Several warbler species sing two different types of song, termed first category and second category, and sometimes known as accented and unaccented, type 1 and type 2, or type A and type B (the nomenclature differs between species and is confusing). First category songs are sung to attract females, are sung early in the season, sung all day until the male is paired up, and then singing drops off significantly. They are often accented, and tend to be sung in repeat mode. Second category songs are considered to have a more aggressive function and are used to maintain territory. They are the predominant songs given at dawn and dusk, increase later in the season, and are sung in male-male interactions and on the edges of territories. In species with accented songs, the second category songs tend to be unaccented (note that in the Blackburnian and Yellow Warbler both song categories are often accented). In species with larger repertoires, there are more second category songs than first category, and they tend to be sung in serial mode.
In "The Singing Life of Birds" Don Kroodsma writes that the male Chestnut-sided Warbler learns accented songs (there are 4-5) in the first year of life, probably in migration. These songs are the same throughout the species' range. The unaccented song is not learnt until the young male arrives on his breeding grounds, and is learnt from neighboring males. Each male learns up to 12 unaccented songs. Each local group of Chestnut-sided Warblers has a different set of unaccented songs, so that throughout the species' range the number of variations is innumerable.
Chestnut-sided Warbler, first category or accented song (July, ME)
unaccented (second category) song (July, ME)
A bird singing accented then unaccented songs (July, ME).
The American Redstart has a repertoire of 1-4 accented and 2-10 unaccented songs (up to 12 total). Accented songs end in a chevron on the sonagram. Individual accented songs tend to be repeated over and over (repeat mode) whereas the unaccented are often sung in variable sequences (serial mode).
First category: accented in repeat mode. This song is heard persistently throughout the season by unmated first spring males (May, NJ)
Second category: unaccented in serial mode, actually two phrases alternating (July, ME)
Songs in serial mode (May, NJ).
Unaccented songs can sound similar to Black-and-white Warbler or other high-pitched species but are shorter (July, ME).
American Redstart and Chestnut-sided warbler singing together (May, NJ).
According to BNA, Yellow Warblers have a repertoire of about 15 songs, which may be accented or unaccented, but it is the mode of singing that defines song classification, independent of whether or not the song is accented, with second category serial mode at dawn, and first category repeat mode predominating during the day.
This bird was recorded at dawn (May, NJ).
phrases 1 and 2
Note the similarity to Chestnut-sided
phrases 7 and 8
Each Hooded Warbler sings one first category accented but several second category non-accented songs.
accented (May, NJ)
unaccented in repeat mode (before sunrise, June, NJ)
Magnolia Warbler first category accented songs can sound very similar to Hooded Warbler (migrant, May, PA).
accented (July, ME)
Magnolia Warbler second category unaccented songs can sound similar to Chestnut-sided, but are generally shorter (July, ME).
An unusual song, difficult to characterize (May, PA).
Prairie Warblers sing several versions of two song types, called group A and B (per BNA), which are equivalent to first and second category respectively.
Group A is a rising series of buzzy notes (June, NJ).
Group B begins with clear notes (June, NJ).
Bird singing both category songs at dawn (Apr, PA).
Several warbler species sing only one version of each of the two song types:
Black-throated Green Warbler. Confusingly, type A songs by this species and the Blackburnian Warbler are second category, the opposite of some other species with type A/type B notation.
first category song (July, ME)
second category is often interspersed with juvenile-like chip calls (July, ME)
Occasionally a bird of one species will sing the song of another species. This Black-throated Green Warbler sang a normal first category song but the second category song was preceded by a Pine Warbler-like trill. This bird returned to the same spot for three successive years, and interestingly, the habitat was typical for Pine Warbler, dry oak/pine woodland, but not for Black-throated Green Warbler; this species breeds only in white cedar bogs in the pine barrens in southern New Jersey (May, NJ).
normal song by this bird
Type A or first category, a simple rising buzz with an end note (migrant, May, NJ)
Type B, or second category, more complex with clear and buzzy notes (July, ME)
This version of the song appears to be a hybrid with a beginning like a second category and ending in a first category-like trill at the end. The bird switches to its other song at 68s, a typical type B or second category song. (July, ME).
change at 68s
A clearer-toned version (migrant, May, PA).
The Black-throated Blue Warbler is another species that has two different song types. The so-called Type 1 song has several relatively pure-toned notes in the beginning. The Type 2 song usually has less notes, all buzzy. It is likely type 2 is second category and used for maintaining territory, and type 1 first category, for attracting females, as BNA states that this song is sung in the center of the territory.
Type 1 (July, ME, juvs in background)
Type 2 (July, ME)
accented (June, NJ)
Blue-winged Warbler (with Common Yellowthroat)
first category (May, NJ)
The second category song often sounds like a plain trill (May, PA).
Pine Warblers have a repertoire of more than one song and some songs are faster than others.
rapid song (June, NJ)
Pine Warbler singing 15 minutes before sunrise, running through an apparent repertoire of four songs in serial mode. The mode identifies this as the second category song, as the same phrases are sung in repeat mode during the day (June, NJ). Incidentally, this is a good way to distinguish a singing Pine Warbler from the similar Chipping Sparrow and Worm-eating Warbler, as those birds sing only one song.
Pine Warblers and Chipping Sparrow (at 10,34,44 and 56s) singing together (May, NJ).
Yellow-rumped Warblers have a variety of song phrases, as shown by these migrants singing in serial mode ie different consecutive phrases (apparently birds on territory sing with less variety). The loose trills tend to fade at the end. Some phrases can sound similar to Chestnut-sided unaccented songs.
(Northern Rough-winged Swallow at 34s, May, PA)
(breeding grounds, July, ME)
Each Canada Warbler sings about 11 different songs, often given in serial mode. The songs do not seem to be classifiable into two types. A flight song has been described. Canadas generally sing in the forest understorey.
The song uniquely starts with the chip call, but note that the phrase at 26s starts with the flight call, which is sometimes also incorporated into the song (migrant, May, PA).
Migrant singing with staccato sets of chips and flight calls (May, PA).
(migrant, May, NJ)
The Yellow-breasted Chat has a highly variable song including mimicry, in this case crow calls (June, NJ)
More examples of mimicry (July, DE):