Experimentally altered plumage brightness of female tree swallows: a test of the differential allocation hypothesis

Berzins, Lisha L.; Dawson, Russell D.

doi:10.1163/1568539x-00003354

Cited by 27 publications

(55 citation statements)

References 73 publications

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“…The brightness of plumage following the manipulation fell within the natural range of plumage brightness for female tree swallows (Berzins and Dawson, 2016). Females in each treatment did not differ by age, body mass, plumage characteristics (see below), or capture date prior to experimental manipulation (all P values > 0.29).…”

Section: Study Area and General Field Methodsmentioning

confidence: 71%

“…I determined the age of females using dorsal plumage colour (Hussell 1983), and ASY females were sequentially allocated to the enhanced, reduced, or control plumage brightness treatments by capture order, after determining a treatment order randomly. Details of the plumage brightness manipulation are described in Berzins and Dawson (2016). Briefly, plumage brightness was enhanced by applying nontoxic permanent blue marker, reduced by applying silicon paste evenly to the dorsal feathers of females, or remained unchanged by treating females with a marker containing water.…”

Section: Study Area and General Field Methodsmentioning

confidence: 99%

“…The spectral analysis for females used in this study is described in Berzins and Dawson (2016). Briefly, I quantified plumage characteristics of female tree swallows by measuring the reflectance of feathers using a JAZ-PX spectrometer with a xenon light source (Ocean Optics, Dunedin, FL, USA).…”

Section: Spectral Analysismentioning

confidence: 99%

“…Among ASY females, those that are more ornamented display plumage that is brighter, with greater UV and blue chroma, and reflects light maximally at shorter wavelengths (i.e., bluer hue; Bentz and Siefferman, 2013). Although it is currently unknown whether bright plumage of ASY females similarly functions as a status signal, females that display bright plumage assortatively mate with bright males , and since bright plumage of females does not appear to be a signal of attractiveness preferred by males (Berzins and Dawson, 2016; Chapter 4), assortative mating in this species likely occurs because females with bright plumage have greater competitive ability.…”

Section: Introductionmentioning

confidence: 99%

“…I tested whether plumage brightness of females influenced nest site retention by experimentally enhancing and reducing the plumage brightness of female tree swallows prior to breeding relative to controls (see Berzins and Dawson, 2016). If plumage brightness is a signal of quality that is socially enforced by conspecifics challenging females with incongruent signals, I predicted that females whose ornamentation was enhanced and reduced, so that their quality and behaviour mismatched, would be less likely to retain their nests (Table 3.1).…”

Section: Introductionmentioning

confidence: 99%

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Determinants of making success in female Tree Swallows (Tachycineta Bicolor)

Berzins¹

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Females from a wide variety of taxa display elaborate ornaments and aggressive behaviours that are similar to those expressed by males. Although recent empirical investigation has demonstrated that ornamental traits and behaviours of females may function by attracting mates or signalling competitive ability when competing against conspecifics for access to mates and resources, less is known about how such traits influence the mating success of free-living female birds. For my research, I experimentally examined how variation in plumage brightness and behaviour of female tree swallows (Tachycineta bicolor) influenced their mating success.Plumage brightness of females had no influence on investment in parental care or mating strategies of males, or the quality of social mate paired to the female. These results suggest that bright plumage is not a signal of attractiveness preferred by male tree swallows.In contrast, I report evidence that plumage brightness of female tree swallows is involved in agonistic interactions with conspecifics. Females whose plumage brightness was enhanced to signal high quality were less able to retain their nest site than females whose plumage brightness was reduced to signal low quality. This suggests that females displaying bright plumage may be challenged by conspecifics of high quality to test the quality signalled by bright plumage, and is supported by the finding that females displaying enhanced plumage brightness suffered social costs, such as delaying breeding and producing low-quality nestlings. Despite these costs, females in the enhanced plumage brightness treatment mated with extra-pair males that were higher quality than their social mate.Behaviour of females, manipulated by elevating testosterone (T), lowered the proportion of extra-pair offspring in the broods of T-treated females. Females manipulated so that the androgenic and estrogenic actions of T were blocked also produced fewer extra-pair iii offspring, and suggest that the androgenic and/or estrogenic actions of T influence extra-pair copulation behavior of female tree swallows. In conclusion, my results show that plumage brightness and behaviour of female tree swallows influence their mating success, and highlight the importance of studies experimentally manipulating ornamental and behavioural traits of free-living female birds prior to breeding.iv

