that allow comparing biodiversity between protected and unprotected sites are lacking in tropical regions. Here we use the largest citizen science biodiversity dataset – eBird – to quantify the extent to which protected areas in eight tropical forest biodiversity hotspots are effective at retaining bird diversity. We find generally positive effects of protection on the diversity of bird species that are forest-dependent, endemic to the hotspots, or threatened or Near Threatened, but not on overall bird species richness. Furthermore, we show that in most of the hotspots examined this benefit is driven by protected areas preventing both forest loss and degradation. Our results provide evidence that, on average, protected areas contribute measurably to conserving bird species in some of the world’s most diverse and threatened terrestrial ecosystems.

Creating benchmark measurements of tropical forest bird communities in large plots

Abstract An understanding of how tropical bird communities might respond to climate change and other types of environmental stressors seems particularly urgent, yet we still lack, except for a few sites, even snapshot inventories of avian richness and abundances across most of the tropics. Such benchmark measurements of tropical bird species richness and abundances could provide opportunities for future repeat surveys and, therefore, strong insight into degrees and pace of change in community organization over time. The challenges of creating a network of benchmarked sites include high variation in detectability among species, general rarity of many species that creates hurdles for use of modern bird counting methods aimed at controlling for variation in detectability, and lack of a standardized protocol to create repeatable inventories. We argue that reasonably complete inventories of tropical bird communities require use of multiple survey techniques to provide internal calibrations of abundance estimates and require multiple visits to improve completeness of richness inventories. We suggest that a network of large (50–100 ha) plots scattered across the tropics can also provide insights into geographic variation in and drivers of avian community structure analogous to insights provided by the Smithsonian Center for Tropical Forest Science Forest Global Earth Observatory network of forest dynamics plots. Perhaps most importantly, large plots provide opportunities for use of multiple survey techniques to estimate abundances while also using some exactly repeatable survey techniques that can greatly improve abilities to quantify change over time. We provide guidance on establishment of and survey methods for large tropical bird plots as well as important recommendations for collection and archiving of metadata to safeguard the long-term utility of valuable benchmark data.

Bats as predators at the nests of tropical forest birds

Nest predation is one of the main causes of bird mortality, and the development of nest anti‐predatory defenses can mold many aspects of bird evolution. Here we report that bats can attack nests in incubation and nestling stages in the Atlantic Forest, Brazil. Although other types of interactions between birds and bats have been reported, including predation of adult individuals and the co‐occurrence in cavity nests, bats may have been underestimated as nest predators. The combination of flying and olfactory skills makes bats functionally different compared to other predators, opening new perspectives on the interpretation of nesting‐birds anti‐predatory strategies. They represented 8% of all recorded potential predations in the bird community studied, being more important than reptiles, and were responsible for 33% of nest losses for at least one bird species. Our data suggest the potential for nest depredation by bats to be an important selective factor in shaping anti‐predatory strategies of nesting birds. Then, the use of devices capable to detect bats will be essential for reliable interpretations of birds nest defense mechanisms in future works.

Diversity of understory birds in a perennial tropical forest at Los Chimalapas, Mexico

The understory has received little attention in studies of tropical forest birds. However, the growing use of camera traps for the study of vertebrates such as mammals has prompted studies on the diversity of terrestrial birds or birds with limited flying capacity. In this study we present an analysis of the diversity of understory birds in a perennial tropical forest of the Chimalapas region, in southeastern Mexico. We collected 967 independent bird records comprising 10 orders, 15 families, 22 genera, and 27 species with a total sampling effort of 8,529 trap-days. The effective number of species indicated the presence of 31 species while Clench's species accumulation model indicated 32, suggesting that over 15% of the species remain to be recorded. Although we did not register all the species potentially present in the understory, bird diversity was higher than in other studies using camera traps. Crax rubra, Tinamus major, and Geotrygon montana were the most abundant species recorded. We obtained records for small-sized (Anthracothorax prevostii, Leptotila plumbeiceps, and Zentrygon albifacies) and migratory (Hylocichla mustelina) species, highlighting the potential of camera traps for their study.

How important is aerial leaf litter for insectivorous birds foraging in a Malaysian tropical forest?

