Long–tailed tits (Aegithalos caudatus) are cooperative breeders in which helpers exhibit a kin preference in their cooperative behaviour. Experiments have found that there are significant differences in the responses of breeders to the vocalizations of kin and non–kin, suggesting that vocal cues may be used for kin recognition in this species. A second experiment investigated whether recognition is achieved on the basis of relatedness or through association to the adult bird. Nestlings were cross–fostered between unrelated broods in order to create broods composed of true and foster siblings. In subsequent years, survivors from experimental broods did not discriminate between true and fostered siblings when making helping decisions, indicating that recognition of “kin” is learned and not genetically determined in the Long Tailed Tit species (Hatchwell et al. 2001).
In the cooperative breeding system of the long-tailed tit (Aegithalos caudatus) failed breeders may become helpers at the nest of another pair to whom they are usually related. In a further experiment, capture–mark–recapture data was used and the MARK program to analyse survival of 482 birds ringed as fledglings and 155 birds ringed as adults. Juvenile males had a higher survival probability than juvenile females across all years whilst their subsequent adult survival was constant. Within sex, the survival probability of juveniles that fledged from nests with helpers was higher than those that did not receive help as nestlings. Failed breeders that became helpers had a higher survival probability (56%) than those failed breeders that did not become helpers (46%). Successful breeders had a survival probability of 56% regardless of whether they received help or not. Failed breeders that became helpers had a lower probability of successfully breeding in a subsequent year (27%) when compared to those failed breeders that did not become helpers (38%). It can therefore be concluded that helpers gain kin-selected fitness benefits through the increased survival of related offspring but not through the increased survival of related breeders. Furthermore, helpers gain direct fitness benefits through increased personal survival, but at a cost of reduced probability of successful future personal reproduction (McGowan et al. 2003).
Outside the breeding season Long Tailed Tits (Aegithalos caudatus) form compact flocks of 3 to 30 birds, composed of family parties (parents and offspring) from the previous breeding season, together with any extra adults that helped to raise a brood. These flocks will occupy and defend territories against neighbouring flocks. The driving force behind the flocking behaviour is thought to be that of winter roosting, being susceptible to cold; huddling increases survival through cold nights. In February–March, all members of the winter flock will pair and attempt to nest, with the males remaining within the winter territory and the females having a tendency to wander to neighbouring territories. The nests are compact, domed constructions made from moss woven together with spider webs and hair. The outside is camouflaged with up to 3,000 flakes of lichen and lined with an average of 1,500 (up to 2,600) small feathers. Nests suffer a high rate of predation with only 17% success (Gaston 1973).
Reference List:
- Gaston.A.J., (1973). The ecology and behaviour of the Long-tailed Tit (Aegithalos caudatus). IBIS, 115, 330-351.
- Hatchwell.J.B., Ross.J.D., Fowlie.K.M., & McGowan.A., (2001). Kin discrimination in cooperatively breeding long–tailed tits (Aegithalos caudatus). Proceedings of the Royal Society in Biological Sciences, 268, 885-890.
- McGowan.A., Hatchwell.J.B., & Woodburn.W.J.R., (2003). The effect of helping behaviour on the survival of juvenile and adult long-tailed tits (Aegithalos caudatus). Journal of Animal Ecology, 72, 491-499.
