Malurus elegans

Abstract: In 33.5 ha of Kam forest in Smith's Brook Reserve, 841 individually colour-banded Malurus elegans, a Western Australian endemic, were studled from 1980-1986 in 24-30 territorial groups. This species is multi-brooded but less so than other Malurus due to their short breeding season; 90% of eggs were laid in October and November. Most nests (85%) were within 300 mm of the ground and more than half in accumulated litter on the forest floor, nest sites liable to be lost following fuel-reduction burning. Clutches of two and three were equally common (mean = 2.43 eggs); fertility was 94%; incubation lasted 14-15 days; nestlings hatched synchronously and fledged 11-12 days later, juveniles were independent of adult provisioning when one month old. Parasitism by cuckoos was rare and predation variable between years. Of eggs laid, 79% hatched and 52% produced fledglings. Repeat nesting was rapid and groups produced an average of 2.5 fledglings and 1.9 independent young per year. M. elegans are co-operative breeders; 82% of groups had helpers, the mean size being four adults. Both adult and juvende survival were high and the limited forest habitat was fully occupied.

Abstract: In April 1994, an intense fire burnt part of Smith's Brook Nature Reserve near Manjimup, Western Australia where we had studied an individually marked population of the Red-winged Fairy-wren Malurus elegans in Karri Eucalyptus diversicolor forest since 1980. We estimated the population size in a 25 ha area at the start of the breeding season each year 1980?95, including two years post-fire. In the 32 territories present in 1993, the entire area of 26 was almost completely burnt to a height of 10 m, with few remaining unburnt patches. The mean population size for the 13 years 1981?93 was 119 birds in a mean of 29 groups. In November 1993, 126 birds were present in 32 groups. In November 1994, following the April fire, there were 114 birds in 31 groups, but nesting substrate was very scarce, breeding was delayed, and only 0.18 yearling males per group were produced, compared with 0.52 for the years 1981?93. By November 1995, the population had fallen to 73 birds in 23 groups with nine territories vacant. The time necessary for the population to recover to its prefire level was estimated from long-term demographic data to be at least 10 years, longer than the present cycle of 7?9 years for prescribed burns in the southern (Karri) State Forests of Western Australia.

Abstract: Density of potential mates has often been proposed to explain the enormous variation in extrapair paternity. However, density is often confounded by other ecological factors that might affect extrapair paternity in their own way. Furthermore, extrapair mating shows strong phylogenetic inertia, making both meaningful intra- and interspecific comparisons difficult. An extreme way to change density is through habitat fragmentation that reduces connectivity between territories. Recently, habitat connectivity was hypothesized to explain the surprising discovery of a virtually monogamous species among the world’s most unfaithful bird genus. The monogamous Malurus coronatus lives in narrow riparian strips that limit contact with neighbors to both extreme ends of territories, whereas Malurus species with high levels of extragroup paternity typically live in high-connected habitat in which they are surrounded by neighbors. Here, we test the habitat geometry hypothesis by comparing levels of extragroup paternity of Malurus elegans living in fragmented low-connected habitat and in high-connected habitat. We found that M. elegans does not have lower levels of extragroup paternity in low-connected habitat (68%) than in high-connected habitat (56% of offspring), indicating that connectivity does not limit opportunities for extragroup paternity. Furthermore, there was no evidence that females in low-connected habitat gained extragroup paternity further away or from less sires or that they were more likely to be closely related to their social mate. We conclude that behavioral plasticity in response to density-dependent cost and benefits of mating behavior does not explain intrageneric variation in extragroup paternity in Malurus. Furthermore, habitat fragmentation may not strongly affect inbreeding risk in this species.