OWLS Strigidae
Owls are easily recognized; most everyone in the world knows about owls. They are considered creatures of mystery or doom or good luck, depending on where you are. They are wonderful birds to discover during the day, like this huge Great Gray Owl (left) in Yosemite Nat'l Park. But they are primarily nocturnal birds, hunting in the dark by using exceptional hearing and eyes that gather light much better than our own. This Buffy Fish-Owl (below right) was hunting over the tennis courts at the Danum research station in lowland Borneo, where I caught it in a flash.
Since owls are night birds, they are difficult to see although their characteristic songs and calls can often be easily heard. I enjoy owls (and there is nothing so pleasant as going to sleep on a camping trips to a chorus of owls), but admit to not being much of an "owler." I tend to enjoy a drink after the sun sets, and there are other things to do indoors at night
Stalking outside in the cold and dark for elusive critters, aiming a flashlight at where one thinks they are and rarely being correct, is not my idea of great fun, but there are field ornithologists who are exceptional at owling (Ben King comes to mind; his judicial use of tape and his insight into where an owl is likely to be sitting in extraordinary). Others are good at imitations and whistles and can "call in" the owls on their own, but I'm not one of them. Perhaps this explains why my percentage of the world's owls seen is much lower than most other families. I much prefer my owls in day roosts, like this Long-eared Owl (left) in a live oak in interior Monterey County. By the next week, this roost was abandoned; this species -- among all Monterey County owls -- is still the most unpredictable. Finding new day roosts of owls is often pure serendipity, although sometimes one is clued in by pellets and white-wash on the ground below the roosts.
Worldwide, a third of world's owl species are of the genus Otus (scops-owls & screech-owls); there are at least 55 species, ranging from abundant species to some of the world's rarest (eg, Seychelles Scops-Owl O. insularis). These are almost entirely nocturnal birds and day-roosts are changed from day to day, like the Western Screech-Owl (below left). In contrast, among the most diurnal of the owls is the Northern Hawk-Owl (below center) found in boreal forests, often hunting from the top of a tree during the long days of the northern arctic summer. Owls of the genus Glaucidium (pygmy-owls & owlets) are primarily crepuscular but can occasional appear in broad daylight to the surprise of all, as did this Northern Pygmy-Owl (below right) that I found sitting on top a telephone pole at mid-morning.
Owls have a variety of interesting breeding habits, but few make much of a nest. The Northern Pygmy-Owl (above right), for example, nests in old woodpecker holes, laying her eggs on the bare floor. The Burrowing Owl (below left) uses chambers in ground squirrel burrows; the male (often bleached white in the sun) stands guard while the shy female stays below incubating. Great Horned Owls (below right) often use abandoned hawk nests early in the season, when the weather is still crisp and cold before the leaves are out on the trees. In Monterey County where I live, they are among the earliest breeders of all our nesting species (details in our Breeding Bird Atlas; Roberson & Tenney 1993).
There is a lot to say about about owls, and the literature is extensive. For the serious field ornithologists, the work of Joe Marshall (1967, 1978, and on Otus with Ben King in Amadon & Bull 1988) is of particular interest since it focuses on both plumage and vocalizations. On-line, check out the Owl Pages, an entire web site devoted to owls (focused primarily on Australia, but including many others from around the world), and Greg Lasley's owl page (photos of a variety of North American, South American, and African owls).
Perhaps the most mysterious of all owls are the little-known denizens of tropical forests. One of the most dramatic and elusive is the Crested Owl (left; photo by Ed Harper in Ecuador), which ranges from southern Mexico to Bolivia but is scarce everywhere. I've heard one and gotten close to seeing it, but this species still eludes me. [I am sooo jealous of Ed Harper's shot].
My best owl photo (on grounds of rarity, not composition or photo quality!) may be this Fraser's Eagle-Owl (right) in eastern Gabon. I am unaware of any other photographs, taken in the wild, of this enigmatic species of the Congo Basin rainforest.
Photos: The Great Gray Owl Strix nebulosa was photographed near Crane Flat, Yosemite Nat'l Park, California, on 22 May 1987. The Buffy Fish-Owl Ketupa ketupu was in Danum Valley Reserve, Sabah, Malaysian Borneo, on 8 Aug 1988. The day-roosting Long-eared Owl was in Vineyard Canyon, Monterey Co., California, on 20 Feb 1995. The Western Screech-Owl Otus kennicottii was in Sacramento, California, in Apr 1980. The Northern Hawk-Owl Surnia ulula was along the McKinley Highway, Alaska, on 9 June 1980. The Northern Pygmy-Owl Glaucidium californicum was in the Warner Mts., Modoc Co., California, in Feb 1981. The pair of Burrowing Owls Speotyto cunicularia were in eastern Contra Costa Co., California, 11 Apr 1998. The Great Horned OwlBubo virginianus was nesting in Wildhorse Canyon, Monterey Co., California, on 5 Apr 1996. The pair of Crested OwlsLophostrix cristata was at La Selva, Ecuador, on 27 July 1990 (photo by Ed Harper). The Fraser's Eagle-Owl Bubo poensis was at Makoukou, eastern Gabon, 15 July 1996.  All photos © D. Roberson, except Crested Owls © W. Edward Harper.
Bibliographic essay

