A review by David E. Quady
Undiscovered Owls, by Magnus Robb & The Sound Approach
The Sound Approach, 2015
308 pages, $59.50—hardcover, with 4 CDs
Peterson Reference Guide to Owls of North America and the Caribbean, by Scott Weidensaul
- Houghton Mifflin Harcourt, 2015
333 pages, $40.00—hardcover
In March 2013, René Pop and Magnus Robb were in a wadi in northern Oman, with the modest goal of improving their understanding of the Pallid Scops-Owl’s vocalizations and photographing the bird. On the fifth night, Robb writes, he
noticed an unfamiliar owl-like hooting in the distance. Pressing “record,” I tried to ignore the large bats picking fruit in the foreground and listened for more clues. A few minutes later the owl, if that was what it was, changed to a pulsed kind of hooting, and there was a nasal, rising answer from the other side of the wadi.
Undiscovered Owls presents the evidence that these were the calls not just of an owl but of a previously unknown species of owl, which Robb named the Omani Owl Strix omanensis.
Since then, further work by Robb and others, including DNA analysis, has determined that the discovery of Strix omanensis was in fact the rediscovery of S. butleri, then called the Hume’s Owl. A re-examination of other “Hume’s” specimens from across the Arabian Peninsula, though, revealed significant genetic differences, and those birds have now been named the Desert Owl S. hadorami; the owl Popp and Robb rediscovered, butleri, now bears the English name Omani Owl.
This fifth volume from The Sound Approach—a team originally comprising Arnoud van den Berg, Mark Constantine, and Magnus Robb, and later expanded to include Dick Forsman, Killian Mullarney, and René Pop—resembles its predecessors in shape and form. The title was inspired by Carl Jung’s The Undiscovered Life (1957) and by Magnus Robb’s recognition that owls helped him discover his own “true self” by escaping from noise, looking for wild places, and being in the dark.
Robb began this work “to discover which owls could be identified according to their sounds, regardless of their official taxonomic rank.” Other goals included learning how to age and sex owls by their sounds, and to better understand what they were up to in the dark.
At its simplest, Unknown Owls can be thought of as a richly annotated audio guide to 41 taxa in nine genera, most of them found in the Western Palearctic. This is a beautifully produced landscape-format book, illustrated with attractive artwork by Håkan Delin and many excellent photographs. At its heart, though, are the four CDs, with more than 4.5 hours of sound recordings. Parrot Crossbills, voles, and two species of midwife toads take up four of the 327 tracks, while the rest are devoted to owls, all but a handful of them Western Palearctic breeding species. By and large these are excellent recordings, most in stereo, all best served by listening through good-quality headphones. Notes identify each recording’s date and location, and a commentary describes what the recording captures. Two-thirds of the tracks are accompanied by annotated spectrograms, color-coded in most cases to indicate the sex and age of the bird that uttered the sounds represented. An example in the book’s introduction explains quite adequately how to read a spectrogram.
Owl sounds are thought to be “hard-wired,” not learned. In recent years, acoustic differences have been confirmed by additional studies (especially DNA analysis) that have led to many species splits, especially in the pygmy-owl genus Glaucidium. Unknown Owls explores those bio-acoustic differences and makes taxonomic judgments based on those and other strands of evidence: genetics, morphology, geography, and ecology. Robb cautions that his “species taxonomy does not follow any existing authority, nor does it pretend to be one,” and that “our species limits are hypotheses and we do not pretend that they are facts.”
But these hypotheses are interesting. I’ll adopt the book’s species names in my summary of three of the splits, and leave it to readers to puzzle out the corresponding names in their own preferred taxonomic authority.
Robb concludes that although the Common Barn Owl (Tyto alba) of the Western Palearctic and the American Barn Owl (T. furcata) share a “perennial screech” call (albeit not entirely identical), each has another call that is evidently not shared: the “courtship screech” of T. alba and a kleak kleak flight call of our T. furcata. It is instructive to hear—and to see, in the spectrograms—the evidence for this split, which some other authorities have also adopted.
In the family Strigidae, the Western Palearctic’s Tengmalm’s Owl (Aegolius funereus) delivers fewer hoots and does so more slowly than does the Boreal Owl (A. richardsoni). The former’s hooting series usually rises more gradually in pitch. DNA analysis suggests that these two populations were separated around 1.8 million years ago. Robb splits them, but their appearance and ecology are so similar that most authorities still regard them as a single species.
The widespread Short-eared Owl presents an especially interesting case. In the nominate subspecies Asio flammeus flammeus of northern Eurasia and North America, the female solicits food with a rising rrrrAh call, whereas females in a Caribbean and South American group have a very different, tomcat-like moan. Through most of Latin America, the Spanish name for the species translates to “field owl,” and the oldest name for any southern taxon is domingensis. Accepting Robb’s split and these names would mean that the Field Owl (Asio domingensis) is the species that occurs seasonally on the Dry Tortugas and the Florida Keys, while the Short-eared Owl is the species recorded in northern Florida.
Undiscovered Owls is an excellent book. Although its main focus is on the Western Palearctic, the author’s taxonomic treatment of some of “our” owls will surely interest birders on this side of the pond. And if readers are even half as much entranced by their sounds as I am, they will join me in trying to become better at understanding the owl vocalizations we hear in the future.
