Generalist Bird Research Articles

Climate cycling did not affect haplotype distribution in an abundant Southern African avian habitat generalist species, the familiar chat (Oenanthe familiaris).

Avian species diversity in Southern Africa is remarkably high, yet the mechanisms responsible for that diversity are poorly understood. While this is particularly true with respect to species endemic to the subregion, it is unclear as to how more broadly distributed African species may have colonized southern Africa. One process that may in part account for the high bird species diversity in southern Africa is a "species pump" model, wherein the region was repeatedly colonized by lineages from areas further north: a pattern related to climate cycling and the eastern African arid corridor. Once occupying southern Africa, with its many varied biomes, it is possible that climate cycling further affected lineages by generating genetic diversity in multiple refugia, a pattern recently shown for several southern African bird species. Here, we used mtDNA to address these questions in a widespread, sedentary habitat generalist bird species, the familiar chat (Oenanthe familiaris). The phylogenetic structure suggests a north-to-south colonization pattern, supporting the "species pump" model. Haplotype diversity was partitioned into two distinct clusters: southern Africa and Malawi (East Africa). Southern African haplotypes were not geographically partitioned, and we hypothesize that this pattern has arisen because this species is a habitat generalist, and as such resilient to habitat-altering climate perturbations. Based on our phylogenetic results, we discuss the validity of currently recognized subspecies.

Forest cover, tree structure, and fruit size as predictors of fruit consumption by birds in two tropical trees from southern Mexico

We evaluate the effect of some variables related to fruit morphology, tree structure, and forest cover on fruit consumption by birds in the tree species Conostegia xalapensis (Melastomataceae) and Bursera simaruba (Burseraceae), in a semi-humid forest of southern Mexico. Foraging observations were made in 20 trees per species from November 2020 to June 2021. We recorded a total of 18 and 22 bird species consuming the fruits of B. simaruba and C. xalapensis, respectively. Flycatchers preferred fruits of B. simaruba, while thrushes largely consumed fruits of C. xalapensis. For large birds, crop size and foliar height diversity were the most influential variables in the removal of B. simaruba fruits, while small birds were positively correlated with the foliar coverage. For C. xalapensis, forest cover negatively influenced fruit consumption by large birds, while the fruit polar diameter had a positive effect on fruit consumption by small birds. Fruit consumption of C. xalapensis by specialist birds showed a positive relationship with forest cover, while the generalists showed a negative relationship. Decreased fruit removal was observed for B. simaruba by both specialist and generalist birds in forest landscapes. Our results can help understand the drivers of the frugivore-plant relationship in semi-humid tropical forests.

Vertebrates and flying insects provide biocontrol services to Australian urban food gardens

Biocontrol by wild insects and other organisms is an important service provided to agriculture, but few studies have linked the role of this service to urban garden crop production. In 15 urban food gardens in Sydney, Australia, we assessed predation and parasitism of two sentinel prey species, recorded pest control activities undertaken by gardeners and the produce yielded by garden crops. We observed substantial removal of sentinel prey (mean removal 22% for Tenebrio molitor larvae and 59% for Helicoverpa armigera) but no parasitism. Vertebrate predators primarily consisted of urban adapted birds and mammals common throughout Australian cities. We measured a range of local and landscape scale environmental variables including plant richness and abundance, light, canopy cover, building density and distance to remnant vegetation. We found that gardeners undertook only basic pest control activities with little chemical use, yet high amounts of produce were harvested. Pest control services were poorly explained by environmental variables. Low active pest control activities, and high predation rates suggest pests are either well controlled or in low numbers in the surveyed urban food gardens. Given the vertebrate predators were generalist birds and mammals common to many parts of urban Australia, the provision of predation services to urban gardens by these taxa could be widespread across the continent.

Impacts of habitat loss and fragmentation on seed dispersal by an Afrotropical bird community in an anthropogenic landscape: Insights from movement models

