ORCID Profile
0000-0002-2851-9379
Current Organisations
University of London
,
University of St Andrews
,
University of Stirling
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Publisher: SAGE Publications
Date: 08-2012
DOI: 10.3184/175815512X13443333441381
Abstract: We analysed inter-in idual body mass variation of Japanese quail (Coturnix coturnix japonica) in an examination of the effectiveness of regulations governing daily food requirements. We measured the daily food intake of 26 adult female quail during a feeding trial over four consecutive days. Non-ingested food was weighed every morning and 70 g of food was provided to each bird for every day of the trial. This represented more than three times the theoretical recommended daily amount of food required by Japanese quail, as described in the literature. We then calculated a female-specific mean daily food requirement and found highly significant variation among in iduals. Daily food intake was significantly repeatable within-female over the trial and mean food intake was highly correlated with female body mass. We suggest that using daily requirements for in iduals based upon ‘population’ means, whilst ignoring differences in body mass among in iduals might have severe consequences for the welfare of birds. Furthermore, these results have significant implications for studies where the aim is to perform identical experimental manipulations (as some studies intend and suggest), resulting in the drawing of unsubstantiated conclusions.
Publisher: The Royal Society
Date: 13-08-2018
Abstract: The use of information provided by others is a common short-cut adopted to inform decision-making. However, instead of indiscriminately copying others, animals are often selective in what, when and whom they copy. How do they decide which ‘social learning strategy’ to use? Previous research indicates that stress hormone exposure in early life may be important: while juvenile zebra finches copied their parents' behaviour when solving novel foraging tasks, those exposed to elevated levels of corticosterone (CORT) during development copied only unrelated adults. Here, we tested whether this switch in social learning strategy generalizes to vocal learning. In zebra finches, juvenile males often copy their father's song would CORT-treated juveniles in free-flying aviaries switch to copying songs of other males? We found that CORT-treated juveniles copied their father's song less accurately as compared to control juveniles. We hypothesized that this could be due to having weaker social foraging associations with their fathers, and found that sons that spent less time foraging with their fathers produced less similar songs. Our findings are in line with a novel hypothesis linking early-life stress and social learning: early-life CORT exposure may affect social learning indirectly as a result of the way it shapes social affiliations. This article is part of the theme issue ‘Causes and consequences of in idual differences in cognitive abilities’.
Publisher: The Royal Society
Date: 17-08-2005
Abstract: There is now considerable evidence that female choice drives the evolution of song complexity in many songbird species. However, the underlying basis for such choice remains controversial. The developmental stress hypothesis suggests that early developmental conditions can mediate adult song complexity by perturbing investment in the underlying brain nuclei during their initial growth. Here, we show that adult male canaries ( Serinus canaria ), infected with malaria ( Plasmodium relictum ) as juveniles, develop simpler songs as adults compared to uninfected in iduals, and exhibit reduced development of the high vocal centre (HVC) song nucleus in the brain. Our results show how developmental stress not only affects the expression of a sexually selected male trait, but also the structure of the underlying song control pathway in the brain, providing a direct link between brain and behaviour. This novel experimental evidence tests both proximate and ultimate reasons for the evolution of complex songs and supports the Hamilton–Zuk hypothesis of parasite-mediated sexual selection. Together, these results propose how developmental costs may help to explain the evolution of honest advertising in the complex songs of birds.
Publisher: Springer Science and Business Media LLC
Date: 04-05-2005
Publisher: The Royal Society
Date: 07-02-2004
Publisher: The Royal Society
Date: 10-2014
Abstract: The quantity and quality of social relationships, as captured by social network analysis, can have major fitness consequences. Various studies have shown that in idual differences in social behaviour can be due to variation in exposure to developmental stress. However, whether these developmental differences translate to consistent differences in social network position is not known. We experimentally increased levels of the avian stress hormone corticosterone (CORT) in nestling zebra finches in a fully balanced design. Upon reaching nutritional independence, we released chicks and their families into two free-flying rooms, where we measured daily social networks over five weeks using passive integrated transponder tags. Developmental stress had a significant effect on social behaviour: despite having similar foraging patterns, CORT chicks had weaker associations to their parents than control chicks. Instead, CORT chicks foraged with a greater number of flock mates and were less choosy with whom they foraged, resulting in more central network positions. These findings highlight the importance of taking developmental history into account to understand the drivers of social organization in gregarious species.
