The author's passion is infectious, and it genuinely made me hear birds differently.

Kroodsma's step-by-step analysis of sonagrams is very clear, and his passion for recording bird vocalizations is persuasive. As for myself, I'm tempted to acquire a parabolic mic and digital recorder and get out there listening. The passages in which Kroodsma details his field work, hour by hour, are less effective.

Some birds learn songs while the song is built into the DNA for others. At present, it is thought that only the songbirds (suborder Passieri of the perching birds), parrots and some hummingbirds. They represent about half the bird species.

Kroodsma's early work was done on Bewick's Wren where he showed that earlier hatching birds learn more songs than later hatching birds, opening the question of whether the greater repertoire provides an advantage to the bird. The author shows how the sonagram can be used to visualize the songs of the American Robin, making variations clearer.


Song Development

The White-crowned Sparrow has five distinct populations in the Point Reyes National Seashore, grouped by distinctive song dialects. It learns songs more readily in it's early natal years; hence from it's father - but can learn songs if dispersal takes him into an area of different dialect. It is uncertain as to whether the song boundaries discourage dispersal and therefore isolate the populations genetically. Some population differences have been documented but it is unclear as to whether they are due to dispersal limitations or to founder effects.

The Song Sparrow learns the songs of his neighbors, preferring songs shared by at least two neighbors. When he hears a song, he responds with the same song (type matching) or a different, shared song (repertoire matching). Type matching is more aggressive and usual in breeding season. Songs appear to allow territories to be defended more efficiently.

The Northern Mockingbird is a mimic, using over 100 songs picked up from other species. These are sung in groups of one to five, separated by two second gaps. The bachelor sings all night in hope of attracting a mate. Once paired, singing is much reduced. While the Mockingbird obtains his large repertoire by borrowing songs, the Gray Catbird (400 songs) and the Brown Thrasher (2000 songs) use improvised songs.

The sub-oscine birds (mostly Neotropical) include the flycatchers, woodcreepers, antbirds, elaenias and manikans. Kroodsma describes his work with the flycatchers to establish that their song is innate and develops without learning. Populations with differing songs are now recognized as being genetically different in spite of almost identical appearance and are identified as different species - for example, the Willow and Alder Flycatchers. The Slaty Antshrike is thought to be as many eight species over it's range from Belize to Brazil.

The Three-Wattled Bellbird, although a sub-oscine, does learn it's song. Two dialects exist - the 'bonk' and the 'quack'. The young birds take six to seven years to perfect their songs. The two dialects have changed since the 1980's, with the whistle declining from 5500 Hz to 3700 Hz. The adult birds appear to be listening to each other resulting in the evolution of the songs over the years. Kroodsma hypothesizes that competition for females causes the males to change their song to make it more attractive.

Marsh and Sedge Wrens generally learn songs from neighbors and exchange them when responding. The North American Sedge Wren is different as it is highly nomadic. Instead, each male generates it's own song set which it uses to respond to neighbors.


Dialects

Western and eastern populations of Marsh Wren have quite different songs. The eastern population sings fewer than 50 songs in rotation. The western population sings over 100 songs, often anticipating it's neighbors sequence. The two populations have a narrow border in the east of Nebraska, but further north the separation occurs over much of Saskatchewan.

Most Black-capped Chickadees in North America sing the same song. Exceptions include three separate dialects in Martha's Vineyard and local dialects in British Columbia. It seems that irruptions occur in the chickadees where young birds travel some distance, allowing the song to be shared. Those populations with their own dialect appear to be localized and non-migratory.

Chestnut-sided Warblers have individual territorial songs, which seem to be used to compete with other males for females. About half of the nestlings in a nest are fathered by the male owning the territory.

Interesting material on the dialects of the towhees and the titmice.


Extremes of Male Song

While the corvids are songbirds, they seem to have few, rather simple calls that hardly qualify as songs. An examination of the Blue Jays, however, shows that they use a number of variations on the basic call for different interactions. They also tend to imitate hawks on occasion.

The trashers are notable for the number of their songs. The Brown Trasher has a repertoire of around 2000 songs; they are repeated suggesting that the bird learns the songs rather than improvises. The Sage Thrasher has on the order of 700 songs, but they are largely songs learned from other songbirds. The Winter Wren is notable for the length of it's songs, being some 7 seconds long.

Kroodsma talks of the most beautiful singers, noting Bachman's Sparrow, the Wood Thrush and the Hermit Thrush. The Wood Thrush sings with two simultaneous pitches, a different pitch produced by each voice box. A number of birds use the two voice boxes to produce different notes, all seeming to use the left voice box for lower pitches and the right for higher. He includes an interesting discussion on the similarities to human music.

The American Woodcock supplements it's song or call with a brief whistle produced by three stiffened feathers at the end of the wings. The Common Snipe also uses feathers but makes sound by directing air over a single feather on the leading edge of the tail.

The Whip-Poor-Will and the Red-Eyed Vireo are among the most tireless of singers, singing over 20,000 songs per night and day, respectively.


The Hour Before Dawn - In this chapter, the author examines the songs of the Eastern Wood-Pewee, the Chipping and Brewer's Sparrows and the Eastern Bluebird in the context of the Dawn Chorus as a competition amongst the male birds.


She Also Sings - Examples of species where the female has a significant song, including the Barred Owl, Carolin Wren and the Northern Cardinal.


Kroodsma's narrative about each species reads like a detective story as he learns about the songs of each, deftly bringing out the excitement of discovery.

Not what I expected. This is really a bird call book. It has music notes for various bird song. Way above my skills. For a more advanced border this book might hit the mark.

Disappointing. Much more detail about the author's life and methods than I cared about. Too little emphasis on categories of bird songs and how to recognize different birds. The emphasis is on using sonograms, which are no doubt helpful to a scientist but were mystifying to me.