Tuesday, 28 February 2012

Drivers of low breeding success in the Lesser Spotted Woodpecker in England: testing hypotheses for the decline

Interesting report on Lesser Spotted Woodpecker in the new issue of Bird Study by Elisabeth C. Charman, Ken W. Smith, Ian A. Dillon, Steve Dodd, Derek J. Gruar, Andrew Cristinacce, Phil V. Grice & Richard D. Gregory. Here is a brief overview of the paper.

Capsule The breeding success of Lesser Spotted Woodpeckers Dendrocopos minor is now lower in England than previously reported and also lower than found in studies elsewhere in Europe.

Lesser Spotted Woodpecker: Thermos

Aims To quantify the breeding success and identify the causes of nest failure. To test the hypotheses that breeding success is related to aspects of food limitation and parental care, and inclement weather during the nesting period, or to interactions with Great Spotted Woodpeckers.

Methods Nests were monitored in three regions of England, recording survival and causes of failure. We measured aspects of food limitation and parental care, rainfall and Great Spotted Woodpecker interactions at nests, to explore whether there was any evidence that these factors were related to breeding success. We compared results to other studies from the UK and continental Europe.

Results Nest survival was 52%. The average number of chicks produced from successful nests was 2.8. Chick-stage daily nest survival was positively related to provisioning rates, indicating that food supply may be limiting. The most common cause of nest failure was presumed starvation of chicks after the disappearance of an adult. Some females ceased visiting nests, leaving provisioning solely to the male. This behaviour has been reported elsewhere in Europe, but in the present study males were unable to compensate fully by increasing their provisioning rates, leading to poor nest survival. Provisioning rates and chick-stage daily nest survival were negatively associated with rainfall. Nest predation by Great Spotted Woodpeckers occurred but was a less frequent cause of failure. Aggressive interactions were recorded between the two woodpecker species but these were unrelated to breeding parameters.

Conclusions Low breeding success is most probably related to food shortages in the breeding period. Simple population modelling using parameters from the present study and from published work shows that if the low productivity that we have observed is replicated throughout Britain, it would be sufficient to account for the observed population decline. However, the possibility that survival rates are also low cannot be ruled out.

Lesser Spotted Woodpecker: Thermos

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