Hermit Hummingbirds Research Articles

Pollinator Relationships, Biogeography, and Phylogenetics

ummingbirds and the flowers they visit are among the most colorful examples of mutualistic relationships between animals and flowering plants. The acrobatics, pugnacious behavior, and startling colors of many hummingbird species have won them the attention of biologists and hobbyists alike. In turn, the large and showy flowers of many of the plants pollinated by hummingbirds make them favorites of horticulturalists and well-collected by botanists. I have studied the systematics and reproductive biology of the neotropical plant genus Aphelandra (Acanthaceae). These plants have long, tubular, brightly colored (yellow, orange, red, and pink), and nectar-rich corollas that are the epitome of the hummingbird-pollinated flower (Faegri and van der Pijl 1966). From more than 100 hours spent observing visitors to Aphelandra flowers, I have documented that they are indeed pollinated by hummingbirds. Most of the plant species have strongly curved corollas that are 5.5-7 cm long (Figure la-d); these are pollinated by hermit hummingbirds (subfamily Phaethorninae), whose long, decurved bills match the

Interactions between nectarivorous birds and the flowers ofAphelandra sinclairianain Panama

ABSTRACTFlowers ofAphelandra sinclairianahave features of flowers pollinated by hermit humming-birds (long corollas) and of those pollinated by territorial humming-birds (dilute nectar, clustered distribution). Flowers in large clumps at the peak of the blooming season were pollinated by two territorial humming-birds, but at the end of the season or in isolated plants the main avian pollinator was the non-territorial hermitPhaethornis superciliosus. Visits by avian nectar thieves were more frequent at high flower densities. The reproductive output of inflorescences was similar at different levels of flower aggregation.Aphelandraflowers in large clumps could exchange pollen with extraterritorial plants because territorial humming-birds did not completely exclude pollinating hermits. The commonest nectar thief at high flower aggregations was the passerineVermivora peregrina, the second most common nectar thief was the hermitPhaethornis longuemareus.

Trapline Foraging by Hermit Hummingbirds: Competition for an Undefended, Renewable Resource

Traplining hummingbirds face a conflict between waiting for undefended floral nectar to accumulate to higher levels of profit and losing accumulated nectar to competitors. The goal of this research was to learn the rules and temporal patterns of flower visitation by Long—tailed Hermit Hummingbirds (Phaethornis superciliosus). Monitors of visits by color—marked individuals, particularly lek males, to natural flowers established patterns of feeding in space and time. Monitors of visits to nectar feeders that were refilled at fixed intervals established patterns of adjustment to nectar availability and competitive losses. Competing hummingbirds tended to segregate among undefended feeding sites, with one individual becoming the primary user of each site. Competition caused hummingbirds to visit a feeder frequently, often before a scheduled refill. In this way one individual could harvest most of the provided nectar. Under conditions of nearly exclusive use of a feeder with artificial nectar, the hummingbirds adjusted their visits to operant (fixed—interval) schedules of food presentation. The scheduled harvesting of floral nectar by traplining hermit hummingbirds thus entails the adaptive use of short, elapsed time intervals.

Ecological Fitting: Use of Floral Nectar in Heliconia stilesii Daniels by Three Species of Hermit Hummingbirds

Ecological Fitting: Use of Floral Nectar in Heliconia stilesii Daniels by Three Species of Hermit Hummingbirds

Synchronous Flower Abscission in Plants Pollinated by Hermit Hummingbirds and the Evolution of One-Day Flowers

Synchronous Flower Abscission in Plants Pollinated by Hermit Hummingbirds and the Evolution of One-Day Flowers

Trapliners in the Trees: Hummingbird Pollination of Erythrina Sect. Erythrina (Leguminosae: Papilionoideae)

Erythrina sect. Erythrina comprises 36 species of hummingbird-pollinated trees and shrubs, distributed principally in Mesoamerica. Avian floral visitors-including nectar thieves as well as pollinators-were observed at 17 populations of 13 species in southern Mexico and Costa Rica. Legitimate pollinators were all hummingbirds with long bills and non-territorial foraging behavior, including in particular two species of Heliomaster. Nectar thieves included a variety of short-billed hummingbirds and passerine birds. Measurements of nectar volume, sugar concentration, and flowering behavior indicate that the caloric value of nectar in open flowers produced by one tree per day is insufficient to support a single hummingbird's energetic requirements; therefore, territorial defense by a hummingbird of a single tree is precluded. The traplining hummingbirds appear to be effective agents of pollen flow among conspecific trees in the typically low-density Erythrina populations. The pollination system of sect. Erythrina is a canopy-level analogue of the high-reward traplining systems involving hermit hummingbirds and understory plants such as Heliconia (Musaceae).

