Frugivory by Toucans (Ramphastidae) at Two Altitudes in the Atlantic Forest of Brazil'
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BIOTROPICA 32(4b): 842-850 2000 Frugivory by Toucans (Ramphastidae) at Two Altitudes in the Atlantic Forest of Brazil' Mauro GalettP Plant Phenology and Seed Dispersal Research Group, Departamento de Ecologia, Universidade Estadual Paulista (UNESP), C.P. 199, 13506-900, Rio Claro, Slo Paulo, Brazil Rudi Laps and Marco A. Pizo3 Departamento de Zoologia, UNICAMP, C.P. 6109, 13081-970, Campinas, Slo Paulo, Brazil ABSTRACT Toucans are prominent components of the tropical American avifauna. Although these birds are very conspicuous, there are few ecological studies focusing on them. In this study, the diets of four sympatric toucans (Rampbastos vitellinus, R. dicolorus, Selenidera maculirostris, and Baillonius baillonz) were assessed by recording feeding bouts at two altitudes in the Atlantic Forest of southeast Brazil. Our results show that toucans are predominantly frugivorous birds (96.5% of the 289 feeding bouts were on fruits). In the lowlands (70 m elev.), only fruits (48 species, 27 families) were recorded, while in the highlands (700 m elev.), toucans were observed feeding on fruits (25 species, 22 families), flowers, leaves, and insects. Non-fruit items were recorded only in the highlands, most of them eaten by B. bailloni. Cecropia glaziovii and Euterpe edulis, two abundant plants in the highland and lowland sites, respectively, and firola ole;fera, a plant that produces lipid-rich arillate fruits, were eaten heavily by the toucans. The number of feeding bouts recorded for R. vitellinus in the lowlands was positively correlated with lipid content of the fruits eaten. The diameters of fruits eaten by toucans varied greatly (range = 0.4-25.0 mm). While the large Rampbastos species not only ate tiny fruits (e.g., Hyeronima alcborneoides) but also large ones (e.g., Krola gardnerz), the toucanets ate piecemeal the large fruits that exceeded their gape width, suggesting that gape size did not limit the use of any fruit by the toucans at our study sites. RESUMO 0stucanos formam urn importante grupo de aves americanas pelo papel que desempenham como dispersores de sementes. Embora sejam conspicuas, hi relativamente poucos estudos ecol6gicos sobre estas aves. Neste estudo, a dieta de quatro espkcies simpitricas de tucanos (Rampbastos vitellinus, R. dicolorw, Selenidera maculirostris, and Bailloniw baillonz) foi investigada atravks do registro de eventos de alimentaGiio em duas ireas localizadas em diferentes altitudes da Mata Atliintica do sudeste do Brasil. 0sresultados mostraram que 0s tucanos siio aves predoninantemente frugivoras (96.5% dos 289 eventos de alimentas50 registrados foram em frutos). Na Area de baixada (700 m a.n.m.), somente frutos (48 espkcies, 27 familias) foram registrados na dieta, enquanto na area montana (700 m a.n.m.) 0s tucanos foram observados alimentando-se de frutos (25 espkcies, 22 familias), flores, folhas e insetos. Itens alimentares diferentes de frutos foram registrados somente na ire, montana, a maioria deles foram consumidos por B. bailloni. Cecropia glaziovii e Euterpe edulis, duas espkcies de plantas abundantes nas ireas montana e de baixada, respectivarnente, e Virola oleifera que produz frutos arilados ricos em lipideos, foram altamente consumidos pelos tucanos. 0 nhmero de eventos de alimentaslo registrado para R. vitellinus na Area de baixada esteve positivamente correlacionado com o contehdo lipidico dos frutos consumidos. 0s diametros dos frutos consumidos pelos tucanos variou consideravelmente (0,4-25,0 mm). Enquanto as espkies de maior porte (Ramphastos spp.) consumiram n6o somente frutos pequenos (e.g, Hyeronima alcbomeoides) mas tambkm frutos grandes (e.g., firola gardnerz), as espkcies menores (S. maculirostris e B. baillonz) comeram aos pedaGos 0s frutos cujos diiimetros excederam a largura de seus bicos, mostrando que a largura do bico em si nso limita o consumo de nenhum fruto pelos tucanos nas ireas estudadas. Key words: Atlantic Forest; figivory; gape size; Rampbastihe; seed dicpersal; toucan. RAMPHASTIDM(TOUCANS AND TOUCANETS) IS AMONG ~ ~ ~ ~ THE OLDEST AVIAN LINEAGES with living descendants Received 13 August 1998; revision accepted 25 Febru- (Sibley & Ahlquist 1990), and is the symbol of the ary 1999. tropical American forests. Since naturalists first vis- Corresponding author. E-mail: [email protected] ited the tropics, toucans have attracted attention Present address: Plant Phenology and Seed Dispersal Research Group, Departamento de Botinica, Universi- due to their large body size, flamboyant colors, and dade Estadual Paulista (UNESP), C.P. 199, 13506-900, long and bizarre beaks (Bates 1863, Goeldi 1894, Rio Claro, SSo Paulo, Brazil. E-mail: [email protected] Van Tyne 1929, Gould & Rutgers 1972). In spite 842 Diet of Toucans in the Atlantic Forest 843 of their conspicuousness, however, toucans are very chosen to investigate the diet of toucans. The study difficult to study in the wild because