The timing of breeding and moult of the yellowmantled widowbird euplectes macrourus in western kenya
TL;DR: The breeding and moulting seasons of Yellowmantled Widowbirds Euplectes mac-rourus at the Kakamega National Reserve in western Kenya were described, and the pattern of grass seed abundance closely matched rainfall.
Abstract: Summary Savalli, U.M. 1993. The timing of breeding and moult of the Yellowmantled Widowbird Euplectes mac-rourus in western Kenya. Ostrich 64:49-56. This paper describes the breeding and moulting seasons of Yellowmantled Widowbirds Euplectes mac-rourus at the Kakamega National Reserve in western Kenya. Egg laying began in May, peaked in June, and continued into September. The presence of brood patches on females followed a similar pattern. Most moulting occurred prior to breeding, in March and April. Rainfall was greatest in April and May, with a second peak in August to September. The pattern of grass seed abundance closely matched rainfall, and breeding appears to start about one month after the start of the rains. An exceptionally dry spell in May and June 1990 may have resulted in few breeding attempts that year.
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TL;DR: It was found that males increased their nest-building speed with increased female breeding activity independently of rainfall, indicating that supply follows demand in this mating market, and the supply of nests was always larger than the demand for nests.
Abstract: The red bishop (Euplectes orix) is a highly polygynous and colonial weaverbird. Males construct several nests within their territories to which they try to attract females, and females are solely responsible for incubation and raising offspring. In this paper, we describe the characteristics of the red bishop’s mating system as a biological market and investigate the role of nests built by males as a traded commodity in a mating market. As timing of breeding in red bishops in arid and semi-arid zones depends on rainfall patterns which are often unpredictable, there are temporal changes in demand for and supply of nests within a breeding season, with breeding activities of males and females being highly synchronised. We found that males increased their nest-building speed with increased female breeding activity independently of rainfall, indicating that supply follows demand in this mating market. The supply of nests was always larger than the demand for nests. Construction costs for nests increased with demand for nests as indicated by shorter nest-building duration and shorter building delays between two consecutively built nests at times of high breeding activity. Males as a trading class are chosen according to the age of their nests offered, with young nests having a higher probability of being accepted by females. Furthermore, female choosiness with regard to nest age decreased when their own market value decreased, as predicted by biological market theory. The temporal changes of breeding activity together with the female preference for young and fresh nests require that males quickly adjust nest-building activity to varying female demand for new nests. However, males with a better adjustment of building speed to female breeding activity did not gain higher mating success.
19 citations
Cites background from "The timing of breeding and moult of..."
...Timing of breeding seasons of birds in southern African arid and semi-arid zones in relation to rainfall has been well studied, and it has been shown that birds can quickly start breeding in response to rainfall (Brooke 1966; Collias and Collias 1978; Craig 1982; Savalli 1993; Lloyd 1999; Friedl 2002)....
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...…of breeding seasons of birds in southern African arid and semi-arid zones in relation to rainfall has been well studied, and it has been shown that birds can quickly start breeding in response to rainfall (Brooke 1966; Collias and Collias 1978; Craig 1982; Savalli 1993; Lloyd 1999; Friedl 2002)....
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01 Jan 2004
TL;DR: A new hypothesis explaining the high incidence of moult-breeding overlaps and low fecundity in tropical birds is proposed, and it is proposed that immunity and moult would limit fecundities in these species.
Abstract: SUMMARY.—Moult-breeding overlap and fecundity limitation in tropical birds: a link with immunity? Plumage moult is a costly maintenance process which conflicts with the requirements for breeding, explaining the avoidance of moult-breeding overlaps in many species. However, moult-breeding overlaps are especially frequent in the tropics, a fact which has been related to protracted breeding seasons and small clutches linked to high nest predation. Here, a new hypothesis explaining the high incidence of moult-breeding overlaps and low fecundity in tropical birds is proposed. Parasites and pathogens of birds may be more prevalent in the tropics than in temperate regions, requiring a higher level of immune responsiveness. There is observational and experimental evidence that moult interferes with immunity, and that the induction of an immune response delays the initiation of postnuptial moult. To avoid this conflict between a necessarily high preparedness of the immune system and plumage renewal, moult would have to be slowed down. Protracted moult processes would imply a high incidence of moult-breeding overlap. This, in turn, would reduce resources necessary for reproduction, leading to small clutches. Immunity and moult would limit fecundity in
18 citations
Cites background from "The timing of breeding and moult of..."
...Moult-breeding overlap is more frequent in the tropics, and appears to be associated to protracted moult processes (Foster, 1974, 1975; Dittami, 1987; Savalli, 1993; Tidemann & Woinarski, 1994; but see Craig, 1996; Milingwa, 1996; Marini & Duraes, 2001)....
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TL;DR: Yellow Bishops have rounder wings than other weaver species, possibly because their larger size affects flight aerodynamics, and the longer duration of primary moult of the Yellow Bishop may be related to food.
Abstract: The grassland biome in South Africa has a summer rainfall and Southern Red Bishops Euplectes orix , Fan-tailed Widows E. axillaris , White-winged Widow E. albonotatus , Red-collared Widow E. ardens and Long-tailed Widow E. progne breed from October or November to March. Primary moult starts in late March or early April. The widows with long tails (Long-tailed and Red-collared Widows) have moult durations of two months, while the widows with shorter tails (White-winged and Fan-tailed Widows) had moult durations of 1.5–1.7 months. Moult ends in late May or early June. Long-tailed Widows have rounder wings than other weaver species, possibly because their larger size affects flight aerodynamics. In the winter rainfall region, Southern Red Bishops and Yellow Bishops E. capensis start breeding after the winter rains, from August–November, and moult starts in early December. Primary moult duration in Yellow Bishops is relatively long, at 3.4 months. Yellow Bishops grow individual primary feathers at an average rate of 21.3 days per feather, while the other species moult primaries more quickly: White-winged Widow 8.1 days, Fan-tailed Widow 11.3 days, and Red-collared Widow 14.4 days. The number of primaries growing simultaneously is similar in the different species. The longer duration of primary moult of the Yellow Bishop may be related to food. Ostrich 2006, 77(3&4): 142–152
12 citations
Cites background from "The timing of breeding and moult of..."