Aerial leaf litter is a vital resource for insectivorous birds in tropical forests, particularly those that rely on dietary litter-dependent arthropods. The present study quantified and determined aerial-leaf litter selection patterns of specialist and regular dead-leaf users. In total, 486 observation sessions were conducted in a lowland tropical forest from February 2014 to September 2015. At least two ‘specialist’ species (over 75% of the observations) and seven ‘regular users’ species (25–74% of the observations) were found foraging for arthropods among aerial curled dead leaves within the aboveground vertical vegetation layers. These species belonged to four genera of the family Timaliidae and Pellorneidae: Cyanoderma, Stachyris, Pellorneum, and Malacopteron. The chestnut-winged babbler (Cyanoderma erythropterum) and the black-throated babbler (Stachyris nigricollis) were two species that heavily exploited the aerial leaf litter, accounting for 89% and 76% of the observations, respectively. The present study indicates that aerial leaf litter could serve as a vital foraging resource for most gleaning forest babblers in Malaysian rainforests. Moreover, niche separation among these dead-leaf foragers occurred due to their differing vertical strata preferences. The variations in body and bill sizes among the studied species suggest that they consume various arthropod sizes and taxonomic groups. A morphological analysis identified Hymenoptera, Coleoptera, and Arachnida as the dominant litter-dependent arthropods, and a molecular analysis revealed the presence of additional insect groups in the aerial leaf litter (e.g. Diptera and Lepidoptera). This study highlights the importance of maintaining undergrowth vegetation that can intercept aerial leaf litter to provide important foraging opportunities for forest bird species.

Acoustic community structure and seasonal turnover in tropical South Asian birds

Abstract Birds produce diverse acoustic signals, with coexisting species occupying distinct “acoustic niches” to minimize masking, resulting in overdispersion within acoustic space. In tropical regions of the world, an influx of migrants from temperate regions occurs during winter. The effects of these migrants on acoustic community structure and dynamics remain unstudied. Here, I show that in a tropical dry forest bird community occurring within an urban area in India, the influx of winter migrants is accompanied by a change in species composition of the acoustic community. However, in spite of this, the acoustic community remains overdispersed in acoustic niche space. The winter community of vocal birds at this study site additionally exhibits lower energy in the 4–7 kHz frequency bands (consistent with species singing less continuously), as well as lower phylogenetic diversity. My data are thus indicative of seasonal turnover in acoustic communities but suggest that acoustic niches and community structure are stable across seasons. Migrants occupy similar regions of acoustic space as residents and are relatively closely related to some of these species. Their arrival, therefore, leads to greater phylogenetic clustering in the winter and thus lower phylogenetic diversity, although the acoustic community remains overdispersed. Studying seasonal dynamics of acoustic communities thus provides valuable insight into assembly processes, as well as a potential framework for long-term monitoring of urban ecosystems.

Connectivity with primary forest determines the value of secondary tropical forests for bird conservation

AbstractSpecies extinctions caused by the destruction and degradation of tropical primary forest may be at least partially mitigated by the expansion of regenerating secondary forest. However, the conservation value of secondary forest remains controversial, and potentially underestimated, since most previous studies have focused on young, single‐aged, or isolated stands. Here, we use point‐count surveys to compare tropical forest bird communities in 20–120‐year‐old secondary forest with primary forest stands in central Panama, with varying connectivity between secondary forest sites and extensive primary forest. We found that species richness and other metrics of ecological diversity, as well as the combined population density of all birds, reached a peak in younger (20‐year‐old) secondary forests and appeared to decline in older secondary forest stands. This counter‐intuitive result can be explained by the greater connectivity between younger secondary forests and extensive primary forests at our study site, compared with older secondary forests that are either (a) more isolated or (b) connected to primary forests that are themselves small and isolated. Our results suggest that connectivity with extensive primary forest is a more important determinant of avian species richness and community structure than forest age, and highlight the vital contribution secondary forests can make in conserving tropical bird diversity, so long as extensive primary habitats are adjacent and spatially connected.Abstract in Spanish is available with online material.

