These birds all have four toes on each foot. There are no webs between their toes. The young are nidicolous, which means that they are hatched naked, blind and helpless. Generally parents take good care of their young, but a few species are nest parasites. One characteristic of birds in this subfamily is that nestlings have decorated palates and tongues.
Nestlings beg for food by crouching with their mouths opened wide, waving their heads.
Estrildids mature rapidly, often in only a few months. On the continent of Australia, there are five different genera of grassfinches, including the genus Taeniopygia of which the Double-barred Finch T. bichenovii and Zebra Finch T. guttata are the sole members. The zebra finch has been fully classified with in the animal kingdom. The best known diagram of this classification is shown below and was created by Richard Zann senior lecturer at the School of Zoology at La Trobe University in Australia. Based on morphology and behavior, the zebra finch can be further classified into two separate subspecies.