Habitat loss and fragmentation can affect seed dispersal by impacting seed dispersers' habitat choices, behavior, and movement patterns. Here we studied seed dispersal by an Afrotropical bird community in an anthropogenic landscape in Kenya. We used telemetry data of six bird species, estimated their habitat choices, behavior, and movement patterns in the forest fragments and the matrix. We then integrated our model estimates into a seed dispersal simulation model with multiple artificial anthropogenic landscapes, experiencing different levels of habitat loss and fragmentation. In our simulations, we included two seed disperser groups: forest specialist and habitat generalist birds that moved in the landscape using a mixture-correlated random walk, and encamped and traveled in the different habitat types. Increased habitat loss diminished seed dispersal distances, where seeds carried by forest specialist dispersers suffered a stronger reduction in dispersal distances compared to habitat generalists, and number of seeds deposited in habitat fragments, where fewer seeds were deposited into the fragments by habitat generalist dispersers compared to forest specialists. The effects of habitat fragmentation were similar to but weaker than that of habitat loss, and most apparent at an intermediate level of habitat loss. Other seed dispersal metrics, including spatial extent of seed rain and nearest neighbor distances among seeds, did not show any strong relationships with either habitat loss or fragmentation. Therefore, movement models offer valuable perspectives on how habitat loss and fragmentation can influence seed dispersal patterns, by reliably estimating habitat choices, behavior, and movement patterns of dispersers, and potentially benefiting efforts to conserve this ecological interaction.

IMPACTS OF INTENSIVE AGRICULTURE ON BIRDS: A REVIEW

Intensive agriculture has had a negative impact on biodiversity and human health across the world. Specifically, bird populations have declined for many years due to soil degradation and agrochemical pollution. This review, which draws on 890 sources, including research articles and literature reviews, examines the interaction between birds and intensive agriculture to better understand its effects and conservation implications. Intensive agricultural activities have resulted in significant population declines among insectivorous and carnivorous birds, while generalist bird populations have increased. The heavy use of pesticides in intensive agriculture affects food availability for birds by reducing invertebrate and vertebrate populations as well as natural vegetation cover, which has a significant impact on bird diversity. Additionally, the accumulation of toxic compounds reduces bird reproductive success. In general, intensive agroecosystems have consistently had lower avian diversity than forest habitats and even lower-impact agricultural systems. However, some agroecosystems, such as rice fields, agricultural drainages, and canal systems, create alternative habitats that can benefit waterfowl. Future work should consider strategies such as restoring and enhancing vegetation edges, preserving natural vegetation, implementing organic farming practices, maintaining water bodies, and providing economic incentives for landowners to conserve biodiversity on their land to promote bird diversity conservation.

Generalist and topologically central avian frugivores promote plant invasion unequally across land-bridge islands.

Seed dispersal by frugivorous birds facilitates plant invasions, but it is poorly known how invasive plants integrate into native communities in fragmented landscapes. We surveyed plant-frugivore interactions, including an invasive plant (Phytolacca americana), on 22 artificial land-bridge islands (fragmented forests) in the Thousand Island Lake, China. Focusing on frugivory interactions that may lead to seed dispersal, we built ecological networks of studied islands both at the local island (community) and at landscape (metacommunity) levels. On islands with P. americana, we found that P. americana impacted local avian frugivory networks more on islands with species-poor plant communities and on isolated islands. Moreover, as P. americana interacted mainly with local core birds (generalists), this indicates reduced seed dispersal of native plants on invaded islands. At the landscape level, P. americana had established strong interactions with generalist birds that largely maintain seed-dispersal functions across islands, as revealed by their topologically central roles both in the regional plant-bird trophic network and in the spatial metanetwork. This indicates that generalist frugivorous birds may have facilitated the dispersal of P. americana across islands, making P. americana well integrated into the plant-frugivore mutualistic metacommunity. Taken together, our study demonstrates that the impact of plant invasion is context-dependent and that generalist native frugivores with high dispersal potential may accelerate plant invasion in fragmented landscapes. These findings highlight the importance of taking the functional roles of animal mutualists and habitat fragmentation into account when managing plant invasions and their impact on native communities.

Erratum for the Research Article “Agriculture and hot temperatures interactively erode the nest success of habitat generalist birds across the United States” by K. S. Lauck et al .

Erratum for the Research Article “Agriculture and hot temperatures interactively erode the nest success of habitat generalist birds across the United States” by K. S. Lauck <i>et al</i> .

Habitat specialization predicts demographic response and vulnerability of floodplain birds in Amazonia.