Direct and Cascading Effects of Landscape Structure on Tropical Forest and Non-forest Frugivorous Birds

Global biodiversity is increasingly threatened by land-use change, but the direct and indirect drivers of species diversity in human-modified tropical landscapes are poorly known. Forest-dependent species are expected to be particularly sensitive to changes in landscape composition (e.g., forest loss) and configuration (e.g., increase of forest edges), both directly and indirectly through cascading landscape effects on local patterns of forest structure and resource availability. In contrast, non-forest-dependent species are probably more strongly related to landscape changes than to local forest patterns, as these species are able to use resources not only from the forest, but also from other landscape elements over larger spatial scales. We tested these hypotheses using structural equation modeling. In particular, we sampled 20 landscapes (115 ha each) from the Brazilian Atlantic rainforest to assess the effect of landscape-scale forest cover and amount of forest edges on the diversity of frugivorous birds, both directly and indirectly through the effect that these landscape variables may have on vegetation complexity and fruit biomass. We separately assessed the response of forest-dependent and non-forest-dependent frugivores to infer potential mechanisms underlying bird assemblages in fragmented landscapes. The diversity of forest-dependent birds mainly decreased with the simplification of vegetation complexity in more deforested landscapes, but increased with increasing fruit biomass in more forested landscapes (indirect effects). Both patterns were significant, thus supporting a strong bottom-up control, i.e., local habitat simplification and resource scarcity in highly deforested landscapes limits the maintenance of forest-dependent birds. Conversely, but as expected, non-forest-dependent birds were more strongly and directly related to landscape-scale patterns. In particular, landscapes with higher forest edge amount showed higher bird species diversity, probably because the increasing length of ecotones and interspersion/juxtaposition of different habitat types in landscapes with more forest edges can increase resource availability and foraging efficiency of non-forest-dependent birds. As the seed dispersal services offered by forest-dependent species cannot be ecologically compensated for by the proliferation of non-forest-dependent species, preventing forest loss is imperative to maintain forest-dependent birds and forest regeneration in this vanishing biodiversity hotspot.

Distribution of Hornbills and Important Hornbill Landscapes - Setting Site Conservation Priorities for Peninsular Malaysia

Malaysia is an important hornbill range country in Asia supporting a total of 10 hornbill species. Malaysia ranks second (collectively with Myanmar and the Philippines) after Thailand and Indonesia (both 13 species respectively) in terms of hornbill diversity per country. Within Malaysia, all 10 species has been recorded in Peninsular Malaysia whereas Sabah and Sarawak have 8 species each. The Great Hornbill Buceros bicornis and Plain-pouched Hornbill Rhyticeros subruficollis do not occur in Borneo. Despite being iconic tropical forest birds, our understanding of its local distribution status, ecology and biology remains limited. In this paper, we conducted a broad examination of the hornbills’ distribution in Peninsular Malaysia based on more recent information gleaned mostly from grey literature e.g. birding trip reports, scientific expedition reports, department annual reports, selected Facebook birding group postings, proceedings, bird databases (MNS Bird-I-Witness) etc. Information from primary literature e.g. local/regional journals were also taken into account where available. The purpose of this exercise is two-fold, (1) to update our knowledge post-Wells (1999) about hornbill distributions in Peninsular Malaysia in light of continuing deforestation and habitat degradation and (2) identify Important Hornbill Landscapes (IHL) in need of protection and conservation to preserve viable hornbill populations.

Collapse of a tropical forest bird assemblage surrounding a hydroelectric reservoir

Hydroelectricity is the world's largest source of ‘renewable’ energy, and deployment will expand considerably in the coming decade, with Asian countries installing the bulk of new generating capacity. Before construction of large hydropower projects, empirical evidence can be utilised to inform public involvement and to realistically ground decision-making processes such as impact mitigation planning and whether or not to build. This study explored changes in avian community richness and diversity among resident forest species surrounding the 165 km2 Chiew Larn reservoir in southern Thailand, thirty years after inundation. Replicated avian point-counts were undertaken on 23 island sites and 24 nearby mainland transects. A total of 108 habitat structure surveys were conducted. Mainland and islands were composed of remarkably similar bamboo-dominated edge habitat. logArea described 82% of the variability in species richness using general linear models and 74% of the variability in community composition using Bray-Curtis non-metric multidimensional scaling. Species richness was similar on mainland and islands; however, the exponential of Shannon diversity was significantly higher on the mainland. Compared to a species pool of recent confirmed records in less disturbed habitat beyond the inundation zone, one fourth of species were missing from mainland sites. The avian community was dominated by a handful of disturbance tolerant species; furthermore, several widespread and ecologically tolerant species were also rare or missing. The disturbance-intolerant assemblage experienced collapse. Terrestrial and other understorey insectivores, species associated with mixed-species foraging flocks, middle storey sallying insectivores, and frugivores were severely depauperate, as were Sundaic endemics and species of conservation concern. An estimated 61 km2 of degraded edge habitat surrounded the reservoir near the study area. Without taking the potential for serious mainland edge effects and associated human disturbance of habitat into consideration, planners will underestimate the potential impact of hydropower development on avian biodiversity.

