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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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Zúñiga-Vega JJ, Pruett JA, Ossip-Drahos AG, Campos SM, Seddon RJ, Price SL, Romero-Diaz C, Rivera JA, Vital-García C, Hews DK, Martins EP. Information out of the blue: phenotypic correlates of abdominal color patches in Sceloporus lizards. ZOOLOGY 2021; 149:125961. [PMID: 34592493 DOI: 10.1016/j.zool.2021.125961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 08/12/2021] [Accepted: 08/19/2021] [Indexed: 11/28/2022]
Abstract
Colorful ornaments are important visual signals for animal communication that can provide critical information about the quality of the signaler. In this study, we focused on different color characteristics of the abdominal patches of males of six lizard species from the genus Sceloporus. We addressed three main objectives. First, we examined if size, brightness, saturation, and conspicuousness of these ornaments are indicative of body size, condition, immune function, or levels of testosterone and corticosterone. Second, we evaluated if the distinct components of these abdominal patches (blue or green patches and black stripes) transmit similar information about the signaler, which would support the redundant signal hypothesis, or if these components are related to different phenotypic traits, which would support the multiple message hypothesis. Third, we compared the phenotypic correlates of these ornaments among our six species to understand the degree of conservatism in the signaling patterns or to find species-specific signals. Using data collected from males in natural conditions and a multi-model inference framework, we found that in most species the area of the patches and the brightness of the blue component are positively related to body size. Thus, these color characteristics are presumably indicative of the physical strength and competitive ability of males and these shared signals were likely inherited from a common ancestor. In half of the species, males in good body condition also exhibit relatively larger blue and black areas, suggesting that the expression of these ornaments is condition-dependent. Abdominal patches also provide information about immunocompetence of the males as indicated by different correlations between certain color characteristics and ectoparasite load, counts of heterophils, and the heterophil:lymphocyte ratio. Our findings reveal that area and brightness of the abdominal patches signal the size and body condition of males, whereas blue saturation and conspicuousness with respect to the surrounding substrate are indicative of immune condition, thus supporting the multiple message hypothesis. However, some of these correlations were not shared by all species and, hence, point to intriguing species-specific signals.
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Affiliation(s)
- J Jaime Zúñiga-Vega
- Departamento de Ecología y Recursos Naturales, Facultad de Ciencias, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Coyoacán, Mexico City, 04510, Mexico.
| | - Jake A Pruett
- Department of Biology, Indiana State University, Science Building Room 283, 600 North Chestnut Street, Terre Haute, IN 47809, USA; Department of Biological Sciences, Southeastern Oklahoma State University, 425 W. University Boulevard, Durant, OK 74701, USA.
| | - Alison G Ossip-Drahos
- Department of Chemistry and Physical Sciences, Marian University, 3200 Cold Springs Road, Indianapolis, IN 46222, USA.
| | - Stephanie M Campos
- Biology Department, Swarthmore College, 500 College Avenue, Swarthmore, PA 19081, USA.
| | - Ryan J Seddon
- Department of Biology, Indiana State University, Science Building Room 283, 600 North Chestnut Street, Terre Haute, IN 47809, USA; Center for Global Communication Strategies, University of Tokyo, 3-8-4 Komaba, Meguro-ku, Tokyo, 153-8902, Japan.
| | - Savannah L Price
- Department of Biology, Indiana State University, Science Building Room 283, 600 North Chestnut Street, Terre Haute, IN 47809, USA.
| | - Cristina Romero-Diaz
- School of Life Sciences, Arizona State University, 427 East Tyler Mall, Tempe, AZ 85287, USA.
| | - Julio A Rivera
- School of Life Sciences, Arizona State University, 427 East Tyler Mall, Tempe, AZ 85287, USA.
| | - Cuauhcihuatl Vital-García
- Departamento de Ciencias Veterinarias, Universidad Autónoma de Ciudad Juárez, Anillo Envolvente y Estocolmo s/n, Colonia Progresista, Ciudad Juárez, Chihuahua, 32310, Mexico.
| | - Diana K Hews
- Department of Biology, Indiana State University, Science Building Room 283, 600 North Chestnut Street, Terre Haute, IN 47809, USA.
| | - Emília P Martins
- School of Life Sciences, Arizona State University, 427 East Tyler Mall, Tempe, AZ 85287, USA.
