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García-Campa J, Müller W, Rodríguez-Juncá A, Morales J. When parents play favorites: brood demand shapes parental preference for offspring UV color. Behav Ecol 2023; 34:700-707. [PMID: 38192276 PMCID: PMC10773300 DOI: 10.1093/beheco/arad040] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 03/01/2023] [Accepted: 04/27/2023] [Indexed: 01/10/2024] Open
Abstract
Parents might initially produce more offspring than they might be able to raise. However, when offspring demand exceeds their parents´ rearing capacity, parents might shift care towards the offspring which yield greater fitness returns to achieve their optimal brood size via brood reduction. Such favoritism could rely on offspring signaling traits if these inform parents about offspring quality and hence about the pay-offs of their investment. Here we investigated whether favoritism of blue tit (Cyanistes caeruleus) parents for an offspring signal (i.e., ultraviolet (UV) plumage coloration) varies with brood demand. To test this, we experimentally blocked the UV reflectance of yellow breast feathers in half of the nestlings of each brood, and then we sequentially performed two opposing brood size manipulations to vary nestling demand below or above parental rearing capacity. In reduced broods, nestlings begged overall less intensely and gained more body mass, supporting that parental rearing capacities sufficed to satisfy brood demand. Moreover, in reduced broods, UV-blocked nestlings (i.e., low-quality offspring) were fed and prey-tested more often. Yet, they begged more than control nestlings, suggesting that they were perhaps treated differently by other family members or which they may exploit parental preferences beyond actual need (at least in reduced nests). Parents flexibly shifted their feeding rate and favoritism in response to short-term changes in family size, as there was no parental preference for enlarged broods. Such flexible parental feeding rules may allow parents to gain the upper hand in parent-offspring conflict. However, we did not find evidence that parental favoritism facilitated brood reduction, at least in conditions where demand was temporally enhanced.
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Affiliation(s)
- Jorge García-Campa
- Department of Evolutionary Ecology, National Museum of Natural Sciences – Spanish National Research Council (CSIC), c/ José Gutiérrez Abascal 2, 28006 Madrid, Spain
| | - Wendt Müller
- Department of Biology, Behavioural Ecology and Ecophysiology Research Group, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium
| | - Alicia Rodríguez-Juncá
- BIOECOMAC, Department of Animal Biology, Edaphology and Geology, University of la Laguna, Tenerife, Canary Islands, Spain
| | - Judith Morales
- Department of Evolutionary Ecology, National Museum of Natural Sciences – Spanish National Research Council (CSIC), c/ José Gutiérrez Abascal 2, 28006 Madrid, Spain
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2
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Experimental evidence that adult UV/yellow colouration functions as a signal in blue tit families — but only for parents. Behav Ecol Sociobiol 2022. [DOI: 10.1007/s00265-022-03145-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Abstract
In bi-parental species, reproduction is not only a crucial life-history stage where individuals must take fitness-related decisions, but these decisions also need to be adjusted to the behavioural strategies of other individuals. Hence, communication is required, which could be facilitated by informative signals. Yet, these signalling traits might have (co-)evolved in multiple contexts, as various family members usually meet and interact during reproduction. In this study, we experimentally explored for the first time whether a colourful plumage trait in adults acts as a signal that regulates multiple intra-family interactions in a bird species, the blue tit (Cyanistes caeruleus). We expected that an experimental reduction of adults’ UV/yellow reflectance (i.e. a reduction of apparent individual quality) should affect the behavioural strategies of all family members. We found evidence for this at least in adults, since the partners of UV-blocked individuals (either males or females) increased their parental investment — perhaps to compensate for the apparent lower condition of their mates. As the UV-blocked adult did not change its provisioning behaviour, the partner presumably responded to the manipulated signal and not to a behavioural change. However, the offspring did not co-adjust their begging intensity to the experimental treatment. It is thus possible that they responded to overall parental care rather than the signal. These results suggest that UV/yellow colouration of adult blue tits may act as quality signal revealing the rearing capacity to mates.
Significance statement
How parents respond to signals of genetic or phenotypic quality of their mates has received significant attention. However, previous studies have primarily focused on the receiver’s response and have not always controlled for the signaller’s behaviour and its investment in reproduction. Our results provide the first experimental evidence that ultraviolet (UV)/yellow colouration acts as a signal of parental quality in the blue tit. Parents responded by increasing their effort when paired with UV-blocked (low-quality) mates, while controlling for the mate’s behaviour. We argue that the reduced expression of the signal triggered a compensatory response in the mate. Interestingly, both males and females responded similarly to changes in mate’s UV/yellow reflectance, suggesting similar rules over investment in response to this trait. However, nestlings, a potential (and often neglected) set of observers of parental signals, did not change their behaviour when raised by an UV-blocked (= low-quality) parent.
