Gerygone feeding Little Bronze Cuckoo @ Chinese Garden by Daniel
"The cuckoos lay their eggs in other birds' nests so that these other parents would take care and feed the cuckoo's young. The adopted parents' original eggs may even be pushed out by the cuckoo. These unknowing parents would merrily keep on feeding their adopted child, even when the kid is bigger than themselves, as seen in this instance." text by laokayu
Thanks to Daniel for allowing me to reproduce his pics here!