Morphology and Ornamentation in Male Magnificent Frigatebirds: Variation with Age Class and Mating Status

Madsen, Kristoffer Hougaard; Dabelsteen, Torben; Osorio,; Osorno,

doi:10.2307/4125304

Cited by 6 publications

(8 citation statements)

References 44 publications

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“…Zuk et al 1990;Birkhead et al 1998;Marchettii 1998;Kraak et al 1999;Badyaev et al 2001;Madsen et al 2007). We also corroborate previous work on U. mjoebergi (Reaney and Backwell 2007) showing that wave rate and male size are not correlated among males that are waving.…”

Section: Discussionmentioning

confidence: 97%

“…This might allow females to more quickly assess variation among males or, by averaging across the different indices, reduce measurement/assessment error to obtain a more accurate estimate of a male's underlying quality (Candolin 2003). Surprisingly, however, the expression of different male sexual traits is often found to be uncorrelated (Zuk et al 1990;Birkhead et al 1998;Marchettii 1998;Kraak et al 1999;Badyaev et al 2001;Madsen et al 2007). If this is the case, how do females choose mates when they pay attention to two or more different sexually selected male traits?…”

Section: Introductionmentioning

confidence: 95%

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The effect of claw size and wave rate on female choice in a fiddler crab

Callander

Jennions

Backwell

2011

J Ethol

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How do females select a mate when they have mating preferences for multiple male traits? In experimental studies, female fiddler crabs (Uca mjoebergi) show a strong preference for males with larger claws and higher wave rates. In the field, there is no correlation between male claw size and observed wave rate. Here we document natural mating behaviour and show that females approach males who wave at a higher rate than nearby competitors. On average, an approached male had a significantly larger claw than his two nearest neighbours but did not differ in size from his two closest waving competitors. In general, smaller males were less likely to wave at approaching females. Females therefore approached mates based directly on wave rate but, because smaller males were less likely to wave, this indirectly resulted in female choice for larger than average males. Our study raises two issues. First, how do we relate the field results to previous experimental studies showing a female preference for larger claws? Second, in U. mjoebergi, males defend smaller neighbours against intruders. Our study suggests that one benefit of such defence coalitions is to decrease the number of immediate competitors present during female mate choice by retaining smaller neighbours.

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Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 95%

The effect of claw size and wave rate on female choice in a fiddler crab

Callander

Jennions

Backwell

2011

J Ethol

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“…This species is likely to be more sensitive to climate variability and human pollution. Cabot’s terns have smaller body size and shorter life spans than the other investigated species [56, 98]. Body size is positively correlated with longevity, since small birds need to feed more frequently than large birds to fulfil their high metabolic rates [99, 100].…”

Section: Discussionmentioning

confidence: 99%

Environmental Predictors of Seabird Wrecks in a Tropical Coastal Area

2016

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Beached bird surveys have been widely used to monitor the impact of oil pollution in the oceans. However, separating the combined effects of oil pollution, environmental variables and methodological aspects of beach monitoring on seabird stranding patterns is a challenging task. The effects of a comprehensive set of oceanographic and climatic variables and oil pollution on seabird strandings in a tropical area of Brazil were investigated herein, using two robust and innovative methods: Generalized Linear Mixed Models and Structural Equation Modeling. We assessed strandings of four resident seabird species along 480 km of beaches divided into 11 sampling areas, between November 2010 and September 2013. We found that increasing the distance from the nearest breeding island reduce the seabird stranding events. Storm activity and biological productivity were the most important factors affecting the stranding events of brown boobies Sula leucogaster, Cabot’s terns Thalasseus acuflavidus and kelp gulls Larus dominicanus. These species are also indirectly affected by warm tropical waters, which reduce chlorophyll-a concentrations. Beach surveys are, thus, useful to investigate the mortality rates of resident species near breeding sites, where individuals are more abundant and exposed to local factors associated with at-sea mortality. In contrast, conservation actions and monitoring programs for far-ranging seabird species are needed in more distant foraging areas. Furthermore, beach monitoring programs investigating the impact of oil pollution on seabirds need to account for the effects of environmental factors on stranding patterns. The present study also demonstrated that seabirds inhabiting tropical coastal waters are sensitive to climate conditions such as adverse weather, which are expected to increase in frequency and intensity in next decades.