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3
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Griffioen M, Iserbyt A, Müller W. Turn taking is not restricted by task specialisation but does not facilitate equality in offspring provisioning. Sci Rep 2021; 11:21884. [PMID: 34750443 PMCID: PMC8575876 DOI: 10.1038/s41598-021-01298-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 10/11/2021] [Indexed: 11/16/2022] Open
Abstract
Sexual conflict arises when two individuals invest in their common offspring because both individuals benefit when their partner invests more. Conditional cooperation is a theoretical concept that could resolve this conflict. Here, parents are thought to motivate each other to contribute to provisioning visits by following the rules of turn taking, which results in equal and efficient investment. However, parents have other tasks besides provisioning, which might hinder taking turns. To investigate restrictions by other care tasks and whether turn taking can be used to match investment, we manipulated brooding duration in female blue tits (Cyanistes caeruleus) during the early nestling phase by changing nest box temperature. As expected, females subjected to cold conditions brooded longer than females under warm conditions. Yet, contrary to our prediction, females had similar visit rates in both treatments, which suggests that females in the cold treatment invested more overall. In addition, the females' turn taking level was higher in the more demanding cold condition (and the calculated randomised turn taking levels of females did not differ), hence females don't seem to be restricted in their turn taking strategy by other care tasks. However, males did not seem to match the females' turn taking levels because they did not adjust their visit rates. Thus, level of turn taking was not restricted by an other sex-specific task in females and did not facilitate a greater investment by their male partners.
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Affiliation(s)
- Maaike Griffioen
- Department of Biology, Behavioural Ecology and Ecophysiology Research Group, University of Antwerp, Wilrijk, Belgium.
| | - Arne Iserbyt
- grid.5284.b0000 0001 0790 3681Department of Biology, Behavioural Ecology and Ecophysiology Research Group, University of Antwerp, Wilrijk, Belgium
| | - Wendt Müller
- grid.5284.b0000 0001 0790 3681Department of Biology, Behavioural Ecology and Ecophysiology Research Group, University of Antwerp, Wilrijk, Belgium
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4
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Ferrer ES, Uribe F, Sanz JJ, Senar JC. Are plumage colour and song redundant ornaments in great tits ( Parus major)? It depends on the colour. Biol J Linn Soc Lond 2021. [DOI: 10.1093/biolinnean/blab063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Abstract
According to current theory, the development of different conspicuous ornaments may provide multiple, redundant or unreliable information. However, multiple visual and acoustic traits have not often been tested at the same time. In this study, we analyse whether black tie size, yellow breast colour indexes (chroma and hue) and song parameters (repertoire size, strophe length, maximum and minimum frequency) are inter-correlated in male great tits (Parus major). We found that males with larger black ties sang greater repertoires and had higher song frequencies, providing redundant information. However, song parameters did not correlate with hue and chroma of the yellow breast coloration, supporting the idea that they convey different units of information. Results therefore stress that since different plumaged patches can transmit very different units of information, bird song will correlate to plumage coloration traits depending on the patch and the colour considered, an aspect rarely taken into account in previous studies relating song to plumage colour traits.
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Affiliation(s)
- Esperanza S Ferrer
- Department of Evolutionary Ecology, National Museum of Natural Sciences (MNCN-CSIC), CalleJosé Gutiérrez Abascal 2, 28006 Madrid, Spain
| | - Francesc Uribe
- Evolutionary and Behavioural Ecology Unit, Museu de Ciències Naturals de Barcelona, P.Picasso s/n, Parc Ciutadella, 08003 Barcelona, Spain
| | - Juan José Sanz
- Department of Evolutionary Ecology, National Museum of Natural Sciences (MNCN-CSIC), CalleJosé Gutiérrez Abascal 2, 28006 Madrid, Spain
| | - Joan Carles Senar
- Evolutionary and Behavioural Ecology Unit, Museu de Ciències Naturals de Barcelona, P.Picasso s/n, Parc Ciutadella, 08003 Barcelona, Spain
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5
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Caro SP, Pierre L, Bergès M, Bakker R, Doutrelant C, Bonadonna F. Mutual mate preferences and assortative mating in relation to a carotenoid-based color trait in blue tits. Behav Ecol 2021. [DOI: 10.1093/beheco/arab080] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Choosing an appropriate sexual partner is a critical decision for many animal species. However, many mechanisms involved in mate choice are still poorly understood. Do both males and females choose their sexual partners, do both sexes use the same criteria for choosing, and do their own phenotype influence the choices they make, are questions that need further investigation. Over two successive experiments conducted in captivity with hand-reared blue tits (Cyanistes caeruleus), we manipulated the color of the chest plumage, a secondary sexual trait that reflects an individual’s condition, to create two different color morphs (one pale and one colored). We then tested whether both sexes express a preference, whether they are attracted to the same morphs, and if the subjects’ own chest color influences the preference they show. Our data reveal that both sexes are choosy, with females tending to be slightly choosier than males. We also show that both sexes preferentially select individuals with a pale chest plumage over colorful individuals, and this was again more pronounced in females. Finally, paler individuals tend to be selected by birds that are themselves pale, even if this phenotype matching was not very robust. Such a preference for paler individuals is intriguing because mates are predicted to associate with individuals displaying higher, not lower, value of quality signals. It could result from adaptive mechanisms related to avoidance of aggressiveness in a confined environment, avoidance of conflicting sexual signals within individuals, or from cultural mechanisms leading to a preference for individuals that match its own phenotype.
