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Van Gestel M, Heylen D, Verheyen K, Fonville M, Sprong H, Matthysen E. Recreational hazard: Vegetation and host habitat use correlate with changes in tick-borne disease hazard at infrastructure within forest stands. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 919:170749. [PMID: 38340833 DOI: 10.1016/j.scitotenv.2024.170749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 02/01/2024] [Accepted: 02/04/2024] [Indexed: 02/12/2024]
Abstract
Studies on density and pathogen prevalence of Ixodes ricinus indicate that vegetation and local host community drive much of their variation between green spaces. Contrarily, micro-geographic variation is understudied, although its understanding could reduce disease risk. We studied the density of infectious nymphal Ixodes sp. ("DIN", proxy for disease hazard), density of questing nymphs ("DON") and nymphal infection prevalence ("NIP") near recreational forest infrastructure. Drag sampling within forest stands and at adjacent benches and trails was combined with vegetation surveys, camera trapping hosts and pathogen screening of ticks. We analysed Borrelia burgdorferi s.l. and its genospecies, with complementary analyses on Rickettsia sp., Anaplasma phagocytophilum, Neoehrlichia mikurensis and Borrelia miyamotoi. DIN was highest in forest interior and at trails enclosed by forest. Lower disease hazard was observed at benches and trails at forest edges. This infrastructure effect can be attributed to variation in vegetation characteristics and the habitat use of tick hosts, specifically roe deer, rodents and songbirds. DON is the main driver of DIN at micro-geographic scale and negatively affected by infrastructure and forest edges. A positive association with vegetation cover in understorey and canopy was observed, as were positive trends for local rodent and songbird abundance. NIP of different pathogens was affected by different drivers. Lower B. burgdorferi s.l. prevalence in the interior of forest stands, driven by its most prevalent genospecies B. afzelii, points towards higher density of uninfected hosts there. B. afzelii was positively associated with understorey containing tall species and with high canopy cover, whereas local bird community composition predicts B. garinii prevalence. A positive effect of songbird abundance and a negative effect of pigeons were observed. Our findings support amplification and inhibition mechanisms within forest stands and highlight that the effect of established drivers of DIN may differ based on the considered spatial scale.
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Affiliation(s)
- Mats Van Gestel
- Evolutionary Ecology Group, Department of Biology, University of Antwerp, Wilrijk, Belgium; Forest & Nature Lab, Department of Environment, Ghent University, Gontrode, Belgium.
| | - Dieter Heylen
- Evolutionary Ecology Group, Department of Biology, University of Antwerp, Wilrijk, Belgium; Interuniversity Institute for Biostatistics and statistical Bioinformatics, Hasselt University, Diepenbeek, Belgium
| | - Kris Verheyen
- Forest & Nature Lab, Department of Environment, Ghent University, Gontrode, Belgium
| | - Manoj Fonville
- National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands
| | - Hein Sprong
- National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands
| | - Erik Matthysen
- Evolutionary Ecology Group, Department of Biology, University of Antwerp, Wilrijk, Belgium
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Song Z, Liker A, Liu Y, Székely T. Evolution of social organization: phylogenetic analyses of ecology and sexual selection in weavers. Am Nat 2022; 200:250-263. [DOI: 10.1086/720270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Jones HH, Sieving KE. Foraging ecology drives social information reliance in an avian eavesdropping community. Ecol Evol 2019; 9:11584-11597. [PMID: 31695870 PMCID: PMC6822049 DOI: 10.1002/ece3.5561] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2019] [Revised: 06/14/2019] [Accepted: 07/26/2019] [Indexed: 11/06/2022] Open
Abstract
Vertebrates obtain social information about predation risk by eavesdropping on the alarm calls of sympatric species. In the Holarctic, birds in the family Paridae function as sentinel species; however, factors shaping eavesdroppers' reliance on their alarm calls are unknown. We compared three hypothesized drivers of eavesdropper reliance: (a) foraging ecology, (b) degree of sociality, and (c) call relevance (caller-to-eavesdropper body-size difference). In a rigorous causal-comparative design, we presented Tufted Titmouse (Baeolophus bicolor) alarm calls to 242 individuals of 31 ecologically diverse bird species in Florida forests and recorded presence/absence and type (diving for cover or freezing in place) of response. Playback response was near universal, as individuals responded to 87% of presentations (N = 211). As an exception to this trend, the sit-and-wait flycatcher Eastern Phoebe (Sayornis phoebe) represented 48% of the nonresponses. We tested 12 predictor variables representing measures relevant to the three hypothesized drivers, distance to playback speaker, and vulnerability at time of playback (eavesdropper's microhabitat when alarm call is detected). Using model-averaged generalized linear models, we determined that foraging ecology best predicted playback response, with aerial foragers responding less often. Foraging ecology (distance from trunk) and microhabitat occupied during playback (distance to escape cover) best predicted escape behavior type. We encountered a sparsity of sit-and-wait flycatchers (3 spp.), yet their contrasting responses relative to other foraging behaviors clearly identified foraging ecology as a driver of species-specific antipredator escape behavior. Our findings align well with known links between the exceptional visual acuity and other phenotypic traits of flycatchers that allow them to rely more heavily on personal rather than social information while foraging. Our results suggest that foraging ecology drives species-specific antipredator behavior based on the availability and type of escape cover.
