Territory configuration moderates the frequency of extra-group mating in superb fairy-wrens.

The frequency of extra-pair paternity (EPP) in socially monogamous birds varies substantially between and within species, but ecological drivers of this variation remain poorly understood. Habitat configuration could influence EPP by moderating access to extra-pair mates, because species occupying territories in a clustered 'honeycomb' configuration have a larger pool of potential extra-group mates in their immediate neighbourhood than those living in linearly arranged territories (e.g. along narrow strips of riparian or fragmented habitat). We exploited variation in the spatial arrangement of territories due to anthropogenic modification of habitat of the cooperatively breeding superb fairy-wren Malurus cyaneus to test whether habitat configuration influenced the frequency of EPP. In this species, most paternity is obtained by males outside the social group [extra-group paternity (EGP)]. We found that the frequency of EGP among groups living in linear strips of roadside vegetation (41% of 44 offspring) was lower than it was for groups living in clustered territories within continuous habitat (59% of 70 offspring). Differences in group size and pair relatedness did not explain differences in EGP associated with territory configuration, although the frequency of EGP was negatively correlated with pair relatedness. Our finding suggests that territory configuration can influence rates of EGP and that anthropogenic habitat fragmentation has the potential to limit access to extra-pair mates, affecting mating systems and ultimately fitness.

Changing bird communities of an agricultural landscape: declines in arboreal foragers, increases in large species.

Birds are declining in agricultural landscapes around the world. The causes of these declines can be better understood by analysing change in groups of species that share life-history traits. We investigated how land-use change has affected birds of the Tasmanian Midlands, one of Australia's oldest agricultural landscapes and a focus of habitat restoration. We surveyed birds at 72 sites, some of which were previously surveyed in 1996-1998, and tested relationships of current patterns of abundance and community composition to landscape and patch-level environmental characteristics. Fourth-corner modelling showed strong negative responses of aerial foragers and exotics to increasing woodland cover; arboreal foragers were positively associated with projective foliage cover; and small-bodied species were reduced by the presence of a hyperaggressive species of native honeyeater, the noisy miner (Manorina melanocephala). Analysis of change suggests increases in large-bodied granivorous or carnivorous birds and declines in some arboreal foragers and nectarivores. Changes in species richness were best explained by changes in noisy miner abundance and levels of surrounding woodland cover. We encourage restoration practitioners to trial novel planting configurations that may confer resistance to invasion by noisy miners, and a continued long-term monitoring effort to reveal the effects of future land-use change on Tasmanian birds.