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Affiliation(s)
- Samuel P Caro
- Department of Behavioural and Evolutionary Ecology, CEFE, Univ Montpellier, CNRS, EPHE, IRD, 1919 route de Mende, 34090 Montpellier, France
- Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Droevendaalsesteeg 10, 6708 PB Wageningen, The Netherlands
| | - Léo Pierre
- Department of Behavioural and Evolutionary Ecology, CEFE, Univ Montpellier, CNRS, EPHE, IRD, 1919 route de Mende, 34090 Montpellier, France
| | - Matthieu Bergès
- Department of Behavioural and Evolutionary Ecology, CEFE, Univ Montpellier, CNRS, EPHE, IRD, 1919 route de Mende, 34090 Montpellier, France
| | - Raldi Bakker
- Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Droevendaalsesteeg 10, 6708 PB Wageningen, The Netherlands
- Department of Animal Science, Behavioural Ecology Group, Wageningen University and Research (WUR), De Elst 1, 6708 WD Wageningen, The Netherlands
| | - Claire Doutrelant
- Department of Behavioural and Evolutionary Ecology, CEFE, Univ Montpellier, CNRS, EPHE, IRD, 1919 route de Mende, 34090 Montpellier, France
| | - Francesco Bonadonna
- Department of Behavioural and Evolutionary Ecology, CEFE, Univ Montpellier, CNRS, EPHE, IRD, 1919 route de Mende, 34090 Montpellier, France
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6
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Badás EP, Autor A, Martínez J, Rivero-de Aguilar J, Merino S. Individual Quality and Extra-Pair Paternity in the Blue Tit: Sexy Males Bear the Costs. Evolution 2020; 74:559-572. [PMID: 31944288 DOI: 10.1111/evo.13925] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 01/07/2020] [Indexed: 01/16/2023]
Abstract
Adaptive explanations for the evolution of extra-pair paternity (EPP) suggest that females seek extra-pair copulations with high quality males. Still, the link between ornamentation, individual quality, and paternity remains unclear. Moreover, honest signaling is essential when explaining EPP because it is needed for sexual selection to occur; yet, it is understudied in multiple ornaments. Because blue tits (Cyanistes caeruleus) show variable color expression in several plumage patches, we tested: (i) over two seasons, whether males in better condition, more ornamented and less infected by blood parasites gain EPP and have higher reproductive success, and (ii) over three seasons, whether mating patterns affect color change. Males with more saturated yellow feathers, brighter tails, and in better condition had higher reproductive success in one of the seasons. Contrary to expectation, in another season, males that gained EPP were parasitized by blood parasites, suggesting increased vector exposure during extra-pair copulations. Our results for two seasons show that males siring more extra-pair young were older and grew brighter cheek or tail feathers for the following season. Despite the increased mating costs, in socially monogamous avian systems, high quality males incur in EPP without compromising traits that may be under sexual selection.
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Affiliation(s)
- Elisa P Badás
- Department of Evolutionary Ecology, National Museum of Natural Sciences, CSIC, Jose Gutierrez Abascal 2, 28006, Madrid, Spain.,School of Biology, The Faculty of Biological Sciences, University of Leeds, LS2 9JT, Leeds, UK
| | - Amaia Autor
- Department of Evolutionary Ecology, National Museum of Natural Sciences, CSIC, Jose Gutierrez Abascal 2, 28006, Madrid, Spain
| | - Javier Martínez
- Department of Biomedicine and Biotechnology (Area of Parasitology), University of Alcalá de Henares, Autovia A2, 28805, Alcalá de Henares, Madrid, Spain
| | - Juan Rivero-de Aguilar
- Institute of Ecology and Biodiversity, Department of Ecological Sciences, Faculty of Sciences, University of Chile, Las Palmeras 3425, Santiago, Chile
| | - Santiago Merino
- Department of Evolutionary Ecology, National Museum of Natural Sciences, CSIC, Jose Gutierrez Abascal 2, 28006, Madrid, Spain
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7
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Leclaire S, Bourret V, Pineaux M, Blanchard P, Danchin E, Hatch SA. Red coloration varies with dietary carotenoid access and nutritional condition in kittiwakes. ACTA ACUST UNITED AC 2019; 222:jeb.210237. [PMID: 31597729 DOI: 10.1242/jeb.210237] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 10/04/2019] [Indexed: 12/21/2022]
Abstract
Carotenoid-based ornaments are common signaling features in animals. Although the mechanisms that link color-based signals to individual condition is key to understanding the evolution and function of these ornaments, they are most often poorly known. Several hypotheses have been posited. They include: (i) the role of foraging abilities on carotenoid acquisition and thereby carotenoid-based ornaments, and (ii) the role of internal processes linked to individual quality on the allocation and conversion of carotenoids in integuments. Here, we tested the influence of dietary carotenoid access versus internal process on gape coloration in black-legged kittiwakes (Rissa tridactyla). This seabird displays a vibrant red gape, whose coloration varies with individual quality in males and is due to the deposition of red ketocarotenoids, such as astaxanthin. We decreased hydroxycarotenoid and ketocarotenoid levels in plasma, but increased efficiency in internal processes linked to nutritional condition, by supplementing breeding males with capelin, a natural energy-rich fish prey. We found that, despite having lower carotenoid levels in plasma, supplemented birds developed redder coloration than control birds, but only in the year when dietary levels of astaxanthin in the natural diet were low. In contrast, in the astaxanthin-rich year, supplemented males had a less-red gape than unsupplemented birds. These results suggest that inter-individual differences in internal processes may be sufficient to maintain the honesty of gape coloration under conditions of low dietary astaxanthin levels. Nonetheless, when inter-individual variations in dietary astaxanthin levels are elevated (such as in the crustacean-rich year), carotenoid access seems a more limiting factor to the expression of gape coloration than internal processes. Therefore, our study revealed a complex mechanism of gape color production in kittiwakes, and suggests that the main factor maintaining the condition dependency of this ornaments may vary with environmental conditions and diet composition.
