Canopy Frugivores Research Articles

Forest Fragmentation and Bird Extinctions: San Antonio Eighty Years Later

We report on the extent of bird extinctions at San Antonio, a fragmented cloud forest site in the western Andes of Colombia, for which surveys dating back to 1911 and 1959 an available. In 1911, 128 forest bird species were present in San Antonio. Twenty‐four species had disappeared by 1959, and since then 16 more species have gone locally extinct, for a total of 40 species or 31% of the original avifauna. We analyzed patterns of extinction in relation to geographic distribution and foraging guilds. We found that in this montane assemblage, being at the limits of the altitudinal distribution was the main correlate of extinction; 37% of the extinct species were at the upper limit of their altiudinal distribution. We also found that the most vulnerable guilds were the understory insectivores and the large canopy frugivores. Our study illustrates the extent of bird extinctions that are currently undocumented in the highly fragmented forests of the northern Andes, where the absence of baseline information on the fauna of unaltered forests is a limiting factor for the development of conservation and management plans. We stress the need to establish data bases and long‐term monitoring projects for the Andean fauna.

Use of an Exotic Tree Plantation by Bornean Lowland Forest Birds

ABsTRAcr.-During May to July 1982, we surveyed birds in primary forest and in differentaged groves of the exotic tree Albizia falcataria at Sabah Softwoods, a lowland tree plantation in Sabah, East Malaysia (formerly British North Borneo). We found that the Albizia was in general attractive to many native birds. About 60% of primary-forest species used the plantation, and the frequency at which individuals were observed in the oldest groves was almost twice that of nearby primary forest. The Albizia attracted birds because, as an extremely fastgrowing legume with thin leaves, it permitted the rapid development of a well-structured secondary forest. It also was heavily infested with pest insects, which provided an abundant food source. Despite its apparent richness, however, the Albizia lacked several important features of natural forest (e.g. canopy fruits and nest holes). As a result, some primary-forest bird groups were poorly represented (e.g. large canopy frugivores and flycatchers) and others could make only limited use of the plantation (e.g. woodpeckers). In addition, the Albizia is expected to lose its diversity as the plantation as a whole ages. Many of the plantation birds were transients from nearby forest that visited daily to feed, and some probably had been displaced by intense logging. The number of daily transients should decrease as primary forest recedes due to logging and development. Refugee species diversity should suffer from attrition as the plantation is cropped and predation and age take their toll. Received 9 March 1992, accepted 20 November 1992.

Foraging, home range use and social behaviour of a group‐living rainforest raptor, the Red‐throated Caracara Daptrius americanus

A stable group of six Red‐throated Caracaras Daptrius americanus was followed over 5 years in a rainforest area of French Guiana and was intensively studied during 52 days in 1989‐90. They bred successfully only twice (1986 and 1990). Communal nest guarding and brood care were observed. Their social behaviour and group‐living habits seem unique among raptors. The 400‐ha all‐purpose, year‐round, group territory was defended by all individuals and was almost fully used. The birds foraged individually, but the cohesion of the group and its coordinated movements were maintained by periodic loud rallying calls. Food sharing of large prey items and even deliberate allofeeding also contributed to the group cohesion. Mature, high, closed‐canopy forest was preferred and 88% of the actively foraging birds were encountered in the understorey, where they had a higher success rate than those hunting in the upper canopy. This may explain why the species' frequency and group size markedly decreased in secondary or disturbed forests. The 12‐hour daily activity period was reduced by an average of 2 hours either by a midday pause (hot weather) or by rains. At least 74% of all food items taken were wasp nests or other insect nests in the foliage, 9% were hard fruits, and the remaining captures were various invertebrates or unidentified items. When the caracaras were raiding a wasp nest, the wasps were kept off probably by a powerful repellent, a striking adaptation unprecedented among birds. Several species of mostly large canopy frugivores regularly formed close associations with the caracaras to forage in the understorey, where they otherwise rarely or never ventured. This new interspecific flocking behaviour is interpreted as an antipredator strategy benefiting from the raptors' warning and mobbing efficiency.

Feeding Behaviour and Foraging Strategies of Captive Phyllostomid Fruit Bats: An Experimental Study

SUMMARY (1) Feeding rhythms, rates, and fruit selectivity were observed in flight cage experiments involving seven species of frugivorous bats (Chiroptera: Phyllostomidae) from two distinct foraging guilds: canopy frugivores specializing on superabundant fruits of canopy trees and groundstorey frugivores specializing on fruits of shrubs and understorey trees of low fecundity. (2) Bat species differed in handling times of individual fruits, feeding rhythms, and fruit species selectivity with groups of bat species corresponding to previously defined guilds. Canopy frugivores fed continuously throughout most of the night and ate each fruit slowly. Groundstorey frugivores fed in a series of discontinuous bouts separated by periods of roosting/sleeping and ate individual fruits rapidly. (3) Bat species differed in cumulative food item feeding rates over 2-4 h experimental periods, but species subsets did not correspond to established guilds. (4) Paired fruit choice tests showed that captive bats selected fruits that wild populations of their species commonly eat. Groundstorey frugivores selected fruits high in nutrient content. Canopy frugivores selected familiar fruits of low nutrient content over nutritionally higher quality fruits that wild conspecifics rarely eat. (5) Exploitation competition for some limited food resources is discussed as a possible mechanism that has led to resource partitioning and foraging specialization in neotropical

