Topic
Sittella
About: Sittella is a research topic. Over the lifetime, 2 publications have been published within this topic receiving 62 citations.
Papers
TL;DR: In the Australian species, the helpers are often adults apparently capable of breeding and it seems possible that the behaviour could have been evolved in adults, and not from immature individuals assisting at the nest, as suggested by Skutch as mentioned in this paper.
Abstract: Records of birds additional to the pair helping at single nests in Australian passerine species are summarized. This behaviour is known to occur in the Ground Cuckoo-Shrike, the Yellow-tailed Thornbill, the blue wrens, the Sittella, four species of honeyeater, the White-winged Chough and Apostlebird, the woodswallows, and the Pied Butcher-bird; and there is a likelihood of its occurrence in the babblers. The proportion of birds showing the behaviour is high in comparison with other avifaunas and it is probably due to some common factor, the likeliest being climate. In species such as the blue wrens, which are rather sedentary, this behaviour can help to maintain the population at a high level in a poor habitat by ensuring nesting success. In other species small nomadic parties are more likely to discover suitable areas, and to contain a breeding pair, while additional birds help in nesting and the rearing of young and can also act as replacements for lost members of the dominant pair. In the Australian species the helpers are often adults apparently capable of breeding and it seems possible that the behaviour could have been evolved in adults, and not from immature individuals assisting at the nest, as suggested by Skutch for other regions. Selection for such behaviour could occur if it is assumed that the dominant pair pass on to their offspring the dual capacity to act as a member of a dominant pair or as a helper in different situations. The reduction or loss of male breeding plumage in subordinate males in the blue wrens might help to prevent the arousal of aggressive reactions associated with such plumages. There appears to be no information available concerning possible factors which inhibit breeding behaviour in subordinate birds or determine the selection of dominant individuals.
59 citations
TL;DR: It is argued that group-living and philopatry in this species probably developed to increase foraging efficiency and reduce vulnerability to predators.
Abstract: In north-eastern New South Wales, Vried Sittellas occur in sedentary groups or clans holding weakly-defended territories of 13-20 ha. Average group size at one site where several birds were colour-banded was 5.4, while groups observed elsewhere in the region averaged 4.9. Simple pairs occurred in 20% of cases. However, group size varied over the year, some breeding groups amalgamating into ‘clans’ during the non-breeding season. Density in the region varied from 0.2 to about 0.5 birds ha –1. Sex ratios were skewed towards males in samples from two separate districts. Five distinct vocalisations were recognised. Roosting was communal, one colour-banded group using 13 different trees over 120 nights. The group roosted consistently earlier, and awoke later, than other local small passerine species. The breeding season was long, from August to January and second broods were occasionally attempted. Because five out of eight birds disappeared in September–October, mortality and/or dispersal seemed highest during the early breeding season. Most nests were built on dead branches of Broad-leaved Stringybarks Eucalyptus caliginosa. Most clutches (74%) of the species were of three eggs, the remainder being two. Nest success was low (20%; n = 49). Nesting attempts in two groups failed four times per season, although some nests were abandoned before laying. Large territories, feeding of the incubating female, and long periods of incubation, nestling and juvenile dependency, as well as a specialised foraging niche and cryptic prey all suggest that food may be limiting for this species. Thus, helpers may normally be required to provide young with sufficient food. However, I argue that group-living and philopatry in this species probably developed to increase foraging efficiency and reduce vulnerability to predators. The species offers exceptional scope for studies of the influence of habitat on sociality and cooperative breeding, and the effects of group size on foraging success.
7 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 1998 | 1 |
| 1969 | 1 |