Effects of roadside edge on nest predators and nest survival of Asian tropical forest birds

Creation of roadside forest edges can have indirect effects on forest bird communities, as edges can promote species detrimental to forest-nesting birds such as nest predators. We assessed species-specific rates of nest survival of understory birds, relative abundances of specific nest predators and predator-specific rates of nest predation relative to the distance from roadside forest edge in a dry evergreen forest in northeastern Thailand. During the breeding seasons (February–August) of 2014–2016 we searched for nests along two, 1-km transects which ran perpendicular from the edge of a five-lane highway into the forest interior. To assess nest predator species, video cameras were placed on active nests of understory birds and multiple techniques were used to assess the relative abundances of the documented nest predators. We found 306 active nests of 26 species and recorded 179 predation events from 13 species of nest predators. Distance to edge influenced the daily nest survival rates for four of seven focal bird species, with three species having higher survival rates nearer to the edge. Four of six predators had higher relative abundances in the forest interior. Rats and the Common Green Magpie (Cissa chinensis) had higher abundances nearer the edge. Snake detections were too few to assess statistically. Nest predation rates for the top three predators, Northern Pig-tailed Macaque (Macaca leonina), Green Cat Snake (Boiga cyanea) and Crested Goshawk (Accipiter trivirgratus) were significantly greater in the forest interior. The fourth-most important, Common Green Magpie, was the only predator responsible for more nest predation events closer to habitat edge compared to interior. Our study suggests that the impacts of edges on nesting success are highly dependent on the nest predator community and the species-specific responses of predators to edges.

Assessing Diet of the Rufous-Winged Philentoma (Philentoma pyrhoptera) in Lowland Tropical Forest using Next-Generation Sequencing

Dietary study provides understanding in predator-prey relationships, yet diet of tropical forest birds is poorly understood. In this study, a non-invasive method, next-generation sequencing (Illumina MiSeq platform) was used to identify prey in the faecal samples of the Rufous-winged Philentoma (Philentoma pyrhoptera). Dietary samples were collected in lowland tropical forest of central Peninsular Malaysia. A general invertebrate primer pair was used for the first time to assess diet of tropical birds. The USEARCH was used to cluster the COI mtDNA sequences into Operational Taxonomic Unit (OTU). OTU sequences were aligned and queried through the GenBank or Biodiversity of Life Database (BOLD). We identified 26 distinct arthropod taxa from 31 OTUs. Of all OTUs, there was three that could be identified up to species level, 20 to genus level, three to family level and five could not assigned to any taxa (the BLAST hits were poor). All sequences were identified to class Insecta belonging to 18 families from four orders, where Lepidoptera representing major insect order consumed by study bird species. This non-invasive molecular approach provides a practical and rapid technique to understand of how energy flows across ecosystems. This technique could be very useful to screen for possible particular pest insects consumed by insectivores (e.g. birds and bats) in crop plantation. A comprehensive arthropod studies and local reference sequences need to be added to the database to improve the proportion of sequences that can be identified.

Contrasting impacts of land‐use change on phylogenetic and functional diversity of tropical forest birds

Abstract Biodiversity conservation strategies increasingly target maintaining evolutionary history and the resilience of ecosystem function, not just species richness (SR). This has led to the emergence of two metrics commonly proposed as tools for decision making: phylogenetic diversity (PD) and functional diversity (FD). Yet, the extent to which they are interchangeable remains poorly understood. We explore shifts in and relationships between FD and PD of bird communities across a disturbance gradient in Borneo, from old‐growth tropical forest to oil palm plantation. We show a marked decline in PD, and an increase in phylogenetic mean nearest taxon distance from forest to oil palm, in line with declining SR across the gradient. However, phylogenetic mean pairwise distance is constrained by forest logging more than by conversion to oil palm, taking account of SR. The decline in FD across the gradient is less severe than in PD, with all metrics indicating relatively high trait diversity in oil palm despite low SR, although functional redundancy is much reduced. Accounting for SR, levels of functional over‐ or under‐dispersion of bird communities are strongly coupled to habitat disturbance level rather than to any equivalent phylogenetic metric. Policy implications. We suggest that while phylogenetic diversity (PD) is an improvement on species richness as a proxy for functional diversity (FD), conservation decisions based on phylogenetic diversity alone cannot reliably safeguard maximal functional diversity. Thus, phylogenetic diversity and functional diversity are related but still complementary. Priority setting exercises should use these metrics in combination to identify conservation targets.