The annual flooding cycle of Amazonian rivers sustains the largest floodplains on Earth, which harbour a unique bird community. Recent studies suggest that habitat specialization drove different patterns of population structure and gene flow in floodplain birds. However, the lack of a direct estimate of habitat affinity prevents a proper test of its effects on population histories. In this work, we used occurrence data, satellite images and genomic data (ultra-conserved elements) from 24 bird species specialized on a variety of seasonally flooded environments to classify habitat affinities and test its influence on evolutionary histories of Amazonian floodplain birds. We demonstrate that birds with higher specialization in river islands and dynamic environments have gone through more recent demographic expansion and currently have less genetic diversity than floodplain generalist birds. Our results indicate that there is an intrinsic relationship between habitat affinity and environmental dynamics, influencing patterns of population structure, demographic history and genetic diversity. Within the floodplains, historical landscape changes have had more severe impacts on island specialists, making them more vulnerable to current and future anthropogenic changes, as those imposed by hydroelectric dams in the Amazon Basin.

Agriculture and hot temperatures interactively erode the nest success of habitat generalist birds across the United States.

Habitat conversion and climate change are fundamental drivers of biodiversity loss worldwide but are often analyzed in isolation. We used a continental-scale, decades-long database of more than 150,000 bird nesting attempts to explore how extreme heat affects avian reproduction in forests, grasslands, and agricultural and developed areas across the US. We found that in forests, extreme heat increased nest success, but birds nesting in agricultural settings were much less likely to successfully fledge young when temperatures reached anomalously high levels. Species that build exposed cup nests and species of higher conservation concern were particularly vulnerable to maximum temperature anomalies in agricultural settings. Finally, future projections suggested that ongoing climate change may exacerbate the negative effects of habitat conversion on avian nesting success, thereby compromising conservation efforts in human-dominated landscapes.

Bird diversity in the forests and coconut farms of Sulawesi, Indonesia

AbstractCoconut farming contributes to the livelihoods of millions of people in tropical countries but is less frequently considered as a threat to biodiversity compared to other palm commodities such as oil palm. The expansion of coconut farming alongside other smallholder agriculture in Sulawesi, Indonesia, is of potential concern as the region is a centre of species endemism. We studied bird diversity and community structure in forests, coconut palm plantations and mixed farmland in Gorontalo Province, northern Sulawesi. Forest and non-forest sites supported similar numbers of species overall, but compared to agricultural areas, forest sites had communities that were more diverse and more even (i.e. different species were present at similar abundances). We found far fewer endemic species in agricultural areas compared to forests, and the communities in palm plantations and mixed farmland sites were dominated by generalist birds, with few indicator taxa. Nevertheless, there was a higher number of endemic species in coconut palm plantations than in mixed farmland sites. These findings mirror patterns of biotic homogenization documented elsewhere in the Wallacea centre of endemism, and imply that coconut palm plantations have comparable biodiversity value to other farmland systems. Increased protection of lowland forests and improved management of coconut farms could be important for supporting the conservation of the endemic birds of Sulawesi in the long term, but this warrants further study.

Feeding Habits and Diet Composition of the African Sacred Ibis in Selected Water-Logged Sites in Dar es Salaam, Tanzania

The African Sacred Ibises Threskiornis aethiopicus are generalist birds that feed on many invertebrates and some vertebrates. However, the diet composition of local T. aethiopicus populations in wetland areas in Dar es Salaam Tanzania was unknown. Sacred Ibises from eight water-logged areas in Dar es Salaam City, Tanzania were studied to determine their feeding habits and diet composition using direct observations and molecular analysis of faecal samples. Snails species identified from sites frequented by T. aethiopicus included Lymnaea natalensis (61.62%), Melanoides tuberculatus (20.64%), Bulinus sp. (17.66%) and Anisus sp. (0.08%), while molecular analysis of the birds’ diet revealed presence of mostly non-native invasive molluscs (Physa acuta, Planorbella trivolvis and Radix natalensis), fungus (Candida parapsilosis) and protozoan ciliate (Vorticella striata). There was no significant association between bird and snail abundance (r = 0.2141, p &gt; 0.05, ns) although snail diversity showed strong negative relationship (r = -0.7904, p &lt; 0.05). Our findings indicate that the African Sacred Ibises do not preferentially feed on snails, but do so as part of their broader diet. The results confirm that the African Sacred Ibis is a generalist feeder and therefore, ecological impacts of its feeding strategies particularly on invasive snails should be further investigated.&#x0D; Keywords: African Sacred Ibis, feeding, diet, molluscs, generalist

Ecomorphology and functional diversity of generalist and specialist bird assemblages in Amazonian white-sand ecosystem habitat patches