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Affiliation(s)
- Sarah Leclaire
- Laboratoire Évolution et Diversité Biologique, UMR5174 (CNRS, Université Paul Sabatier), 118 route de Narbonne, 31062 Toulouse, France
| | - Vincent Bourret
- Cambridge Infectious Diseases Consortium, Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB30ES, UK
| | - Maxime Pineaux
- Laboratoire Évolution et Diversité Biologique, UMR5174 (CNRS, Université Paul Sabatier), 118 route de Narbonne, 31062 Toulouse, France
| | - Pierrick Blanchard
- Laboratoire Évolution et Diversité Biologique, UMR5174 (CNRS, Université Paul Sabatier), 118 route de Narbonne, 31062 Toulouse, France
| | - Etienne Danchin
- Laboratoire Évolution et Diversité Biologique, UMR5174 (CNRS, Université Paul Sabatier), 118 route de Narbonne, 31062 Toulouse, France
| | - Scott A Hatch
- Institute for Seabird Research and Conservation, 12850 Mountain Place, Anchorage, AK 99516, USA
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8
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Bruinjé AC, Coelho FEA, Paiva TMA, Costa GC. Aggression, color signaling, and performance of the male color morphs of a Brazilian lizard (Tropidurus semitaeniatus). Behav Ecol Sociobiol 2019. [DOI: 10.1007/s00265-019-2673-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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9
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Pagani-Núñez E, Barnett CRA, Senar JC. Age and sex differences in niche use at molt and its effect on plumage coloration characteristics in a bird. Curr Zool 2018; 65:251-260. [PMID: 31263483 PMCID: PMC6595419 DOI: 10.1093/cz/zoy062] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 07/17/2018] [Indexed: 01/16/2023] Open
Abstract
Bird plumage is often very colorful and can communicate the quality of the bearer to conspecifics. These plumage-based signals of quality are composed of multiple pigments (e.g., melanin and carotenoids). Therefore, sex and age classes, which often show marked differences in plumage coloration, may have different dietary needs for the different plumage components and this might promote preferences for different dietary niches at different molting stages. However, no study has addressed the role that changes in niche use play in the expression of multiple component plumage signals in birds. We used stable isotope analysis to test the hypothesis that niche use is related to age and sex and to differently cultured plumage patches, yellow carotenoid-based and black melanin-based, in great tits Parus major. We recorded high niche overlap between plumage patches, although δ15N was higher in black than yellow plumage. Niche overlap was relatively low for age classes and relatively high for sex classes, and age classes showed a contrasting pattern of niche overlap between carotenoid- and melanin-based plumages. Moreover, δ13C, but not δ15N, had a significant negative relationship with carotenoid-based plumage, which was only apparent in juveniles. Taken together, our results demonstrate that niche use had a moderate influence on plumage coloration characteristics of great tit individuals, mostly associated with δ13C rather than with δ15N and with age rather than with sex. Therefore, our study is significant because it confirms the relevance of niche use during ornament production in free-living birds.
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Affiliation(s)
- Emilio Pagani-Núñez
- State Key Laboratory of Biocontrol, Department of Ecology/School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Craig R A Barnett
- Department of Zoology, Graduate School of Science, University of Kyoto, Kitashirakawa-oiwake-cho, Sakio-ku, Kyoto, Japan
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10
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Laczi M, Kötél D, Török J, Hegyi G. Mutual plumage ornamentation and biparental care: consequences for success in different environments. Behav Ecol 2017. [DOI: 10.1093/beheco/arx099] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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11
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Sexual and non-sexual social preferences in male and female white-eyed bulbuls. Sci Rep 2017; 7:5847. [PMID: 28724892 PMCID: PMC5517633 DOI: 10.1038/s41598-017-06239-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 06/12/2017] [Indexed: 11/22/2022] Open
Abstract
While the function of ornaments shaped by sexual selection is to attract mates or drive off rivals, these signals may also evolve through social selection, in which the social context affects the fitness of signallers and receivers. Classical ‘mate choice’ experiments often reveal preferences for ornaments, but few studies have considered whether these are strictly sexual or reflect general social preferences. Indeed, an alternative possibility is that ornaments evolve through ‘non-sexual social selection’ (hereafter ‘social selection’). We examined the role of ornamentation (yellow ventral patch) and familiarity (individuals recognize group mates with which they have had previous interactions) on mate choice (opposite-sex stimuli preference) and social choice (same-sex stimuli preference) in both male and female white-eyed bulbuls (Pycnonotus xanthopygos). In the mate choice test, females preferred unfamiliar males with increased yellow. There were no biologically important differences in male preferences based on familiarity or intensity of patch colour. In the social choice test, females preferred to associate with familiar females. Males preferred to associate with familiar males but also preferred to associate with less ornamented males. Our results suggest that ornamentation and familiarity are important features, playing different roles in males and females, in both social and sexual selection processes.