Gamebird responses to anthropogenic forest fragmentation and degradation in a southern Amazonian landscape.

Although large-bodied tropical forest birds are impacted by both habitat loss and fragmentation, their patterns of habitat occupancy will also depend on the degree of forest habitat disturbance, which may interact synergistically or additively with fragmentation effects. Here, we examine the effects of forest patch and landscape metrics, and levels of forest disturbance on the patterns of persistence of six gamebird taxa in the southern Brazilian Amazon. We use both interview data conducted with long-term residents and/or landowners from 129 remnant forest patches and 15 continuous forest sites and line-transect census data from a subset of 21 forest patches and two continuous forests. Forest patch area was the strongest predictor of species persistence, explaining as much as 46% of the overall variation in gamebird species richness. Logistic regression models showed that anthropogenic disturbance—including surface wildfires, selective logging and hunting pressure—had a variety of effects on species persistence. Most large-bodied gamebird species were sensitive to forest fragmentation, occupying primarily large, high-quality forest patches in higher abundances, and were typically absent from patches <100 ha. Our findings highlight the importance of large (>10,000 ha), relatively undisturbed forest patches to both maximize persistence and maintain baseline abundances of large neotropical forest birds.

&lt;b&gt;Nepal’s National Red List of Birds&lt;/b&gt;

The main objectives of the Nepal National Bird Red Data Book were to provide comprehensive and up-to-date accounts of all the bird species found in Nepal, assess their status applying the IUCN Guidelines at Regional Levels, identify threats to all bird species and recommend the most practical measures for their conservation. It is hoped that the Bird RDB will help Nepal achieve the Convention on Biological Diversity target of preventing the extinction of known threatened species and improving their conservation status. As population changes of Nepal’s birds have been studied for only a few species, assessments of species’ national status were mainly made by assessing changes in distribution. Species distribution maps were produced for all of Nepal’s bird species except vagrants and compared to maps that were produced in 1991 using the same mapping system. Of the 878 bird species recorded, 168 species (19%) were assessed as nationally threatened. These comprise 68 (40%) Critically Endangered species, 38 (23%) Endangered species and 62 (37%) Vulnerable species. A total of 62 species was considered Near Threatened and 22 species Data Deficient. Over 55% of the threatened birds are lowland grassland specialists, 25% are wetland birds and 24% tropical and sub-tropical broadleaved forest birds. Larger birds appear to be more threatened than smaller birds with 98 (25%) non-passerine species threatened and 67 (14%) passerine species. Habitat loss, degradation and fragmentation are the most important threats. Other threats include chemical poisoning, over-exploitation, climate change, hydropower, invasive species, intensification of agriculture, disturbance, and limited conservation measures and research. Measures to address these threats are described. It was also concluded that re-assessments of the status of certain bird groups carried out every five years and the setting up of a national online system for storing and reporting bird sightings would be useful.

Limited carbon and biodiversity co‐benefits for tropical forest mammals and birds

The conservation of tropical forest carbon stocks offers the opportunity to curb climate change by reducing greenhouse gas emissions from deforestation and simultaneously conserve biodiversity. However, there has been considerable debate about the extent to which carbon stock conservation will provide benefits to biodiversity in part because whether forests that contain high carbon density in their aboveground biomass also contain high animal diversity is unknown. Here, we empirically examined medium to large bodied ground-dwelling mammal and bird (hereafter "wildlife") diversity and carbon stock levels within the tropics using camera trap and vegetation data from a pantropical network of sites. Specifically, we tested whether tropical forests that stored more carbon contained higher wildlife species richness, taxonomic diversity, and trait diversity. We found that carbon stocks were not a significant predictor for any of these three measures of diversity, which suggests that benefits for wildlife diversity will not be maximized unless wildlife diversity is explicitly taken into account; prioritizing carbon stocks alone will not necessarily meet biodiversity conservation goals. We recommend conservation planning that considers both objectives because there is the potential for more wildlife diversity and carbon stock conservation to be achieved for the same total budget if both objectives are pursued in tandem rather than independently. Tropical forests with low elevation variability and low tree density supported significantly higher wildlife diversity. These tropical forest characteristics may provide more affordable proxies of wildlife diversity for future multi-objective conservation planning when fine scale data on wildlife are lacking.

