Guarea

Abstract: Three species of wood warblers ( Parulidae), the bay-breasted, chestnut-sided, and tennessee warblers, eat fruit in the winter on Barro Colorado Island, Panama. A seasonal pattern of frugivory was observed for the two congeners (baybreasted and chestnut-sided), both species displaying a strong peak in frugivory in the late dry season. They also were highly frugivorous earlier in the winter, during a general fruiting low, in response to the fruit crops of Lindackeria laurina and Casearia spp. Chestnut-sided and bay-breasted warblers occur commonly at only a few species of fruiting trees, mainly Miconia argentea and Lindackeria laurinia. These trees were visited by warblers far out of proportion to the relative abundance of warblers among small omnivorous forest birds. Lindackeria was visited almost exclusively by warblers. While the mechanisms are not clear, Lindackeria appeared to be specialized for dispersal by warblers to a degree not reported for any other migrant-dispersed fruits in the tropics. Warblers were more frugivorous in 1978-1979 than 1977-1978. This situation may be a result of the lack of overlap in fruit production in Miconia and Lindackeria in 1978-1979. The bay-breasted warbler was more frugivorous than the chestnut-sided warbler during both winters. The spacing system of the two species may play a prominent role in this difference. Chestnut-sided warblers defend small territories, a circumstance which makes preferred fruiting trees an undependable food supply. Bay-breasted warblers aggregate from a large area to feed on preferred trees, so fruit supply is more predictable. Bay-breasted and tennessee warblers (and other migrants such as red-eyed vireo) are far more intraspecifically gregarious than are most tropical forest residents. It is possibly the tendency to visit fruiting trees in large flocks that makes migrants potentially good dispersers for some plants. MIGRANT WOOD WARBLERS (Parulidae), like many other primarily insectivorous birds, are often observed visiting fruiting trees in tropical areas (Leck 1972, Howe and De Steven 1979, Morton 1980). Fruit is such an energy-rich and easily procured food that some opportunistic frugivory should be expected by many bird species. The importance, however, of warbler frugivory to warbler populations or to the plants that warblers visit is poorly understood. Few data have been gathered on use of fruit by warblers through entire winters, though observers in the Panama Canal Zone generally have found migrant warblers to be frugivorous during the late dry season (March-April), during a period of general fruit abundance, a seasonal pattern shared by a number of small, omnivorous tropical birds (Morton 1973). Leck (1972) found that warblers, as other opportunistic frugivores, visited Hamelia patens Jacq. (Rubiaceae) on Barro Colorado Island (BCI) only in the late dry season despite the fact that fruit was also produced in the late wet season. Competition for Hamelia berries was intense in the late wet season, and Leck hypothesized that only more specialized frugivores can forage on the scarce fruit. These findings suggest that the degree of frugivory in warblers is determined by the general abundance of fruit rather than by the availability of any particular species. Morton (1980), however, found that most warblers frugivorous in the Canal Zone during the late dry season fed on Miconica argeztea (Sw.) DC. (Melastomataceae). Howe and De Steven (1979) working on BCI found that tennessee warblers (Vermivora peregrina) and other inigrants were the most frequent visitors to Guarea glabra Vahl. (Meliaceae), a small understory tree, during the late dry season. The importance, of warbler frugivory to, the plants they visit is even less clear. Leck ( 1972 ), basing his conclusions on observations of plants in the BCI laboratory clearing, believed that migrants were uncommon at fruiting trees in lowland tropical areas. Howe and De Steven (1979), however, found that migrants, by virtue of their sheer abundance, were important in dispersing seeds of Guarea glabra. They suggested that fruit production by Guarea may be timed to attract migrants that are drifting north from South America. Morton (1971) suggested that Didyniopanax morototoni (Aubl.) Dec. and Planch (Araliaceae) may time fruit production to coincide with the passage of eastern kingbirds (Tyrannus tyrannus). More observations are needed to generalize further from these two views. In this paper I examine the frugivorous behavior of