Breeding phenology of blue tits in Mediterranean stone pine plantations: effects of nestboxes and holm oaks.

A blue tit Cyanistes caeruleus population nesting in a Mediterranean stone pine plantation Pinus pinea in the Sierra Morena, Spain, was studied during 2007–2009. Nestboxes were distributed 50 m apart in a grid and territory size, territory location, number of Iberian holm oaks Quercus ilex in territories and number of conspecific neighbours were determined. Laying date, clutch size, hatching success, fledging success and fledgling mass were also recorded. Linear transects were carried out both within and outside the area where nestboxes were located. Over 50% of nestboxes remained unoccupied. The number of conspecific neighbours was positively associated with territory size. Occupied nestboxes had more holm oaks in their vicinity than did unoccupied nestboxes. Breeding success and fledgling mass were similar across territories although laying was earlier in larger territories and in those rich in holmoaks. Clutch size declined with laying date. Blue tits nesting in stone pine plantations are limited in their breeding phenology by the availability of holm oaks in the vicinity of the nest and by territory size. Holm oaks and territory size are more important for attainment of breeding condition by females than for raising nestlings.