Flowering patterns of long-lived Heliconia inflorescences: implications for visiting and resident nectarivores.

Flowering patterns of four Heliconia (Heliconiaceae) species in Trinidad, West Indies were examined for their predictability and availability to the nectarivores that rely on Heliconia floral nectar. Principal flower visitors are trapling hermit hummingbirds; inflorescences are inhabited by nectarivorous hummingbird flower mites that move between inflorescences by riding in the hummingbirds' nares. Heliconia inflorescences flower for 40-200 days, providing long-term sources of copious nectar (30-60 μl per flower), but each Heliconia flower lasts only a single day. As an inflorescence ages the interval increases between open flowers within a bract; wet-season inflorescences produce open flowers more slowly than dry-season conspecifics.Estimated daily energy expenditures for hermit hummingbirds demonstrate that slow production of short-lived open flowers plus low inflorescence density preclude territorial defense of Heliconia by the hermits. Heliconia flowering patterns are viewed as a means of (i) regulating reproductive investment by the plants through staggered flower production over long periods of time, and (ii) maintaining outcrossing by necessitating a traplining visitation pattern by its hummingbird pollinators. I suggest that Heliconia exhibit a two-tiered pollination system by using hermit hummingbirds primarily for outcrossing and using hummingbird flower mites primarily for self-pollination.

Variable Nectar Secretion in a Heliconia Species Pollinated by Hermit Hummingbirds

The average flower of Heliconia psittacorum, an herb pollinated by hermit hummingbirds on Trinidad, secreted 66.4 ,I of nectar. Variation among flowers was extremely high; of 215 flowers examined over a 15 day period, 29 secreted less than 10 ,ul of nectar, whereas 24 secreted more than 120 microliters. The frequency distribution of nectar volumes was platykurtic. There was no spatial or temporal pattern to the appearance of blanks within the clone examined, although bonanzas occurred only on ramets growing in wet soil. This pattern contrasts strongly with the uniformly large nectar volumes reported for other Heliconia species or other plants pollinated by hermit hummingbirds. THE NECTAR VOLUMES ENCOUNTERED by a forager may vary widely from flower to flower within a single plant population. Some variation may result from erratic visits by previous foragers who removed nectar from some flowers but overlooked others. Variation may also result from different secretion rates among individual flowers. For example, at Monteverde, Costa Rica, each of the five species of hummingbird-pollinated plants examined had bonanza-blank patterns of nectar secretion (Feinsinger 1978). Some flowers secreted large volumes of nectar (bonanzas), but most flowers, even those on plants with bonanza flowers, secreted little nectar or none whatsoever (blanks). All five plant species occupied early successional habitats and attracted opportunistic hummingbirds having relatively short, straight bills. Bonanza-blank patterns of nectar secretion have not been reported for plant species that produce a few long, curved flowers per plant and utilize hummingbirds with long, curved bills, especially non-territorial hermit hummingbirds, as pollen vectors. Apparently, these flowers secrete large, consistent nectar volumes. For example, the neotropical herb genus Heliconia contains many species adapted for bird pollination (Stiles 1975, 1979). Many Heliconia have long flowers pollinated by hermits, whereas others have somewhat shorter flowers and attract shortbilled hummingbirds. Regardless of the type of hummingbird involved, each of the nine Heliconia species examined by Stiles (1975) secreted quite consistent quantities of nectar. Stiles (1975: fig. 6) reported mean cumulative volumes ranging from 45 to 115 Al per flower, depending on the plant species, with little variation around the mean and no blanks. Therefore, I expected to find consistently large volumes in the flowers of Heliconia psittacorum, which grows in poorly drained savannas on Trinidad. Observations on temporal patterns in nectar secretion during one day, however, suggested that considerable flower-to-flower variation existed. This stimulated a more intensive study, reported here. METHODS Numerous ramets of Heliconia psittacorum occur in an open, poorly-drained, savanna-like field near Simla Research Station in the Arima Valley of Trinidad. On the evening of 30 July 1977, I marked 25 ramets that had active inflorescences, and bagged each inflorescence with mosquito netting. Ramets 18-25 were on a slight rise of land, and therefore grew in better-drained soil than ramets 1-17. At about 1230 h on each of the following 15 days, I checked each inflorescence for open flowers. The accumulated nectar volume in each open flower was measured with microcapillary tubes. Since secretion ceases soon after 1030 h in this species and flowers last a single day (Feinsinger, unpublished), this volume was the flower's entire secretion. On 14 August 1977, after the last measurement, I excavated representative ramets to determine the extent of cloning. Hummingbird visits to H. psittacorum flowers in the same field (often on the same ramets) were monitored on 11 different days, from May 1977 through March 1978. Observation periods lasted the first six daylight hours.

