Its an interesting life the beautifully coloured birds of the forest lead, and the more we find out about them, the more curious they get. There are nine species of the dainty fairy wrens (genus Malurus) in Australia, and together they cover most of the continent. Generally, the most well-known is the superb fairy wren (Malurus cyaneus), as it is the common species that occurs across the populated areas of South Australia, Victoria, New South Wales and south-east Queensland. Fairy wrens are known for the males’ striking plumage – bright blue in most species, but red and purple in others – but their other claim to fame is their rampant infidelity.
Fairy wrens live in small groups where generally there is an adult pair, and offspring from the previous breeding season stick around to help with the next season’s young. It’s a happy family picture, with the adults and helpers working together. But when researchers looked closer, they discovered that while there was a breeding male and a breeding female in each territory, they weren’t usually breeding with each other.
The red-winged fairy wren (Malurus elegans) is endemic to south-west Western Australia, and it is one of the few fairy wren species in which both the male and female offspring from the previous breeding season stick around to help out with the next season’s young. With all these closely related individuals kicking around together, is the extra pair mating a way to avoid inbreeding?
This is a question that researcher Dr Lyanne Brouwer has sought to investigate. She and the usual field team were constrained by COVID travel restrictions, so I thought it sounded like a fun and interesting project to lend a hand on. Which is how I decided to spend my January break – in the towering forests of the south west, trying to keep an eye on these tiny birds.
Just my luck that the red-wings are among the shyest of the fairy wrens, keeping to the thick understory vegetation! But the weather has been pleasantly mild, and the forest full of rufous treecreepers, white-breasted robins, western rosellas and ‘twenty-eight’ parrots. Much excitement ensues when I finally get a decent look at a little group of the fairy wrens hopping about the tangled vegetation. On day two, as I was quietly watching a group from a conveniently placed log, I saw the breeding adults and their helpers bring little caterpillars and grubs consistently down to one spot in thick vegetation just above the ground. I was so excited to discover that they were taking food to tiny nestlings still in their dome nest.
Its been a great trip so far and glorious to be out in the field again, watching the birds. I’m particularly interested to also learn about how environmental change – for example the drying of the south-west, fragmentation of habitat, novel species such as kookaburras and introduced predators – will mean for the function of these groups of little birds. Will their ways of life adapt to the changes? Will they find enough genetic variation when the size of the habitat patches shrink, or the amount of food changes? I look forward to learning more about these teeny little critters.
Further reading:
Brouwer, L., Van de Pol, M., Atema, E., Cockburn, A., 2011. Strategic promiscuity helps avoid inbreeding at multiple levels in a cooperative breeder where both sexes are philopatric. Molecular Ecology 20, 4796–4807.