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Affiliation(s)
- Harrison H. Jones
- Department of Wildlife Ecology and ConservationUniversity of FloridaGainesvilleFLUSA
- Department of BiologyUniversity of FloridaGainesvilleFLUSA
| | - Kathryn E. Sieving
- Department of Wildlife Ecology and ConservationUniversity of FloridaGainesvilleFLUSA
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McQueen A, Kempenaers B, Dale J, Valcu M, Emery ZT, Dey CJ, Peters A, Delhey K. Evolutionary drivers of seasonal plumage colours: colour change by moult correlates with sexual selection, predation risk and seasonality across passerines. Ecol Lett 2019; 22:1838-1849. [PMID: 31441210 DOI: 10.1111/ele.13375] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Accepted: 07/22/2019] [Indexed: 12/12/2022]
Abstract
Some birds undergo seasonal colour change by moulting twice each year, typically alternating between a cryptic, non-breeding plumage and a conspicuous, breeding plumage ('seasonal plumage colours'). We test for potential drivers of the evolution of seasonal plumage colours in all passerines (N = 5901 species, c. 60% of all birds). Seasonal plumage colours are uncommon, having appeared on multiple occasions but more frequently lost during evolution. The trait is more common in small, ground-foraging species with polygynous mating systems, no paternal care and strong sexual dichromatism, suggesting it evolved under strong sexual selection and high predation risk. Seasonal plumage colours are also more common in species predicted to have seasonal breeding schedules, such as migratory birds and those living in seasonal climates. We propose that seasonal plumage colours have evolved to resolve a trade-off between the effects of natural and sexual selection on colouration, especially in seasonal environments.
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Affiliation(s)
- Alexandra McQueen
- School of Biological Sciences, Monash University, VIC, Clayton Campus, 3800, Australia
| | - Bart Kempenaers
- Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Eberhard Gwinner Str, 82319, Seewiesen, Germany
| | - James Dale
- Institute of Natural and Mathematical Sciences, Massey University, Auckland, 0745, New Zealand
| | - Mihai Valcu
- Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Eberhard Gwinner Str, 82319, Seewiesen, Germany
| | - Zachary T Emery
- School of Biological Sciences, Monash University, VIC, Clayton Campus, 3800, Australia
| | - Cody J Dey
- Great Lakes Institute for Environmental Research, University of Windsor, 401 Sunset Avenue, Windsor, ON, Canada
| | - Anne Peters
- School of Biological Sciences, Monash University, VIC, Clayton Campus, 3800, Australia
| | - Kaspar Delhey
- School of Biological Sciences, Monash University, VIC, Clayton Campus, 3800, Australia
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Visscher DR, Unger A, Grobbelaar H, DeWitt PD. Bird foraging is influenced by both risk and connectivity in urban parks. JOURNAL OF URBAN ECOLOGY 2018. [DOI: 10.1093/jue/juy020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- D R Visscher
- Department of Biology, The King's University, Edmonton, AB T6B 2H3, Canada
| | - A Unger
- Department of Biology, The King's University, Edmonton, AB T6B 2H3, Canada
| | - H Grobbelaar
- Department of Biology, The King's University, Edmonton, AB T6B 2H3, Canada
| | - P D DeWitt
- Science and Research Branch, Ontario Ministry of Natural Resources & Forestry, Peterborough, ON K9J 3C7, Canada
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Understory avifauna exhibits altered mobbing behavior in tropical forest degraded by selective logging. Oecologia 2016; 182:743-54. [PMID: 27417548 DOI: 10.1007/s00442-016-3695-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 07/07/2016] [Indexed: 10/21/2022]
Abstract