Publisher: Elsevier BV
Date: 08-2015
Publisher: Elsevier BV
Date: 11-2014
DOI: 10.1016/J.YGCEN.2014.08.013
Abstract: Physiological constraints on colouration have been widely reported especially in birds, which trade-off antioxidant responses against colourful costly signals. One female extended phenotypic trait, which might also highlight important physiological trade-offs, is the pigmentation of their eggshells. In ground-nesting species, producing eggs that are visually undetectable by predators is the best camouflage strategy. However, the condition-dependence of eggshell pigmentation, and the pigments role in oxidative stress, may constrain females to trade-off between their antioxidant capacity and maximising the camouflage of their eggs when they deposit eggshell pigments. Developmental stress is one factor that influences female antioxidant capacity, and could lead to variations in eggshell pigmentation that might have crucial consequences on in idual fitness if egg crypsis is compromised especially under stressful conditions. We investigated the interaction between developmental and breeding conditions with respect to eggshell pigmentation in Japanese quail. We studied 30 females that bred under both control and stressful conditions, and were exposed to pre- and/or post-natal stress, or neither. Pre- and post-natal stress independently influenced eggshell pigmentation strategies under stressful breeding conditions. Under stressful reproduction, eggshell protoporphyrin concentration and maculation were affected by pre-natal stress, whereas eggshell reflectance and biliverdin concentration were influenced by post-natal stress. These changes may reflect potential adaptive strategies shaped by developmental stress, but additional data on the benefit of egg crypsis in quail, combined with studies on the role of both pigments on chick survival, will help to clarify whether early life stress can enhance fitness through eggshell pigmentation when developmental and reproductive environments match.
Publisher: The Royal Society
Date: 22-11-2004
Publisher: Elsevier BV
Date: 08-2003
DOI: 10.1016/S0018-506X(03)00124-7
Abstract: In a wide range of bird species, females have been shown to express active preferences for males that sing more complex songs. Current sexual selection theory predicts that for this signal to remain an honest indicator of male quality, it must be associated with an underlying cost of development or maintenance. There has been considerable debate questioning the costs associated with song production and learning. Recently, the nutritional stress hypothesis proposed that song complexity could act as an indicator of early developmental history, since the song control nuclei in the brain are laid down early in life. Here we test the nutritional stress hypothesis, by investigating the effects of dietary stress on the quality of adult song produced. In addition, we tested the effects of elevated corticosterone during development on song production to test its possible involvement in mediating the effects of developmental stress. The results demonstrate that both dietary restriction and elevated corticosterone levels significantly reduced nestling growth rates. In addition, we found that experimentally stressed birds developed songs with significantly shorter song motif duration and reduced complexity. These results provide novel experimental evidence that complex song repertoires may have evolved as honest signals of male quality, by indicating early developmental rearing conditions.
Publisher: Public Library of Science (PLoS)
Date: 03-12-2013
Publisher: The Royal Society
Date: 07-06-2003
Publisher: The Company of Biologists
Date: 2012
DOI: 10.1242/JEB.077370
Abstract: A relationship has been suggested between eggshell colour and female body condition based on the opposing antioxidant properties of the two main eggshell pigments: the antioxidant biliverdin (blue-green) and the pro-oxidant protoporphyrin (brown). We hypothesised that experimentally food-restricted females with low antioxidant capacity would deposit more protoporphyrin and less biliverdin in their eggshells, resulting in eggshells of reduced brightness but increased colour intensity. Two eggs were collected at the beginning and two at the end of a 2-week period from each of 24 female Japanese quails that were either food-restricted or receiving ad libitum food (i.e. controls) during that time. Reflectance spectra were recorded and analysed using spectral shape descriptors, chromatic and achromatic contrasts were computed accounting for avian visual sensitivities, and eggshell pigments were quantified. We examined both spot and background pigmentation and found no significant effect of food restriction on eggshell reflectance. However, food-restricted females in lower body condition increased the deposition of protoporphyrin and decreased the amount of biliverdin invested into their eggshells. We hypothesise that in species laying brown-spotted eggshells, females modulate eggshell pigment investment in response to their body condition. According to this hypothesis, we predict that females maintain eggshell colour to limit visible changes that could be detected by predators and thereby conceal their eggs, although this work has yet to be conducted. We suggest that further experimental work on egg camouflage under different environmental conditions will elaborate the process of pigment deposition and the physiological costs to females of laying heavily pigmented eggshells.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for karen spencer.