Plasticity in Nest Composition in Relation to Nest-Site Characteristics in the Red-breasted Flycatcher ( Ficedula parva )

Abstract

The nest is an important part of reproduction of many altricial bird species and nest construction is varied, for example in site selection, shape and construction material. We studied nest composition in the Red-breasted Flycatcher (Ficedula parva), breeding in natural holes in primeval stands of the Białtowieża Forest. The nests were constructed of three main elements: moss, which was detected in all nests, dry leaves and hair. Moss was found in all nests and comprised on average more than 84% of nest mass. The proportion of moss was dependent on the living/dead status of the tree but not on the depth of the nest cavity or its height above the ground. In cavities located in live trees the proportion of moss in the nest was, on average, higher than in dead trees. The moss in the nests of the Red-breasted Flycatcher can regulate moisture (humidity), provide protection from rain and water from the tree, i.e. from the inner walls of the nest cavity, and can play a role as camouflage in passive protection against predators. Variation in nest construction suggests plasticity in the behaviour of the female Red-breasted Flycatcher in using nest components in relation to nest site characteristics and environmental conditions.