INTERACTIVE COMMUNICATION BETWEEN MALE AND FEMALE GREAT TITS (PARUS MAJOR) DURING THE DAWN CHORUS

Auk, The, Jan 2004 by Gorissen, Leen, Eens, Marcel

ABSTRACT.-Studies of the dawn chorus in birds have focused mainly on the behavior and song output of males and on the function(s) of male song. Less attention has been paid to the females' behavior and to communication between members of a pair. In Great Tits (Parus major), males sing vigorously at dawn in the vicinity of the female's nest hole just before and during egg laying. We studied the female's vocal behavior during the dawn chorus as well as communication between pair members. All females vocally interacted with their mates from inside the nest box. Females produced a sound with a very low sound-pressure level only audible from few meters, which we have named the "quiet call." This quiet call was unique to females and was only produced from inside the nest box. To our knowledge, our study is the first to show that both members of a pair vocally interact during the dawn chorus. Given that many temperate-zone bird species have similar life histories as the Great Tit, it is very likely that similar interactive behavior occurs in other (song)birds. This interactive behavior may provide a new and manipulable tool for testing hypotheses about the dawn song and can be used as a future bioassay of male vocalizations. Received 20 February 2003, accepted 5 October 2003.

RESUME. -Les etudes portant sur les chants emis a l'aube chez les oiseaux se sont interessees principalement au comportement, au son et aux fonctions du chant chez le male. Moins d'attention a ete portee sur le comportement des femelles et aux communications entre les membres d'un couple. Chez Parus major, a l'aube, les males chantent vigoureusement aux alentours des trous de nidification des femelles et ce juste avant et durant reclusion des ufs. Nous avons etudie le comportement vocal des femelles pendant l'emission de chants a l'aube ainsi que la communication entre les membres d'un couple. Toutes les femelles interagissaient vocalement avec leur partenaire de l'interieur du nichoir. Les femelles produisaient un son de tres faible pression, audible seulement svir quelques metres, que nous avons appele le �chant silencieux�. Ce chant silencieux etait unique aux femelles et il etait seulement produit de l'interieur du nichoir. Selon nos connaissances, cette etude est la premiere a montrer que les deux membres d'un couple interagissent vocalement au cours des chants emis a l'aube. Etant donne que de nombreuses especes d'oiseaux de la zone temperee ont des traits d'histoire de vie similaires a Parus major, il est tres probable que ce meme comportement interactif existe chez d'autres oiseaux (chanteurs). Ce comportement interactif pourrait fournir un nouvel outil pour tester des hypotheses sur les chants a l'aube et les vocalisations des males.

IN EARLY SPRING, just before sunrise, many male songbirds in the northern temperate zone demonstrate their singing abilities in what is commonly referred to as the dawn chorus. Although dawn choruses of many species have been studied extensively, its functions remain poorly understood. Several hypotheses have been proposed to explain why male birds sing more intensely at dawn than later in the day. According to Staicer et al. (1996), those hypotheses can be classified roughly into three categories: (1) singing more intensely at dawn could serve as a function intrinsic to the singer's internal state (e.g. hormonal state); (2) dawn, singing could have a social function (inter- or intrasexual) that is best served at dawn; and (3) birds might sing more at dawn because of the daily timing of environmental selective pressures.

Most recited functions of dawn song are mate attraction, mate guarding, and territory defense (Mace 1987, Slagsvold et al. 1994, Catchpole and Slater 1995). Recently, Staicer et al. (1996) have formulated four new hypotheses to explain the function of dawn song. The first states that dawn song may be a consequence of elevated levels of hormones that influence song (Orcadian cycles hypothesis). Alternatively, dawn singing might stimulate hormone production in singers and as a result prepare them for social interactions (self-stimulation hypothesis). Further, dawn song may stimulate mates (mate-stimulation hypothesis) or signal social relationships among neighboring birds (social dynamics hypothesis).

Until now, studies of dawn singing activity have focused primarily on the male's behavior and song output. We are not aware of any reports of vocal interactions between males and females during the dawn chorus (except for duetting species) in the north temperate zone. However, there are some reports of female vocalizations that function in intersexual communication. Female Red-winged Blackbirds (Agdaius phoeniceus) utter a "chit" call in response to the songs of their mates and in several nest-associated contexts, such as the arrival at and departure from their nests (Beletsky and Orians 1985, Birks and Beletsky 1987). Some female birds produce vocalizations that are specific to the context of copulation (Montgomerie and Thornhill 1989, Langmore et al. 1996). Nagle et al. (2002) recently suggested that adult female Canaries (Serinus canaria) provide information about their sexual interest and attract the attention of particular males by calling in response to male song.