In understanding the impacts of selective logging on biodiversity, relatively little is known about the critical behavioral link between altered forest conditions and population persistence. Predator-mobbing is a widespread anti-predator behavior in birds that expresses a well-known trade-off influencing prey survival under predation risk. Here, we ask whether the predator-mobbing behavior of understory forest birds is altered by selective logging and associated forest structural changes in the highly endangered lowland rainforest of Sumatra. At four study sites spanning a gradient of logging-induced forest degradation, we used standardized mobbing and owl call playbacks with predator model presentation to elicit the predator-mobbing behavior of understory prey birds, compared birds' mobbing intensity across sites, and related variation in this intensity to forest vegetation structure. We found that selective logging altered birds' predator-mobbing intensity (measured by behavioral conspicuousness and propensity to approach the predator) as well as forest structure, and that vegetative changes to canopy and understory were correlated with contrasting responses by the two major bird foraging guilds, gleaning versus flycatching birds. We additionally discuss the implications of our findings for further hypothesis testing pertaining to the impacts of selective logging on the ecological processes underlying prey mobbing behavior, particularly with regards to predator-prey interactions and prey accruement of energy reserves.
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Barnier F, Duncan P, Fritz H, Blanchard P, Rubenstein DI, Pays O. Between-gender differences in vigilance do not necessarily lead to differences in foraging-vigilance tradeoffs. Oecologia 2016; 181:757-68. [DOI: 10.1007/s00442-016-3614-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 03/16/2016] [Indexed: 11/29/2022]
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Morán-López T, Alonso CL, Díaz M. Landscape effects on jay foraging behavior decrease acorn dispersal services in dehesas. ACTA OECOLOGICA-INTERNATIONAL JOURNAL OF ECOLOGY 2015. [DOI: 10.1016/j.actao.2015.07.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Mathot KJ, Nicolaus M, Araya‐Ajoy YG, Dingemanse NJ, Kempenaers B. Does metabolic rate predict risk‐taking behaviour? A field experiment in a wild passerine bird. Funct Ecol 2014. [DOI: 10.1111/1365-2435.12318] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Kimberley J. Mathot
- Evolutionary Ecology of Variation Group Max Planck Institute for Ornithology Eberhard Gwinner Straβe DE‐82319 Seewiesen Germany
- Department of Behavioural Ecology and Evolutionary Genetics Max Planck Institute for Ornithology Eberhard Gwinner Straβe DE‐82319 Seewiesen Germany
| | - Marion Nicolaus
- Evolutionary Ecology of Variation Group Max Planck Institute for Ornithology Eberhard Gwinner Straβe DE‐82319 Seewiesen Germany
- Department of Behavioural Ecology and Evolutionary Genetics Max Planck Institute for Ornithology Eberhard Gwinner Straβe DE‐82319 Seewiesen Germany
| | - Yimen G. Araya‐Ajoy
- Evolutionary Ecology of Variation Group Max Planck Institute for Ornithology Eberhard Gwinner Straβe DE‐82319 Seewiesen Germany
- Department of Behavioural Ecology and Evolutionary Genetics Max Planck Institute for Ornithology Eberhard Gwinner Straβe DE‐82319 Seewiesen Germany
| | - Niels J. Dingemanse
- Evolutionary Ecology of Variation Group Max Planck Institute for Ornithology Eberhard Gwinner Straβe DE‐82319 Seewiesen Germany
- Department of Behavioural Ecology and Evolutionary Genetics Max Planck Institute for Ornithology Eberhard Gwinner Straβe DE‐82319 Seewiesen Germany
- Behavioural Ecology Department Biology II Ludwig‐Maximilians University of Munich Groβhadener Straβe 2 DE‐ 82152 Planegg‐Martinsried Munich Germany
| | - Bart Kempenaers
- Department of Behavioural Ecology and Evolutionary Genetics Max Planck Institute for Ornithology Eberhard Gwinner Straβe DE‐82319 Seewiesen Germany
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Pascual J, Senar JC, Domènech J. Are the Costs of Site Unfamiliarity Compensated With Vigilance? A Field Test in Eurasian Siskins. Ethology 2014. [DOI: 10.1111/eth.12243] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jordi Pascual
- Evolutionary and Behavioural Ecology Research Unit (CSIC); Natural History Museum of Barcelona; Barcelona Spain
| | - Juan Carlos Senar
- Evolutionary and Behavioural Ecology Research Unit (CSIC); Natural History Museum of Barcelona; Barcelona Spain
| | - Jordi Domènech
- Evolutionary and Behavioural Ecology Research Unit (CSIC); Natural History Museum of Barcelona; Barcelona Spain
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11