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“…One should thus focus on the variable showing the most individual differences, as well as the least redundancy, with the more classical variables (hue, brightness, and saturation). Our a priori expectation was that higher directionality would increase both WPY and EPY because it would signal good individual condition (Madsen et al 2007;Meadows et al 2012) and consequently be preferred by females. However, our results showed that males with higher back directionality had less WPY, a lower proportion of WPY in the nest, and an equal number of EPY than males with lower back directionality.…”

Section: The Importance Of Directionality In the Number Of Wpymentioning

confidence: 99%

“…Repeatable individual differences in directionality can however be measured using a recently developed technique (Meadows et al 2011;Van Wijk et al 2016). It has been suggested that plumage exhibiting a high directionality would have a more ordered microstructure (Madsen et al 2007;Meadows et al 2012), a feature that could indicate better condition. This property may be a distinct channel of information about an individual (Van Wijk et al 2016), and including this variable when studying sexual selection of iridescent coloration in birds has the potential to reveal new insights into male quality.…”

Section: Introductionmentioning

confidence: 99%

The influence of iridescent coloration directionality on male tree swallows’ reproductive success at different breeding densities

Wijk

Bourret

Bélisle

et al. 2016

Behav Ecol Sociobiol

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Conspicuous coloration in males of numerous bird species has been related to sexual selection. However, iridescent coloration is a complex trait that has received little attention despite its potential importance as a signal of individual condition. Directionality, the change in brightness when the animal moves under direct sunlight, has never been linked to fitness although being an integral part of iridescent coloration. Using 214 male tree swallows (Tachycineta bicolor) from a 2-year study, we investigated how different components of iridescent coloration were related to four measures of fitness (number of extra-pair and within-pair young produced, proportion of within-pair young in the nest and annual reproductive success) across different breeding densities. In addition to classical components of coloration (hue, brightness, saturation), we used directionality-measured as an angular breadth of color reflection-to quantify the iridescent coloration of male crown and back. Our results showed that all components of iridescent coloration we studied were related to at least one of the four measures of fitness. A negative association was detected between directionality and the number of withinpair young produced, suggesting that this plumage characteristic could be a signal of paternal care. Crown and back coloration were associated to different fitness components, and density modulated the slope of some of these relationships. Altogether, our results showed that different selective pressures could act on the multiple components of iridescent coloration via both withinpair and extra-pair components of reproductive success. Also, environmental conditions like breeding density are important factors influencing sexual selection processes. Significance statementThe idea that colorful plumage in males is the result of sexual selection is widely recognized. However, evidence of sexual selection on iridescent plumage is scarce. In birds displaying iridescent plumage, the brightness change occurring when the bird moves, called directionality, is striking and could be informative for females when choosing a mate. Using 214 male tree swallows, we found that directionality was related to the number of young produced by a male. As nests were distributed in 40 different farms, a high variability of breeding densities occurred in the study system. Breeding density highly influenced the relationship between color components of iridescent plumage and the number of young produced by a male. This study emphasizes the importance to quantify the angular properties of iridescent plumage as well as to take into account breeding density when studying sexual selection. Communicated by E. Fernandez-JuricicElectronic supplementary material The online version of this article (

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Morphology and Ornamentation in Male Magnificent Frigatebirds: Variation with Age Class and Mating Status

Cited by 6 publications

References 44 publications

The effect of claw size and wave rate on female choice in a fiddler crab

The effect of claw size and wave rate on female choice in a fiddler crab

Environmental Predictors of Seabird Wrecks in a Tropical Coastal Area

The influence of iridescent coloration directionality on male tree swallows’ reproductive success at different breeding densities

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