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Nature Diary with Tanya Loos
F
OR me, Spring does not start on September 1. It starts when our local flora and fauna changes in response to a shift in the season – longer days, and slightly higher temperatures.
In late August bright yellow tones enliven our bush and gardens, with the first wattles flowering and bulbs such as daffodils pushing through the winter mulch. And the soundscape changes too… On a recent sunny and relatively warm day (I think it was a blistering 11 degrees!) I heard a repeated descending whistle, “tseeuw tseeeuw”. And high up in an almost dead eucalypt I could see a very small bird with a very loud call. A bronze-cuckoo, one of the smallest cuckoos in the world. More often heard than seen, bronze-cuckoos are brown and white striped underneath, with a lovely green shimmer on the wings and back. This one, with a descending whistle call was a Horsfield’s bronze-cuckoo. The Horsfield’s looks very similar to a close relative the shining bronze-cuckoo who has a rising call, and a subtly different breast stripe pattern. The bronze-cuckoos fly down to our forests each Spring to carry out their dastardly business of tricking parent birds of other species into raising their young. Being so small, the host birds are also small: most often superb fairy-wrens and small brown bush birds such as thornbills, but also sometimes robins. When the female bronze-cuckoo is ready to lay her eggs, she waits on an inconspicuous perch, secretly watching her chosen host species build their nest. It is most important that she hides, for if the host species see her they will abandon the nest, and build another one elsewhere. After the eggs are laid, and the parents are away feeding, the female sneaks into the nest and lays one egg in just a few seconds. After the young cuckoo is born, they get to work. Even though they are blind and featherless like most baby birds born in nests, they are certainly not harmless. Within 24 – 30 hours, the tough little chick sets about evicting all the fairy wren or thornbill eggs from the nest. They even have a special little hollow in their back in which they balance the host’s egg as they push it from the nest. All cuckoo chicks that evict eggs have this clever morphological modification. Then, when the cuckoo is born, the chick does not have to compete for food, and is the sole beneficiary of the parents’ hard work raising this intruder. Bronze-cuckoos are usually the first cuckoos to start calling at this time of year. Later, as it warms up further, we will hear the descending trill of the fan-tailed cuckoo, the rising somewhat crazy call of the pallid cuckoo, and perhaps even the very loud “kooeel” of the eastern koel.
"The bronze-cuckoos fly down to our forests each Spring to carry out their dastardly business of tricking parent birds of other species into raising their young."
Tanya Loos is a keen field naturalist who spends a lot of time wandering around the bush in our beautiful region. She loves writing about nature and science - she blogs at https://tanyaloos.wordpress.com/ Image: Patrick Kavanagh
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