Global anthropogenic changes are significantly impacting the ecology and evolution of many species. Among temperate taxa, changes to reproductive phenology as a result of warming springs are apparent. However, how such responses to abiotic change interact with biotic impacts resulting from human management interventions are less clear. Here we examine the response of a range of breeding metrics (laying date, clutch size, hatching and fledging success) to interactions between climatic variables and changes in conspecific density (and hence intraspecific competition) resulting from changes in nestbox provision. Using a 37-year dataset on the Great Tit Parus major we found little evidence for interacting effects of these two drivers. Instead we found that either climatic or competitive effects were the key influence on different metrics. Annual mean laying date substantially advanced with a warming climate, whereas clutch size, hatching success and fledging success were significantly inversely associated with conspecific density. Annual variance in clutch size and hatching success increased weakly with measures of conspecific density, but there was no association between either climatic or density measures and the annual variance in laying date or fledging success. Increasing conspecific densities therefore resulted in years with lower, but more variable, reproductive rates. These results highlight the importance of adaptive provisioning of nestboxes to enhance reproductive output of hole-nesting birds regardless of climate-induced phenological change. Such management is likely to be appropriate for assisting with sustaining populations responding to a changing climate.
Bibliographical noteFunding Information
ERC Consolidator Grant. Grant Number: 310820
We thank the many volunteers who monitor the nest-boxes in Treswell Wood, especially Dan & Gill Bardsley,John Bartley, Richard du Feu, Phil May and Keith Sted-man, and the owners of the wood, NottinghamshireWildlife Trust. All monitoring work was conductedunder licence from the British Trust for Ornithologyand Nottinghamshire Wildlife Trust. We thank TomHouslay for statistical advice and two anonymousreviewers. T.W.B. is currently funded by the EuropeanUnion’s Horizon 2020 research and innovation pro-gramme under Marie Skłodowska-Curie grant agreementno. 747120, and S.B. is supported by ERC ConsolidatorGrant 310820.
- adaptive management
- clutch size
- laying date