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3
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Cain KE, Griffith SC, Kruuk LEB. Sex and morph differences in age-dependent trait changes in a polymorphic songbird. J Evol Biol 2021; 34:1691-1703. [PMID: 34528324 DOI: 10.1111/jeb.13930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 08/30/2021] [Accepted: 08/31/2021] [Indexed: 11/27/2022]
Abstract
There is growing evidence of important variation in how animals age, in particular in how the expression of traits changes with age among different species and populations. However, less is known about variation within populations, which may include variation in ageing patterns between different types of individuals (e.g. sexes or distinct polymorphisms) and between different types of traits (e.g. general traits versus those used in social signalling contexts). We used 6 years of longitudinal data to examine age-related changes in trait expression in a captive population of Gouldian finches (Erythrura gouldiae), a socially monogamous songbird with genetically determined colour morphs that differ in behaviour and physiology. We contrasted ageing patterns of different types of traits (social signalling vs. size-related) in both sexes and in two colour morphs, using a mixed model approach to account for both within- and between-individual effects. We found pronounced sex differences in how social signalling traits change with age, showing a quadratic pattern in males, but not changing with age in females. In contrast, we observed no sex-specific ageing patterns in size traits. We also found subtle morph differences in how size-related traits changed with age, with black morphs stable or increasing with age while red morphs showing a decline with age. Finally, we found an interesting sex by morph interaction in one important social signal (headband width). These results highlight the importance of using within-individual approaches to understand ageing patterns across types of individuals (sex, morph, etc.) and the need for further research on the ageing patterns of traits that may experience different selective pressures.
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Affiliation(s)
- Kristal E Cain
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia.,School of Biological Science, University of Auckland, Auckland, New Zealand
| | - Simon C Griffith
- Department of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Loeske E B Kruuk
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
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4
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McQueen A, Delhey K, Barzan FR, Naimo AC, Peters A. Male fairy-wrens produce and maintain vibrant breeding colors irrespective of individual quality. Behav Ecol 2020. [DOI: 10.1093/beheco/araa128] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Conspicuous colors may signal individual quality if high-quality individuals produce more elaborate colors or have a greater capacity to invest in color maintenance. We investigate these hypotheses using repeated within-individual observations and experimentally induced color production in a wild bird, the superb fairy-wren (Malurus cyaneus). Male superb fairy-wrens undergo an annual molt from brown, nonbreeding plumage to an ultraviolet-blue and black breeding plumage. Color maintenance is especially relevant for this species because structural, ultraviolet-blue plumage colors are particularly susceptible to fading. Further, only the most sexually attractive males molt to breeding plumage early (before spring) and thereby keep their colors for an extended time before the breeding season. Our results show that (i) sexually attractive, early-molting males do not have higher quality breeding colors and (ii) breeding colors are not impacted by experimentally inducing males to molt early and while in low body condition. We found that (iii) breeding colors do not fade but remain consistent or become more saturated within individuals over time. Despite this, (iv) males do not spend more time preening while in breeding plumage. Instead, males keep their colors in pristine condition by re-molting parts of their breeding plumage throughout the breeding season, suggesting an alternative, potential cost of maintaining ornamental colors. We conclude that variation in structural breeding colors is unlikely to indicate individual quality in superb fairy-wrens.
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Affiliation(s)
- Alexandra McQueen
- School of Biological Sciences, Monash University, Wellington Road, Clayton, Victoria, Australia
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Burwood Highway, Burwood, Victoria, Australia
| | - Kaspar Delhey
- School of Biological Sciences, Monash University, Wellington Road, Clayton, Victoria, Australia
- Max Planck Institute for Ornithology, Eberhard-Gwinner-Straße, Seewiesen, Germany
| | - Flavia R Barzan
- School of Biological Sciences, Monash University, Wellington Road, Clayton, Victoria, Australia
- Departamento de Recursos Naturales y Gestión Ambiental, Estación Experimental Agropecuaria Paraná, Instituto Nacional de Tecnología Agropecuaria (INTA) and CONICET, Oro Verde, Entre Ríos, Argentina
| | - Annalise C Naimo
- School of Biological Sciences, Monash University, Wellington Road, Clayton, Victoria, Australia
| | - Anne Peters
- School of Biological Sciences, Monash University, Wellington Road, Clayton, Victoria, Australia
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5
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Sexually dichromatic coloration of female Iberian green lizards correlates with health state and reproductive investment. Behav Ecol Sociobiol 2020. [DOI: 10.1007/s00265-020-02915-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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6
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Abstract
Colourful ornaments often communicate salient information to mates, and theory predicts covariance between signal expression and individual quality. This has borne out among pigment-based signals, but the potential for 'honesty' in structural coloration is unresolved. Here, I synthesized the available evidence to test this prediction via meta-analysis and found that, overall, the expression of structurally coloured sexual signals is positively associated with individual quality. The effects varied by the measure of quality, however, with body condition and immune function reliably encoded across taxa, but not age nor parasite resistance. The relationship was apparent for both the colour and brightness of signals and was slightly stronger for iridescent ornaments. These results suggest diverse pathways to the encoding and exchange of information among structural colours while highlighting outstanding questions as to the development, visual ecology and evolution of this striking adornment.
