Winter food provisioning reduces future breeding performance in a wild bird

Plummer, Kate E.; Bearhop, Stuart; Leech, David I.; Chamberlain, Dan; Blount, Jonathan D.

doi:10.1038/srep02002

Cited by 75 publications

(78 citation statements)

References 38 publications

(61 reference statements)

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“…Variation in supplementary food consumption was linked to a number of demographic traits at the individual level, but at this level, we found no evidence of carry-over effects of winter seed consumption on reproductive success. Our results suggest that negative effects of supplementary feeding demonstrated previously (Harrison et al 2010, Plummer et al 2013a may have arisen through increased food availability influencing population demography, for example increasing the survival of low-quality individuals and potentially increasing resource competition during the breeding season. Additionally, temporally limiting the availability of supplementary food, as we did here, and which might occur in garden environments, may also prevent the development of carry-over effects.…”

Section: Discussionmentioning

confidence: 66%

Individual variation in winter supplementary food consumption and its consequences for reproduction in wild birds

Crates

Firth

Farine

et al. 2016

Journal of Avian Biology

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The provision of wild birds with supplementary food has increased substantially over recent decades. While it is assumed that provisioning birds is beneficial, supplementary feeding can have detrimental 'carry-over' effects on reproductive traits. Due to difficulties in monitoring individual feeding behaviour, assessing how individuals within a population vary in their exploitation of supplementary food resources has been limited. Quantifying individual consumption of supplementary food is necessary to understand the operation of carry-over effects at the individual level. We used Radio Frequency Identification (RFID) technology and automated feeders to estimate individual consumption of supplementary winter food in a large wild population of great tits Parus major and blue tits Cyanistes caeruleus. Using these data, we identified demographic factors that explained individual variation in levels of supplementary food consumption. We also tested for carry-over effects of supplementary food consumption on recruitment, reproductive success and a measure of survival. Individual variation in consumption of supplementary food was explained by differences between species, ages, sexes and years. Individuals were consistent across time in their usage of supplementary resources. We found no strong evidence that the extent of supplementary food consumption directly influenced subsequent fitness parameters. Such effects may instead result from supplementary food influencing population demographics by enhancing the survival and subsequent breeding of less competitive individuals, which reduce average breeding parameters and increase density-dependent competition. Carry-over effects of supplementary feeding are not universal and may depend upon the temporal availability of the food provided. Our study demonstrates how RFID systems can be used to examine individual-level behaviour with minimal effects on fitness.

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Section: Discussionmentioning

confidence: 66%

Individual variation in winter supplementary food consumption and its consequences for reproduction in wild birds

Crates

Firth

Farine

et al. 2016

Journal of Avian Biology

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“…A similar study on the same species (Plummer et al 2013a) proved that quality of food provided during winter is also important, as fat provision had negative effects on egg quality in the subsequent breeding season, whereas this effect was mitigated when fat was amended with vitamin E. A possible explanation for this result is that birds may have become dependent on such easily accessible, energy-rich food source; though it may have enhanced their overwinter survival, it reduced their dietary diversity, leading to that they failed to build up reserves of key nutrients important in egg formation. In a follow-up study with the same design (Plummer et al 2013b) fat supplement had similarly no effect on clutch size, but had detrimental effects on the number, weight and size of fledged young. In a three-year long study of woodland great tits and blue tits, several week long food supplementation until hatching yielded some surprising outcome, as the authors found reduction in both clutch size and number of hatched young in the treated groups (Harrison et al 2010).…”

Section: Changes In Resource-based Forcesmentioning

confidence: 93%

“…in the House Sparrow (Peach et al 2008. Nestling size also strongly predicts later fledging success in the Great Tit (Plummer et al 2013b), and size prior to fledging is known to be a good predictor of later recruitment as a breeding adult in many bird species (Schwagmeyer & Mock 2008). Thus, the quantity and/or quality of nestling food is one of the most crucial factors for chicks, as early nutritional conditions strongly affect both their survival and development.…”

