Figure 2. Three different song types of Northern Cardinal.
A. Made of up of 2 types of syllables. B. Made up of 1 type of syllable. C. Made up of 4 types of syllables, the last of which is a chirr. The first 2 song types, or variants of them, are common over much of the cardinal’s range, as are songs made up of the first 2 syllable types of the third song. The durations of songs shown here are typical, but occasional songs consist of only a single syllable, and songs of 20 s or longer are also occasionally sung (SLH). (Part A recorded from male; B and C from females singing from their nests.) Part A shows terminology used to describe songs. Syllables are consistently repeated short sounds or ordered sets of 2–3 short sounds. The syllables sung by an individual or local population of cardinals can be sorted into discontinuous sets of syllable types, defined on the basis of close similarity in sonogram shape (pattern and timing of frequency modulation). A song type is defined by the order and identity of its syllable types. Sonograms prepared by staff of Borror Laboratory of Bioacoustics (BLB), Ohio State University, using a Kay Elemetrics DSP 5500 Sona-Graph with effective bandwidth of 150 Hz (200 pt. transform size), from recordings made by SLH, Rice County, Minnesota, 22 June 1990 (A), 23 July 1990 (B), and 21 June 1990 (C).