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Capsule The provision of supplementary food in early spring led to an advance in laying date and increased productivity for the Great Spotted Woodpecker. Aims To use the experimental provision of supplementary food in the prebreeding period to investigate the role of food supply in determining laying date, subsequent synchrony with natural food availability and the impact on productivity for the Great Spotted Woodpecker. Methods Supplementary food in the form of fat blocks was provided at 13 feeding stations distributed over half of a 100-ha study wood from early February until late April 2011 with the other half of the wood left unfed. The breeding parameters (first egg date, clutch size, number of young fledged per nest and nest success) of Great Spotted Woodpeckers were monitored throughout the wood and data from the 'fed' and 'unfed' zones compared. The same breeding parameters collected throughout the wood in the five preceding years (2006-10) when there was no supplementary feeding were used to provide control data. The temporal pattern in the abundance of the main natural prey was monitored using caterpillar frass traps. Results In 2011, the mean first egg date for woodpecker nests in the fed zone of the wood was 4-5 days earlier than for those nests in the unfed zone. Nests in the fed zone were almost twice as productive as those in the unfed zone even though the supplementary feeding stopped before the main period of chick rearing. There were no differences in the breeding parameters in the two zones of the wood in the control years when there was no supplementary feeding. 2011 was a very warm spring and the natural prey abundance peaked very early so that none of the woodpeckers were well synchronized with their main breeding season prey. However, the small advancement in first egg date meant the supplemented birds were better synchronized than the controls. Conclusion The response of Great Spotted Woodpeckers to supplementary feeding suggests they may be limited in their ability to shift their breeding period to maintain synchrony with their natural prey in the breeding season. This has important implications for the response of the birds to warm springs which are expected to be more frequent under future climate change. Use of garden feeders by Great Spotted Woodpeckers has the potential to increase breeding success and may be one of the many factors contributing to their current population increase.

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