...Savalli (1993) described the pre-nuptial moult in the Yellowmantled Widowbird E. macrourus in western Kenya....
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TL;DR: A detailed analysis of how rainfall affects timing and duration of the breeding season, breeding activity and breeding success in a colony of Red Bishops in the Addo Elephant National Park in the Eastern Cape, South Mrica is presented.
Abstract: Although the Red Bishop, Euplectes orix, is a very common resident throughout most of southern Mrica, the factors affecting timing and duration of the breeding season are not well understood. In general, the timing of the breeding season seems to be related to local rainfall patterns. Craig (1982a) showed that, over the whole range of the Red Bishop in southern Mrica, clutches were laid in or shortly after the onset of the rainy season, with only 1% of records before, or more than one month after, the rainy season. Furthermore, it is not clear how the local rainfall pattern affects the amount of breeding activity or breeding success in a given year. Brooke (1966) was the first to draw attention to the possibility that rainfall might affect the onset of prenuptial moult, timing of breeding and clutch size in Red Bishops. He collected rainfall and breeding data for Red Bishops in Zimbabwe suggesting that poor rain in November (the month before the usual start of the breeding season) delays both the onset of the prenuptial moult and the start of breeding. In addition, Brooke (1966) found that the average clutch size was reduced in years with poor November rain. By contrast, Craig (1982a) found no correlation between October rainfall and breeding activity in a Red Bishop colony studied near Pietermaritzburg, KwaZuluNatal, South Africa. Here I present a detailed analysis of how rainfall affects timing and duration of the breeding season, breeding activity and breeding success in a colony of Red Bishops in the Addo Elephant National Park in the Eastern Cape, South Mrica (330 26'S; 250 45'E). A colony of individually marked Red Bishops was studied during four consecutive breeding seasons (1993/94 to 1996/97). The breeding site was a small dam surrounded by an inner band of bullrushes (Typha capensis) and an outer band of reeds (Phragmites australis). Rainfall data
12 citations
TL;DR: During the breeding season, male Yellowmantled Widowbirds defend territories from conspecifics but do not exclude Marsh Widowbirds E. hartlaubi, and during the non-breeding season they form mixed species flocks with other finches.
Abstract: Summary Savalli, U. M. 1993. The behaviour of male Yellowmantled Widowbirds Euplectes macrourus in western Kenya. Ostrich 64: 57–62. Male Yellowmantled (Yellowbacked) Widowbirds Euplectes macrourus use two displays in territorial defense. The territory boundary display involves a specific, upright posture along with the hiss-trill vocalization, but the song does not have a visual component. Courtship displays involve flicking up the wings and tail, sometimes leaning toward the female with the tail elevated, and a slow, bouncing flight display. The swivelling display described by Emlen (1957) was not observed, and seems to be replaced by the flicking displays. During the breeding season, male Yellowmantled Widowbirds defend territories from conspecifics but do not exclude Marsh Widowbirds E. hartlaubi. At night they form communal roosts off their territories. During the non-breeding season they form mixed species flocks with other finches. Male widowbirds are most active in display before 10h00, and often ...
5 citations
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TL;DR: It is reported here that males in which the tail was experimentally elongated showed higher mating success than males having normal or reduced tails: males with shortened tails held their territories as long as did other males.
Abstract: Darwin's1 hypothesis that male secondary sexual ornaments evolve through female preferences is theoretically plausible2–7, but there is little experimental field evidence that such preferences exist8–10. I have studied female choice in relation to male tail length in the long-tailed widowbird, Euplectes progne, and report here that males in which the tail was experimentally elongated showed higher mating success than males having normal or reduced tails. The possibility that intrasexual competition among males maintains the long tail was not supported: males with shortened tails held their territories as long as did other males. These results suggest that the extreme tail length in male long-tailed widowbirds is maintained by female mating preferences.
823 citations
01 Jan 1965
198 citations
TL;DR: Investigation of sexual selection in the lekking Jackson's widowbird found that tail length was positively related to a measure of body condition, which is of interest with regard to the suggestions that sexual ornaments may serve as indicators of male viability.
Abstract: Sexual selection through female mate choice was investigated in the lekking Jackson's widowbird by applying multivariate selection analysis to observational data from four leks. Males perform a stereotyped jump display on small display courts (“dance rings”) constructed by the males in open grassland. Females visit the lek solely for mating and nest on their own, away from the lek area. Few cases of interference during courtship and absence of position effects on mating success indicated that female choice within the leks was not pre-empted by male-male competition. In a set of 11 male traits with mating success as the dependent fitness measure, significant selection differentials (covariances) were found for the length of the conspicuous tail and the rate of the jump display, suggesting sexual selection of these traits. They also showed the largest selection gradients (partial effects) and thereby seem to be the cues on which females base their choice. The success of males in obtaining copulations appears to depend on two components: display rate and lek attendance affect the number of female visits, whereas tail length seems to primarily influence the chance of copulating with a visiting female. Tail length was positively related to a measure of body condition, which is of interest with regard to the suggestions that sexual ornaments may serve as indicators of male viability.
121 citations