The family Aeogothelidae comprises bird species which were traditionally classified as belonging to the order Caprimulgiformes. Recent studies suggest that they are more closely related to the Apodiformes and not the swifts and the hummingbird. This led scientists to begin considering it as belonging to a distinct order.

The classification of the Aegothelidae is as follows: they belong in the class Aves , order Caprimulgiformes, suborder Caprimulgi and family Aegothelidae These birds can be described as ranging from small to medium in size, nocturnal birds that are colored with typically big heads that contain large eyes which are forward facing and which are found within a facial disk. They have small wings and feet, their feet bearing long toes that have equally long claws and the wings are rounded.

They measure between 18 to 30 cm and weigh between 29 to 98 grams.

In the order Caprimulgiformes, to which the family Aegothelidea belong, owlet nightjars are the most prominent distinctive group, exhibiting some features that make them resemble the owls which belong to the order Strigiformes. Some of the striking similarities that make these two bird species resemble one another is their facial disk with the eyes which are not only large but also forward facing, their habit of nestling in the holes, their spotless eggs as well as several other anatomical features. DNA studies also lend credence to this view, suggesting early evolutionary divergence of these birds from other members which belong to the family Caprimulgiformes. The family is believed to have evolved in the early tertiary, as fossil evidence from the Upper Eocene suggests.

Behavior

Owlet-nightjars are found in hidden roosts during the day which are commonly in holes and in trees. They are most active at night or when darkness is approaching. This begins late in the evening and goes on till predawn light. Not much can be said of the social organization of these species because of their highly concealed nocturnal behavior.

The Australian owlet nightjar is so far the only bird species that has been thoroughly studied better. Here, a pair of birds that can reside together in one whole year and normally in a larger family. The pair has been observed to roost in close proximity throughout one calendar year without changing partners but can occasionally alter the roosting site. The owlet nightjars have a trademark night call that announces their presence and which can be used by those who are studying it to identify the bird species. Without doubt, these birds communicate with one another using the voice function.

Diet and feeding ecology of the owlet nightjars

Insects make up the most of the owlet nightjar’s diet, although it is normally supplemented with other spineless organisms notably spiders and millipedes. Other species, like the mountain owlet jar, also has earthworms in its diet. The diets of several other species remain mysterious to date because the birds are in hiding during day time and are not seen hunting for food at night.