Rufous Owl

Rufous Owl
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Strigiformes
Family:	Strigidae
Genus:	Ninox Gould, 1846
Species:	N. rufa

The Rufous Owl (Ninox rufa), also known as Rufous Boobok, is a species of owl in the Strigidae family. It was first classified in 1846 by John Gould, an English ornithologist. Ninox rufa’s common name reflects the rufous colored feathers that these owls are covered with in adulthood. While it is a rather uncommon species of owl, Ninox Rufa has a wide range of habitats including Australia, Indonesia, and Papua New Guinea.^{[1] [2]}

The Rufous Owl is a large owl species, ranging in weight from 700 grams to 1700 grams, depending on gender and age. It is only slightly smaller than the largest owl in Australia, the Powerful Owl (Ninox strenua), which typically weighs between 1050 grams and 1700 grams.^[3] The Rufous Owl is a generalist predator and generally solitary. It seldom becomes aggressive except in situations in which it feels its nest or offspring are threatened.

Description

The Rufous Owl is a large bird, often growing 46 to 57 centimeters in length, with a wingspan of 100 to 120 centimeters. Females typically weight 700 to 1050 grams (24.75 to 37 ounces), while the males typically weight 1050 to 1300 grams (37 to 46 ounces). Both sexes have relatively small heads compared to their body and tail, but the heads of the male are flatter and broader than those of the female. Juveniles are much smaller, usually 49 to 54 millimeters at birth, and are covered in downy white pelage. The forehead, neck, back, and upper wings of the adults owls are usually a dark reddish-brown color with light brown barring scattered throughout. The face is dark brown, and the neck, breast and under part is rufous colored with thin cream colored bars. The underside of the wings are light brown with thick cream bars. Its hooked bill is light gray and is surrounded by black bristles at its base. It has golden-yellow eyes.

Taxonomy

Ninox Rufa is an owl species in the family Strigidae. The following shows the taxonomic classification of the species:

Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Strigiformes
Family: Strigidae
Genus: Ninox
Species: N. rufa

The five subspecies include Ninox rufa rufa (Gould, 1846), Ninox rufa aruensis (Schlegal, 1866), Ninox rufa humeralis (Bonaparte, 1850), Ninox rufa meesi (I.J. Mason & Schodde, 1980), and Ninox rufa queenslandica (Matthews, 1911). These subspecies differ slightly in size and color.^[4]

Distribution and habitat

Ninox Rufa has a wide geographic range. It is native to Australia, Indonesia, and Papua New Guinea. In Australia, it is found in the following regions: Arnhem Land, the northern Kimberleys, the eastern Cape York Peninsula, and the Mackay District of eastern Queensland. It is the only exclusively tropical owl in Australia.^[5] The global population size of Ninox rufa has yet to be determined, but the species is considered uncommon to rare.^[3]

Ninox rufa inhabits terrestrial ecosystems.^[1] The Rufous Owl most often lives in rainforests and the margins of rainforests.^[1] Additional habitats may include forests, moist savannas, and inland wetlands.

Behavior

Rufous Owls are characterized by having rather shy and elusive natures but are known to become aggressive if threatened. They are almost exclusively nocturnal birds and will remain in their nests during the day. They are generally not very vocal, except during the breeding season. During this time, males and females will communicate to one another using calls of various pitches. The voice of the female is of a higher pitch than the male’s.

Breeding

The Rufous Owl has a regular breeding season from June to September, depending on the warmth of its habitat. To initiate breeding, the mate will utter a double call which will attract a female to him. As she flies toward him, the female will give excited thrills in return. Eggs are typically laid in nest located in the trunks or limbs of trees. Some nest are built as high as thirty meters above the ground in order to protect them from ground-dwelling predators. Following breeding, the male owl will build the nest and the female will lay one to two eggs inside. The eggs require 37 days of incubation. Once born, the young owls are dependent on their parents for many months, often until the following breeding season. The adult males and females will both aggressively defend their nests against predators and intruders while the young still reside inside.^[6]

Feeding

The Rufous Owl is a skilled and powerful hunter, capable of capturing a wide variety of prey. Their diet is extremely diverse, ranging from birds and insects to small mammals such as flying foxes. Mammal prey sizes have been recorded from small rodents of 5 to15 grams to larger rodents such as the Northen Brushtail Possum (1100 to 2000 grams). Typically, the Rufous Owl will hunt the juveniles of these larger prey species. Mammals that the Rufous Boobook has been documented to feed upon include the following: Pteropus scapulatus, Pteropus alecto, Phascogale tapoatafa, Trichosurus arnhemensis, Petaurus breviceps, Mesembriomys gouldii, Conilurus penicillatus, Isoodon macrourus, Rattus tunneyi, Rattus colletti, and others.^{[3] [7]}

Seasonal changes in selection of prey have been determined from extensive studies in Australia.^[3] For instance, when ground vegetation is more dense during the wet season, these owls appear to prey more often on other birds than ground-dwelling mammals. Selection of prey is also largely dependent upon the availability of species during the different seasons. In order to catch their prey, Rufous Boobooks have been observed to utilize several predation methods. They may take prey from perches, snatch from tree foliage while in flight, chase while in flight, or swoop from the air and catch their prey from the ground or water below.^[6]

Conservation

According to the IUCN Red List of Threatened Species, Ninox rufa is not listed as a vulnerable species. It was most recently classified in 2008 as a species of “least concern.” While its population size does appear to be decreasing, its rate of decline is not considered rapid enough to be considered under the vulnerable category. The species has experienced less than 30% decline over the last ten years or three generations. However, the Rufous Owl, like many other birds, is subject to the threats of hunting, clearing of forests, and forest fires during the dry seasons.^[1]

References

1. ^ ^{a b c d} BirdLife International 2009. Ninox rufa. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. <www.iucnredlist.org>. Downloaded on 30 March 2011.
2. ^ Kanowski, J. “The Abundance of the Rufous Owl Ninox rufa in Upland and Highland Rainforests of North-east Queensland.” EMU 98 (1998): 58-61.
3. ^ ^{a b c d} Estbergs, J. A., and R. W. Braithwaite. "The Diet of the Rufous Owl Ninox Rufa Near Cooinda in the Northern Territory." EMU 85 (1984): 202-05. Web.
4. ^ Integrated Taxonomic Information System Report. < http://www.itis.gov/index.html>.
5. ^ Bouglouan, Nicole. "Rufous Owl." Oiseaux-birds. Web. 02 Apr. 2011. <http://www.oiseaux-birds.com/card-rufous-owl.html>.
6. ^ ^{a b} Lewis, Deane P. "Rufous Owl - Ninox Rufa." The Owl Pages. 25 Apr. 2005. Web. 02 Apr. 2011. <http://www.owlpages.com/owls.php?genus=Ninox&species =rufa>.
7. ^ Legge S., Heinsohn R., Blackman C. and Murphy S. (2003) "Predation by Rufous Owls on Eclectus Parrots and Other Animals at Iron Range National Park, Cape York." Corella 27: 45-46.