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Fletcher, Kevin
Publications (4 of 4) Show all publications
Fletcher, K., Xiong, Y., Fletcher, E. & Gustafsson, L. (2018). Glucocorticoid response to both predictable and unpredictable challenges detected as corticosterone metabolites in collared flycatcher droppings. PLoS ONE, 13(12), Article ID e0209289.
Open this publication in new window or tab >>Glucocorticoid response to both predictable and unpredictable challenges detected as corticosterone metabolites in collared flycatcher droppings
2018 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 13, no 12, article id e0209289Article in journal (Refereed) Published
Abstract [en]

In most vertebrate animals, glucocorticoid hormones are the chief mediators of homeostasis in response to ecological conditions and as they progress through their lifecycle. In addition, glucocorticoids are a major part of the stress response and stress induced elevations of the hormone can make it difficult to assess glucocorticoid secretion in response to changes in life-stage and current environmental conditions in wild animals. Particularly when quantifying circulating levels of glucocorticoids in the blood which fluctuate rapidly in response to stress. An alternative method of quantifying glucocorticoids is as hormone metabolites in faeces or urine giving a historical sample related to the gut passage time and urinary tract that is less sensitive to stressful events which cause spikes in the circulating hormone level. Although the concentration of glucocorticoid metabolites are influenced by faecal mass thereby potentially affecting any differences in hormone metabolites detected amongst samples. In the present study, we aimed to detect changes in levels of corticosterone, the primary bird glucocorticoid, in relation to the phase of reproduction, in a breeding population of collared flycatchers by sampling corticosterone metabolites in droppings. We also tested how corticosterone metabolite concentrations were affected by ambient temperature and related to body condition in adult birds. Our results indicate that the upregulation of corticosterone between incubation and nestling feeding in female birds is crucial for successful reproduction in this species. Also, females appear to downregulate corticosterone during incubation in response to lower ambient temperature and poorer body condition. Our results did not indicate a relationship between dropping mass and corticosterone metabolite concentrations, which suggests that our findings were linked to the regulation of corticosterone in response to predictable and unpredictable challenges.

National Category
urn:nbn:se:uu:diva-373230 (URN)10.1371/journal.pone.0209289 (DOI)000453841700051 ()30571789 (PubMedID)
Swedish Research CouncilSwedish Research Council Formas
Available from: 2019-01-14 Created: 2019-01-14 Last updated: 2019-01-14Bibliographically approved
Fletcher, K. (2017). Causes and consequences of life-history variation: The effects of parasites, glucocorticoids, and environmental conditions in the collared flycatcher (Ficedula albicollis). (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Causes and consequences of life-history variation: The effects of parasites, glucocorticoids, and environmental conditions in the collared flycatcher (Ficedula albicollis)
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Life-history is the study of all the different stages of life that affect reproductive success and survival between the birth and death of an organism. The reproductive output of an organism is constrained by many things including time, resource, disease agents and environmental conditions. In addition, lineage-specific traits and the limitations of the physiological systems can limit how an organism responds to ecological processes, and thus constrains the variation of life histories represented in nature. Central to the theory of life history are the trade-offs that organisms make during their lifetime to maximise their reproductive potential. In this thesis, I focus on the effect of haemosporidian blood parasites on host life history, in relation to the glucocorticoid response and environmental conditions. The host study species is a population of collared flycatchers (Ficedula albicollis), a species that provides bi-parental care, located in the south of Gotland. We show that nestling condition predicts parasite infection and that parasite-mediated selection can start early on in the birds’ life. We also found a link between Lower levels of glucocorticoids and parasite infection, which might indicate a trade-off between immunity and reproductive effort. Adult birds’ upregulated glucocorticoids in response to an increase in reproductive effort and a predictable change in energy demand during reproduction. I also show that glucocorticoids respond to changing environmental conditions. These results together accentuate the importance of the plasticity of the glucocorticoid response to reproductive success. Moreover, higher levels of hormone during reproduction predicted survival to the next breeding season. In nestlings, glucocorticoid levels increased as a consequence of parent infection status and an increase in reproductive effort. Overall, our results indicate that the glucocorticoid response is context dependent. Finally, female collared flycatchers might pay a fitness cost as a consequence of parasite infection, but can still reproduce successfully suggesting that they can tolerate the parasite. To further our understanding of costs related to parasite infection, we must understand better the mechanisms that enable the host to tolerate infection. This study indicates that glucocorticoids provide a useful tool to detect how wild birds respond to predictable and unpredictable challenges.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. p. 38
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1569
Collard flycatcher, Haemosporidian blood parasite, glucocorticoid, life history
National Category
Evolutionary Biology
urn:nbn:se:uu:diva-330848 (URN)978-91-513-0091-7 (ISBN)
Public defence
2017-11-24, Zootissalen, Norbyvägen 18D, Uppsala, 10:00 (English)
Available from: 2017-10-30 Created: 2017-10-05 Last updated: 2017-11-01
Griesser, M., Mourocq, E., Barnaby, J., Bowgen, K. M., Eggers, S., Fletcher, K., . . . Ekman, J. (2017). Experience buffers extrinsic mortality in a group-living bird species. Oikos, 126(9), 1258-1268
Open this publication in new window or tab >>Experience buffers extrinsic mortality in a group-living bird species
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2017 (English)In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 126, no 9, p. 1258-1268Article in journal (Refereed) Published
Abstract [en]

Extrinsic mortality has a strong impact on the evolution of life-histories, prey morphology and behavioural adaptations, but for many animals the causes of mortality are poorly understood. Predation is an important driver of extrinsic mortality and mobile animals form groups in response to increased predation risk. Furthermore, in many species juveniles suffer higher mortality than older individuals, which may reflect a lower phenotypic quality, lower competitiveness, or a lack of antipredator or foraging skills. Here we assessed the causes of mortality for 371 radio tagged Siberian jays. This sedentary bird species lives in family groups that contain a breeding pair as well as related and unrelated non-breeders. Ninety-five percent of death were due to predation (n = 59 out of 62 individuals) and most individuals were killed by Accipiter hawks. Multivariate Cox proportional hazards models showed that non-breeders had a lower survival than breeders, but only in territories in managed forest with little visual cover. Examining breeders, only sex influenced survival with males having a lower survival than females. For non-breeders, juveniles had lower survival than older non-breeders, and those on managed territories had lower survival than those on unmanaged territories. Additionally, a low feather quality reduced the survival probability of non-breeders only. Thus, living on managed territories and having a low feature quality affected only non-breeders, particularly juveniles. These findings add to previous research demonstrating that juvenile Siberian jays acquire critical antipredator skills from experienced group members. Thus, experience can buffer extrinsic mortality, highlighting that group living not only provides safety in numbers, but also provide social opportunities to learn critical life-skills.

National Category
Ecology Environmental Sciences
urn:nbn:se:uu:diva-334928 (URN)10.1111/oik.04098 (DOI)000408908700005 ()
Swedish Research CouncilSwedish Research Council FormasLars Hierta Memorial Foundation
Available from: 2017-12-01 Created: 2017-12-01 Last updated: 2017-12-01Bibliographically approved
Fletcher, K. (2017). Relating life history and physiology.
Open this publication in new window or tab >>Relating life history and physiology
2017 (English)Report (Other academic)
p. 24
Introductory research essay / Department of Animal Ecology, Evolutionary Biology Centre, Uppsala University, ISSN 1404-4919 ; 106
National Category
urn:nbn:se:uu:diva-322741 (URN)
Available from: 2017-05-29 Created: 2017-05-29 Last updated: 2017-05-31Bibliographically approved

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