|Institution:||University of Oslo|
|Full text PDF:||https://www.duo.uio.no/handle/10852/11720
Abstract In temperate areas, we tend to see an advancement of spring as the global climate is changing at a rate that may be hard for long distance migrant birds to track. Caterpillars are the most common prey type for pied flycatcher (Ficedula hypoleuca) nestlings, and the abundance of this food source peaks later with increasing altitude. Thus, I expected birds that settle at higher altitudes to have better synchronized their offspring’s need with food abundance. One aim of this study was to see if pied flycatchers had higher occupation rates and breeding success with increasing altitude, and if so, was this correlated to aversion to/competition with tits? I also wanted to see if the adverse effects of spells of bad weather had stronger impact if it occurred early in the nestling phase. During the spring and summer of 2009, I conducted a field study in the Dæli forest on the outskirts of Oslo, Norway. The study area had about 500 available nest boxes, in which pied flycatchers bred in 54 of them. In the present study, I examined the effects of altitude, laying dates and bad weather on breeding performance (clutch size, hatching-, fledging- and nesting success, number of young fledged and fledgling body mass). My results showed no difference in breeding success with altitude; however, one indication of pied flycatchers preferring to breed high in the terrain was the higher occupation rates of nest boxes in these areas. It may be that there are phenological advantages in relation to nutrition higher above sea level, or, the higher occupation rates might be a result of less competition with tits for nest boxes and food. Even in years with no apparent mistiming between breeding and the caterpillar peak, chicks’ survival chances are strongly reduced when they are exposed to extreme rainfall early in the nestling phase. This one-year study is to be treated as preliminary, and further studies are needed.