Family Book: I rating (out of 5 possible)
Burton, J. A., ed. 1973. Owls of the World: their Evolution, Structure and Ecology. E.P. Dutton & Co., New York.

This is not a successful book for those interested in owl identification, taxonomy, distribution, or vocalizations (ie, birders). But it doesn't really aim at that audience -- as one can tell from its title -- and its text may fulfill that goal for a general audience. It just happens that the book attempts to have illustrations of all the world's owls -- some nice photos intermixed with some marginal art and some zoo shots -- and range maps. There apparently is a new edition that I've not seen.
Because there was no overshadowing world book, there are many books that cover bits of the world. Some examples are Voous' (1989) Owls of the Northern Hemisphere -- which does have some very fine artwork, including field sketches, by Ad Cameron, and a good solid text on biology -- and Karalus & Eckert's (1974) The Owls of North America -- which is similar is style but has a sparser text and tries (not always successfully) to illustrate by paintings all the races of North American owls. I am aware of similar books on South Africa, or Australia, etc. All these are "coffee-table" books, but many other types of book exist. The literature on owls is extensive.

There is a new book by Koenig, Weick & Becking (advertised as due out Dec. 1998) entitled Owls: A Guide to the Owls of the World, which looks in advertising to be in the same genre as the Pica Press books. I have not seen this book, but I note the advertising claim that it covers "all 206 world species." This suggests to me that the authors (who appear to be European) have adopted some variation of the phylogenetic species concept and essentially split all island forms out as separate "species." This could be a disaster; a fairly recent survey of the owls by Amadon & Bull (1988) which included a reassessment of the genus Otus by Joe Marshall & Ben King (splitters both who emphasize vocalizations) detailed only 162 species (a few more have been discovered since then). As I say, I've not seen the new Owls book, but treat it with caution. It apparently comes with a double CD with voices of many species.

Vocalizations of owls are important. A useful cassette accompanied Marshall's (1978) work on Asian owls. For the New World, the tape by Hardy et al. (1990) is outstanding.

Other literature cited:

Amadon, D., and J. Bull. 1988. Hawks and owls of the world: a distributional and taxonomic list. Proc. West. Found. Vert. Zool. Vol. 3, No. 4: 295-357.

Hardy, J. W., B. B. Coffey, Jr., and G. B. Reyard. 1990. Voices of New World Owls. Rev. ed.  Florida Mus. Nat. Hist. & Ara Records, Gainesville, FL. [Cassette tape]

Karalus, K. E., and Eckert, A. W. 1974. The Owls of North America. Doubleday, New York.

Marshall, J. T., Jr. 1967. Parallel variation in North and Middle American screech-owls. Monograph of West. Found. Vert. Zool., No. 1.

Marshall, J. T., Jr. 1978. Systematics of smaller Asian night birds based on voice. Ornithol. Monograph 25. Amer. Ornith. Union, Washington, D.C. [with cassette tape]

Roberson, D., and C. Tenney, eds. 1983. The Atlas of the Breeding Birds of Monterey County, California. Monterey Pen. Audubon Soc., Carmel, CA.

Voous, K. H. 1989. Owls of the Northern Hemisphere. M.I.T. Press, Cambridge, MA.

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