Dietary specialization and fruit availability among frugivorous birds on Sulawesi

Abstract

Over 20 months I collected data on the diet composition and fruit availability for 23 frugivorous bird species (pigeons, parrots, hornbills and passerines) in two lowland rain forests on Sulawesi, Indonesia. Using these data I determined species dependency on fruit, diet composition, diet breadth and the availability of their fruit resources. Fruit dependency ranged from 44 to 100% of diets across the assemblage, with significant inter‐order differences reflecting shared evolutionary history within orders. By contrast, diet breadths did not differ between bird orders owing to high within‐order variability, possibly as a result of species‐specific foraging strategies. Overall, no significant relationship existed between fruit dependency and diet breadth, which indicated that they are not interchangeable measures of dietary specialization, but that each provided important information on dietary specialization, and enabled assessment of resource requirements and availability. The assemblage consumed the fruits of 120 species representing 40 plant families. Figs (Ficus spp.) were of great importance across the assemblage and comprised 57% of all fruit‐eating records. For hornbills, passerines and pigeons, figs accounted for substantial proportions of monthly feeding records (= 58%) and were consumed whatever the availability of other fruits. Figs were therefore a fundamental part of species’ diets, possibly every month, and not merely important during times of relative scarcity of other fruit. Conservation of fig trees both inside and outside protected areas is likely to be important in maintaining healthy populations of figs and the frugivorous birds that depend on them.

Dispersal Modes and Spatial Patterns of Tree Species in a Tropical Forest in Arunachal Pradesh, Northeast India

“…), four species of doves (Streptopelia, Macropygia and Chalcophaps), four barbet species (Megalaima), three parakeet species (Psittacula and Loriculus), two leaf bird (Chloropsis) species, fairy bluebird (Irena puella), and two oriole species (Oriolus). Several other forest birds that are nectarivores/insectivores (e.g., white-eyes, flowerpeckers, cuckoos and cuckoo-shrikes, babblers, Tropical Conservation Science | ISSN 1940-0829 | tropicalconservationscience.org laughing thrushes, drongos, red-headed trogon [Harpactes erythrocephalus]) also occasionally include fruit in their diet [27,28]. Green pigeons are known to specialise on fig fruits but are seed predators [29,30]; parakeets are also seed predators [31].…”

“…Seed piles of tree species regurgitated by ungulates are found on the forest floor and it was possible to assign to species (sambar, common muntjac, and wild pig) because these piles are associated with tracks, bedding, and resting sites of the species. The dispersal modes of 28 tree species were established from published records on the diets of birds/mammals from several studies in other Asian forests [27,[33][34][35][36] and fruit characteristics [37][38][39], and from literature on plant seed dispersal [40][41]. The rest were assigned based on direct observations.…”

Relationships between bird‐dispersed plants and avian fruit consumers with different feeding strategies in Japan

“…Among them, the brown-eared bulbul consumed the fruits of 185 species based on the controlled dietary information (Table 1) and can thus be assumed to be the most prominent avian seed disperser in the study region. The high diversity of plant species consumed by the gulpers have been found in other studies, both in tropical regions (Corlett 1998;Kitamura et al 2002;Bollen et al 2004;Walker 2007) and in temperate regions (Wheelwright 1986;Fuentes 1994). The diversity of the plant species consumed by birds might, however, be affected by the more abundant dietary records collected for these birds, and especially for the brown-eared bulbul and Naumann's thrush (Table 1), because estimates of the diversity of dietary items can depend on the abundance of dietary records (Walker 2007).…”

Conservation value of secondary forest habitats for endemic birds, a perspective from two widely separated tropical ecosystems

“…Accipitridae Cosmopolitan 3 4 18 31 33 Columbidae Australasia 3 8 24 20 56 Psittacidae Australasia 5 6 10 5 51 Cuculidae Cosmopolitan 2 5 15 22 20 Centropidae Cosmopolitan 1 1 2 3 5 Tytonidae Australasia 1 1 4 1 7 Strigidae Cosmopolitan 1 1 3 12 9 Coraciidae Asia 1 1 2 1 1 Bucerotidae Asia 2 2 2 8 1 Picidae Asia 1 1 2 18 0 Campephagidae Australasia 3 3 10 11 18 Corvidae Cosmopolitan 1 2 2 8 4 Timallidae Asia 1 1 2 35 0 Petroicidae Australasia 1 1 1 0 23 Sturnidae Asia 3 4 11 7 11 Dicaeidae Asia 2 2 3 12 6 Zosteropidae Cosmopolitan 1 2 7 7 11 (Walker 2007). Th ese can provide Ͼ 50% of the total diet of frugivorous species in the tropics (Corlett and Primack 2005).…”