This year our local currawong has reared two channel-billed cuckoo chicks. Both have made it to fledging. The poor parent bird is run ragged trying to feed two hungry demanding chicks that are now a lot larger than her.
Channel-billed cuckoos are parasitic birds. That is, they lay their eggs in the nests of other birds, rather than rearing their own chicks. They are migratory, travelling from New Guinea and some parts of Indonesia, to Northern and Eastern Australia to breed here, during August to October. They make the return journey from January to March.
The eggs are commonly laid in the nests of currawongs, magpies, ravens, magpie-lark, and choughs. Their eggs are small in size relative to the size of the bird, and are similar in appearance to the host birds whose nests they utilise. This enables the eggs to be incubated by the host bird, rather than being rejected. Once the chicks have hatched, the parent birds will rear them as if they are their own chicks. Unlike some other cuckoos, channel-billed cuckoo chicks don't push out the host's own chicks. However, the host's chicks rarely survive alongside the channel-billed cuckoos, probably because the channel-billed cuckoo chicks grow so quickly, and are very demanding. As the channel-billed cuckoo arrives in the South Easterly areas after the beginning of the nesting season of the pied currawong, they make use of the later nesting of the season.
Once fledged and self-feeding, fruits and berries will compose a significant portion of the channel-billed cuckoo's diet, (they're particularly partial to figs), in addition to large insects, and occasionally eggs and nestlings. The fledged juveniles continue to beg for food insistently, for quite a long time, before they will eventually begin self-feeding. In this case here, the currawong continues to feed these two large demanding fledglings, which - so far at least - show no inclination to attempt to seek food for themselves. Their loud, plaintive, and desperate sounding cries for food are heard at dawn, and then again around 3pm, and again at dusk. The poor currawong must be exhausted.
How they instinctively know when, and how to migrate at the appropriate time, is quite amazing, considering that they're not reared by migratory birds.