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Wintering birds avoid warm sunshine: predation and the costs of foraging in sunlight. Oecologia 2013; 174:713-21. [DOI: 10.1007/s00442-013-2804-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 10/03/2013] [Indexed: 10/26/2022]
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Villén-Pérez S, Carrascal LM, Seoane J. Foraging patch selection in winter: a balance between predation risk and thermoregulation benefit. PLoS One 2013; 8:e68448. [PMID: 23874632 PMCID: PMC3709897 DOI: 10.1371/journal.pone.0068448] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 05/29/2013] [Indexed: 11/28/2022] Open
Abstract
In winter, foraging activity is intended to optimize food search while minimizing both thermoregulation costs and predation risk. Here we quantify the relative importance of thermoregulation and predation in foraging patch selection of woodland birds wintering in a Mediterranean montane forest. Specifically, we account for thermoregulation benefits related to temperature, and predation risk associated with both illumination of the feeding patch and distance to the nearest refuge provided by vegetation. We measured the amount of time that 38 marked individual birds belonging to five small passerine species spent foraging at artificial feeders. Feeders were located in forest patches that vary in distance to protective cover and exposure to sun radiation; temperature and illumination were registered locally by data loggers. Our results support the influence of both thermoregulation benefits and predation costs on feeding patch choice. The influence of distance to refuge (negative relationship) was nearly three times higher than that of temperature (positive relationship) in determining total foraging time spent at a patch. Light intensity had a negligible and no significant effect. This pattern was generalizable among species and individuals within species, and highlights the preponderance of latent predation risk over thermoregulation benefits on foraging decisions of birds wintering in temperate Mediterranean forests.
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Affiliation(s)
- Sara Villén-Pérez
- Department of Biogeography and Global Change, Museo Nacional de Ciencias Naturales, Madrid, Spain.
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Pascual J, Senar JC. Differential effects of predation risk and competition over vigilance variables and feeding success in Eurasian siskins (Carduelis spinus). BEHAVIOUR 2013. [DOI: 10.1163/1568539x-00003114] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Many investigations have studied the effects of predation risk and competition over vigilance and feeding success, but they have proven to be difficult to discriminate. Moreover, none of the studies that have avoided the confusion has considered all the vigilance variables, food intake rate and time spent in the foraging patch. In this study, we designed an experiment with Eurasian siskinsCarduelis spinusforaging on three bird table feeders: one with low predation risk and competition, one with low predation risk and high competition and one with high predation risk and intermediate competition. Birds responded to increasing interference competition by increasing mean scan durations (probably due to the birds having to be vigilant for both other flock members and predators) and maintaining the length of mean inter-scan durations, while they responded to increasing predation risk by reducing mean inter-scan durations (probably in order to detect the predator sooner) while maintaining similar length of mean scan durations. Birds were often ejected from the feeder or departed because of disturbances, so time spent on feeders was reduced both because of competition and predation risk. Pecking rates were affected by competition but not by predation risk. Our results clearly show that birds vigilance strategy while foraging might be very different when they are mainly concerned with scanning for predators or when they primarily monitor competing flock companions. In addition, they stress the importance of recording all the vigilance and feeding variables when studying the effect of ecological factors over the foraging behaviour of birds.