they live in sites, Saibadela and Carmo Research Stations, were the forest canopy, are rarely captured in mist nets, located at 70 and 700 m elevation encompassing and usually have large territories (Terborgh et al. lowland and highland areas of the reserve, respec- 1990). Of the 42 extant species, we have more than tively. Extensive areas of pristine forest surrounded a minimum knowledge of ecology and natural his- the sites. Straight-line distance between the two tory for only a few species, mainly those inhabiting sites is ca 25-30 km. Costa Rica and Panama (Skutch 1944, 1958, The vegetation at the lowland site consisted of 1971, 1972; Stiles & Skutch 1989; Beltran 1992; primary forest and small patches of secondary Riley & Smith 1992). Toucans have a broad diet growth near human settlements (Almeida-Scabia that includes mainly fruits, but also flowers, ar- 1996). The highland vegetation, in contrast, was thropods, and small vertebrates (Remsen et al. mainly late secondary with patches of primary for- 1993). Based on stomach contents recorded on est (Pizo et al. 1996). The lowland site was sub- museum specimen labels, Remsen et al. (1993) jected to higher temperature (annual mean CLZ found that 93.5 percent of the 326 stomachs an- 24“C, range 3-42°C) and precipitation (4000 mm/ alyzed contained only fruit remains; however, few yr) than the highland site (annual mean tempera- systematic data regarding the foods taken by tou- ture ca 17”C, range 4-38°C; annual precipitation cans in the wild are available. 1600 mm/yr). Both sites experienced a period of In the Neotropics, toucans, as well as cotingas, dry-cold weather from April to August (more pro- represent a model of large canopy fruit-eating birds nounced at the highland site), and a wet-hot pe- (Snow 1976). Their widespread distribution over riod from September to March. different habitats and altitudes makes them partic- Five toucan species were found at PEI: (1) the ularly interesting for investigating inter- and intra- Spot-billed Toucanet or “araGari-poca” (Selenidera specific differences in diet and foraging strategies rnaculirostrix 33 cm total length; 140 g body at different altitudes. These birds have been con- weight; gape width of 24.6 2 1.2 mrn). Lengths, sidered “specialist” seed dispersers that provide weights, and gape widths were taken from Sick “high-quality’’ seed dispersal (McKey 1975, Snow (1993), Dunning (1993), and Laps (1996), respec- 1981), but we have few data on frugivory by tou- tively, and the species occured in both study sites cans (.fHowe 1977, 1981, 1993). but was more common in the lowlands; (2) the Five species of toucans occur in the Brazilian Saffron Toucanet or “araGari banana? (Baillonius Atlantic Forest (Sick 1993). We investigated the bailloni: 35 cm total length; 139 g body weight; diets of four of these species (Rarnphastos vitellinus, gape width of 23.8 2 0.8 mm) which was observed R. dicolorus, Selenidera maculirostris, and Bailonius commonly in the highlands but was rare in the baillonz) occurring in two sites located at different lowlands, where it occured mainly in forest edges altitudes in a Brazilian Atlantic Forest reserve. We and secondary forests (Aleixo & Galetti 1997); (3) were especially interested in answering the follow- the Green-billed Toucan or “tucano de bico verde” ing questions: (1) what are the contributions of (Rarnphastos dicolorus: 48 cm total length; 400 g fruit and non-fruit items to the diets of toucans?; body weight; gape width of 30.0 -+ 1.1 mm) which (2) how do diets of toucans vary altitudinally?; and was common in the highlands and was a winter (3) is gape size an important determinant of fruit migrant in the lowlands, where invariably it was selection by the toucans? For the lowlands, where observed in mixed flocks with R. vitellinus; (4) the we determined the chemical composition of fruits Channel-billed Toucan or “tucano de bico preto” eaten by toucans, we additionally asked (4) is the (Rarnphastos vitellinux 46 cm total length; 390 g contribution of fruits to the diet of toucans asso- body weight; gape width of 3 1.1 2 1.6 mm) which ciated with the lipid, protein, and carbohydrate was almost restricted to the lowlands, occurring at contents of the fruits? the highlands only as a sporadic visitor; and (5) the “araGari de bico branco” (Pteroglossusaracart) which STUDY SITES AND METHODS was observed only once in the highlands and not included in this study. This study was carried out at Parque Estadual In- Data were collected during 43 months at the tervales (hereafter PEI; 24“16’S, 48”25’W), a 490- highland site (December 1989-December 1991 km2 forest reserve in the Serra de Paranapiacaba and August 1992-January 1994) and 24 months mountains of southeast Brazil (Aleixo & Galetti at the lowland site (January 1994-December 1997). Two sites located at different altitudes were 1995). The method used to quantify the diet of 844 Galetti, Laps, and Pizo toucans was based on feeding bouts (Galetti 1993, comprising 59 percent of the feeding bouts record- 1996).