title: Clutch size and cavity excavation in parids (Paridae): the limited breeding opportunities hypothesis tested.
authors.affiliation: Department of Biology, University of Oulu, POB 333, FIN-90571 Oulu, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Mönkkönen
authors.forename: M
authors.initials: M
authors.lastname: Orell