A telemetry study of the social organization of a tawny owl (Strix aluco) population

Abstract

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Melanin-based colour polymorphism signals aggressive personality in nest and territory defence in the tawny owl (Strix aluco)

“…Nestlings leave the nest box even before they are able to fly, at an age of 25-30 days, but parents continue to feed and protect them until they are about 2 months old (Sunde 2008). Because of their 5-10 % larger size and 20-25 % greater body mass (Glutz von Blotzheim 1987), females are also responsible for the majority of nest defence against predators (Wallin 1987), whereas in territorial disputes, males and females are equally active (Sunde and Bølstad 2004). The response to an individual that challenges the territory by singing is most frequent and intense in autumn, when territories are established, and during reproduction (Galeotti 1990;Appleby et al 1999).…”

“…The response to an individual that challenges the territory by singing is most frequent and intense in autumn, when territories are established, and during reproduction (Galeotti 1990;Appleby et al 1999). Vocalization rate of breeding individuals is higher in sites where floaters are more abundant (Sunde and Bølstad 2004). Thus, territorial disputes are frequent and playback experiments mimic a natural situation.…”

Floater strategies and dynamics in birds, and their importance in conservation biology: towards an understanding of nonbreeders in avian populations

“…In such cases floaters can become a drain on breeders, mainly because: (1) owners may spend a great deal of time and energy chasing floaters from their territories (Sunde & Bølstad, 2004;Carrete, Don´azar & Margalida, 2006a), with floater intrusions representing an additional cost during reproduction (Birkhead, 1982;Sandell & Diemer, 1999;Pilz & Smith, 2004;Bretagnolle, Mougeot & Thibault, 2008); (2) high levels of floater pressure may oblige owners to reduce the sizes of their territories (Norton, Arcese & Ewald, 1982); (3) floaters may compete for food with territory owners; (4) in some species (notably raptors) the intruders can kill owners in territorial fights (Newton, 1979).…”

Selective Predation of Tawny Owls (Strix aluco) on Yellow-Necked Mice (Apodemus flavicollis) and Bank Voles (Myodes glareolus)

“…The deciduous parts of the forest houses a well studied population of tawny owls mostly breeding in nest boxes in well-defined territories (Sunde & Bølstad 2004). During two years (2003,2007) with population peaks of A.f and M.g., following major beech (Fagus sylvaticus) mast crops the preceding autumns, we collected prey from tawny owl nest boxes and live captured reference animals (25 March-10 May).…”