The Ecological Impact of Nectar‐Robbing Bees and Pollinating Hummingbirds on a Tropical Shrub

The consequences of nectar robbing by highly social bees were studied at 71 patches of the forest—edge shrub, Pavonia dasypetala (Malvaceae) at two tropical moist forest habitats in central Panama. Groups of Trigona (Trigona) ferricauda (Apidae: Meliponinae) arrived at flowers in early morning; each bee dominated a single flower that it perforated to rob nectar (Fig. 1). Robbers in each patch aggressively defended their feeding sites from the sole pollinator of the plant, the Hermit Hummingbird Phaethornis superciliosus (Trochilidae: Phaethorninae). Less visitation by hummingbirds and reduced seed production resulted from nectar robbing. Flower number in patches was not associated with visitation per flower by pollinators, but patches having the most flowers were entered more often by P. superciliosus. In contrast, thieving P. longuemareus and robbing T. ferricauda showed no patch preference related to total flower number. Seed production per flower was not related to the total number of flowers presented in patches at one time. The average proportion of robbed flowers through the entire flowering episode of P. dasypetala was 36% among 66 patches at one site and 35% among 5 patches at a second site. Reduced seed production was not caused directly by robber damage to flowers, but indirectly through successful deterrence of birds via joint attacks by bees on and near the flower visited by a hummingbird. Further, although fewer seeds were produced by robbed flowers overall, robbed and unrobbed flowers in patches that were heavily robbed did not differ in seed production. Thus robbing primarily influenced reproductive success at the level of the flower patch. P. dasypetala was self—pollinating, yet unrobbed flowers that were not bagged produced 67% more seeds than those not visited by P. superciliosus. Persistent robbing by Trigona may result in selective advantage for autogamous or apomictic P. dasypetala.

COMPETITION BETWEEN HERMIT HUMMINGBIRDS PHAETHORNINAE AND INSECTS FOR NECTAR IN A COSTA RICAN RAIN FOREST

SummaryHummingbirds in the tropical rainforests of southwestern Costa Rica face intense competition from stingless bees Trigona that steal nectar from hummingbird flowers. Here we document both interference and exploitative competition between bees and hummingbirds at scarlet, hummingbird pollinated flowers of Passiflora vitifolia. Aggressive stingless bees prevented Long‐tailed Hermit Hummingbirds Phaethornis superciliosus from feeding at nearly one‐third of the passion flowers approached. In exclusion experiments, bees and hummingbirds each removed most of the nectar from treated flowers. Experimental exclusion of bees also increased hummingbird use of both natural and artificial flowers.

Ecology and Evolution of Lek Mating Behavior in the Long-Tailed Hermit Hummingbird

Ecology and Evolution of Lek Mating Behavior in the Long-Tailed Hermit Hummingbird

Foraging for Insects by a Tropical Hummingbird

Evolutionary-ecological studies of tropical plants and animals have illustrated that certain tropical organisms respond to differences between wet and dry seasons. Certain species of trees show distinct flowering and fruiting patterns in relation to the dry season in various regions of Costa Rica (Janzen 1967). It has been hypothesized that wetter habitats could be expected to contain a greater proportion of those predators specialized for feeding upon small insects than would drier habitats (Janzen and Schoener 1968). This reasoning stems primarily from the observation that there is a distinct paucity of small insects associated with drier habitats, because of problems of desiccation associated with small body size (Janzen and Schoener 1968). Similar arguments can be made for changes in local distributions and abundances of these predators between wet and dry seasons. Despite these interesting ideas, studies on seasonal patterns of interactions between insectivorous vertebrates and their prey have not appeared in the literature. Such experimental studies are needed as a vehicle for increasing our understanding of tropical communities and the impact of season upon their temporal and spatial persistence. This paper discusses foraging for insects in one Costa Rican species, the Long-tailed Hermit Hummingbird, Phaethornis superciliosus (hereafter referred to as Phaethornis). This species ranges from southern M6xico to Bolivia and Brazil, inhabiting thinned forests and woodland borders (Slud 1964). Certain aspects of the biology of this species and the Little Hermit (P. longuemareus) have been studied in Costa Rica (Skutch 1951, 1964), while other species of Phaethornis have been similarly studied elsewhere (Skutch 1950; Snow and Snow 1964). However, there are no published accounts of long-term, systematic studies on foraging for any members of this large genus. While it has been suggested that most species of hummingbirds spend relatively little time foraging for insects (at least from data available on the Anna Hummingbird; see Pearson 1954), Slud (1964) alludes briefly to active insect foraging by Phaethornis, and Wagner (1946) contends that insects are a major food source for many species of hummingbirds. However, quantitative data on such foraging for any species are lacking. The data discussed here are from two