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Affiliation(s)
- Thomas E White
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2106, Australia
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7
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Leary CJ, Baugh AT. Glucocorticoids, male sexual signals, and mate choice by females: Implications for sexual selection. Gen Comp Endocrinol 2020; 288:113354. [PMID: 31830474 DOI: 10.1016/j.ygcen.2019.113354] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 12/01/2019] [Accepted: 12/06/2019] [Indexed: 12/29/2022]
Abstract
We review work relating glucocorticoids (GCs), male sexual signals, and mate choice by females to understand the potential for GCs to modulate the expression of sexually selected traits and how sexual selection potentially feeds back on GC regulation. Our review reveals that the relationship between GC concentrations and the quality of male sexual traits is mixed, regardless of whether studies focused on structural traits (e.g., coloration) or behavioral traits (e.g., vocalizations) or were examined in developmental or activational frameworks. In contrast, the few mate choice experiments that have been done consistently show that females prefer males with low GCs, suggesting that mate choice by females favors males that maintain low levels of GCs. We point out, however, that just as sexual selection can drive the evolution of diverse reproductive strategies, it may also promote diversity in GC regulation. We then shift the focus to females where we highlight evidence indicating that stressors or high GCs can dampen female sexual proceptivity and the strength of preferences for male courtship signals. Hence, even in cases where GCs are tightly coupled with male sexual signals, the strength of sexual selection on aspects of GC physiology can vary depending on the endocrine status of females. Studies examining how GCs relate to sexual selection may shed light on how variation in stress physiology, sexual signals, and mate choice are maintained in natural populations and may be important in understanding context-dependent relationships between GC regulation and fitness.
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Affiliation(s)
- Christopher J Leary
- Department of Biology, University of Mississippi, PO Box 1848, University, MS 38677, USA.
| | - Alexander T Baugh
- Department of Biology, Swarthmore College, 500 College Avenue, Swarthmore, PA 19081, USA
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8
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Jerem P, Jenni-Eiermann S, McKeegan D, McCafferty DJ, Nager RG. Eye region surface temperature dynamics during acute stress relate to baseline glucocorticoids independently of environmental conditions. Physiol Behav 2019; 210:112627. [PMID: 31348931 PMCID: PMC6739691 DOI: 10.1016/j.physbeh.2019.112627] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 07/22/2019] [Accepted: 07/22/2019] [Indexed: 02/06/2023]
Abstract
Reactions to acute stressors are critical for survival. Yet, the challenges of assessing underlying physiological processes in the field limit our understanding of how variation in the acute stress response relates to fitness in free-living animals. Glucocorticoid secretion during acute stress can be measured from blood plasma concentrations, but each blood sample can only provide information for one point in time. Also, the number of samples that can be extracted from an individual in the field is usually limited to avoid compromising welfare. This restricts capacity for repeated assessment, and therefore temporal resolution of findings within- and between-acute stress responses - both of which are important for determining links between acute stress and fitness. Acute stress induces additional body surface temperature changes that can be measured non-invasively, and at high frequencies using thermal imaging, offering opportunities to overcome these limitations. But, this method's usefulness in the field depends on the extent that environmental conditions affect the body surface temperature response, which remains poorly understood. We assessed the relative importance of individual physiology (baseline glucocorticoid concentrations) and environmental conditions (air temperature and relative humidity) in determining the eye region surface temperature (Teye) response to acute stress, in wild blue tits (Cyanistes caeruleus) during trapping, handling and blood sampling. When controlling for between-individual baseline variation, Teye initially dropped rapidly below, and then recovered above baseline, before declining more slowly until the end of the test, 160 s after trap closure. One measure of the amplitude of this response - the size of the initial drop in Teye - was dependent on environmental conditions, but not baseline corticosterone. Whereas, two properties defining response dynamics - the timing of the initial drop, and the slope of the subsequent recovery - were related to baseline corticosterone concentrations, independently of environmental conditions. This suggests inferring the acute stress response using thermal imaging of Teye will be practical under fluctuating environmental conditions in the field.