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Affiliation(s)
- Jordi Pascual
- Behavioural and Evolutionary Ecology Research Unit (CSIC), Natural History Museum of Barcelona, P Picasso s/n, 08003 Barcelona, Spain
| | - Juan Carlos Senar
- Behavioural and Evolutionary Ecology Research Unit (CSIC), Natural History Museum of Barcelona, P Picasso s/n, 08003 Barcelona, Spain
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Carrascal L, Seoane J, Villén-Pérez S. Temperature and food constraints in wintering birds — an experimental approach in montane Mediterranean oakwoods. COMMUNITY ECOL 2012. [DOI: 10.1556/comec.13.2012.2.12] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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15
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Meer E, Pays O, Fritz H. The Effect of Simulated African Wild Dog Presence on Anti-predator Behaviour of Kudu and Impala. Ethology 2012. [DOI: 10.1111/eth.12003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Makin DF, Payne HFP, Kerley GIH, Shrader AM. Foraging in a 3-D world: how does predation risk affect space use of vervet monkeys? J Mammal 2012. [DOI: 10.1644/11-mamm-a-115.1] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Detecting predators and locating competitors while foraging: an experimental study of a medium-sized herbivore in an African savanna. Oecologia 2011; 169:419-30. [DOI: 10.1007/s00442-011-2218-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Accepted: 11/26/2011] [Indexed: 10/14/2022]
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19
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Tvardíková K, Fuchs R. Tits recognize the potential dangers of predators and harmless birds in feeder experiments. J ETHOL 2011. [DOI: 10.1007/s10164-011-0310-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Tvardíková K, Fuchs R. Do birds behave according to dynamic risk assessment theory? A feeder experiment. Behav Ecol Sociobiol 2010. [DOI: 10.1007/s00265-010-1075-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Beauchamp G. Relationship between Distance to Cover, Vigilance and Group Size in Staging Flocks of Semipalmated Sandpipers. Ethology 2010. [DOI: 10.1111/j.1439-0310.2010.01778.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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22
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Carrascal LM, Galván I, Gordo O. Partial least squares regression as an alternative to current regression methods used in ecology. OIKOS 2009. [DOI: 10.1111/j.1600-0706.2008.16881.x] [Citation(s) in RCA: 482] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Griesser M, Nystrand M. Vigilance and predation of a forest-living bird species depend on large-scale habitat structure. Behav Ecol 2009. [DOI: 10.1093/beheco/arp045] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Kurvers RHJM, Roberts ML, McWilliams SR, Peters A. Experimental manipulation of testosterone and condition during molt affects activity and vocalizations of male blue tits. Horm Behav 2008; 54:263-9. [PMID: 18468606 DOI: 10.1016/j.yhbeh.2008.03.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2007] [Revised: 03/18/2008] [Accepted: 03/20/2008] [Indexed: 11/20/2022]
Abstract
Testosterone (T) is a key hormone regulating behavioral trade-offs in male birds, shifting investment towards sexual and competitive behaviors. However, the role of T in regulating male behavior during the molt has received very little attention, although this is a crucial life-history stage. Since the effect of T on behavior may be condition-dependent, particularly during the costly molt period, we studied the effects of T and condition in a two-way design. We manipulated T under two dietary regimes (standard and improved, resulting in an enhanced condition) in captive blue tits (Cyanistes caeruleus) undergoing the first pre-basic molt. T treatment increased song frequency, indicating that song is T-dependent also at this time of year. Males on the improved diet sang less than males in relatively worse condition, providing no support for song as an indicator of male condition. T-treated males exhibited greater locomotor activity than control males, but only when fed the standard diet. Neither T- nor diet-treatment affected plumage maintenance (preening). Although T treatment resulted in a delay in molt progress all birds completed the molt. Taken together our results show that during the molt male birds are sensitive to relatively small fluctuations in T. Similar to its commonly observed effects during the breeding season, T stimulated an increase in song and locomotion. While there might be some benefits associated with such T effects, these must be traded-off against costs associated with conspicuous behavior and increased molt duration.
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Affiliation(s)
- Ralf H J M Kurvers
- Sexual Signaling Group, Max Planck Institute for Ornithology, Vogelwarte Radolfzell, Schlossallee 2, D-78315 Radolfzell, Germany.
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