Abstract
In some birds, yearling males (subadults) are less brightly coloured than the adult ones. To explain this phenomenon known as delayed plumage maturation (DPM), several hypotheses have recently been proposed.
The aim of this paper was to test predictions of status signal hypothesis (SSH). This hypothesis claims that the adults less frequently attack dull coloured subadult males, and consequently DPM facilitates survival of subadults during the first breeding season.
The experiments were performed in two habitats in the Prague suburbs: a housing estate and garden city. Subadult and adult males of the black redstart (Phoenicurus ochruros) were exposed to stuffed dummies of both age categories.
Contrary to predictions of SSH, brown (subadult like) coloration of the dummy had no suppressive effect on defensive behaviour of the resident males. On the other hand, subadult males were more active in vocal territorial defence such as singing and producing snarl and whistle sounds during the experiments.
The def