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Affiliation(s)
- Paul Jerem
- Department of Evolution, Behaviour and Environment, School of Life Sciences, University of Sussex, Falmer, UK.
| | | | - Dorothy McKeegan
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
| | - Dominic J McCafferty
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
| | - Ruedi G Nager
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
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9
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Berg ML, Knott B, Ribot RFH, Buchanan KL, Bennett ATD. Do glucocorticoids or carotenoids mediate plumage coloration in parrots? An experiment in Platycercus elegans. Gen Comp Endocrinol 2019; 280:82-90. [PMID: 31002829 DOI: 10.1016/j.ygcen.2019.04.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 04/10/2019] [Accepted: 04/15/2019] [Indexed: 11/29/2022]
Abstract
Conspicuous coloration can indicate phenotypic quality, and may reflect exposure or vulnerability to stress, or access to essential nutrients such as pigments. Although the production of pigmented colours is well understood, much less is known about how structural colours are affected by physiological state. In this study, we tested whether glucocorticoids (corticosterone) predicted expression of plumage coloration in an Australian parrot, the crimson rosella (Platycercus elegans). Parrots provide an interesting and unique test, as they possess conspicuous coloration produced by distinctive pigments known as psittacofulvins, in addition to structural coloration. We have previously documented that coloration in P. elegans is condition-dependent and responds to dietary manipulation. Here, n = 21 P. elegans underwent a dietary manipulation (including food restriction or carotenoid supplementation) during which they moulted, and the change in reflectance was measured for three structural and three pigmentary plumage patches. Stress-induced corticosterone (10 min after handling) measured at the start of the experiment predicted change in coloration in two pigmentary patches (crown and front). We also found that change in stress-induced corticosterone during the experiment was associated with the change in coloration of the crown and two structural patches (cheek and epaulette). Baseline corticosterone (<3 min after handling) was not associated with any measure of coloration. We found no effects of dietary manipulation on baseline or stress-induced corticosterone, but carotenoid supplementation was associated with an increase in a measure of chronic stress (heterophil/lymphocyte ratio), and the corticosterone response to handling decreased over the course of the study. Our results suggest that corticosterone may be linked to colour expression more broadly than previously recognised, including psittacofulvin and structural coloration in parrots, and they confirm the independence of plumage pigmentation in parrots from carotenoid accumulation. Moreover, our study provides new insight into the stress responses of Psittaciformes, one of the most highly threatened avian orders.
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Affiliation(s)
- Mathew L Berg
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Australia; School of Biological Sciences, University of Bristol, United Kingdom.
| | - Ben Knott
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Australia; School of Biological Sciences, University of Bristol, United Kingdom
| | - Raoul F H Ribot
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Australia; School of Biological Sciences, University of Bristol, United Kingdom
| | - Katherine L Buchanan
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Australia; School of Biosciences, Cardiff University, United Kingdom
| | - Andrew T D Bennett
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Australia; School of Biological Sciences, University of Bristol, United Kingdom
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10
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Holveck MJ, Guerreiro R, Perret P, Doutrelant C, Grégoire A. Eggshell coloration indicates female condition during egg-laying: a field experiment in blue tits. Biol J Linn Soc Lond 2019. [DOI: 10.1093/biolinnean/blz082] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractSeveral selection pressures may explain the evolution of avian eggshell coloration patterns. In cavity-nesting species, there are two main non-exclusive hypotheses. The sexually selected eggshell colour hypothesis proposes that eggshell coloration is a sexually selected signal of female and offspring quality used by males that influences paternal care or future re-mating decisions. The structural function hypothesis proposes that pigments help strengthen the eggshell and are present at higher levels and at the blunt end of the egg when females face calcium shortages. We tested whether eggshell coloration (brown spots on a white ground colour) in blue tits (Cyanistes caeruleus) could reliably indicate female condition at laying by forcing females to produce two consecutive clutches, thus increasing their reproductive costs. Three measures of eggshell coloration – the area covered by spots as well as white ground UV-chroma and brightness – changed between clutches; the fourth measure, spot distribution, did not. The changes were more dramatic in young and lower-quality females. All the measures varied with female quality (i.e. body condition and/or laying date). Overall, higher-quality females produced more colourful (larger, more concentrated spotted surface area; higher UV-chroma) and less bright (i.e. putatively more pigmented) eggshells, a result that is generally in line with past research. We found a clear empirical link between eggshell coloration and female condition in blue tits, an important step in determining whether eggshell coloration is a sexual signal, but which does not exclude a potential concomitant structural function.
