Most temperate zone passerines defend territories during the breeding seaso
n. Commonly the size of these territories is estimated by plotting the sing
ing locations of the males. However, an individual's activities need not be
restricted to the area used for singing. So far, only little quantitative
information has been available to determine how the singing territory relat
es to the activity range of male songbirds. Here, we present a study in whi
ch we used radio-tracking techniques to collect quantitative data on the sp
atial behaviour of 11 male territorial Nightingales (Luscinia megarhynchos)
. The results show that the singing territories made up only about 50 % of
the activity ranges. Nevertheless, males spent over 90 % of the time within
the singing territory. Singing territories almost never overlapped but act
ivity ranges overlapped in all cases with the activity range of at least on
e neighbour. Males intruded into neighbouring territories throughout the se
ason but the longest excursions were made before and during the female fert
ile period. The time spent for forays correlated significantly with song ra
te and territories of males with higher song rates in turn were less freque
ntly the object of forays by other males. Song rate can be indicative of ma
le quality, so that our findings strongly suggest that foray behaviour is r
elated to male quality in nightingales.