Diurnal variation in corticosterone release among wild tropical forest birds.

BackgroundGlucocorticoids are adrenal steroid hormones essential to homeostatic maintenance. Their daily variation at low concentrations regulates physiology and behavior to sustain proper immunological and metabolic function. Glucocorticoids rise well above these baseline levels during stress to elicit emergency-state responses that increase short-term survival. Despite this essence in managing life processes under both regular and adverse conditions, relationships of glucocorticoid release to environmental and intrinsic factors that vary at daily and seasonal scales are rarely studied in the wild.MethodsThis study on 41 passerine species of the Ecuadorian Chocó applied a standardized capture-and-restraint protocol to examine diurnal variation in baseline and stress-related release of corticosterone, the primary avian glucocorticoid. Tests for relationships to relative body mass, hemoglobin concentration, molt status and date complemented this evaluation of the time of day effect on corticosterone secretion in free-living tropical rainforest birds. Analyses were also partitioned by sex as well as performed separately on two common species, the wedge-billed woodcreeper and olive-striped flycatcher.ResultsInterspecific analyses indicated maximum baseline corticosterone levels at the onset of the active phase and reductions thereafter. Stress-related levels did not correspond to time of day but accompanied baseline reductions during molt and elevations in birds sampled later during the September - November study period. Baseline corticosterone related negatively to hemoglobin in the wedge-billed woodcreeper and stress-related levels increased with body mass in the olive-striped flycatcher. There were no substantial sex-related differences.ConclusionsThe results of this study suggest a diurnal rhythmicity in baseline corticosterone release so robust as to emerge in pooled analyses across a highly variable dataset. While this detection in nature is singular, correspondent patterns have been demonstrated outside of the tropics in captive model species. Congruity in daily rhythms and links to physiological and life-history state across disparate taxa and environments may promote the yet unresolved utility of corticosterone release as a global metric for population health. However, certain results of this study also deviate from laboratory and field research at higher latitudes, cautioning generalization. Environmental distinctions such as high productivity and tempered seasonality may precipitate unique life-history strategies and underlying hormonal mechanisms in tropical rainforest birds.Electronic supplementary materialThe online version of this article (doi:10.1186/s12983-016-0151-3) contains supplementary material, which is available to authorized users.

Shifting agriculture supports more tropical forest birds than oil palm or teak plantations in Mizoram, northeast India

ABSTRACT Conversion of tropical forests and diverse multicrop agricultural land to commercial monocultures is a conservation concern worldwide. In northeast India, landscapes under shifting agriculture (or jhum) practiced by tribal communities are increasingly being replaced by monoculture plantations (e.g., teak, oil palm). We compared oil palm and teak plantations, shifting agricultural fields, and forest fallows (0–8 yr regeneration) with tropical rainforest edge and interior sites in Dampa Tiger Reserve, Mizoram, India. Twenty replicate transects were surveyed in each of the 5 study strata for vegetation structure, bird species richness and density, bird abundance, and species composition. Tree density and canopy and vertical structure were lowest in oil palm plantations, intermediate in teak plantations and jhum, and highest in rainforest sites. Tree density in jhum (4.3 stems per 100 m2) was much higher than in oil palm plantations (0.5 stems per 100 m2), but lower than in rainforest (6.8–8.2 stems ...

What determines the timing and duration of the nesting season for a tropical dry forest bird, the White-throated Magpie-Jay (Calocitta formosa)?

ABSTRACT The factors affecting the timing of nesting in tropical birds remain poorly understood. We investigated the phenology of White-throated Magpie-Jay (Calocitta formosa) nesting in the dry forest of northwest Costa Rica, a region characterized by a severe 5-month dry season followed by a very rainy wet season. We examined whether nesting was associated with climate, diet, risk of parasite infection to nestlings, risk of nest predation, and opportunity to re-nest. Groups of White-throated Magpie-Jays nested repeatedly, initiating nests over a 7-month period that spanned the transition from the dry to early wet season. The diet of adults and the composition of food fed to broods varied seasonally in parallel with changes in vegetation condition and climate associated with the transition from dry to wet season. Fledgling transition to nutritional independence occurred exclusively in the wet season when caterpillars and other arthropods were a large component of the diet. The timing of groups’ last nest...