Effects of nestboxes and males on female song activity in the European starling: an experimental study Denitza Z. Pavlova 1,2) , Rianne Pinxten 1) , Veerle M. Darras 3) & Marcel Eens 1,2) ( 1 Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium; 3 Laboratory of Comparative Endocrinology, K.U. Leuven, Naamsestraat 61, B-3000 Leuven, Belgium) (Accepted: 18 July 2007) Summary Environmental, contextual or social factors influencing song in female songbirds have been little studied. Female European starlings Sturnus vulgaris sing robustly throughout most of the year, except during the breeding season when their song production dramatically de- creases. Here we experimentally investigated the effect of the presence of males and/or nest- boxes on song production in captive female starlings during the breeding season. Spontaneous song activity of two experimental groups and one control group (housed with nestboxes, but no males) was observed for one month from the end of March onwards. Additionally, we tested whether female song rate is related to oestradiol plasma levels. The experimental re- sults showed that song rate significantly decreased with the progressing of the breeding sea- son and this process seemed not to be regulated by oestradiol. Nestboxes clearly promoted song production, as previously found in male starlings, while the presence of males nega- tively affected female song rate. Taken together these results indicate that, in the course of the breeding period, the suppressive influence of the day length and the presence of males on female song production override the stimulating effect of nestboxes, and that engagement in breeding activities is largely incompatible with singing in female starlings. Keywords: female song, song rate, seasonal variation, oestradiol, European starling. 2) E-mail addresses of corresponding authors: denitza.pavlova@ua.ac.be; marcel.eens@ua.ac.be © Koninklijke Brill NV, Leiden, 2007 Behaviour 144, 1255-1271 Also available online - www.brill.nl/beh