Does cavity reuse affect timing of reproduction and fledgling success in the Black Woodpecker?

摘要

Nesting in old cavities may be adaptive for birds as it may offer an advantage of earlier laying and higher fitness through more recruiting offspring. Black Woodpeckers frequently use old cavities, which gives the opportunity to test how this behavioraffects the timing and the success of reproduction. In this paper, we have tested a prediction that excavating a new cavity causes a delay in breeding, and that it is linked to lower productivity. We found that in the Wielkopolski National Park (westernPoland) Black Woodpeckers nested exclusively in European beeches, mainly in living trees, and most frequently in their old cavities. The median relative egg-laying date in old cavities was 5.5 days earlier than in new cavities. We did not find a difference in clutch size between old and new cavities due to its low variation in the population. The proportion of offspring surviving to the end of the nestling period was 0.812 in old cavities and 0.632 in new cavities, although this did not differ significantly. However, survivorship dropped rapidly in the hatching period, especially in new cavities. In Black Woodpecker, the number of fledglings that succeeded was best explained by a model including the age of the cavity and the relative laying date. Theestimated parameters of the best ranked model revealed that the number of fledglings is affected by the age of the cavity as it was higher for old cavities than for new cavities. This study shows that nest reuse is adaptive for primary excavators as it offers time and energy savings needed for cavity excavation, and increases productivity, compared to those pairs of birds that are forced to excavate a new cavity. These data are consistent with the hypothesis that cavity excavation is energetically expensive and support the prediction of tradeoffs between nest building and different components of reproduction. Responsible forest management should consider the need to protect living beeches with old cavities, which are frequently used by Black Woodpeckers.