In late summer through early spring, it is interesting to listen to young birds as they learn to sing. The songs are identifiable to species, but are not normal.
Young birds in their first year begin babbling like babies as they learn to sing. This is known as subsong. At some point later in the year or early the next year the song begins to take on the sounds of an adult, with normal phrases intermingled with babbling, or misplaced or additional phrases mixed in. This is known as plastic song. By the time the birds reach their breeding grounds, the songs have become crystallized.
This is a Field Sparrow singing in Montgomery County, PA in early February. Two of the song phrases are good examples of plastic song, with additional notes added on after the trill. Each of the four phrases has a slightly different trill at the end. Only one crystallized song will be sung on territory a couple of months from now, the other versions will be discarded.
Also heard is a singing Song Sparrow and a calling Red-winged Blackbird.
Field Sparrow plastic song, the complex or dawn song (Mar, PA).
Song Sparrow subsong. The song is a jumble of notes with no structure (Oct, PA).
The first 16 secs of subsong:
This young Song Sparrow was singing nearby on the same day, but has advanced to plastic song, with the song delivered in discrete phrases, but each phrase is different from the next (Oct, PA).
The following three species of sparrow are frequently heard practicing songs during the winter:
Fox Sparrow (Nov, NJ).
White-throated Sparrow (Oct, PA).
White-crowned Sparrow, subsong by immature (Oct, PA)
plastic song by immatures (Nov, NJ).
American Tree Sparrow plastic song and flock calls by single bird (also Carolina Wren, with Red-winged Blackbird, Field Sparrow, Song Sparrow in background, Mar, PA).
A Winter Wren singing beside a creek in March, PA. The (plastic) songs are often longer than normal, and vary from one another. The first song is 22 seconds long!
When they get on territory eastern birds will sing only one to three crystallized songs.
first song (time scale reduced)
Carolina Wren plastic song (July, NJ). Successive song phrases are all different, whereas adult males sing the same song many times before switching to a new one.
House Wren plastic song (Sep, PA).
This bird has advanced a little, with a trill at the end of each phrase (Sep, PA).
First four phrases:
Sedge Wren plastic song. This bird fledged only three weeks previously (Oct, PA).
Black-capped Chickadee, probable plastic song (July, ME).
Gray Catbird subsong or plastic song (Sep, NJ).
Male Northern Cardinal plastic song (females also sing). There is a disjunction between the vertical (made by the right syrinx) and horizontal (made by a switch to the left syrinx) portions of the L-shaped notes. In the crystallized song, the transition is seamless. The notes of the song are variable, and more modulated than in the crystallized song (Feb, PA).
Eastern Towhee plastic song, no two consecutive song phrases are the same (Mar, PA, with Tufted Titmouse singing)