Topic
Euplectes ardens
About: Euplectes ardens is a research topic. Over the lifetime, 5 publications have been published within this topic receiving 426 citations.
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TL;DR: It is proposed that the “multiple receiver hypothesis” can explain the coexistence of multiple handicap signals, and the trade‐off between signal expressions might contribute to the inverse relation between nuptial tail elongation and coloration in the genus Euplectes (bishops and widowbirds).
Abstract: Sexual displays often involve several different ornamental traits. Yet most indicator models of sexual selection based on a single receiver (usually a choosy female) find that multiple handicap signals should be unstable.Here we study reasons for this contradiction, analyzing signal function, signal content, and trade-offs between signals in the polygynous red-collared widowbird Euplectes ardens. Males have both a long, graduated tail and a red carotenoid collar badge. Territory-holding "residents" have slightly shorter tails than the nonbreeding "floaters," but their carotenoid collars are 40% larger, and they have (on the basis of reflectance spectrometry and objective colorimetry) a 23-nm more long-wave ("redder") hue than floaters. This corroborates experimental evidence that the red collar is selected by male contest competition, whereas female choice is based almost exclusively on male tail length. Tail length is negatively correlated with the carotenoid signal, which together with body size and condition explains 55% of the variation in tail length. The trade-off in tail length and carotenoid investment is steeper among residents, suggesting an interaction with costs of territory defense. We propose that the "multiple receiver hypothesis" can explain the coexistence of multiple handicap signals. Furthermore, the trade-off between signal expressions might contribute to the inverse relation between nuptial tail elongation and coloration in the genus Euplectes (bishops and widowbirds).
266 citations
TL;DR: Redness and, to a lesser extent, size of the carotenoid ornament both seem to independently indicate male dominance status or fighting ability in male contest competition.
Abstract: Carotenoid-based plumage ornaments are typically considered to be sexually selected traits, functioning as honest condition-dependent signals of phenotypic quality, but few studies have addressed the function of carotenoid color variation in male contest competition. Using two experiments, we investigated the status signaling function of the variable (ranging from yellow to red) carotenoid throat patch (collar) in the polygynous, sexually dimorphic red-collared widowbird (Euplectes ardens). First, we tested if the red collar functions as a dominance signal by painting spectrometrically controlled collar patches onto the brown plumage of nonbreeding males and staging dyadic male contests over food resources. Red-collared males dominated orange males, which in turn dominated the control brown and novel blue collars. Red dominance persisted when the collar manipulations were reversed within dyads and also when tested against testosterone implanted males. In the second experiment the collar size and color of breeding males were manipulated in the field before and after territories were established. All males with enlarged red and most with enlarged orange or reduced red collars obtained territories, whereas most males with reduced orange and all with blackened (removed) collars failed to establish or retain territories. In addition, among the territorial males, those with reduced signals defended smaller territories, received more intrusions, and spent more time in aggressive interactions. Redness and, to a lesser extent, size of the carotenoid ornament both seem to independently indicate male dominance status or fighting ability in male contest competition. Copyright 2002.
166 citations
TL;DR: It is suggested that females may gain indirect genetic benefits of higher-quality offspring without incurring the high costs of sharing territories, as shown in the finding of strong female preference for longertailed males.
Abstract: We explored characteristics and patterns of nest distribution, and their putative costs and benefits to breeding females, in polygynous Red-collared Widowbirds (Euplectes ardens). Red-collared Widowbirds differ from most other Euplectes species, in that male nestbuilding is reduced to simple nest-rings used in courtship; females alone position and build nests in the territories. Females used only 37% of available territory area for nesting and aggregated at the centers of territories, possibly to take advantage of male vigilance from prominent central perches or to avoid harassment by neighbors. However, irrespective of territory size or number of females on the territory, females maintained relatively even spacing, with nests ∼15 m apart. Nest predation rates were higher (28.2% day−1) during the nestling period than during incubation (14.6%), but independent of the number of actively nesting females on a territory. During synchronous nestling stages, however, birds nesting close to other birds i...
6 citations
TL;DR: It is argued that the assumptions of the FA hypothesis are too simplistic for this conclusion to be drawn with a high degree of confidence that the tail is not a reliable signal of male quality in the Red-collared Widowbird.
Abstract: Fluctuating asymmetry (FA) may provide a direct test of whether sexual selection via “arbitrary traits” or “good genes” is responsible for the evolution of epigamic traits, because FA is an epigenetic measure of stress during development. However, tests of the FA hypothesis have yielded equivocal results, and the debate between arbitrary traits and good genes continues. The FA hypothesis predicts a negative relationship between ornament size and asymmetry. In non-ornamental traits, a U-shaped relationship between trait size and asymmetry is expected. We tested these predictions in the Red-collared Widowbird (Euplectes ardens) by examining the relationship between size and asymmetry in the length of the tail, tarsus, and wing. We found no significant linear or second-order polynomial relationships between trait size and asymmetry. Furthermore, no relationship existed between asymmetry and two indices of body condition. This suggests that the tail is not a reliable signal of male quality in the Red...
5 citations
Journal Article•
TL;DR: In this paper, the changes in observed densities of bird species in a suburban environment in Groenkloof, Pretoria were monitored over five years, and the populations of fourteen species were found to increase during the study period and six species to decrease.
Abstract: The changes in observed densities of bird species in a suburban environment in Groenkloof, Pretoria were monitored over five years. The populations of fourteen species were found to increase during the study period and six species were found to decrease. The Amethyst Sunbird Nectarinia amethystina was found to be predominantly a non-breeding migrant, and strong evidence for seasonal movements by part of the Karoo Thrush Turdus smithi population was produced. Daily movements in and out of the study area are described for some species, most notably the Red-collared Widowbird Euplectes ardens. The Grey-headed Bush Shrike Malaconotus blanchoti apparently became established as a resident of the suburban habitat during the study period. The medium term changes in density of woodland species were found to be on average significantly smaller than those at a rural site 100 km north of the study site.
4 citations