The New Zealand owlet-nightjar (Aegotheles novaezealandiae), is an extinct bird species that was formerly endemic to New Zealand. It is recognized as the largest known species within the family Aegothelidae (owlet-nightjars). In Māori, the indigenous language of New Zealand, it is called Ruru hinapō. This species is characterized by its enlarged body size, reduced wings, and strong legs. It is believed to have been either flightless or had very minimal flight ability. The New Zealand owlet-nightjar went extinct in the late 13th century, prior to significant human settlement in New Zealand. Consequently, little is known about its plumage, breeding habits, or behavior; most available information regarding its morphology and behavior is derived from remnants, bones, and DNA analysis.
Taxonomy The New Zealand owlet-nightjar (Aegotheles novaezealandiae) belongs to the order Aegotheliformes within the monotypic family Aegothelidae, commonly known as owlet-nightjars. This family contains a single genus, Aegotheles. The exact number of species in this genus is debated, with many sources indicating twelve species. Currently, Aegotheles species are found across Australia and New Guinea, with Aegotheles novaezealandiae being the only owlet-nightjar native to New Zealand. This species was first discovered in the 19th century in New Zealand's Holocene fissures and caves. The New Zealand owlet-nightjar was initially classified under the genus Megaegotheles due to distinct morphological traits, but was later reassigned to the genus Aegotheles. Researchers noted that its enlarged body size and unique wing and leg proportions set it apart from other Aegotheles species. However, as more molecular and genetic data became available, it was determined that the morphological differences were not sufficient to warrant a separate classification. In general, the lineage of owlet-nightjars (Aegotheles) has proven challenging to define, primarily due to interspecific variations in plumage color and pattern. Additionally, the elusive and nocturnal nature of these birds makes them difficult to observe and study. As a result, most characteristics used for classification of these species are linked to genetic data rather than solely their morphology. Owlet-nightjars should not be confused with nightjars, which belong to the family Caprimulgidae. A 2003 analysis of DNA sequences confirmed that owlet-nightjars constitute a distinct family, Aegothelidae. It is now understood that owlet-nightjars are more closely related to swifts and hummingbirds than to nightjars.
Description The New Zealand owlet-nightjar is an extinct bird species that became extinct in the late 13th century. In Māori, it is referred to as Ruru hinapō. This species is recognized as the largest owlet-nightjar in recorded history. They ranged in weight between 150-200g. Estimates of their weight are based on allometric measurements of their bones. The New Zealand owlet-nightjar was a nocturnal bird that inhabited a range of environments across New Zealand, including dense forests, caves, and shrublands. Since this species went extinct before the widespread development of human civilization in New Zealand, no physical traits have been recorded; inferences about their appearance are derived almost exclusively from bone remains and DNA analysis. Owlet-nightjars (genus Aegotheles) are typically small to medium-sized birds characterized by broad, weak bills and an upright posture. Their weak bills are adapted for catching insects. They possess a facial disc with forward-facing eyes, which helps in sound localization and enhances hearing ability. Owlet-nightjars also do not reflect light from their eyes in the dark, which is a feature that distinguishes them from nightjars. These morphological traits found in the Aegotheles genus are consistent with those found in New Zealand owlet-nightjar remains. The wings of New Zealand owlet-nightjars were somewhat larger in size to those of other Aegotheles species, but they had very notably enlarged hind limbs. This suggests that they were either very weak fliers or lacked the ability to fly altogether. Their strong legs likely enabled them to navigate steep elevations, such as trees or rocky surfaces, compensating for their limited flight ability.
Plumage Owlet-nightjars (genus Aegotheles) typically possess plumage that allows them to camouflage within their surroundings, contributing to their difficulty in being observed. Although it cannot be said for certain that the New Zealand owlet-nightjar had coloration that provided effective camouflage, it is likely they did based on their lineage to closely related species within the genus that do exhibit cryptic coloration. These colors may include various shades of brown and gray. The plumage of juvenile owlet-nightjars varies among species; some exhibit a darker brown appearance, while others have a paler coloration with white feathers in certain areas. Due to this variation and the general lack of knowledge regarding juvenile owlet-nightjars, little can be said about the plumage of Aegotheles novaezealandiae juveniles. Generally, owlet-nightjars do not display strong sexual dimorphism, with males and females showing no significant differences in size or coloration.
Bones Remains of the New Zealand owlet-nightjar have been recovered in various locations across New Zealand's islands. In a study conducted by R.J. Scarlett in 1968, the following observations and measurements of Aegotheles novaezealandiae bones were recorded. These measurements indicate they are the largest known member of the genus Aegotheles. These measurements do not account for all individuals of Aegotheles novaezealandiae but provide informative estimates of their general sizes:
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