Helping at the nest, allofeeding and social status in immature arabian babblers
Arabian babblers, Turdoides sqamiceps, are cooperatively breeding, group territorial birds, occurring in desert habitats. Non-breeders participate in several types of cooperative behaviour, including care of eggs, nestlings and fledglings, and bringing food to one another (allofeeding). This paper reports on observations of helping with eggs and young, and peer allofeeding, performed by immature babblers, fledged the previous season or earlier in the same season. The birds were from a babbler population studied since 1971 in the Arava valley of eastern Israel. They belonged to groups in which all individuals had been colourringed and were accustomed to human observers. Individuals and nests in the territories of these groups could be watched from distances of 1–2 m without causing alarm, so fine details of behaviour could be observed in the field. In most allofeeding interactions observed, a more dominant individual brought food to a subordinate. Sometimes the subordinate bird avoided accepting the proferred food, and was then hit or chased by the bird that had attempted to feed it. Occasionally a subordinate bird attempted to feed a more dominant individual. Dominant birds always refused to take food offered by a subordinate, and hit or chased any subordinate attempting to feed them. Frequencies of visits to nests were correlated with helper rank for those visits where the incoming bird displaced a previous visiter from the nest. Frequences of visits to unattended nests, however, were not correlated with helper rank. Similarly, frequencies of feeding visits to fledglings were correlated with helper rank until incubation of the next brood began. After this, the correlation disappeared. Numerous instances of aborted nest visits were observed in which a helper, often carrying food, arrived at the nest-tree but left again without visiting the nest. In many other cases, a helper arrived at the nest-tree but delayed visiting the nest for several minutes. Aborted and delayed visits usually occurred when a more dominant bird was in the vicinity of the nest. This suggests interference between helpers. Direct interference between helpers visiting fledglings was occasionally observed. In such cases, a more dominant helper snatched food from a subordinate approaching fledglings, and then fed this food to the fledglings itself. Interference between helpers, and conflict between proferers and recipients of food during allofeeding, are not easily explained by kin selection or reciprocity. On the other hand, such behaviour is readily explained by a hypothesis which suggests that individuals may increase their social status in the group by performing cooperative behaviour. Babblers that establish status by demonstrating ability to bear the short-term costs of cooperative behaviour, rather than through direct aggression towards rivals, are likely to forge collaborative relationships with other group members. Since babblers must collaborate to establish and defend a territory, such relationships are essential to reproductive success.
KeywordsCooperative Behaviour Social Rank Cooperative Breeding Reciprocal Altruism Nest Visit
Unable to display preview. Download preview PDF.
- Brown JL (1974) Alternate routes to sociality in jays with a theory for the evolution of altruism and communal breeding. Am Zool 14:63–80Google Scholar
- Brown JL, Brown RH (1981) Kin selection and individual selection in babblers. In: Alexander RD, Tinkle DW (eds) Natural selection and social behavior. Blackwell, London, pp 244–256Google Scholar
- Emlen ST (1978) The evolution of cooperative breeding in birds. In Krebs J, Davies N (eds) Behavioural Ecology: An evolutionary approach. Blackwell Scientific Publications, London, England, pp 245–281Google Scholar
- Emlen ST (1981) Altruism, kinship and reciprocity in the whitefronted bee-eater. In: Alexander RD, Tinkle DW (eds) Natural selection and social behavior. Blackwell, London, pp 217–230Google Scholar
- MacRoberts MH, MacRoberts BR (1976) Social organization and behavior of the Acorn Woodpecker in central coastal California. Ornithol Monogr 21:1–115Google Scholar
- Sokal RR, Rolf FJ (1969) Biometry. W.H. Freeman, San FranciscoGoogle Scholar
- Woolfenden EG, Fitzpatrick J (in press) The Florida Scrub Jay: Demograph of a cooperative breeding bird. Princeton University Press, Princeton, New JerseyGoogle Scholar
- Zahavi A (1976) Cooperative nesting in Eurasian birds. Proc XVI Int Ornithol Congr (Canberra, Australia) pp 685–693Google Scholar
- Zahavi A (1981) Natural selection, sexual selection and the selection of signals. In: Scudder GGE, Reveal JC (eds) Evolution today. Proc 2nd Int Congr Syst Ecol pp 133–138Google Scholar