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12
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13
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Pagani-Núñez E, Renom M, Mateos-Gonzalez F, Cotín J, Senar JC. The diet of great tit nestlings: Comparing observation records and stable isotope analyses. Basic Appl Ecol 2017. [DOI: 10.1016/j.baae.2016.11.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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14
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Colour ornamentation in the blue tit: quantitative genetic (co)variances across sexes. Heredity (Edinb) 2016; 118:125-134. [PMID: 27577691 PMCID: PMC5234477 DOI: 10.1038/hdy.2016.70] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 07/08/2016] [Accepted: 07/15/2016] [Indexed: 02/03/2023] Open
Abstract
Although secondary sexual traits are commonly more developed in males than females, in many animal species females also display elaborate ornaments or weaponry. Indirect selection on correlated traits in males and/or direct sexual or social selection in females are hypothesized to drive the evolution and maintenance of female ornaments. Yet, the relative roles of these evolutionary processes remain unidentified, because little is known about the genetic correlation that might exist between the ornaments of both sexes, and few estimates of sex-specific autosomal or sex-linked genetic variances are available. In this study, we used two wild blue tit populations with 9 years of measurements on two colour ornaments: one structurally based (blue crown) and one carotenoid based (yellow chest). We found significant autosomal heritability for the chromatic part of the structurally based colouration in both sexes, whereas carotenoid chroma was heritable only in males, and the achromatic part of both colour patches was mostly non heritable. Power limitations, which are probably common among most data sets collected so far in wild populations, prevented estimation of sex-linked genetic variance. Bivariate analyses revealed very strong cross-sex genetic correlations in all heritable traits, although the strength of these correlations was not related to the level of sexual dimorphism. In total, our results suggest that males and females share a majority of their genetic variation underlying colour ornamentation, and hence the evolution of these sex-specific traits may depend greatly on correlated responses to selection in the opposite sex.
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15
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Lucass C, Iserbyt A, Eens M, Müller W. Structural (UV) and carotenoid-based plumage coloration - signals for parental investment? Ecol Evol 2016; 6:3269-79. [PMID: 27252832 PMCID: PMC4870211 DOI: 10.1002/ece3.2107] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 02/29/2016] [Accepted: 03/13/2016] [Indexed: 11/11/2022] Open
Abstract
Parental care increases parental fitness through improved offspring condition and survival but comes at a cost for the caretaker(s). To increase life-time fitness, caring parents are, therefore, expected to adjust their reproductive investment to current environmental conditions and parental capacities. The latter is thought to be signaled via ornamental traits of the bearer. We here investigated whether pre- and/or posthatching investment of blue tit (Cyanistes caeruleus) parents was related to ornamental plumage traits (UV crown coloration and carotenoid-based plumage coloration) expressed by either the individual itself (i.e. "good parent hypothesis") or its partner (i.e. "differential allocation hypothesis"). Our results show that neither prehatching (that is clutch size and offspring begging intensity) nor posthatching parental investment (provisioning rate, offspring body condition at fledging) was related to an individual's UV crown coloration or to that of its partner. Similar observations were made for carotenoid-based plumage coloration, except for a consistent positive relationship between offspring begging intensity and maternal carotenoid-based plumage coloration. This sex-specific pattern likely reflects a maternal effect mediated via maternally derived egg substances, given that the relationship persisted when offspring were cross-fostered. This suggests that females adjust their offspring's phenotype toward own phenotype, which may facilitate in particular mother-offspring co-adaptation. Overall, our results contribute to the current state of evidence that structural or pigment-based plumage coloration of blue tits are inconsistently correlated with central life-history traits.
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Affiliation(s)
- Carsten Lucass
- Department of Biology, Behavioural Ecology and Ecophysiology Group University of Antwerp Universiteitsplein 1 2610 Antwerp Wilrijk Belgium
| | - Arne Iserbyt
- Department of Biology, Behavioural Ecology and Ecophysiology Group University of Antwerp Universiteitsplein 1 2610 Antwerp Wilrijk Belgium
| | - Marcel Eens
- Department of Biology, Behavioural Ecology and Ecophysiology Group University of Antwerp Universiteitsplein 1 2610 Antwerp Wilrijk Belgium
| | - Wendt Müller
- Department of Biology, Behavioural Ecology and Ecophysiology Group University of Antwerp Universiteitsplein 1 2610 Antwerp Wilrijk Belgium
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16
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Berzins LL, Dawson RD. Experimentally altered plumage brightness of female tree swallows: a test of the differential allocation hypothesis. BEHAVIOUR 2016. [DOI: 10.1163/1568539x-00003354] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The differential allocation hypothesis posits that individuals should invest in the current reproductive attempt according to the attractiveness of their mate, but studies of allocation by males when female traits are manipulated to be more attractive are lacking. In the current study, we experimentally enhanced and reduced the plumage brightness of female tree swallows (Tachycineta bicolor) relative to controls to examine whether males adjust investment in parental care according to female attractiveness, while simultaneously performing a brood size manipulation. Contrary to our predictions, we found no evidence that males provisioned nestlings according to the plumage brightness of females. However, we found that nestling quality and fledging success were lowest when female plumage brightness was reduced and brood size was enlarged. This may be due to the plumage brightness treatment influencing agonistic interactions with other females, and may suggest that plumage brightness is a signal assessed by females.
