Speckled warblers break cooperative rules: absence of helping in a group-living member of the Pardalotidae JANET L. GARDNER, ROBERT D. MAGRATH & PENNY D. OLSEN School of Botany and Zoology, Australian National University (Received 9 March 2003; initial acceptance 17 April 2003; final acceptance 20 August 2003; MS. number: 7641) In the majority of cooperatively breeding bird species, subordinates help the dominant pair to provision the young, regardless of the origin of groups and relatedness between members. Within the family that includes speckled warblers, Chthonicola sagittata, there is considerable variation in social organization and parental behaviour, but the societies of other group-living species in this family are of kin, and subordinates provision the young of breeders. Speckled warblers differ in that offspring are never philopatric, and breeding groups comprise unrelated individuals. We used behavioural observations and DNA fingerprinting to examine genetic parentage and the mating system of the group-living speckled warbler in Canberra, Australia. Speckled warblers breed as pairs or in trios consisting of a female with two males. Alpha males are socially dominant to beta males and maintain dominance through aggression. Beta males never helped to feed nestlings or fledglings, even though they competed for copulations and in one case gained paternity of two of three young in a brood. The social system is therefore polyandrous but not cooperative. As well as competing for copulations with females on their own territories, beta males and single males (those that had lost their breeding partner) regularly undertook extraterritorial forays, most often when the neighbouring female was fertile. Failure by beta males to help even with broods containing their own offspring may be adaptive in this species and may result from increased opportunity for extrapair fertilizations or enhancement of prospects for future reproduction through the formation of alliances with females. Ó 2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. The vast majority of bird species breed as a simple pair, but in at least 3% of species, groups of individuals cooperate to rear young (Brown 1987). In cooperatively breeding species, subordinates usually help the dominant pair to provision the young, regardless of whether groups are of kin or comprise unrelated individuals (Brown 1987; Emlen 1991; Cockburn 1998). Subordinates can benefit from helping either indirectly through the enhanced produc- tion of nondescendant kin (kin selection: Brown 1987; Emlen 1995) or directly by increasing their own chances of survival or reproduction, either immediately or in the future (review in Cockburn 1998). Thus, helping appears to be an integral part of group living in both kin-based and polyandrous societies. Despite its wide occurrence and variety of benefits, help is not universal within group-living species. Help may be provided on particular territories, only by some individ- uals or to nestlings but not fledglings, and the degree of help given may vary. For example, in dunnocks, Prunella modularis, both the decision to help and the amount of help given are dependent on paternity within the brood, assessed by the number of copulations gained during the fertile period (Burke et al. 1989; Davies 1992). Similarly, subordinate white-browed scrubwrens, Sericornis frontalis, are more likely to provision the offspring of an unrelated female, but if they choose to help, they do so at a rate equal to that of the dominant pair (Magrath & Whittingham 1997). In other species, helping is directed only towards kin. Longtailed tit, Aegithalos caudatus, helpers are failed breeders that provide care to the broods of kin members of their social group. In the absence of close kin they fail to become helpers (Russell & Hatchwell 2001). Although helping is rare in western bluebirds, Sialia mexicana (7% of pairs have helpers), it is also confined to kin, and usually occurs on territories where both parents, rather than one, are present (Dickinson et al. 1996). Finally, grey jay, Perisoreus canadensis, subordinates feed young only during the fledgling period, and are excluded from the nest area by breeders (Waite & Strickland 1997; Strickland & Waite 2001). Far less common than variable patterns of help are cases in which subordinates never provide help; only three cases have been documented. Siberian jays, P. infaustus, live in groups that consist of adults and philopatric young Correspondence: J. L. Gardner, School of Botany and Zoology, Australian National University, Canberra, ACT 0200, Australia (email: janet.gardner@anu.edu.au). 719 0003e3472/03/$30.00/0 Ó 2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. ANIMAL BEHAVIOUR, 2004, 67, 719e728 doi:10.1016/j.anbehav.2003.08.017