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Affiliation(s)
- Marie-Jeanne Holveck
- CEFE UMR 5175, Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France
| | - Romain Guerreiro
- CEFE UMR 5175, Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France
| | - Philippe Perret
- CEFE UMR 5175, CNRS, Univ Montpellier, Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France
| | - Claire Doutrelant
- CEFE UMR 5175, CNRS, Univ Montpellier, Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France
| | - Arnaud Grégoire
- CEFE UMR 5175, Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France
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11
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Huq M, Bhardwaj S, Monteiro A. Male Bicyclus anynana Butterflies Choose Females on the Basis of Their Ventral UV-Reflective Eyespot Centers. JOURNAL OF INSECT SCIENCE (ONLINE) 2019; 19:5355579. [PMID: 30794728 PMCID: PMC6390274 DOI: 10.1093/jisesa/iez014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Indexed: 06/09/2023]
Abstract
Butterflies often use their dorsal and ventral wing color patterns for distinct signaling functions. Color patterns on hidden dorsal wing surfaces are often used in sexual signaling, while exposed ventral patterns are often used to ward off predator attacks. At rest, however, part of the ventral forewings are often hidden by the hindwings, allowing individuals to also use the patterns on this wing surface for sexual signaling. Here, we test this hypothesis in Bicyclus anynana (Butler, Lepidoptera, Nymphalidae) butterflies by first determining the degree of sexual dimorphism in ventral forewing patterns, focusing on the eyespots, from both wet and dry season forms, and then testing the role of the larger ventral forewing eyespots of dry season females in male mate choice. We also test male investment in reproduction. We show that ventral forewing UV-reflective eyespot centers, in addition to dorsal forewing eyespot centers previously examined in this species, play a role in sexual signaling as males preferentially mated with females with their ventral eyespot centers intact instead of blocked with black paint. This male preference, however, did not translate into a detectable higher reproductive investment via a single mating toward ornamented females. This study provides an example of how ventral forewing patterns, often hidden by hindwings, are used in sexual communication, in this case by females to attract males.
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Affiliation(s)
- Manizah Huq
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Shivam Bhardwaj
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Antónia Monteiro
- Department of Biological Sciences, National University of Singapore, Singapore
- Science Division, Yale-NUS College, Singapore
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12
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Sarpong K, Madliger CL, Harris CM, Love OP, Doucet SM, Bitton PP. Baseline corticosterone does not reflect iridescent plumage traits in female tree swallows. Gen Comp Endocrinol 2019; 270:123-130. [PMID: 30392885 DOI: 10.1016/j.ygcen.2018.10.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 10/03/2018] [Accepted: 10/23/2018] [Indexed: 01/08/2023]
Abstract
The production of high quality secondary sexual traits can be constrained by trade-offs in the allocation of energy and nutrients with other metabolic activities, and is mediated by physiological processes. In birds, the factors influencing male plumage quality have been well studied; however, factors affecting female plumage quality are poorly understood. Furthermore, it remains uncertain which physiological traits mediate the relationship between body condition and ornaments. In this three-year study of after-second-year female tree swallows (Tachycineta bicolor), we investigated (1) the relationship between baseline corticosterone near the end of the brood-rearing period (CORTBR) and feather colour characteristics (hue, saturation, brightness) the following year, and (2) the relationship between baseline corticosterone measured during incubation (CORTI) and brood rearing (CORTBR), and feather colour in the same year. To control for reproductive effort, we included reproductive parameters as covariates in all analyses. In this first study between CORT and the plumage colour characteristics of a species bearing iridescent feathers, we did not find any relationship between CORTBR and the colour of subsequently-produced feathers, nor did we find any relationship between CORT and the colour of feathers displayed during that breeding season. If CORT levels at the end of breeding carry over to influence the immediately subsequent moult period as we expect, our results generally indicate that structural plumage quality may not be as sensitive to circulating CORT levels compared to carotenoid-based colouration. Future studies, particularly those employing experimental manipulations of CORT during moult in species with iridescent traits, are necessary to fully determine the role glucocorticoids play in mediating the quality of secondary sexual characteristics.
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Affiliation(s)
- Keneth Sarpong
- Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada.
| | - Christine L Madliger
- Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada.
| | - Christopher M Harris
- Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada.
| | - Oliver P Love
- Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada.
| | - Stéphanie M Doucet
- Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada.
| | - Pierre-Paul Bitton
- Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada.
