A birding big year presents certain constraints. Some birds are easier to see during the breeding season, while others are easier to see during the winter. Migration occurs more or less simultaneously along multiple flyways. Some species have limited ranges or are recorded most reliably in places that are difficult to access because of terrain, security restrictions, or expense. Some species are best seen on pelagic voyages. A birder attempting a big year needs to take all of these factors into account when building a big year schedule and also leave some flexibility to chase rare bird sightings.
As challenging as that might seem, a butterfly year presents additional difficulties. While some species, like Monarchs or Painted Ladies, can be observed for most of the year (especially in warm locations), many butterflies have very short flight dates – some only fly for a week or two. Some have very limited ranges or are only found where one uncommon host plant occurs. Butterfly watching is also more constrained by weather conditions than birding since butterflies are exothermic: if it is cold or rainy, butterflies will not be active. Thus a butterfly watcher's plans for a given location could be foiled by a few days of rain or the disappearance of a host plant. Pyle encountered uncooperative weather and habitat degradation repeatedly during his big year.
Mariposa Road chronicles Pyle's big year from the first butterfly he recorded at his home in Washington state through multiple cross-continent trips to its denouement in Key West. Along the way he travels to places as remote as northern Alaska (in pursuit of alpines, arctics, and sulfurs) and as urbanized as southern California (in search of some range-limited blues and skippers). Since many butterflies reach the northern limit of their range in Florida and Texas, he makes multiple visits to both states to record as many of those species as possible. He even finds time for a week in Oahu and Kauai to search for endemic Hawaiian butterflies.
A big year narrative can risk being a dull catalogue of hits and misses, but Pyle's prose is lively and engaging. Pyle describes not only where he went but also why he went there and why he considered certain butterflies to be "grails." He further enriches the text with background information about the ecology of interesting butterflies and the naturalists who discovered or gave their names to butterfly species. (For example, Hessel's Hairstreak is named for an amateur naturalist who realized a New Jersey population of hairstreaks showed significant, consistent differences with "Olive" Juniper Hairstreaks.) Pyle enlivens the text with stories about the people he met along the way and various mishaps, including car trouble and his unfortunate habit of losing important things.
I am not going to say how many species Pyle recorded, but he seemed to be mostly satisfied with the results. There were some near misses, either because he arrived a week late (or early) or because he was not fast enough with his binoculars or net. But in the end he achieved a respectable species total and raised a substantial sum for the Xerces Society, for whom he also kept a sporadic blog during the big year.
Despite its length (over 500 pages), Mariposa Road: The First Butterfly Big Year is a relatively fast read and holds the reader's attention. While I was reading it, I found myself wanting to go out and chase hairstreaks and skippers. I found it helpful to keep a butterfly guide close by (in my case Brock and Kaufman's Butterflies of North America), as many of the rare or western species were unfamiliar to me. The book should appeal to readers who have an interest in butterflies or who enjoy reading big year accounts. It should also appeal to readers who like Pyle's previous work, which includes Chasing Monarchs, in which Pyle followed the southward migration of Monarchs from British Columbia to Mexico, and The National Audubon Society Field Guide to North American Butterflies.