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Affiliation(s)
- Lisha L. Berzins
- Ecosystem Science and Management, University of Northern British Columbia, 3333 University Way, Prince George, BC, Canada V2N 4Z9
| | - Russell D. Dawson
- Ecosystem Science and Management, University of Northern British Columbia, 3333 University Way, Prince George, BC, Canada V2N 4Z9
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Ferrer ES, García-Navas V, Bueno-Enciso J, Barrientos R, Serrano-Davies E, Cáliz-Campal C, Sanz JJ, Ortego J. The influence of landscape configuration and environment on population genetic structure in a sedentary passerine: insights from loci located in different genomic regions. J Evol Biol 2015; 29:205-19. [DOI: 10.1111/jeb.12776] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Revised: 10/07/2015] [Accepted: 10/12/2015] [Indexed: 11/29/2022]
Affiliation(s)
- E. S. Ferrer
- Grupo de Investigación de la Biodiversidad Genética y Cultural; Instituto de Investigación en Recursos Cinegéticos (CSIC-UCLM-JCCM); Ciudad Real Spain
- Departamento de Ciencias Ambientales; Facultad de Ciencias Ambientales y Bioquímica; Universidad de Castilla-La Mancha; Toledo Spain
| | - V. García-Navas
- Grupo de Investigación de la Biodiversidad Genética y Cultural; Instituto de Investigación en Recursos Cinegéticos (CSIC-UCLM-JCCM); Ciudad Real Spain
- Departamento de Ciencias Ambientales; Facultad de Ciencias Ambientales y Bioquímica; Universidad de Castilla-La Mancha; Toledo Spain
- Institute of Evolutionary Biology and Environmental Studies; University of Zurich; Zurich Switzerland
| | - J. Bueno-Enciso
- Departamento de Ciencias Ambientales; Facultad de Ciencias Ambientales y Bioquímica; Universidad de Castilla-La Mancha; Toledo Spain
| | - R. Barrientos
- Departamento de Ciencias Ambientales; Facultad de Ciencias Ambientales y Bioquímica; Universidad de Castilla-La Mancha; Toledo Spain
| | - E. Serrano-Davies
- Departamento de Ciencias Ambientales; Facultad de Ciencias Ambientales y Bioquímica; Universidad de Castilla-La Mancha; Toledo Spain
| | - C. Cáliz-Campal
- Grupo de Investigación de la Biodiversidad Genética y Cultural; Instituto de Investigación en Recursos Cinegéticos (CSIC-UCLM-JCCM); Ciudad Real Spain
- Department of Integrative Ecology; Estación Biológica de Doñana (EBD-CSIC); Seville Spain
| | - J. J. Sanz
- Departamento de Ecología Evolutiva; Museo Nacional de Ciencias Naturales (CSIC); Madrid Spain
| | - J. Ortego
- Department of Integrative Ecology; Estación Biológica de Doñana (EBD-CSIC); Seville Spain
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18
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Hegyi G, Kötél D, Laczi M. Direct benefits of mate choice: a meta-analysis of plumage colour and offspring feeding rates in birds. Naturwissenschaften 2015; 102:62. [DOI: 10.1007/s00114-015-1311-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 08/30/2015] [Accepted: 09/04/2015] [Indexed: 10/23/2022]
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19
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Lucass C, Korsten P, Eens M, Müller W. Within‐family parent–offspring co‐adaptation in a wild bird: on static traits, behavioural reaction norms, and sex differences. Funct Ecol 2015. [DOI: 10.1111/1365-2435.12492] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Carsten Lucass
- Department of Biology‐Ethology University of Antwerp Universiteitsplein 1 2610 Antwerp Wilrijk Belgium
| | - Peter Korsten
- Behavioural Ecology and Self‐Organization group Centre for Ecological and Evolutionary Studies University of Groningen Nijenborgh 7 9747 AG Groningen The Netherlands
- Department of Animal Behaviour Bielefeld University PO Box 10 01 3133501 Bielefeld Germany
| | - Marcel Eens
- Department of Biology‐Ethology University of Antwerp Universiteitsplein 1 2610 Antwerp Wilrijk Belgium
| | - Wendt Müller
- Department of Biology‐Ethology University of Antwerp Universiteitsplein 1 2610 Antwerp Wilrijk Belgium
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20
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Pagani-Núñez E, Valls M, Senar JC. Diet specialization in a generalist population: the case of breeding great tits Parus major in the Mediterranean area. Oecologia 2015; 179:629-40. [PMID: 25983114 DOI: 10.1007/s00442-015-3334-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 04/26/2015] [Indexed: 11/29/2022]
Abstract
The analysis of diet specialization provides key information on how different individuals deal with similar food and habitat constraints within populations. Characterizing parental diet specialization at the moment of breeding, and the consistency of these preferences under different levels of effort, may help us to understand why parents exploit alternative resources. We investigated these questions in a species commonly considered a generalist: a breeding population of Mediterranean great tits Parus major. Our aim was to determine whether they are specialists or generalists at the pair level, and the consistency of this behaviour under different levels of effort. Using proportional similarity and mean pairwise overlap indices, we found that parents showed great variability in prey selection between territories. That is, they displayed a small niche overlap. Interestingly, the most specialized breeding pairs showed a tendency to have larger broods. Additionally, we experimentally manipulated brood size and found that parents showed high short-term consistency in their foraging behaviour. They precisely adjusted the number of provisioning trips to the number of nestlings, while they were unable to modify prey proportions or prey size after brood size was changed. We can therefore characterize their foraging strategies as highly consistent. Our results suggest that although the great tit may be considered a generalist at the species or population level, there was a tendency for trophic specialization among breeding pairs. This high inter- and intrapopulation plasticity could account for their great success and wide distribution.
