A practical guide to bird watching in Sonoma County, California
(Unless otherwise indicated, all phone numbers are in the 707 area code)
© Colin Talcroft, 2009, 2010, 2011, 2012, 2013, 2014
Unless noted, all photos by the author. If you would like to use one of my images, please ask for permission for non-commercial use with proper credit or commercial use with proper compensation.
BOOK REVIEW
Rare Birds of North America
The plates are superb. Rare Birds of North America is a pleasure just to browse through. The birds pictured are likely to be unfamiliar and seem exotic to North American birders used to birding at home. Half the pleasure of turning the pages is the way the illustrations spur the imagination. These are the rare--often extremely rare--birds that could show up....
The authors, however, make an excellent case for the idea that vagrancy is less random than we may think. The book begins by saying “Our overriding interest when considering vagrant birds in North America has been to look for patterns of occurrence” and clear patterns there are. A rare bird is here defined as a species that, on average, has occurred no more than five times a year (five individuals) in the area of coverage since 1950 or so, when birding and field ornithology are assumed to have begun to become widely popular in North America, but the bulk of the data analyzed is from the late 1970s to the cut-off date before publication, reflecting a take-off in field reports available for study from around that time. The authors admit that definitions of rarity are inevitably arbitrary, but rational assumptions appear to have been made in setting parameters for the book, and these assumptions are discussed in detail.
In looking for patterns, the authors focus on the relationship between migration and vagrancy, a discussion that forms the bulk of the text aside from the species accounts. Migration can be considered the enabler of vagrancy. Clearly, birds that do not migrate are unlikely to stray far from home. It’s the regular, long-distance movements of bird populations that set the stage for vagrancy. While the prodigious feats of long-distance flying and navigation of migratory birds are well known, how birds find their way remains something of a mystery. The authors point out that the best working theories we have are that birds navigate either by celestial landmarks (using positions of the sun and other stars) or by sensing the Earth’s magnetic field, but also that our understanding of bird navigation during migration is “still rather nascent” and that other factors come into play as well. Vagrancy is assumed to be the result of some kind of failure of the tools birds have to find their way--whatever those tools may be. The authors are careful also to consider how statistical patterns of vagrancy are affected by human attention: we see more vagrants if we look for them; we see more where we look for them; we see more in places that are more easily accessible to people and more frequently visited; we detect more vagrant geese, perhaps, than vagrant hummingbirds, simply because a goose is more conspicuous than a hummer.
With these caveats, six types of vagrancy are identified: Drift, misorientation, overshooting, dispersal, association, and disorientation, and some vagrants are called false vagrants--apparent vagrants or vagrants by numerical definition that may actually be more common than we realize (because they inhabit places few birders go). Each of the six types of vagrancy is defined and then discussed using examples. Drift, for instance, usually involves land birds migrating over water that encounter adverse weather conditions that don’t allow them to turn back or land. These birds will attempt to press on and keep to their preferred course, but at some point energy constraints make it more sensible to drift with the winds than to expend energy fighting bad weather making no headway. “We know nothing of the nature of the tipping point, when a bird decides to give up trying to achieve its normal migratory goal, but it’s clear that something like this happens regularly.” For example, birds migrating north along the East Asian coast in the spring appear susceptible to being pushed east by bad weather, accounting for a regular pattern of Asian vagrants coming down in the Aleutian Islands or, further east, the Pribilof Islands. The book is valuable for its discussion of each of the six types of vagrancy and the practical impact these “mistakes” have on known population movements and of how recognized patterns of rare bird sightings in North America fit into the theoretical framework presented.
A following section attemps to answer a very specific question: “Where Do North American Vagrants Come From?” The authors divide source populations of North American vagrants into Old World species, New World species, and pelagic species, and present tables of occurrence in North America broken down by location and season, with attention to relevant differences between patterns among land birds and water birds. A discussion of feather topography, molt, and aging of birds follows, ending the introductory section. The remainder of the book is species accounts.
The species accounts are ordered in fairly typical fashion, roughly taxonomically, with water birds preceding land birds. Each species account includes: species name; a summary of known distribution in North America (that is, its record of vagrancy in North America--sometimes just one or two historical sightings); taxonomical information (information about subspecies, etc.); distribution and status information (information about normal breeding and non-breeding ranges, and about abundance in the bird’s normal range); comments on patterns of North American vagrancy of the species based on the statistical record of its vagrancy here; and then field identification information (field marks, comparisons with similar species, comments on age, sex, and seasonal variation, and notes on habitat and behavior--in other words, the sort of information found in a typical field guide. Where relevant, normally occurring similar species are illustrated side by side with the bird in the main entry--for example, our Spotted Sandpiper (Actitis macularia) is shown alongside the illustrations for vagrant Common Sandpiper (Actitis hypoleucos). One effect of these pairings is to make it abundantly apparent how difficult it may be to identify some rare vagrants; differences can be exceedingly subtle. How many times are vagrants seen but missed--assumed to be the local species and not examined closely?
My one complaint about Rare Birds of North America is that it’s not sure whether it’s a reference book or a field guide. It’s designed like a field guide, and the bulk of the book is in the species accounts (like a field guide), but it’s a heavy hardcover book that few people will want to carry. It may be too attractive to throw in the car, where it will inevitably become damaged, and, given the rarity of the birds the book covers, there would be some extravagance involved in having it always at the ready anyway. It will most likely end up on bookshelves as a reference book, and one that in large measure duplicates the content of field guides for the regions North American vagrants come from*. Some of the text may be too technical to sustain the interest of the more casual birder. Having said all that, Rare Birds of North America does very well what it sets out to do: present a highly specific subset of the world’s birds while elucidating the factors that make that subset meaningful. As noted above, it’s beautifully printed and illustrated. Rare Birds of North America is a useful, if highly selective, book that will certainly appeal to serious North American birders that enjoy chasing rarities or to the armchair ornithologist that dreams about chasing rarities.
*Note, however, that an ebook version is available through iBooks. For more information, go to: https://itunes.apple.com/us/book/rare-birds-of-north-america/id720890496?mt=11
Rare birds of North America
By Steve N. G. Howell, Ian Lewington, Will Russell (illus.)
Princeton University Press, 2014
Hardcover, 448 pages
Retail price: $35.00
Recommended for serious birders