Scott Weidensaul’s engaging Peterson Reference Guide covers the 39 owl species known to breed north of Guatemala or in the Caribbean. The authoritative species accounts run the gamut from fairly well-studied species to three Central American pygmy-owls whose accounts are replete with phrases like “no information,” “essentially unstudied,” and “poorly known.” Excellent photographs illustrate aspects of the owls’ lives, such as behavior around the nest. Ambitious range maps depict seasonal and subspecies ranges, and the recordings of owl vocalizations available at the publisher’s website enliven the text’s descriptions.
Besides the 19 owls that breed in the ABA area, the book covers five endemic Caribbean species (the Puerto Rican Screech-Owl, Cuban Pygmy-Owl, and Ashy-faced, Bare-legged, and Jamaican Owls) and 15 Central American species whose breeding ranges extend into Mexico. The Oriental Scops-Owl and the Northern Boobook, two vagrant Old World species that have each reached Alaska twice, receive brief mention. The very useful “How to Use This Book” section also includes a rundown of Caribbean species known to have gone extinct before or after European colonization.
Each species account here is prefaced by indications of length, wingspan (where known), and mass. Weidensaul cites his references for the data on mass, which are broken out by sex and subspecies where possible; in a reassuring touch, he also identifies data omitted because of doubts about its accuracy. Banding returns provide most of the longevity data, which for most owls is quite limited; few species have been banded in significant numbers.
A section on systematics, taxonomy, and etymology includes discussion of the subspecies that occur in the book’s coverage area, including those not universally recognized. It also airs taxonomic opinions that differ from the AOU’s current classification, which the book follows. The origin and meaning of a species’ scientific and English names are given, along with the names by which it is known in Spanish, French, and native languages, where relevant. Thorough sections on distribution address breeding and non-breeding seasons, migration and other movements, and post-fledging dispersal, then conclude with a mention of the species’ distribution outside the area covered here.
The writing in the sections treating identification and vocalizations is especially vivid. Reading that a Barn Owl’s upper-parts are “the color of a perfectly baked biscuit dusted with campfire ash” conjures an image that stays with you. Mention that the male Elf Owl’s “chatter song” is often memorably likened to the yipping of an excited puppy made me wonder why I hadn’t thought of that apt comparison.
There follow sections on habitat and niche, nesting and breeding, and behavior, all clearly written and bound to contain something new to any reader. I did not know, for example, that the Black-and-white Owl, among the least studied owls in the Americas, lays just a single egg in each nesting attempt. The concluding section, on status, describes the species’ abundance and the threats to its survival as judged by IUCN/Birdlife International and governmental bodies.
Photographs depict each species and its key field marks. The images range in number from 19 for the Snowy Owl to one each for the Tamaulipas and Central American Pygmy-Owls. Many illustrate a behavioral trait, such as the Puerto Rican Screech-Owl’s drooped wing posture, or kleptoparasitism as two Short-eared Owls and a Northern Harrier skirmish over a freshly caught vole. The photographs are excellent, so it is “more,” rather than “better,” that the reader seeks. The sexually dimorphic Tamaulipas Pygmy-Owl, with the female much redder than the slightly smaller male, cries out for a second photo, or at least an indication of which sex is depicted in the single image provided. Another unfulfilled wish is for a photograph of the distinctively buffier brooksi subspecies of the Northern Saw-whet Owl, resident in Haida Gwaii off British Columbia.
Weidensaul notes that range maps “are the hardest element for an author to create and the easiest to fault,” and warns that his are not free of mistakes, compromises, or generalizations. But he provides quite detailed maps, and I commend him for it. Shading distinguishes summer, winter, and permanent ranges, hatching denotes where these ranges are irregularly occupied, and a grid pattern indicates rarely occupied regions. Range limits are precisely depicted, most notably for the Flammulated Owl: 36 blobs of color define the “archipelago of disjunct pockets” that make up this species’ breeding distribution in western mountains. Three polytypic species, the Great Horned Owl and the Eastern and Western Screech-Owls, are given multicolor maps delineating subspecies ranges.
Each of the species accounts includes a description of the male’s territorial call, and most also describe other vocalizations. For adults, these can include copulation solicitation and pair contact calls; for juveniles, raspy begging calls and chittering calls around the nest. The written descriptions are good, but actual recordings are more likely to be remembered, and so the publisher’s website offers free access to 86 high-quality downloadable cuts from the Macaulay Library of the Cornell Lab of Ornithology.
This is an excellent entry in the Peterson Reference Guide series. It is thorough, up to date, heavily referenced, and well written—and unlikely to gather much dust on my bookshelf.
– Dave Quady lives in Berkeley, California, and currently serves as President of Western Field Ornithologists. He has birded throughout California, in all of the other 49 states, and in nearly as many other countries. Dave likes all owls, but is especially intrigued by the ones he hasn’t seen or heard yet: The books he reviews here are full of them.
Quady, D. 2016. New Owl Books—and New Owls [a review of Undiscovered Owls, by Magnus Robb & the Sound Approach, and of The Peterson Reference Guide to Owls of North American and the Caribbean, by Scott Weidensaul]. Birding 48 (4): 65-66.