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Section: Study Area and General Field Methodsmentioning

confidence: 71%

Section: Study Area and General Field Methodsmentioning

confidence: 99%

Section: Spectral Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Determinants of making success in female Tree Swallows (Tachycineta Bicolor)

Berzins¹

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Seasonal patterns in reproductive success of temperate‐breeding birds: Experimental tests of the date and quality hypotheses

Harriman

Dawson

Bortolotti

et al. 2017

Ecology and Evolution

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For organisms in seasonal environments, individuals that breed earlier in the season regularly attain higher fitness than their late‐breeding counterparts. Two primary hypotheses have been proposed to explain these patterns: The quality hypothesis contends that early breeders are of better phenotypic quality or breed on higher quality territories, whereas the date hypothesis predicts that seasonally declining reproductive success is a response to a seasonal deterioration in environmental quality. In birds, food availability is thought to drive deteriorating environmental conditions, but few experimental studies have demonstrated its importance while also controlling for parental quality. We tested predictions of the date hypothesis in tree swallows (Tachycineta bicolor) over two breeding seasons and in two locations within their breeding range in Canada. Nests were paired by clutch initiation date to control for parental quality, and we delayed the hatching date of one nest within each pair. Subsequently, brood sizes were manipulated to mimic changes in per capita food abundance, and we examined the effects of manipulations, as well as indices of environmental and parental quality, on nestling quality, fledging success, and return rates. Reduced reproductive success of late‐breeding individuals was causally related to a seasonal decline in environmental quality. Declining insect biomass and enlarged brood sizes resulted in nestlings that were lighter, in poorer body condition, structurally smaller, had shorter and slower growing flight feathers and were less likely to survive to fledge. Our results provide evidence for the importance of food resources in mediating seasonal declines in offspring quality and survival.

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Social signal manipulation and environmental challenges have independent effects on physiology, internal microbiome, and reproductive performance in tree swallows (Tachycineta bicolor)

et al. 2023

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The social environment that individuals experience appears to be a particularly salient mediator of stress resilience, as the nature and valence of social interactions are often related to subsequent health, physiology, microbiota, and overall stress resilience. Relatively few studies have simultaneously manipulated the social environment and ecological challenges under natural conditions. Here, we report the results of experiments in wild tree swallows (Tachycineta bicolor) in which we manipulated both ecological challenges (predator encounters and flight efficiency reduction) and social interactions (by experimental dulling of a social signal). In two experiments conducted in separate years, we reversed the order of these treatments so that females experienced either an altered social signal followed by a challenge or vice‐versa. Before, during, and after treatments were applied, we tracked breeding success, morphology and physiology (mass, corticosterone, and glucose), nest box visits via an RFID sensor network, cloacal microbiome diversity, and fledging success. Overall, we found that predator exposure during the nestling period reduced the likelihood of fledging and that signal manipulation sometimes altered nest box visitation patterns, but little evidence that the two categories of treatment interacted with each other. We discuss the implications of our results for understanding what types of challenges and what conditions are most likely to result in interactions between the social environment and ecological challenges.

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Experimentally altered plumage brightness of female tree swallows: a test of the differential allocation hypothesis

Cited by 27 publications

References 73 publications

Determinants of making success in female Tree Swallows (Tachycineta Bicolor)

Determinants of making success in female Tree Swallows (Tachycineta Bicolor)

Seasonal patterns in reproductive success of temperate‐breeding birds: Experimental tests of the date and quality hypotheses

Social signal manipulation and environmental challenges have independent effects on physiology, internal microbiome, and reproductive performance in tree swallows (Tachycineta bicolor)

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