ABSTRACT Birds that inhabit white-sand ecosystems (WSE) in the Amazon are adapted to habitats distributed as isolated patches. These environments occur in sandy soils that are extremely poor in nutrients, have low floristic diversity and support bird assemblages restricted to WSE. We investigated whether bird species specialized in WSE have morphological or ecological traits that distinguish them from generalist birds that share the same habitat but are not restricted to WSE. We collected morphological and ecological data from 22 specialist and 102 generalist bird species from WSE and described their ecomorphological diversity using multivariate analyses and measures of functional diversity. Understory insectivorous species that move alone or in pairs, were the group with the most species among specialist birds from WSE. In contrast, canopy frugivorous species that form mono- or heterospecific groups were more frequent among generalist species. Specialist and generalist birds overlapped extensively in ecomorphological space, with specialists occupying a narrower space compared to generalists. Functional diversity, however, was not different between specialist and generalist species when controlling for the number of species within the communities. Further studies comparing the ecomorphological diversity of bird assemblages of other environments in the Amazon may highlight the ecological pressures leading to the functional diversity of specialist species in WSE observed in this study.

Using stable isotopes to measure the dietary responses of Costa Rican forest birds to agricultural countryside

How human modification of native habitats changes the feeding patterns and nutritional ecology of tropical birds is critical to conserving avian biodiversity, but tropical bird diets are laborious to investigate using the traditional methods of diet analysis. Stable isotope analysis provides a cost-effective and efficient proxy to identify general foraging patterns, especially when dietary shifts spanning multiple trophic levels have occurred due to ecosystem disturbance or transformation. To characterize the diets of forest bird species that persist in tropical agricultural countryside, we compared feather carbon (δ13C) and nitrogen (δ15N) isotope values of four species caught and radio-tracked in a 270 hectare forest reserve, smaller forest remnants (including mature forest, secondary forest, and riparian strips), and coffee plantations in mid-elevation (ca. 800–1,400 m) southern Costa Rica. Bird habitat choice had a significant effect on diet composition as revealed by δ13C and δ15N values. Three of the four species studied showed evidence of significantly reduced consumption of invertebrates in coffee plantations, with the isotope values of two species (Tangara icterocephala and Mionectes oleaginous) indicating, by comparison, nearly a doubling of invertebrate consumption in forest remnants. Our results suggest that coffee plantations are deficient in invertebrates preferred by forest generalist birds that forage in both native forest remnants and coffee plantations. In this region, typical of mountainous American tropics, small forest remnants and a larger forest reserve provide critical dietary resources for native forest birds that utilize the agricultural countryside.

Azimuthal sound localization in the chicken.

Sound localization is crucial for the survival and reproduction of animals, including non-auditory specialist animals such as the majority of avian species. The chicken (Gallus gallus) is a well-suited representative of a non-auditory specialist bird and several aspects of its auditory system have been well studied in the last decades. We conducted a behavioral experiment where 3 roosters performed a sound localization task with broad-band noise, using a 2-alternative forced choice paradigm. We determined the minimum audible angle (MAA) as measure for localization acuity. In general, our results compare to previous MAA measurements with hens in Go/NoGo tasks. The chicken has high localization acuity compared to other auditory generalist bird species tested so far. We found that chickens were better at localizing broadband noise with long duration (1 s; MAA = 16°) compared to brief duration (0.1 s; MAA = 26°). Moreover, the interaural difference in time of arrival and level (ITD and ILD, respectively) at these MAAs are comparable to what measured in other non-auditory specialist bird species, indicating that they might be sufficiently broad to be informative for azimuthal sound localization.

Effects of artificial reservoirs on evapotranspiration and bird´s fauna

San Luis is an Argentine province whose semi-arid climate led to the construction of artificial water bodies throughout its territory, generating concern about the environmental and hydrological effects, on a local and regional scale, that these reservoirs could cause. In this sense, evapotranspiration (ET), the main water loss in any ecosystem, represents an important part of the water balance. Likewise, bird communities respond to the presence of new water mirrors, where the humidity represents one of the most relevant variables determining the vegetation composition and food availability. For this reason, ET was related to bird richness and abundance in this study, using ET as a surrogate of humidity. Thus, based on remotely sensed ET data, the time-space dynamics of the ET were determined before and after the construction of the reservoirs, obtaining space thresholds of their impact. In addition, the bird’s composition, and abundance were related to water mirrors here and correlated with the ET and vegetation dynamics. Results indicate an increase in the ET means values up to 500 m from the reservoir’s banks. New water mirrors, higher ET values, and heterogeneous habitats with moderate disturbance correlate to high bird diversity. Reservoirs used for touristic purposes are related to new urbanizations and generalist birds.