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Affiliation(s)
- E Pagani-Núñez
- Evolutionary Ecology Associate Research Unit (CSIC), Natural History Museum of Barcelona, Psg. Picasso s/n., 08003, Barcelona, Spain. .,Behavioral and Community Ecology, Conservation Biology Group, College of Forestry, Guangxi University, No. 100 Daxue Road, Nanning, 530005, Guangxi, People's Republic of China.
| | - M Valls
- Evolutionary Ecology Associate Research Unit (CSIC), Natural History Museum of Barcelona, Psg. Picasso s/n., 08003, Barcelona, Spain
| | - J C Senar
- Evolutionary Ecology Associate Research Unit (CSIC), Natural History Museum of Barcelona, Psg. Picasso s/n., 08003, Barcelona, Spain
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21
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Ferrer ES, García-Navas V, Bueno-Enciso J, Sanz JJ, Ortego J. Multiple sexual ornaments signal heterozygosity in male blue tits. Biol J Linn Soc Lond 2015. [DOI: 10.1111/bij.12513] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Esperanza S. Ferrer
- Departamento de Ciencias Ambientales; Facultad de Ciencias Ambientales y Bioquímica; Universidad de Castilla-La Mancha; Avda. Carlos III s/n 45071 Toledo Spain
- Grupo de Investigación de la Biodiversidad Genética y Cultural; Instituto de Investigación en Recursos Cinegéticos IREC (CSIC-UCLM-JCCM); Ronda de Toledo s/n 13071 Ciudad Real Spain
| | - Vicente García-Navas
- Departamento de Ciencias Ambientales; Facultad de Ciencias Ambientales y Bioquímica; Universidad de Castilla-La Mancha; Avda. Carlos III s/n 45071 Toledo Spain
- Grupo de Investigación de la Biodiversidad Genética y Cultural; Instituto de Investigación en Recursos Cinegéticos IREC (CSIC-UCLM-JCCM); Ronda de Toledo s/n 13071 Ciudad Real Spain
- Evolution and Genetics of Love, Life and Death Group; Institute of Evolutionary Biology and Environmental Studies; University of Zurich; Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Javier Bueno-Enciso
- Departamento de Ciencias Ambientales; Facultad de Ciencias Ambientales y Bioquímica; Universidad de Castilla-La Mancha; Avda. Carlos III s/n 45071 Toledo Spain
| | - Juan José Sanz
- Departamento de Ecología Evolutiva; Museo Nacional de Ciencias Naturales (CSIC); C/ José Gutiérrez Abascal 2 28006 Madrid Spain
| | - Joaquín Ortego
- Conservation and Evolutionary Genetics Group; Department of Integrative Ecology; Estación Biológica de Doñana (EBD-CSIC); Avda. Américo Vespucio s/n 41092 Seville Spain
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22
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Beck ML, Hopkins WA, Hawley DM. Relationships among plumage coloration, blood selenium concentrations, and immune responses of adult and nestling tree swallows. J Exp Biol 2015; 218:3415-24. [DOI: 10.1242/jeb.123794] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 08/26/2015] [Indexed: 12/18/2022]
Abstract
In a number of taxa, males and females both display ornaments that may be associated with individual quality and could be reliable signals to potential mates or rivals. We examined the iridescent blue/green back and white breast of adult tree swallows (Tachycineta bicolor) to determine if plumage reflectance was related to adult or offspring immune responses. We simultaneously addressed the influence of blood selenium levels and the interaction between blood selenium and plumage coloration on adult and nestling immunity. Selenium is a well-known antioxidant necessary for mounting a robust immune response but its importance in wild birds remains poorly understood. In females, the brightness of white breast coloration was positively associated with bactericidal capacity, but there was no association with blood selenium. In contrast, male bactericidal capacity was associated with an interactive effect between dorsal plumage coloration and blood selenium concentrations. Males with bluer hues and greater blue chroma showed increased bactericidal capacity as blood selenium concentrations increased, while bactericidal capacity declined in greener males at higher blood selenium concentrations. In nestlings, bactericidal capacity was positively associated with nestling blood selenium concentrations and white brightness of both social parents. These results suggest that white plumage reflectance is indicative of quality in tree swallows and that greater attention should be paid to the reflectance of large white plumage patches. Additionally, the role of micronutrients, such as selenium, in mediating relationships between physiology and signals of quality, should be explored further.
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Affiliation(s)
- Michelle L. Beck
- 106 Cheatham Hall, Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA 24061-0321, USA
| | - William A. Hopkins
- 106 Cheatham Hall, Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA 24061-0321, USA
| | - Dana M. Hawley
- 2125 Derring Hall, Department of Biology, Virginia Tech, Blacksburg, VA 24061-0406, USA
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23
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Montoya B, Torres R. Male skin color signals direct and indirect benefits in a species with biparental care. Behav Ecol 2014. [DOI: 10.1093/beheco/aru204] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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24
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Grunst ML, Grunst AS, Parker CE, Romero LM, Rotenberry JT. Pigment-specific relationships between feather corticosterone concentrations and sexual coloration. Behav Ecol 2014. [DOI: 10.1093/beheco/aru210] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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25
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Pagani-Núñez E, Uribe F, Hernández-Gómez S, Muñoz G, Senar JC. Habitat structure and prey composition generate contrasting effects on carotenoid-based coloration of great titParus majornestlings. Biol J Linn Soc Lond 2014. [DOI: 10.1111/bij.12352] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Emilio Pagani-Núñez
- Evolutionary Ecology Associate Research Unit (CSIC); Natural History Museum of Barcelona; Psg. Picasso s/n. 08003 Barcelona España (Spain)
| | - Francesc Uribe
- Evolutionary Ecology Associate Research Unit (CSIC); Natural History Museum of Barcelona; Psg. Picasso s/n. 08003 Barcelona España (Spain)
| | - Sergio Hernández-Gómez
- Evolutionary Ecology Associate Research Unit (CSIC); Natural History Museum of Barcelona; Psg. Picasso s/n. 08003 Barcelona España (Spain)
| | - Guillermo Muñoz
- Evolutionary Ecology Associate Research Unit (CSIC); Natural History Museum of Barcelona; Psg. Picasso s/n. 08003 Barcelona España (Spain)
