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R. E. Moreau.

Bio: R. E. Moreau. is an academic researcher. The author has contributed to research in topics: Seasonal breeder & Dry season. The author has an hindex of 1, co-authored 1 publications receiving 118 citations.

Papers
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Journal ArticleDOI
03 Apr 2008-Ibis
TL;DR: The observed timing of breeding seasons can be secured only by external factors regulating an internal rhythm, and in some communities and categories of birds the “reasons” for the observed breeding seasons are intelligible.
Abstract: Summary. 1 For the present purpose Africa is divided into everyreen, semi-arid and intermediate (deciduous) types of count?, all of which occur in all latitudes south of the Sahara. 2 “Breeding season” is limited to the months during which eggs are laid by the species concerned in the given area and all records are interpreted accordingly. As a basis for ascertaining the curve of breeding activity in a given area through the year the number of species laying in each month has been ascertained and calculated as a percentage of the total for all species for the whole year. 3 A definite peak in the curve of breeding activity is evident everywhere except in certain areas within about four degrees of the Equator. 4 In one part of this inner tropical belt there may be no distinct breeding season for must groups of birds (Congo), but in East Africa a double breeding season is the rule, with peaks coinciding with the two rainy seasons. 5 Even so close to the Equator as 5°s. the (single) breeding season in evergreen forest is as restricted as in other types of country and its time-relation to the rains varies locally. 6 In the “ intermediate” type of country characterized by 4–6 months drought each year the timing of the peak breeding season varies from the end of the rains, at Cape Town, to the start of the rains in Natal and several weeks before the rains in areas 23° - 10° S. 7 The key to this local difference is that at Cape Town the rains fall in the cold season, so that vegetation and insects are slow to flush. In the warmer conditions in which the rains begin in Natal the flush comes at once. And further north the dominant vegetation and its associated insects flush towards the end of the drought and well in advance of the rains. 8 From Natal northwards the breeding season for all birds combined shows a progressively less marked peak. The reason is that the seasons of certain ecological categories (1) water birds, (2) raptors and scavengers, (3) ground birds, (4) grass birds, (5) the other birds, tend to diverge. 9 The raptors and scavengers are everywhere the earliest breeders, the biggest species laying by the middle of the dry season. The water birds lay to a large extent towards the end of the rain, and after. The ground birds tend to lay as soon as the grass fires are over and before the heavy rains have induced a lush growth of herbage. The grass birds lay later than most-others, when the grass has grown high. 10 In semi-arid areas the breeding seasons are on the whole similar to the foregoing, with most birds breeding when the vegetation flushes, whether just before or after rain has fallen. But the “semi-and” birds are notably sensitive to rainfall; breeding that has begun is checked if the rains are interrupted. 11 In some communities and categories of birds the “reasons” for the observed breeding seasons are intelligible, the best food-supply or the safest nesting apparently being secured. In others the reasons are not obvious; and the degree to which the breeding seasons are restricted is often incomprehensible. 12 The observed timing of breeding seasons can be secured only by external factors regulating an internal rhythm. Day-length, rainfall and humidity, temperature and visual stimuli are each considered briefly. Each may be effective on some species in some areas, but no one generally.

123 citations


Cited by
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Journal ArticleDOI
01 Dec 1992-Ecology
TL;DR: It is suggested that arthropod abundance is a crucial factor governing the timing of breeding activities, even in species that normally include a high proportion of nectar and fruits in their diet, and that, in tropical habitats receiving > 1500 mm of rain per year, breeding in nectarivores and frugivores in the dry season may be related to the lower reduction inArthropod numbers over the less severe drought period.
Abstract: We studied avian breeding and molting activity in relation to rainfall, tem- poral fluctuations in food resource abundance, and food exploitation by birds, in four arid and semiarid tropical habitats in Venezuela. Twice a month we used mist nets to monitor changes in breeding and molting conditions of captured birds and forced them to regurgitate to determine their diet and feeding guild membership. Food abundance was assessed by measuring the flowering and fruiting seasonality of marked plants and by evaluating ar- thropod abundance with four different trapping methods. Flowering activity was limited largely to the wet season. Fleshy fruits, although produced year-round, were also more abundant in the rainy period. Arthropod abundance followed the same general pattern with numbers highest in the wet season and lowest in the dry season. Birds of all feeding guilds predominantly bred and molted during the wet season, synchronously with the highest abundance of most food resources. However, the diet analysis revealed a higher occurrence of arthropods coupled with a sharp decrease in the intake of vegetable matter during the birds' breeding season. Consequently, we suggest that arthropod abundance is a crucial factor governing the timing of breeding activities, even in species that normally include a high proportion of nectar and fruits in their diet. We also postulate that, in tropical habitats receiving > 1500 mm of rain per year, breeding in nectarivores and frugivores in the dry season may be related to the lower reduction in arthropod numbers over the less severe drought period.

256 citations

Journal ArticleDOI
TL;DR: Probably the most valuable of his many contributions to the field of avian physiology was his ability to relate laboratory experimentation to the natural environment.
Abstract: We wish to dedicate this paper to the memory of Professor A. J. Marshall whose untimely death occurred while it was in press. Professor Marshall was formerly the head of the Department of Zoology, St. Bartholomew's Hospital Medical College, London, and subsequently held the Foundation Chair of Zoology and Comparative Physiology, Monash University, Australia. Probably the most valuable of his many contributions to the field of avian physiology was his ability to relate laboratory experimentation to the natural environment. Much of the thought contained in the present paper has been stimulated by his approach and pioneer studies.

251 citations

Journal ArticleDOI
01 Sep 2000-Ecology
TL;DR: Spotted Antbirds, monogamous understory insectivores, started breeding in Panama in May and continued until September/ October, indicating that tropical seasons were as predictable for Spotted Antbird (predictability 70%) as they are for many north temperate birds.
Abstract: Tropical wet forests are commonly perceived as stable and constant envi- ronments. However, many rain forest organisms reproduce seasonally. To understand the proximate regulation of life history events in tropical organisms, we asked three questions: (1) How predictable are seasonal changes in the tropical rain forest? (2) Can tropical organisms anticipate environmental seasonality, despite the presumed lack of long-term environmental cues in near-equatorial areas? (3) What environmental cues can tropical organisms use? We studied Spotted Antbirds, monogamous understory insectivores, which started breeding in Panama (9? N) in May (wet season) and continued until September/ October. Breeding patterns were consistent between years, indicating that tropical seasons were as predictable for Spotted Antbirds (predictability 70%) as they are for many north temperate birds. Individual Spotted Antbirds shut down reproductive capacity (i.e., de- creased gonad size) from October until February. In March, during the height of the dry season and about six weeks ahead of the wet season, gonads started to grow again. The growth rate of gonads was influenced by the amount of rainfall, which has been shown to correlate with food abundance. Gonad growth was paralleled by changes in luteinizing hormone, but not in testosterone, which remained at very low plasma levels year-round. The latter contrasts with the pattern for most migratory temperate-zone birds. Seasonal changes in reproductive activity correlated strongly with changes in the tropical photoperiod, but weakly with light intensity and rainfall, and not with temperature. Thus, Spotted Ant- birds likely anticipated rain forest seasonality using long-term cues (tropical photoperiod) and fine-tuned their reproductive activities using short-term cues (food/rainfall). The use of long-term environmental information could apply to most vertebrate species that live in the tropics.

196 citations