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Mercedes S. Foster

Publications and source records attributed to Mercedes S. Foster.

12 recordsLinked to original sources
USGS2017

Delayed maturation, neoteny, and social system differences in two manakins of the genus Chiroxiphia

Long‐tailed manakins ( Chiroxiphia linearis ) and swallow‐tailed manakins ( C. caudata ) are closely related, sexually dichromatic, lek‐breeding species in which male mating success is highly skewed. Males of both species delay plumage maturation. Before reaching the definitive state, they wear a sequence of feather coats less conspicuous than that of the adult. Nondefinitive plumages probably enhance male survival in the two species; in C. caudata they may also enhance breeding success of young males, who may be fully reproductively mature their first year. In C. linearis testicular development is retarded along with that of plumage, although males may be physiologically capable of breeding prior to the acquisition of the definitive plumage. This difference probably reflects differences in the social systems of the two species. Five hypotheses have been proposed to explain the evolution of delayed plumage maturation. The sexual‐selection, cryptic‐breeder, and winter‐adaptation hypotheses suggest that it functions primarily to enhance survival of young males. The juvenile‐ and female‐mimicry hypotheses emphasize enhancement of immediate mating success. Support is provided for all but the female‐mimicry hypothesis; it is argued that data are more consistent with juvenile mimicry and a neotenic origin of nondefinitive plumages.

Evolution↗
USGS2009

Avifauna of the Pongos Basin, Amazonas Department, Peru

We provide an inventory of the avifauna of the Pongos Basin, northern Amazonas Department, Peru based on museum specimens collected during expeditions spanning >60 years within the 20th century. Four hundred and thirty-eight species representing 52 families are reported. Differences between lowland and higher elevation avifaunas were apparent. Species accounts with overviews of specimen data are provided for four species representing distributional records, two threatened species, and 26 species of Nearctic and Austral migrants, of which six are considered probable migrants.

Wilson Journal of Ornithology↗
USGS2008

Potential effects of arboreal and terrestrial avian dispersers on seed dormancy, seed germination and seedling establishment in Ormosia (Papilionoideae) species in Peru

The relative effectiveness of arboreal or terrestrial birds at dispersing seeds of Ormosia macrocalyx and O. bopiensis (Fabaceae: Papilionoideae) were studied in south-eastern Peru. Seeds of both species were either scarified, to represent seed condition after dispersal by terrestrial birds, or left intact, to represent seed condition after dispersal by arboreal birds. Seeds were distributed along forest transects, and germination, seedling development and mortality were monitored to determine the successes of the two groups at producing seedlings. Scarified seeds germinated with the early rains of the dry-to-wet-season transition, when erratic rainfall was interspersed with long dry spells. Intact seeds germinated 30 d later when the rain was more plentiful and regular. Intact seeds of O. macrocalyx gave rise to significantly more seedlings (41.1% vs. 25.5%) than did scarified seeds, in part, because significantly more seedlings from scarified seeds (n = 20) than from intact seeds (n = 3) died from desiccation when their radicles failed to enter the dry ground present during the dry-to-wet-season transition. Also, seedlings from scarified seeds were neither larger nor more robust than those from intact seeds despite their longer growing period. Results are consistent with the hypothesis that dispersal effectiveness of arboreal birds, at least for O. macrocalyx, is greater than that of terrestrial birds. Screen-house experiments in which seedlings developed under different watering regimes supported this result. Numbers of seedlings developing from intact and scarified seeds of O. bopiensis did not differ significantly.

Journal of Tropical Ecology↗
USGS2008

Freeze-frame fruit selection by birds

The choice of fruits by an avian frugivore is affected by choices it makes at multiple hierarchical levels (e.g., species of fruit, individual tree, individual fruit). Factors that influence those choices vary among levels in the hierarchy and include characteristics of the environment, the tree, and the fruit itself. Feeding experiments with wild-caught birds were conducted at El Tirol, Departamento de Itapua, Paraguay to test whether birds were selecting among individual fruits based on fruit size. Feeding on larger fruits, which have proportionally more pulp, is generally more efficient than feeding on small fruits. In trials (n = 56) with seven species of birds in four families, birds selected larger fruits 86% of the time. However, in only six instances were size differences significant, which is likely a reflection of small sample sizes.