migrant warblers both from the viewpoint of the various warbler species populations and of the trees visited by warblers. I will consider the seasonal and year-to-year variation in frugivory of warblers, the breadth of the fruit diet of warblers, interspecific differences in use of fruit, and relative abundance of warblers at their favorite fruiting trees. BIOTROPICA 13(3): 215-223 1981 215 This content downloaded from 207.46.13.149 on Wed, 19 Oct 2016 04:02:26 UTC All use subject to http://about.jstor.org/terms The species I studied, the bay-breasted and chestnut-sided warblers, are characteristic of woodlands and forests of Central Panama (Eisenmann 1957). The bay-breasted warbler, the more common species during the study, breeds in the boreal forests of North America and winters mainly from central Panama eastward to northern South America. The chestnut-sided warbler breeds in deciduous second growth of eastern North America and winters from central Panama westward to Honduras. While data presented in this paper are generally restricted to these two species, the tennessee warbler will be discussed since it may be an important frugivore in

Abstract: Seed fall in a Brazilian subtropical lower montane, moist forest was measured over a year using 120 traps that had a total collecting surface of 174 M2. Twenty-two thousand seeds from 227 plant species were collected. Wind-dispersed species released seeds mainly during the late dry season and early wet season. Among nonwind-dispersed species, large-seeded species matured seeds primarily during the wet season. Small-seeded species were much less seasonal. This difference in seasonality may stem from a correlation between seed size and mode of animal dispersal. Arrival probability per collection period, approximated as the percentage of traps hit by free seeds of each species, was regressed against several independent variables. For nonwind-dispersed species, the logarithm of seed area best predicted arrival probability of free seeds, being inversely related to it. Existence of this inverse relationship has often been supposed but only now demonstrated. THE REPRODUCTIVE BIOLOGY of any seed-plant population is believed to reflect evolutionary compromise among various conflicting aspects of reproduction (Harper et al. 1970, Stebbins 1971). Of these, seed size is fundamental because it apparently influences many other aspects of reproduction. This paper examines relationships in a tropical forest between seed size and two other reproductive parameters: the temporal and spatial extent of seed fall. Numerous workers have assumed that small seeds are more widely dispersed than large ones (e.g., Harper et al. 1970), yet substantial data to test this idea have been lacking. Because of the great temporal and spatial spans over which seed dispersal occurs, the dispersal process at the community level is likely to remain intractable to direct study. Instead of attempting to measure dispersal, I measured arrival probabilities of free seeds at fixed locations. Arrival probability is clearly a crucial component of dispersibility. Seed size has also been hypothesized to influence the temporal pattern of seed fall in tropical forests. Smythe (1970) reported fruiting of largeseeded species in a Panamanian forest to be synchronous, whereas small-seeded species were less seasonal in fruiting time. I sought to determine whether such temporal patterns occur in another neotropical forest. STUDY SITE AND METHODS The study was conducted in a virgin evergreen forest at 800-900 m elevation in Reserva Biologica Nova Lombardia, Municipio de Santa Tereza, Espirito Santo, Brazil, at latitude 19? 53' S. The site is surrounded by several square kilometers of old-growth forest, although some agricultural clearings exist less than 2 km away. Jackson (1978) provides climatic data for the site. Reserva Nova Lombardia experiences a moderate temperature differential between winter (June-August) and summer (December-February) and a long but not severe dry season (April-September). In the Holdridge Life Zone System (Holdridge 1967) the vegetation is classified as Subtropical Lower Montane Moist Forest. As measured by frequency along line transects, the commonest trees are Manilkara elata (Sapotaceae), Lucumza laurifolia (Sapotaceae), Campomazesia warmingiana (Myrtaceae), Guarea petiolulata (Meliaceae), Emimotuni zitens (Icacinaceae), Didymnopanax longipetiolatuxm (Araliaceae), Nectandra puberula (Lauraceae), Psidiuni macrospermnuni (Myrtaceae), Ocotea