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13
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James C, Asher L, Herborn K, Wiseman J. The effect of supplementary ultraviolet wavelengths on broiler chicken welfare indicators. Appl Anim Behav Sci 2018; 209:55-64. [PMID: 30510331 PMCID: PMC6222521 DOI: 10.1016/j.applanim.2018.10.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 09/19/2018] [Accepted: 10/01/2018] [Indexed: 10/29/2022]
Abstract
Qualities of the light environment are important for good welfare in a number of species. In chickens, UVA light is visible and may facilitate flock interactions. UVB wavelengths promote endogenous vitamin D synthesis, which could support the rapid skeletal development of broiler chickens. The aim of the study was to investigate the impacts of Ultraviolet wavelengths (UV) on welfare indicators in broiler chickens. Day-old Ross 308 birds reared under commercially representative conditions were randomly assigned to one of three lighting treatments: A) White Light Emitting Diode (LED) and supplementary UVA LED lighting (18-hour photoperiod); B) White LED with supplementary UVA and UVB fluorescent lighting providing 30 micro watts/cm2 UVB at bird level (on for 8 h of the total photoperiod to avoid over-exposure of UVB); C) White LED control group, representative of farm conditions (18-hour photoperiod). Welfare indicators measured were; feather condition (day 24, n = 546), tonic immobility duration (day 29, n = 302), and gait quality, using the Bristol Gait Score (day 31, n = 293). Feather condition was improved in male broilers in the UVA treatment (A), compared to the control treatment (C). Birds in the UVA treatment had shorter tonic immobility durations compared to the control treatment (C), suggesting lower fearfulness. Broilers reared in UVA (A) and UVA + UVB (B) had better Bristol Gait Scores compared to the control (C). Together these results suggest UV may be beneficial for broiler chicken welfare. While treatment A and B both provided UVA, the improvements in welfare indicators were not consistent, which may be due to exposure time-dependent beneficial effects of UVA. The modification of commercial lighting regimes to incorporate UVA wavelengths for indoor-reared broiler chickens would be an achievable change with significant positive impacts on bird welfare.
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Affiliation(s)
- Charlotte James
- Department of Animal Sciences, University of Nottingham, Sutton Bonington Campus, Leicestershire, UK
| | - Lucy Asher
- Centre for Behaviour and Evolution IoN, Newcastle University, Henry Wellcome Building, Newcastle, UK
| | - Katherine Herborn
- Centre for Behaviour and Evolution IoN, Newcastle University, Henry Wellcome Building, Newcastle, UK
| | - Julian Wiseman
- Department of Animal Sciences, University of Nottingham, Sutton Bonington Campus, Leicestershire, UK
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14
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Hegyi G, Laczi M, Kötél D, Csizmadia T, Lőw P, Rosivall B, Szöllősi E, Török J. Reflectance variation in the blue tit crown in relation to feather structure. ACTA ACUST UNITED AC 2018; 221:jeb.176727. [PMID: 29615523 DOI: 10.1242/jeb.176727] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Accepted: 03/21/2018] [Indexed: 11/20/2022]
Abstract
Structural plumage colour is one of the most enigmatic sexually selected traits. The information content of structural colour variation is debated, and the heterogeneity of the findings is hard to explain because the proximate background of within-species colour differences is very scarcely studied. We combined measurements of feather macrostructure and nanostructure to explain within-population variability in blue tit crown reflectance. We found that sexual dichromatism in aspects of crown reflectance was explained only by feather macrostructure, whereas nanostructural predictors accounted for some of the age-related differences in reflectance. Moreover, we found that both mean reflectance and spectral shape traits reflected a combination of quantity and regularity aspects in macrostructure and nanostructure. This rich proximate background provides ample scope for reflectance to convey various types of information on individual quality.