Wilson Journal of Ornithology↗
USGS1993

Research, conservation, and collaboration: The role of visiting scientists in developing countries

As awareness of environmental problems and the need to protect our natural resources or use them wisely has grown, scientists have become increasingly interested in conservation. Some individuals are involved in conservation-related activities through research or teaching, but most of us participate only as citizens concerned about the world in which we live. Often, we decline to take an active role in conservation issues because we think that "it will take too much time away from our science," or that it is "too much trouble." Both perspectives, I think, are inaccurate. Sometimes investigators fail to participate because they are ignorant of the ways in which scientists (or scientific organizations) interface with conservation - in other words, of how one goes about getting personally involved. Whatever the reason, this lack of involvement is unfortunate, because scientists, and especially "whole organism" biologists (including ornithologists), can make unique contributions to conservation programs, as scientists , without a significant increase in effort or any change in the quality of their work. At the same time, they reap both professional and personal rewards.

The Auk↗
USGS1990

[Book review] No Woman Tenderfoot by Harriet Kofalk

The subject of this biography, identified in the subtitle “Florence Merriam Bailey, Pioneer Naturalist,” was truly a remarkable ornithologist. The bibliography of her writings, included in the book, lists more than 130 articles, a major portion of which were based on her own field work in what was then the wild and unsettled west. Among the titles are the acclaimed “Handbook of Birds of the Western united States,” published in 1902, and the monumental “Birds of New Mexico,” which appeared in 1928. Her contributions were recognized by her colleagues who elected her as a “Fellow” of the American Ornithologists’ Union in 1929 and three years later awarded her its prestigious Brewster Medal.

The Wilson Bulletin↗
USGS1988

Hotshots, hotspots, and female preference in the organization of lek mating systems

We critically review the female-preference and hotspot models, the two most widely accepted recent explanations of lek organization. On the basis of what we believe are the inadequacies of these models-too great a reliance on the presumed acuity of female discrimination, the assumption that females have full freedom of choice within the lek, and insufficient recognition of the importance of male-male interactions-we develop an alternative set of hypotheses, which we call the hotshot model, to explain the development and maintenance of lek behavior. Our model attributes strong male mating skew to the interaction between (1) simplified and conservative mating rules of females and (2) social dominance among males. We demonstrate the importance of male-male dominance relationships in lek and non-lek court mating systems. We then argue that a strong mating skew among males forces novice males entering a population to adopt a long-term mating strategy that involves delayed breeding (floating) and subordinate lek behavior. The structure of leks is created by a complex of malemale interactions, with conflict between hotshots (who attempt to control lek mating) and subordinates, who may benefit from disrupting lek activities. Explanations for the number of males in an arena and inter-arena distances are based on modifications of the hotspot and female-preference models. We suggest specific field tests to help distinguish which hypothesis best models the behavioral interactions that produce lek mating.

American Naturalist↗
USGS1987

Additions to the reptile fauna of Paraguay with notes on a small herpetological collection from Amambay

Specimens in a small collections of reptiles and amphibians from Parque Nacional Cerro Cora, Departamento Amambay, Paraguay are reported. Included are the first records of Bachia bresslaui, Phrynops gibbus, and Ololygon fuscomarginata for that country. Brief notes on morphology, distribution, and natural history of species collected are included. The systematic status of Phrynops tuberculatus vanderhaegei is evaluated.

Studies on Neotropical Fauna and Environment↗
USGS1983

Nutritional value of the aril of Trichilia cuneata, a bird-dispersed fruit

Fruits of Trichilia cuneata (Meliaceae), a common tree in drier forests of Central America, are eaten by a number of birds. The fruits are 10 to 12 mm in diameter, covered by a yellowish-brown, capsular exocarp, and contain three to six seeds distributed among three locules. Each seed is covered by an orangish-red aril that averages 59.7 percent lipid and 15 1 percent protein, which makes this species one of the most nutritious known. The fleshy tissue of only 15 of 59 other species for which we found data contained at least 10 percent protein (dry wt.). Only nine species of 57 had fleshy tissue containing more than 40 percent lipid (dry wt.). Between 1971 and 1972, weights of whole fruits decreased by 36 percent, perhaps in response to a severe drought in the area. The decrease was not equally distributed among component tissues of the fruit. Exocarp decreased by 36 percent, aril by 4 percent, and seeds by 62 percent. However, the reduction in weight per seed was not so dramatic, for two reasons. First, the number of seeds per fruit decreased by 26 percent. Secondly, many seeds did not develop. Thus, the decrease in weight per normally developed seed was only 18 percent. The fruit of Trichilia cuneata was attractive to both specialized (4 species) and opportunistic (11 species) frugivorous birds and is intermediate ("a generalist") in several dispersal-related characteristics.

Biotropica↗