Matrix quality determines the strength of habitat loss filtering on bird communities at the landscape scale

Abstract Habitat loss represents a major threat to biodiversity, however, the modulation of its effects by the nonhabitat matrix surrounding habitat patches is still undervalued. The landscape matrix might change community assembly in different ways. For example, low‐quality matrices can accentuate environmental filtering by reducing resource availability and/or deteriorating abiotic conditions but they may also excessively limit dispersal of organisms and make communities more prone to ecological drift. To understand how matrix quality modulates the effects of habitat loss, we quantified the relative importance of environmental filter and ecological drift in bird communities across more local (400 m buffer around sampling sites) and broader (2 km focal landscapes) gradients of habitat loss embedded in low‐ and high‐quality matrices. We used a trait‐based approach to understand habitat loss filtering effects on occurrences of forest specialist and habitat generalist birds. We found that low‐quality matrices, composed mainly of low‐productive pasturelands, increased the severity of habitat loss filtering effects for forest specialist birds, but only at the landscape scale. Bird occurrences were in general higher in high‐quality matrices, that is, more heterogeneous and with low‐contrasting edges, indicating the role of the matrix quality in attenuating species extinction risks at the landscape scale, probably due to mass effect. Moreover, forest specialists presented a strong negative response to habitat loss filtering across different functional traits, while generalists presented a high variability in traits response to habitat loss. Synthesis and applications: We raised evidence in supporting that landscape habitat loss filtering may be relaxed or reinforced depending on the quality of the matrix, evidencing that matrix quality has a strong impact in modulating community assembly processes in fragmented landscapes. In practical terms, it means that improving matrix quality may help in maintaining the high diversity of birds even without any increase in native forest cover.

Long-term trends in forest bird populations reflect management changes in Central European forests

In areas where forest is under long-term human influence, we can expect that forest bird populations will be affected by changes in forest management. Consequences of such forest management changes can be studied using long-term population trajectories of habitat-defined groups of bird species because various species are associated to different habitat types. Here we focused on 51 species of common forest birds in Czechia, a central European country, using data from a nation-wide breeding bird monitoring scheme collected from 1982 to 2019. Important changes in forest management took place over this time period in Europe and we asked whether the trends in Czech forest bird populations reflected these changes. For this purpose, we defined nine groups according to the species’ habitat associations in respect of stand size, vegetation layers and tree species composition. We calculated annual population indices using log-linear models with Poisson distribution for every species and composed these annual indices into multispecies indicators (MSIs). MSI of all forest birds, as well as MSIs of three groups of habitat generalists showed significant increases over the focal period. The groups of more specialized species showed more variable population trajectories: birds of the shrub layer decreased, whereas birds of the forest canopy and birds of broad-leaved trees increased, and populations of birds of forest edges, forest interior and coniferous trees were stable. These patterns in forest bird populations are consistent with forest maturation and increasing wood volume that took place in Czech forests over several decades. Such changes in forest environment are likely consequences of the change in purposes of forest management from fuel wood to timber harvesting that took place in 20th century resulting in a longer rotation period. Increases in species associated with broad-leaved trees can be explained by replacement of coniferous stands by stands of broad-leaved trees indicating recovery of forest environment towards more natural conditions as majority of the forested area would be naturally covered by broad-leaved vegetation in Czechia. In addition, the occurrence of some broad-leaved trees within coniferous stands, a common practice in Czech forestry, may also provide benefits to populations of bird species associated with broad-leaved trees. Taken together, these results support suitability of current forest management for forest birds that corresponds to recent findings from several other European regions. However, we should take this conclusion with caution because the increases of generalist birds may be also driven by factors outside the forest environment.

Two Types of Auditory Spatial Receptive Fields in Different Parts of the Chicken's Midbrain.