declinata (Lauraceae), Andira stipulacea (Leguminosae), Clusia grandiflora (Guttiferae), Terminalia ijanuariensis (Combretaceae), Leandra alpestris (Melastomaceae), Sideroxylon gardnerianum (Sapotaceae), Cybianzthus cunieifolius (Myrsinaceae), Ocotea nmacropoda (Lauraceae), Copaifera langsdorffi (Leguminosae), and Ficus doliaria (Guttiferae) (A. Ruschi, pers. comm.). Falling seeds and fruits were sampled with 120 horizontally placed rectangles of green, plastic window screen. Each corner of a screen was secured with plastic cord to a vertical bamboo stake at one meter above the ground. Screens measured 1.4x1.2 m when flat (area 1.68 Mi2), but trap sag reduced the average collecting surface per trap to 1.44 m2?. The mesh in the screen was 1.2 mm square. The seed traps were set in two straight lines approximately 200 m apart. Sixty traps comprised each transect, with 6 m between adjacent traps. One transect began at midslope on a hill (836 m elevaBIOTROPICA 13(2): 121-13

Abstract: Seed dispersal of Guarea glabra and G. kunthiana (Meliaceae) in Monteverde, Costa Rica was studied to determine how seed predation and secondary dispersal affect the distribution of seeds available for recruitment. The arillate seeds are consumed mainly by birds that regurgitate or defecate the seeds intact. After dispersal, 45.6% of G. glabra and 26.6% of G. kunthiana seeds were buried 1–3 cm in the soil, presumably by scatterhoarding rodents such as agoutis (Dasyprocta punctata). G. glabra seeds that were not cached were eaten mostly by beetles, and 33.7% of the seeds remained cached after 12 wk. The cached G. glabra seeds did not germinate, however, perhaps as a result of experimental procedures used to mark the seeds. In greenhouse experiments, G. glabra seeds buried to mimic scatterhoarding had higher germination success than seeds on the soil surface. G. kunthiana seeds not cached were eaten by peccaries (Tayassu tajacu) and other seed predators (60%) or were inviable (10%). Only nine (7.5%) viable G. kunthiana seeds remained in caches after 12 wk. Secondary dispersal resulted in a rearrangement of the seed shadow. G. glabra seeds were moved to sites with less leaf litter and lower vegetation density, while G. kunthiana seeds were moved farther from conspecific trees and closer to fallen logs during secondary dispersal. Considering the high rates of seed predation in the field for both species, the germination advantages for G. glabra in the greenhouse, and the shifts in microhabitat during scatterhoarding, it is likely that secondary dispersal by scatterhoarding rodents is an important stage in Guarea recruitment.RESUMEN. Dispersion de semillas de Guarea glabra y G. kunthiana (Meliaceae) en Monteverde, Costa Rica fureon examinadas para determinar como la predacion de semillas y dispersion secundaria afectan la distribucion de semillas disponibles para recrutamiento. Las semillas ariladas son consumidas principalmente por aves que regurgitan o defecan la semilla intacta. Luego de dispersion, 30–45% de las semillas fueron enterradas 1–3 cm en el suelo, posiblemente por roedores que disperan y acumulan como al agouti (Dasyprocta puncaata). Semillas de G. kunthiana que no fueron escondidas fueron comidas por pecaris (Tayassu tajacu) y otros predadores de semillas (60%) o no fueron viables (10%). Solo neuve (7.5%) semillas viables de G. kunthiana permanecieron en los escondites luego de 12 semanas. En contraste, semillas de G. glabra que no fueron escondidas fueron comidas mayormente por escarabajos que por pecaris, y 33.7% de las semillas permanecieron escondidas luego de 12 semanas. Las semillas esconditas de G. glabra enterradas para imitar dispersion y acumulion tuvieron una germinacion mayor que semillas en la superficie del suelo. Dispersion secundaria resulto en un rearreglo de la sombra de semillas. Las dos especies experimentaron un leve aumento neto en la distancia promedio de conspecificos en frutos luego de dispersion y acumulacion. Semillas de G. kunthiana fueron movidas cerca de troncos caidos durante dispersion secundaria, mientras semillas de G. glabra fueron movidas a lugares con menos lecho de hojas y baja densidad de vegetacion. Considerando la alta proporcion de predacion de semillas en el campo para ambas especies, la ventaja de germinacion de G. glabra en el invernaculo, y el cambio en micrambiente durante dispersion y acumulacion, es posible que dispersion secundaria por roedores que dispersan y acumulan es importante in etapas de recrutamiento en Guarea.