Pre- and Post-Foraging Movements of Frugivorous Birds in an Eastern Deciduous Forest Woodland, USA

I monitored avian frugivore pre-and post-foraging behavior at ten treefall gaps and six undisturbed sites in an eastern deciduous forest woodland in USA from 1981 to 1983. Frugivores usually made only one foraging visit to a fruiting plant while in a treefall gap. Frugivore species foraged at different heights in the canopy. Postforaging movements of canopy frugivores were faster than understory frugivores. Canopy frugivores never took fruit from canopy plants although understory frugivores took fruit from canopy plants. Frugivore movements away from treefall gaps were oriented toward the nearest gap with abundant fruit. These results indicated that frugivores will disperse small seeds farther than large seeds and that canopy frugivores have a higher probability of dispersing seeds into treefall gaps than do understory frugivores.

Distributional Changes in the Colombian Avifauna: A Preliminary Blue List

Some important man-caused changes in the distributions of Colombian bird populations are discussed. Examination of the changes is based on a preliminary Blue List of 135 species with declining populations. Canopy frugivores dominate the list, followed by terrestrial and aquatic species, respectively. There are proportionately more highland species on the list than lowland species. Two regions, the central Colombian highlands, and the Cauca-Magdalena lowlands contain more declining species than other avifaunal regions. Almost two-thirds of Colombia's endemic species have been placed on the list. Some species have profited from deforestation or other human activities, and these are discussed. RESUMEN. Se discuten algunos cambios importantes, causados por el hombre, en las distribuciones de poblaciones de aves colombianas. El reconocimiento de los cambios esta basado en la Lista Azul preliminar de 135 especies con poblaciones en disminuci6n. Los frugivoros del tope del bosque dominan la lista, seguidos respectivamente por especies terrestres y acuaticas. Proporcionalmente en la lista hay mas especies de tierras altas que de tierras bajas. Dos regiones, las tierras altas del centro de Colombia y las tierras bajas de Cauca-Magdalena, presentan mas especies en disminucion que otras regiones de avifaunas. Casi dos tercios de las especies endemicas de Colombia estan incluidas en la lista. Se discute tambien la ganancia que obtuvieron otras aves por la deforestation y otras actividades humanas. In this paper I examine changes in the distributions of Colombian bird populations. Olivares (1970) and Lehmann (1970) discussed some effects of environmental change on birds in Colombia and mentioned examples of species that have profited or been harmed by these changes. However, neither author attempted to provide a comprehensive overview of the country's avifauna. Some of Colombia's endangered or threatened species are discussed in the International Council for Bird Preservation (ICBP) Bird Red Data Book (King 1981). Unfortunately, little other information has been compiled on distributional changes of Colombian birds. Furthermore, bird populations in Colombia (or most anywhere in developing regions of the world) are not systematically surveyed or evaluated like they are through the Blue List for North America (Arbib 1971), the Christmas Bird Counts, or more recently the natural heritage inventories of The Nature Conservancy. There is no systematic research on endangered Colombian species either by government or private agencies. In order to examine distributional changes in Colombia's avifauna a preliminary Blue List was prepared. This list is similar in concept to that initiated in North America in 1971 by Robert Arbib (Arbib 1971). The latter list, updated annually, includes North American birds that are of special concern because they appear to be ... giving indications of non-cyclic population decline or range contractions, either locally or widespread (Arbib 1971). Species on the list may be fairly common locally, or even widespread, but because of habitat reduction, chemical contamination, hunting pressure, or other causes, their populations appear to be in decline. As noted by Arbib (1971, 1972) the Blue List is essentially an early warning system that focuses attention on problem species and may help alert the scientific community, government agencies, and the public to situations where action is needed. I include on the present list (Table 1) most species whose geographical ranges in Colombia are believed to have declined by at least 50 percent. Unlike the North American Blue List, I also include all endangered species listed by the ICBP Bird Red Data Book (King 1981) because information on these species is scarce. I exclude species known only from one or a few localities near the Colombian border, or species known only from Bogota specimens without precise locality (Meyer de Schauensee 1 948). I also exclude a considerable number of species whose ranges probably have contracted by 50 percent or more due to deforestation since pre-Colombian times but that still occur commonly wherever tracts of forestland remain. Examples of species in this