Breeding biology of the Great Tit in two maritime pine forests in the region of Figueira da Foz (Beira Litoral, Portugal)

During the spring of 2003 some aspects of the breeding biology of the Great Tit Parus major were studied in two maritime pine (Pinus pinaster) forests of Figueira da Foz, using nest boxes. One study site was located in Mata Nacional do Urso (MU), close to an industrial area and the other was located in Mata Nacional de Quiaios (MQ), a forested area with no direct influence of industrial pollution. The total occupation rate of nest boxes for all species was significantly higher in MQ, but the nest-boxes occupation rates by Great Tits were similar in both areas. The number of fledglings per pair, hatching success, survival rate and breeding success were similar between the two study areas. However, clutch size and brood size were marginally significantly larger in MU. Therefore, the results provide evidence that breeding close to an industrial complex does not influence directly the Great Tit, but it may affect others species that also breed in nest boxes. Interspecific competition mechanisms seem to be more important in the breeding biology of the Great Tit, which might dissimulate the effects induced by pollution.