Section: Seress G and Liker Amentioning

confidence: 99%

Habitat urbanization and its effects on birds

Seress

Liker²

2015

Acta Zool Acad Sci H

182

135

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By transforming landscapes, human activity creates new types of habitats with altered environmental characteristics that never existed before. As the process of habitat urbanization bears impact on more and more natural habitats, it is essential for us to understand the changes we bring forth in the ecological forces shaping urban animal communities. Birds are perhaps the most frequently studied model organisms by urban ecologists. It is a well known general pattern that urban avian communities have typically reduced species richness, while the density of a few successful species is often higher in cities than in adjacent more natural habitats. But it is less understood which mechanisms generate and uphold these community-level changes. In this review we discuss the most important components of the urban environment influencing birds' physiology, behaviour or morphology, and compile several recent studies to illustrate their effects. To understand urban food webs we also review the results of bottom-up and top-down approach which suggest that altered food availability and predation may play key roles in forming recent urban bird communities. We encourage future research to focus more on experimental, manipulative studies, that would help us not just to realize general patterns but shed more light on the mechanisms, the underlying processes prompting changes in urban bird communities.

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“…Nonetheless, urban environments are linked to reductions in fitness and health in a substantial number of organisms (Chamberlain et al, 2009;Murray et al, 2015). Hence, urban habitats are sometimes considered ecological traps which attract organisms, for example by anthropogenic food availability, but are insufficient for supporting successful rearing of offspring (Plummer et al, 2013;Sumasgutner et al, 2014;Lamb et al, 2017). There is a need, therefore, to understand the mechanisms by which urbanization reduces reproductive success.…”

Section: Introductionmentioning

confidence: 99%

Elevated Immune Gene Expression Is Associated with Poor Reproductive Success of Urban Blue Tits

et al. 2017

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Urban and forest habitats differ in many aspects that can lead to modifications of the immune system of wild animals. Altered parasite communities, pollution, and artificial light at night in cities have been associated with exacerbated inflammatory responses, with possibly negative fitness consequences, but few data are available from free-living animals. Here, we investigate how urbanization affects major immune pathways and experimentally test potentially contributing factors in blue tits (Cyanistes caeruleus) from an urban and forest site. We first compared breeding adults by quantifying the mRNA transcript levels of proteins associated with anti-bacterial, anti-malarial (TLR4, LY86) and anti-helminthic (Type 2 transcription factor GATA3) immune responses. Adult urban and forest blue tits differed in gene expression, with significantly increased TLR4 and GATA3, but not LY86, in the city. We then experimentally tested whether these differences were environmentally induced by cross-fostering eggs between the sites and measuring mRNA transcripts in nestlings. The populations differed in reduced reproductive success, with a lower fledging success and lower fledgling weight recorded at the urban site. This mirrors the findings of our twin study reporting that the urban site was severely resource limited when compared to the forest. Because of low urban survival, robust gene expression data were only obtained from nestlings reared in the forest. Transcript levels in these nestlings showed no (TLR4, LY86), or weak (GATA3), differences according to their origin from forest or city nests, suggesting little genetic or maternal contribution to nestling immune transcript levels. Lastly, to investigate differences in parasite pressure between urban and forest sites, we measured the prevalence of malaria in adult and nestling blood. Prevalence was invariably high across environments and not associated with the transcript levels of the studied immune genes. Our results support the hypothesis that inflammatory pathways are activated in an urban environment and suggest that these differences are most likely induced by environmental factors.

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Winter food provisioning reduces future breeding performance in a wild bird

Cited by 75 publications

References 38 publications

Individual variation in winter supplementary food consumption and its consequences for reproduction in wild birds

Individual variation in winter supplementary food consumption and its consequences for reproduction in wild birds

Habitat urbanization and its effects on birds

Elevated Immune Gene Expression Is Associated with Poor Reproductive Success of Urban Blue Tits

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