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Affiliation(s)
- Gergely Hegyi
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary
| | - Miklós Laczi
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary.,The Barn Owl Foundation, Temesvári út 8, H-8744 Orosztony, Hungary
| | - Dóra Kötél
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary
| | - Tamás Csizmadia
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary
| | - Péter Lőw
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary
| | - Balázs Rosivall
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary
| | - Eszter Szöllősi
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary
| | - János Török
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary.,Ecology Research Group of the Hungarian Academy of Sciences, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary
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15
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Losdat S, Blount JD, Marri V, Maronde L, Richner H, Helfenstein F. Effects of an early-life paraquat exposure on adult resistance to oxidative stress, plumage colour and sperm performance in a wild bird. J Anim Ecol 2018. [DOI: 10.1111/1365-2656.12822] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Sylvain Losdat
- Institute of Biology; University of Neuchâtel; Neuchâtel Switzerland
- Institute of Ecology and Evolution; University of Bern; Bern Switzerland
| | - Jonathan D. Blount
- Centre for Ecology & Conservation; College of Life & Environmental Sciences; University of Exeter; Penryn UK
| | - Viviana Marri
- Institute of Ecology and Evolution; University of Bern; Bern Switzerland
| | - Lea Maronde
- Institute of Ecology and Evolution; University of Bern; Bern Switzerland
| | - Heinz Richner
- Institute of Ecology and Evolution; University of Bern; Bern Switzerland
| | - Fabrice Helfenstein
- Institute of Biology; University of Neuchâtel; Neuchâtel Switzerland
- Institute of Ecology and Evolution; University of Bern; Bern Switzerland
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16
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Jerem P, Jenni-Eiermann S, Herborn K, McKeegan D, McCafferty DJ, Nager RG. Eye region surface temperature reflects both energy reserves and circulating glucocorticoids in a wild bird. Sci Rep 2018; 8:1907. [PMID: 29382942 PMCID: PMC5789886 DOI: 10.1038/s41598-018-20240-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 01/10/2018] [Indexed: 01/29/2023] Open
Abstract
Body temperature of endotherms shows substantial within- and between-individual variation, but the sources of this variation are not fully understood in wild animals. Variation in body temperature can indicate how individuals cope with their environment via metabolic or stress-induced effects, both of which may relate to depletion of energy reserves. Body condition can reflect heat production through changes to metabolic rate made to protect energy reserves. Additionally, changes in metabolic processes may be mediated by stress-related glucocorticoid secretion, which is associated with altered blood-flow patterns that affect regional body temperatures. Accordingly, both body condition and glucocorticoid secretion should relate to body temperature. We used thermal imaging, a novel non-invasive method of temperature measurement, to investigate relationships between body condition, glucocorticoid secretion and body surface temperature in wild blue tits (Cyanistes caeruleus). Individuals with lower body condition had lower eye-region surface temperature in both non-breeding and breeding seasons. Eye-region surface temperature was also negatively correlated with baseline circulating glucocorticoid levels in non-breeding birds. Our results demonstrate that body surface temperature can integrate multiple aspects of physiological state. Consequently, remotely-measured body surface temperature could be used to assess such aspects of physiological state non-invasively in free-living animals at multiple life history stages.
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Affiliation(s)
- Paul Jerem
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK.
| | | | - Katherine Herborn
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK.,Institute of Neurobiology, Newcastle University, Newcastle, UK
| | - Dorothy McKeegan
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK
| | - Dominic J McCafferty
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK
| | - Ruedi G Nager
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK
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17
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Fargevieille A, Grégoire A, Charmantier A, Del Rey Granado M, Doutrelant C. Assortative mating by colored ornaments in blue tits: space and time matter. Ecol Evol 2017; 7:2069-2078. [PMID: 28405273 PMCID: PMC5383486 DOI: 10.1002/ece3.2822] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 01/06/2017] [Accepted: 01/28/2017] [Indexed: 01/16/2023] Open
Abstract
Assortative mating is a potential outcome of sexual selection, and estimating its level is important to better understand local adaptation and underlying trait evolution. However, assortative mating studies frequently base their conclusions on small numbers of individuals sampled over short periods of time and limited spatial scales even though spatiotemporal variation is common. Here, we characterized assortative mating patterns over 10 years in four populations of the blue tit (Cyanistes caeruleus), a passerine bird. We focused on two plumage ornaments-the blue crown and the yellow breast patch. Based on data for 1,657 pairs of birds, we found large interannual variation: assortative mating varied from positive to negative. To determine whether there was nonetheless a general trend in the data, we ran a within-study meta-analysis. It revealed that assortative mating was moderately positive for both ornaments. It also showed that mating patterns differed among populations and especially between two neighboring populations that displayed phenotypic divergence. Our results therefore underscore that long-term studies are needed to draw broad conclusions about mating patterns in natural populations. They also call for studying the potential role of assortative mating in local adaptation and evolution of ornaments in both sexes.
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Affiliation(s)
| | - Arnaud Grégoire
- CEFE UMR5175 CNRS - Université de Montpellier Montpellier France
| | - Anne Charmantier
- CEFE UMR5175 CNRS - Université de Montpellier Montpellier France
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18
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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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19
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Arnold KE, Herborn KA, Henderson LJ, Adam A, Alexander L, Evans N. Individual variation in corticosterone and personality traits in the blue tit Cyanistes caeruleus. BEHAVIOUR 2016. [DOI: 10.1163/1568539x-00003408] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Variation in personality traits is predicted to reflect physiology, but the extent to which variations in stress hormones derive from differences in personality and/or state-dependent factors remains unclear. To investigate this, wild blue tits (Cyanistes caeruleus) were briefly brought into captivity and scored for personality and corticosterone (Cort) concentrations. More active females had lower baseline Cort than less active individuals. Exploratory tendency and neophobia did not co-vary with baseline Cort. Stress-induced Cort concentrations were correlated negatively with exploratory tendency and haematocrit, but positively with mass gain in captivity. Therefore, baseline and stress-induced Cort concentrations in wintering blue tits were associated with state-dependent variables, sex, age and personality traits. Key to interpreting the physiology of personality traits seems to be their interactions with other traits that mediate ability to utilise resources, and thus influence an individual’s perception of its current and future energy balance.
