Factors Affecting Timing of Breeding in the Tawny Owl

Abstract

Relevant variables characterising factors suspected to affect timing of breeding in birds may be difficult to measure. Then, easily available proxies, i.e. variables that are expected to vary consistently with some affecting factors, may be used instead. In the present study on tawny owls, I used besides individual characteristics of parent birds both detailed measurements of the prey base of territories, local and general indices of vole abundance as well as local and general weather conditions as explanatory variables. Owls tended to breed the earlier the older and the heavier they were. Breeding was the earlier the higher the abundance of water voles and the proportion of field voles in the territorial prey samples. Owls bred earlier when the local abundance of small voles in the preceding autumn was high. Regional vole indices showed no associations with timing of owls' breeding. Single winter weather variables did not show any significant associations neither. In combination with the advancing effect of water vole abundance, however, the delaying effect of the depth of the snow cover in March was significant. Models based on different data sets showed different kinds of associations between the abundance of small voles and timing of breeding in owls. The best models in which both intrinsic and extrinsic explanatory variables (characteristics of parent birds and environmental factors, respectively) were included did not differ considerably from each other. The occurrence of water voles in prey samples governed the best models. The results suggest, that without detailed knowledge on the prey base of territory, misleading results may emerge and the importance of small voles in governing breeding of owls may be overemphasised.

Field investigation of Turtle doves’ courtship: vocal calls versus arc-flight

“…Despite, what is more effective (song or visual), female recipients are widely known by their sensitivity to male signals and respond with varying behaviours between acceptance and refuse (Neunuebel et al 2015;Pennycuick 2015;Finton et al 2017). In general, studies of audiovisual communications in birds are focused on controlled experiments in laboratories (Caryl 1981;Krieg and Getty 2016;Ullrich et al 2016), while captivity results can be very different from natural expressions (Solonen 2013).…”

Diet and reproduction in coastal and inland populations of the Tawny Owl Strix aluco in southern Finland

“…In Finland, the beginning of the breeding activities in the Tawny Owl seems to be dependent on the availability of small voles (Microtus spp., Myodes spp.) (Solonen 2013(Solonen , 2014 or wWater vVoles Arvicola amphibius (Kekkonen et al 2008 ;Solonen 2013 ), while the breeding success (production of young) seems to be governed by the availability of small voles (Solonen and Karhunen 2002 ).…”