The optic tectum (OT) is an avian midbrain structure involved in the integration of visual and auditory stimuli. Studies in the barn owl, an auditory specialist, have shown that spatial auditory information is topographically represented in the OT. Little is known about how auditory space is represented in the midbrain of birds with generalist hearing, i.e., most of avian species lacking peripheral adaptations such as facial ruffs or asymmetric ears. Thus, we conducted in vivo extracellular recordings of single neurons in the OT and in the external portion of the formatio reticularis lateralis (FRLx), a brain structure located between the inferior colliculus (IC) and the OT, in anaesthetized chickens of either sex. We found that most of the auditory spatial receptive fields (aSRFs) were spatially confined both in azimuth and elevation, divided into two main classes: round aSRFs, mainly present in the OT, and annular aSRFs, with a ring-like shape around the interaural axis, mainly present in the FRLx. Our data further indicate that interaural time difference (ITD) and interaural level difference (ILD) play a role in the formation of both aSRF classes. These results suggest that, unlike mammals and owls which have a congruent representation of visual and auditory space in the OT, generalist birds separate the computation of auditory space in two different midbrain structures. We hypothesize that the FRLx-annular aSRFs define the distance of a sound source from the axis of the lateral visual fovea, whereas the OT-round aSRFs are involved in multimodal integration of the stimulus around the lateral fovea.SIGNIFICANCE STATEMENT Previous studies implied that auditory spatial receptive fields (aSRFs) in the midbrain of generalist birds are only confined along azimuth. Interestingly, we found SRFs s in the chicken to be confined along both azimuth and elevation. Moreover, the auditory receptive fields are arranged in a concentric manner around the overlapping interaural and visual axes. These data suggest that in generalist birds, which mainly rely on vision, the auditory system mainly serves to align auditory stimuli with the visual axis, while auditory specialized birds like the barn owl compute sound sources more precisely and integrate sound positions in the multimodal space map of the optic tectum (OT).

Abundance predominates over niche factors as determinant of the frequency of interactions between frugivorous birds and plants

AbstractNeutral and niche factors influence the structure of frugivory and seed dispersal networks. While the former refers to the abundance of interacting species, niche factors refer to traits that mediate interactions between species (e.g., morphology). The challenge is to unravel in which circumstances one kind of factor predominates over the other, or how much variation is explained by each factor. We investigated the relative contributions of abundance and trait matching (considering fruit's size, pulp mass to seed mass ratio, and lipid content, and bird's degree of frugivory, body mass, and gape width) as drivers of the frequency of interactions between frugivorous birds and fleshy fruits in an area of Cerrado second‐growth vegetation in Brazil. We expected that the abundance of species would be the most important factor due to the predominance of common small‐bodied generalist bird species and small‐seeded fleshy‐fruited plants. Species abundance was indeed an important factor explaining interactions, although in limited fashion. This is because niche factors also helped to explain bird–plant interaction frequencies in the community, particularly the mass ratio of fruits and, to a lesser extent, their lipid content through its interaction with abundance and its negative correlation with mass ratio. In addition to the importance of both bird and plant abundances, these results underscore the role played by plant functional traits in maintaining community function and ecosystem services even in habitats dominated by common generalist birds and small‐seeded plants.Abstract in Portuguese is available with online material.

Limited-Distance Pollen Dispersal and Low Paternal Diversity in a Bird-Pollinated Self-Incompatible Tree.

Bird pollination in Asia is regarded as an uncommon phenomenon and, therefore, only a few investigations on mating pattern and paternity in fruits of Asian bird-pollinated plants have been conducted. Here, we examined spatial genetic structure, pollen dispersal, and multiple paternity in a natural population of Bombax ceiba (B. ceiba) (Malvaceae) in Hainan Island, South China, using simple sequence repeat (SSR) markers. A low genetic diversity (He = 0.351 ± 0.0341 and 0.389 ± 0.043, respectively, for adults and offspring) and bottleneck effects were observed. Genetic kinship was significant within 400 m or in 1,800–3,800 m. Both the mating pattern and paternity analysis confirmed obligate xenogamy and a low multiple paternity in B. ceiba. There was a strongly negative relationship between the frequency of matings and the distance between mating pairs. The average pollen dispersal distance was 202.89 ± 41.01 m (mean ± SE) and the farthest distance of > 1 km was recorded. Realized mating events showed an extremely leptokurtic distribution within 1,200 m, suggesting that the pollen dispersal distance was consistent with the optimal foraging theory of generalist birds such as Zosterops spp. and Pycnonotus spp. Paternity per tree ranged from two to six and the average effective number of pollen donors per maternal plant was 3.773, suggesting a low level of paternity diversity as compared to other bird-pollinated plants. We concluded that optimal foraging behavior by generalist birds could explain the leptokurtic pollen dispersal distribution and predominantly near-neighbor matings in B. ceiba. The limited pollen dispersal distance and low multiple paternity were consistent with low fruit setting rate (3.27 ± 0.93%) in this self-incompatible tree, which was caused mainly by the restricted flight distance of birds and human disturbances. Low genetic diversity and significant spatial genetic structure might have largely resulted from logging and human collection of fruits.