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Affiliation(s)
- Kathryn E. Arnold
- Environment Department, University of York, Wentworth Way, Heslington YO10 5NG, UK
| | - Katherine A. Herborn
- Centre for Behaviour and Evolution, IoN, Newcastle University, Henry Wellcome Building, Framlington Place, Newcastle NE2 4HH, UK
| | - Lindsay J. Henderson
- Centre for Behaviour and Evolution, IoN, Newcastle University, Henry Wellcome Building, Framlington Place, Newcastle NE2 4HH, UK
| | - Aileen Adam
- Institute of Biodiversity, Animal Health and Comparative Medicine, School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
| | | | - Neil Evans
- Institute of Biodiversity, Animal Health and Comparative Medicine, School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
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20
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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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21
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Moore FR, Shuker DM, Dougherty L. Stress and sexual signaling: a systematic review and meta-analysis. Behav Ecol 2015. [DOI: 10.1093/beheco/arv195] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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22
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23
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Mating success is predicted by the interplay between multiple male and female traits in the small hairy maggot blowfly. Anim Behav 2014. [DOI: 10.1016/j.anbehav.2014.09.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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24
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Henderson LJ, Evans NP, Heidinger BJ, Adams A, Arnold KE. Maternal condition but not corticosterone is linked to offspring sex ratio in a passerine bird. PLoS One 2014; 9:e110858. [PMID: 25347532 PMCID: PMC4210198 DOI: 10.1371/journal.pone.0110858] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 09/22/2014] [Indexed: 11/19/2022] Open
Abstract
There is evidence of offspring sex ratio adjustment in a range of species, but the potential mechanisms remain largely unknown. Elevated maternal corticosterone (CORT) is associated with factors that can favour brood sex ratio adjustment, such as reduced maternal condition, food availability and partner attractiveness. Therefore, the steroid hormone has been suggested to play a key role in sex ratio manipulation. However, despite correlative and causal evidence CORT is linked to sex ratio manipulation in some avian species, the timing of adjustment varies between studies. Consequently, whether CORT is consistently involved in sex-ratio adjustment, and how the hormone acts as a mechanism for this adjustment remains unclear. Here we measured maternal baseline CORT and body condition in free-living blue tits (Cyanistes caeruleus) over three years and related these factors to brood sex ratio and nestling quality. In addition, a non-invasive technique was employed to experimentally elevate maternal CORT during egg laying, and its effects upon sex ratio and nestling quality were measured. We found that maternal CORT was not correlated with brood sex ratio, but mothers with elevated CORT fledged lighter offspring. Also, experimental elevation of maternal CORT did not influence brood sex ratio or nestling quality. In one year, mothers in superior body condition produced male biased broods, and maternal condition was positively correlated with both nestling mass and growth rate in all years. Unlike previous studies maternal condition was not correlated with maternal CORT. This study provides evidence that maternal condition is linked to brood sex ratio manipulation in blue tits. However, maternal baseline CORT may not be the mechanistic link between the maternal condition and sex ratio adjustment. Overall, this study serves to highlight the complexity of sex ratio adjustment in birds and the difficulties associated with identifying sex biasing mechanisms.
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Affiliation(s)
- Lindsay J. Henderson
- Department of Neurobiology, Physiology and Behavior, University of California Davis, Davis, California, United States of America
- College of Medical, Veterinary & Life Sciences, The University of Glasgow, Glasgow, United Kingdom
| | - Neil P. Evans
- College of Medical, Veterinary & Life Sciences, The University of Glasgow, Glasgow, United Kingdom
| | - Britt J. Heidinger
- College of Medical, Veterinary & Life Sciences, The University of Glasgow, Glasgow, United Kingdom
- Department of Biological Sciences, North Dakota State University, Fargo, North Dakota, United States of America
| | - Aileen Adams
- College of Medical, Veterinary & Life Sciences, The University of Glasgow, Glasgow, United Kingdom
| | - Kathryn E. Arnold
- College of Medical, Veterinary & Life Sciences, The University of Glasgow, Glasgow, United Kingdom
- Environment Department, The University of York, York, United Kingdom
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