| | - Juan Carlos Senar
- Evolutionary Ecology Associate Research Unit (CSIC); Natural History Museum of Barcelona; Psg. Picasso s/n. 08003 Barcelona España (Spain)
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26
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Pagani-Núñez E, Senar JC. Are colorful males of great tits Parus major better parents? Parental investment is a matter of quality. ACTA OECOLOGICA-INTERNATIONAL JOURNAL OF ECOLOGY 2014. [DOI: 10.1016/j.actao.2013.11.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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27
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Leitão AV, Monteiro AH, Mota PG. Ultraviolet reflectance influences female preference for colourful males in the European serin. Behav Ecol Sociobiol 2013. [DOI: 10.1007/s00265-013-1623-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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28
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Roulin A, Ducrest AL. Genetics of colouration in birds. Semin Cell Dev Biol 2013; 24:594-608. [PMID: 23665152 DOI: 10.1016/j.semcdb.2013.05.005] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2012] [Revised: 04/19/2013] [Accepted: 05/01/2013] [Indexed: 01/01/2023]
Abstract
Establishing the links between phenotype and genotype is of great importance for resolving key questions about the evolution, maintenance and adaptive function of phenotypic variation. Bird colouration is one of the most studied systems to investigate the role of natural and sexual selection in the evolution of phenotypic diversity. Given the recent advances in molecular tools that allow discovering genetic polymorphisms and measuring gene and protein expression levels, it is timely to review the literature on the genetics of bird colouration. The present study shows that melanin-based colour phenotypes are often associated with mutations at melanogenic genes. Differences in melanin-based colouration are caused by switches of eumelanin to pheomelanin production or by changes in feather keratin structure, melanoblast migration and differentiation, as well as melanosome structure. Similar associations with other types of colourations are difficult to establish, because our knowledge about the molecular genetics of carotenoid-based and structural colouration is quasi inexistent. This discrepancy stems from the fact that only melanin-based colouration shows pronounced heritability estimates, i.e. the resemblance between related individuals is usually mainly explained by genetic factors. In contrast, the expression of carotenoid-based colouration is phenotypically plastic with a high sensitivity to variation in environmental conditions. It therefore appears that melanin-based colour traits are prime systems to understand the genetic basis of phenotypic variation. In this context, birds have a great potential to bring us to new frontiers where many exciting discoveries will be made on the genetics of phenotypic traits, such as colouration. In this context, a major goal of our review is to suggest a number of exciting future avenues.
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Affiliation(s)
- Alexandre Roulin
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
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García-Navas V, Ortego J, Ferrer ES, Sanz JJ. Feathers, suspicions, and infidelities: an experimental study on parental care and certainty of paternity in the blue tit. Biol J Linn Soc Lond 2013. [DOI: 10.1111/bij.12079] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Vicente García-Navas
- Grupo de Investigación de la Biodiversidad Genética y Cultural; Instituto de Investigación en Recursos Cinegéticos (CSIC-UCLM-JCCM); Ronda de Toledo s/n; 13071; Ciudad Real; Spain
| | - Joaquín Ortego
- Grupo de Investigación de la Biodiversidad Genética y Cultural; Instituto de Investigación en Recursos Cinegéticos (CSIC-UCLM-JCCM); Ronda de Toledo s/n; 13071; Ciudad Real; Spain
| | - Esperanza S. Ferrer
- Grupo de Investigación de la Biodiversidad Genética y Cultural; Instituto de Investigación en Recursos Cinegéticos (CSIC-UCLM-JCCM); Ronda de Toledo s/n; 13071; Ciudad Real; Spain
| | - Juan José Sanz
- Departamento de Ecología Evolutiva; Museo Nacional de Ciencias Naturales (CSIC); Calle José Gutiérrez Abascal, 2; 28006; Madrid; Spain
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30
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Female blue tits with brighter yellow chests transfer more carotenoids to their eggs after an immune challenge. Oecologia 2013; 173:387-97. [PMID: 23512200 DOI: 10.1007/s00442-013-2617-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Accepted: 02/05/2013] [Indexed: 10/27/2022]
Abstract
Female ornaments are present in many species, and it is more and more accepted that sexual or social selection may lead to their evolution. By contrast, the information conveyed by female ornaments is less well understood. Here, we investigated the links between female ornaments and maternal effects. In birds, an important maternal effect is the transmission of resources, such as carotenoids, into egg yolk. Carotenoids are pigments with antioxidant and immunomodulatory properties that are crucial for females and developing offspring. In blue tits, we evaluated whether ultraviolet (UV)/blue and yellow feather colouration signals a female's capacity to allocate carotenoids to egg yolk. Because mounting an immune response is costly and trade-offs are more detectable under harsh conditions, we challenged the immune system of females before laying and examined the carotenoid level of their eggs afterward. A positive association between feather carotenoid chroma and egg carotenoid level would be expected if yellow colouration signals basal immunity. Alternatively, if female colouration more generally reflects maternal capacity to invest in reproduction under challenging conditions, then other components of colouration (i.e. yellow brightness and UV/blue colouration) could be linked to maternal capacity to invest in eggs. No association between egg carotenoid levels and UV/blue crown colouration or female yellow chest chroma was found; the latter result suggests that yellow colouration does not signal immune capacity at laying in this species. By contrast, we found that, among females that mounted a detectable response to the vaccine, those with brighter yellow chests transmitted more carotenoids into their eggs. This result suggests yellow brightness signals maternal capacity to invest in reproduction under challenging conditions, and that male blue tits may benefit directly from choosing brighter yellow females.
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