Sex Ratio Constancy in the Red-Winged Blackbird

Fiala, Kent L.

doi:10.2307/2407861

Cited by 53 publications

(47 citation statements)

References 12 publications

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“…In two previous studies of sexually dimorphic species, parents did not adjust their overall feeding rates in response to the overall sex ratio of the brood, suggesting males and females were being fed similar amounts (Fiala 1981 a;Roskaft and Slagsvold 1985). In neither of these studies, however, was information available on food acquisition by individual nestlings.…”

Section: Discussionmentioning

confidence: 87%

“…Male nestlings, when they are the larger sex, have higher energetic demands (Fiala and Congdon 1983;Slagsvold etal. 1986;Teather and Weatherhead 1988) and require more food (Fiala 1981 a;Teather 1987) than their sisters. If the competitive advantage they gain by being larger does not offset these greater energy requirements, then males, rather than females, would be more likely to suffer when food is limiting.…”

Section: Discussionmentioning

confidence: 99%

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An experimental study of competition for food between male and female nestlings of the red-winged blackbird

Teather

1992

Behav Ecol Sociobiol

111

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Ten experimental broods of red-winged blackbird (Agelaius phoeniceus) nestlings, experimentally manipulated to contain two males and two females of similar age, were observed with the aid of video cameras to determine (a) which nestling characteristics were most important in influencing its chances of being fed and (b) if males and females differed with respect to these characteristics. Nestlings that could reach highest while begging were most successful at obtaining food from parents during individual feeding bouts. However, while there was a tendency for nestlings that begged earlier to be offered food first, a nestling's position in the nest during these bouts did not influence its feeding success. Males begged more than often females and were offered more food by parents. Males were also more likely to be fed when they begged. This was most likely because males, being larger than females, were able to reach higher while begging. Neither sex was more likely to beg sooner or occupy certain positions in the nest. However, while males that had been transferred from other nests received less food than natal males, there were no differences in food acquisition between transferred and natal females. Differences in the relative success of males and females under different conditions may help explain differences in fledgling sex ratios observed in many dimorphic species.

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Section: Discussionmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

An experimental study of competition for food between male and female nestlings of the red-winged blackbird

Teather

1992

Behav Ecol Sociobiol

111

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“…In most species of birds with sexual size dimorphism, the population sex ratio at hatching and fledging in any given year was not significantly biased (Howe 1977;Fiala 1981;Ryder 1983;Blank and Nolan 1983;Weatherhead 1983); however, the sex ratio varied seasonally, with the more expensive sex being produced when food was most abundant. In Eurasian kestrels (F. tinnunculus), the proportion of males declined over the breeding season (Dijkstra et al 1990), but we did not find a similar trend for American kestrels (Fig.…”

Section: Temporal Variation In Sex Ratiosmentioning

confidence: 92%

“…The Julian date on which the first egg of a clutch was laid was considered to be the laying date for that brood. We tallied the total number of males and females in the population that hatched on each Julian date and weighted the resulting sex ratio by the number of clutches started on that day (see Fiala 1981). Laying dates were also divided into two groups, "early" and "late", so that there were equal numbers of broods in each category.…”

Section: Methodsmentioning

confidence: 99%

“…In some species, the greater mortality of the more expensive sex during the nestling period leads to a population sex ratio biased towards the cheaper sex at fledging (Howe 1977;Fiala 1981;Roskaft and Slagsvold 1985). Population sex ratios of other species are not biased, but sex does vary with attributes of the clutch (Ryder 1983;Bortolotti 1986).…”

Section: Introductionmentioning

confidence: 99%

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Facultative sex ratio manipulation in American kestrels

Wiebe

Bortolotti

1992

Behav Ecol Sociobiol

218

150

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For animals that are sexually dimorphic in size, the larger sex is expected to be more costly to raise to independence. Manipulating offspring sex ratios may thus be one means by which parents can fine-tune their reproductive effort to resource availability. Parents in poor physical condition or during poor food years should produce more of the cheaper (smaller) sex. We examined the sex ratios of 259 broods of American kestrels (Falco sparverius) between 1988 and 1990 in relation to food abundance (small mammals) and various attributes to the parents. The proportion of males at hatching increased as the food supply declined, and both male and female parents in poor physical condition were more likely to have male-biased broods than those in good condition. The mortality of eggs and young did not appear to be responsible for the biased sex ratios. The sex ratio was independent of the laying date; however, it was correlated with female body size. Small females produced more sons, perhaps because small size is more detrimental for females than males.

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Sex ratio manipulation within broods of house wrens, Troglodytes aedon

Albrecht

2000

Animal Behaviour

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Sex Ratio Constancy in the Red-Winged Blackbird

Cited by 53 publications

References 12 publications

An experimental study of competition for food between male and female nestlings of the red-winged blackbird

An experimental study of competition for food between male and female nestlings of the red-winged blackbird

Facultative sex ratio manipulation in American kestrels

Sex ratio manipulation within broods of house wrens, Troglodytes aedon

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