Thursday, March 17, 2011

Hawks at a Distance: Identification of Migrant Raptors

On first shake, the identification of North American birds of prey (hawks, eagles, accipiters and falcons) might not look like too much of a challenge. If you toss in Black and Turkey Vultures which look and migrate in a similar fashion to true hawks, there are only twenty widespread species across the continent, with a handful of less common species restricted to the southern borderland, the tip of Florida or specialized areas such as coastal California and the Grand Canyon. Moreover, some species are highly distinctive, Swallow-tailed Kite being an obvious example.

However, as with many bird groups, things become more complicated the closer you look. One soon discovers that extremely familiar species such as Red-tailed Hawk comprise five discrete populations (Eastern, Western, Harlan's, Fuertes, and Florida), and there is considerable individual variation within each of these populations. Some common species can be darn hard, Cooper's Hawk and Sharp-shinned Hawk are familiar to every North American birder but are notoriously difficult to identify reliably (and I stress reliably). So 'hawks' represent a deep well for the identification enthusiast and there is a thriving market for innovative texts on field identification.

In 2005, Jerry Liguori published a slim but very informative book called "Hawks from Every Angle: How to identify raptors in flight". This was designed for the enthusiasts who gather at hawk migration sites in the spring and fall to watch passing birds. The new book "Hawks at a distance" is similar in design and content but raises the bar a notch by focusing on identification of the 'core species' when viewed from a greater distance, thereby mimicking the more typical experience of a hawk watch. One of the mantras of skilled bird identification is knowing the common species as well as possible. This is achieved through hours of deliberate study and continuous practice. Expert birders spend just as much time looking carefully at common birds as they do looking at uncommon ones, something that beginning birders often forget.

"Hawks at a distance" considers 28 species, chosen on their likely occurrence at migration watch points across the Continent. Northern Hawk-Owl, Barn Owl, Short-eared Owl and Common Raven are thrown in for good measure because they are occasionally mistaken for accipiters, falcons or small buteos. Each species treatment begins with a beautiful full page 'portrait' photo (no brainer identifications) and then moves to the world of pepper dots on a blue sky. The text describes the species from the perspective of a distant view, discussing shape, the way the wings are held in a glide, wing beat cadence and so on. This is followed by sets of six image of birds in flight and arranged by age or sex. A paragraph length legend explains the take home messages evident in the pictures. One minor criticism is that the locations and dates are not given for any of the photographs. I can't help thinking how much more accessible this information would be in the form of video. Either to walk us through the points or to actually show the different flight styles or the way soaring birds rock from side to side. Style of movement is an important aspect to identification that is difficult to communicate and is absorbed by real world experience.

At the rear of the book we find an extensive collection of gray scale images showing multiple views (46 or so) of each species in near silhouette. These remind me of the outlines of small Eurasian eagles that I traced from books as a kid, hoping to one day see these species for real at an exotic watch point or mountain range in the Mediterranean or Asia Minor. I stuck the tracings to the ceiling above my bed hoping to soak the slight differences in shape every time I opened my eyes. Liguori's montages are a very useful reminder of the visual challenges that North American birds of prey pose. Remember what I said about Sharp-shinned and Cooper's Hawks? Just looking at the panels of these two species arranged on opposing pages (172-173) sends a shiver down my spine. The eye eventually notices the differences but they are subtle, not evident at every angle and difficult to capture in words. I'd be interested to know if these montages show many different individuals or are generated from runs of shots taken in sequence. Regardless, an aspiring hawkwatcher would do well to spend some time in the pre-season carefully working over these powerful images to get their eye in.

The book begins with a quirky but thoughtful forward by Pete Dunne who considers the progress in North American field guides from the stand point of viewing and identifying birds from ever increasing distances. It is probably intuitive to most birders that shape and posture become increasingly important as birds get further but Dunne makes the valuable point that plumage details also transform, spots becoming lines, streaking becoming dark patches and so on. This is something that David Sibley incorporated into his field guide paintings.

We are certain moving into a new phase of North American birding, with greater emphasis on understanding and applying gestault identification criteria rather than relying on details that can only be seen at close range. There are plenty of other bird groups that could do with a similar treatment, waterfowl being an obvious example. More of this when I discuss 'The Crossley ID Guide' in a future posting.

'Hawks at a distance' is a neat little book and valuable reference.

Title: Hawks at a Distance: Identification of Migrant Raptors
Author: Jerry Liguori
Publisher: Princeton University Press
Publication date: 2011
Dimensions: 216 pp., 6 x 8 1/2 inches
Artwork: 558 color photos, 896 halftone photos, 2 tables.
List Price: US$19.95 (paper)
ISBN13: 978-0-691-13559-5

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