This male purple-backed fairywren (Malurus assimilis) is one of more than 500 of its species that reside in Brookfield Conservation Park. Banded as a fledgling in 2013, he was a helper in his natal territory in 2014. He became the dominant male in 2015, a role he has maintained ever since. By convention, we call this bird "URP", as his color bands read (from left leg to right, top to bottom): maUve-Red-Pink. (Photo by Allison Johnson, used with permission. Check out more of Allison's beautiful photos and illustrations at her website!)

On birds and Brookfield (Part 1)

This week I'll be introducing a few of the resident bird species from the field site, and sharing a bit about the location.

Brookfield Conservation Park

Situated just west of Blanchetown (home of the famed William R. Randell Lock and Weir, or "Lock 1"), Brookfield Conservation Park sits at the western edge of the Murray Mallee biogeographic region between the Murray River to the east and the Barossa Valley/Mount Lofty Ranges to the west. Much of the surrounding landscape has been cleared over the last century for industrial uses and agricultural development. Brookfield itself was formerly a sheep station and charcoal-production site. In 1971, the site was purchased by the Brookfield Zoo (Chicago, Illinois, USA) and set aside for conservation of the southern hairy-nosed wombat (Lasiorhinus latifrons). In 1977, the park was gifted to the government of South Australia, and it has since been administered by the Department for Environment and Water.

 

The expression of the southern hairy-nosed wombat (Lasiorhinus latifrons ) is one of perpetual worry. A wombat casts a concerned glance at the photographer outside of its warren in Brookfield Conservation Park. The smallest of the three extant species of wombat, this nonetheless formidable beast of a marsupial still clocks in at 40–70 lbs (18–32 kg). (Photo by Donald Hobern licensed under CC BY 2.0)

The region is arid, receiving 200–300 mm of rainfall annually, and was historically dominated by mallee scrub habitat. Though at first it seems a harsh and forbidding environment, the park supports a rich diversity of plant and animal species. Over 100 species of birds have been recorded in the park, including both Australia's largest (the emu, Dromaius novaehollandiae) and smallest (weebill, Smicrornis brevirostris) native birds.

 

A male splendid fairywren (Malurus splendens) in breeding (nuptial) plumage. Crown and cheek feathers are made erect during intraspecific aggressive interactions and courtship displays. (Photo by Ron Knight licensed under CC BY 2.0)

Fairywrens

The fairywrens are small (6–16 g), insectivorous birds endemic to Australia and New Guinea. Most species of true fairywrens (Malurus sp.) exhibit marked sexual dichromatism, with breeding males exhibiting vibrant plumage patterns accented by azure auriculars, carnelian mantles, and amethyst crowns. Though socially monogamous, with a breeding male and female defending a territory together for several successive years, fairywrens are biologically promiscuous. Both males and females regularly engage in extra-pair copulations, and the young produced by a breeding female are seldom solely the progeny of her social mate.

Fairywrens demonstrate cooperative breeding, wherein individuals live in family groups led by a dominant breeding male and female. The pair is often accompanied by one or more auxiliary individuals. These subordinate "helpers", most of which are male offspring from previous years, may assist in defending the breeding territory from intrusion by neighboring groups and help contribute to the success of nesting attempts.

 

Until recently, the purple-backed fairywren (Malurus assimilis) was considered a subspecies of the variegated fairywren (M. lamberti). The 2018 split followed the geographic barrier formed by the Great Dividing Range, with the nominate variegated fairywren restricted to the Eastern Highlands and coastal regions from Townsville to Sydney. This male purple-backed fairywren was photographed in the Northern Territory. (Photo by Christopher Watson licensed under CC BY-SA 3.0)

Three species of fairywren are resident breeders at Brookfield Conservation Park. Since the early 1990s, the park has hosted a long-term study of animal behavior and ecology using splendid and purple-backed fairywrens (Malurus splendens and M. assimilis, respectively) as models. This research, led by Dr. Stephen Pruett-Jones of the University of Chicago, has yielded important insights into communication, sexual selection, and social behavior. In addition, the study has generated a wealth of individual-level behavioral data for members of the focal species. The availability of this information will inform and enhance my own research by supplying a more detailed look at the histories and characteristics of individual birds.

Splendid and purple-backed fairywrens prefer the relatively dense and canopied woodland habitat dominated by Eucalyptus mallee, saltbush (Atriplex spp.), and porcupine grass (Triodia sp.). In contrast, the white-winged fairywren (M. leucopterus) occurs in the open, bluebush (Maireana spp.)-dominated areas in the western half of Brookfield.

 

Male white-winged fairywrens (Malurus leucopterus) generally don't moult into full blue-and-white breeding ("nuptial") plumage until 4–6 years of age. Unornamented ("dull") males are sexually mature by their second year, and may pair with a female to defend a small territory, but will remain socially subordinate to males in full breeding plumage. (Photo by Andreas Trepte, www.photo-natur.net, licensed under CC BY-SA 4.0)

Though nominally equivalent, the breeding and social systems of these three species are far from identical. Average group size is much smaller in the splendid fairywren, for instance, than in either of the other two species. Pair breeding (when no helpers share a territory with the breeding pair) is relatively common in this species, with one (or occasionally two) male helpers remaining on the natal territory during their second year. The presence of both male and female helpers is much more commonly observed in purple-backed fairywren family groups, which regularly retain individuals for several years.

The social biology of the white-winged fairywren is particularly complex, and has not been well characterized. In contrast to most other species in the family, male white-winged fairywrens don’t moult into the blue-and-white breeding ("alternate" or "nuptial") plumage until they are 4–6 years of age. Though sexually mature, these unornamented ("dull") males are socially subordinate to males in ornamented ("bright") plumage. A single ornamented male presides over several subgroups sharing a large territory, forming a complex hierarchical clan system.

Further reading

• The Fairywren Project is a citizen science endeavor led by Allison Johnson and Joe Welklin. Check out their outstanding website to learn more about the 10 species of Australian fairywrens and find out how you can get involved!

• Birds SA maintains a checklist of the 139 species of birds that have been reported in Brookfield Conservation Park.