Home range and territoriality of Australian owlet-nightjars Aegotheles cristatus in diverse habitats

Abstract

Sedentary Australian owlet-nightjars Aegotheles cristatus roost in cavities year-round, and are thought to mate for life and maintain stable home ranges throughout the year. These factors lead to the prediction that they should be highly territorial, yet nothing is known about their home range requirements or level of site fidelity. I used radio-telemetry coupled with GPS recordings to determine home range size in the semi-arid zone of central Australia (13 birds over two winters) and in a eucalypt woodland in the Northern Tablelands of NSW (14 birds over one calendar year). The mean home range in the eucalypt woodland was 17.7 ha based on the minimum convex polygon (MCP) method and 17.4 ha based on the fixed kernel contour (95%), whereas it was 23.8 ha and 24.1 ha based on the MCP and kernel methods in the desert respectively. With the exception of mated pairs (range overlap 41.9%), there was little overlap among individuals in home range areas (\13.0%), even in the densely populated woodland. Home range size did not differ significantly between seasons or study sites; nor was it correlated with arthropod abundance. Owlet-nightjars exhibited high site fidelity, using the same home range throughout the year with a 68% overlap between seasons. These data, plus anecdotal records of aggression and vocalizations, suggest that this species is highly territorial, yet individuals live in close proximity to conspecifics. The degree of territoriality may be due to the obligate cavity roosting behaviour of owlet-nightjars and the need to defend areas with known roost hollows.

Early age at first breeding and high natal philopatry in the Red‐necked Nightjar Caprimulgus ruficollis

“…Resident caprimulgids seem to exhibit high adult site fidelity (Jackson 1985, Doucette 2010) and these results suggest that the natal philopatry of a migratory nightjar species is also very high. This is unusual given that natal philopatry is typically very low for migratory birds (Weatherhead & Forbes 1994).…”

“…I used data from an intensive study of Red-necked Nightjars inhabiting Mediterranean shrublands in the northwestern border of the Doñana National Park (SW Iberian Peninsula, 37°7′N, 6°33′W) during 2008À2012 (Camacho 2013a). Here, Red-necked Nightjar density is moderate to high compared with other populations of caprimulgids (Doucette 2010), with 158 different adult individuals caught in the 2058-ha area in 1 year (author's unpubl. data).…”

Group Size does not Influence Territory Size and Overlap in a Habituated Population of a Cooperative Breeding Himalayan Galliforme Species

“…fragmented habitats (Pasinelli et al 2001, Bellis et al 2004, Doucette 2010, primarily to help determine whether such fragmented habitats are able to support the spatial ecological requirements that maintain cooperative breeding systems. This study examines whether group size influences territory size and territory overlap, in a threatened cooperative breeding Galliforme species occupying fragmented Himalayan tree-line habitats.…”

“…We calculated the minimum percentage overlap of two intersecting neighbouring groups based on all three fixed kernel territory estimators since these percentages are based on territory size, which differs between groups. Degree of overlap was calculated using the following index (Atwood & Weeks 2003, Doucette 2010:…”

Is it possible to acoustically identify individuals within a population?

“…To acquire this knowledge, the locations and movements of animals should be tracked across reproductive seasons or even across many years (Doucette 2010;Lopes et al 2013;Hays et al 2014). In biological studies, individuals are usually physically marked and tracked using radio transmitters (Doucette 2010), satellite loggers (Kennedy et al 2014), geolocators (Bächler et al 2010), colored and numbered bands (Lopes et al 2013;Neubauer et al 2012), tags (Ale et al 2011), medical cautery units (Ekner et al 2011), tattoos or dyes (Nietfeld et al 1994). Physically marking animals requires time, effort, and resources, and researchers have to catch an individual at least once.…”