Primary Song is distinctive and dramatic, carries over long distances, and is the easiest method of identifying the species. Described as an “exquisitely sweet, haunting song. Two low, soft notes (seldom heard) followed by long, loud, high, liquid trill and two shorter, descending notes” (78: 988). Song is variable, both locally and geographically. Oberholser (20: 920) noted song is “one of the few bird vocalizations that can be recognized at 70 mph. . . . Texas birders, otherwise addicted to air-conditioned automobiles, leave windows open when driving through ranchland for purpose of hearing Cassin's Sparrow song.” Also remarked as being of “indescribable sweetness and pathos, especially when heard during the still hours of the night” (78: 988). Clearly, the Primary Song invokes strong positive memories in its listeners, similar to the reaction of people to the Primary Song of Bachman's Sparrow in the pine woods of the Deep South (108).
Primary Song. Figure 3. Primary Song given by male in flight or from exposed perch. When giving Flight Song (“skylarking”), male flies directly upward to height of 2–6 m (mean 4.6 m, n = 42) (3), giving introductory notes as the male rises with trembling wing strokes at an angle of 30–60° (8). Male then floats downward on set wings while singing trill, final two descending notes given just before landing. Apex of skylark may occasionally reach 12–15 m, especially during intense boundary disputes (3). Flight posture has head up, tail fanned, and legs stretched downward. Song flight often extends 5–15 m (78) and is most often given in the presence of a female (29). Thompson et al. (109) observed Flight Song initiated by some males from bare patches of ground, rather than song perches, in restored Texas grassland patches with few shrubs.
Borror (8) gave a detailed analysis of Primary Song. His sonogram analyses detected more structure to song than typically given in verbal descriptions; typical song includes: 1–5 introductory notes, a prolonged buzzy trill, followed by a weak, high-pitched note, two louder, lower pitched notes, a second weak, high-pitched note, then a final, low buzzy whistle (8). The high-pitched notes are often not mentioned in song descriptions, but are visible on sonograms. Final whistle is sometimes dropped.
Complex Song. Also called Chitter Flight Song. The complex song typically starts as a rapid series of Psit notes that transition into a warbled chattering series (3). More warbled than Chitter Call (see below). Sometimes embedded in series of Primary Songs; this behavior also described as “primary song preceded by series of chips, trills, and buzzy notes (29). Similar to Complex Song of Bachman's Sparrow (108, JBD). Can be given either while perched or in flight; when given in flight most often by a mated male that did not give long Primary Song bouts. May function to reinforce pair bond or as Alarm Call. Given in precopulatory courtship display and during nest initiation (29). Also elicited by approach of neighboring, unmated male (3). Playback of Complex Song typically produces a stronger reaction that of Primary Song, and playback of Primary Song often induces Complex Song.
Whisper Song. Heard in late summer. Very soft, consists of a few preliminary notes, then an assortment of trills. May last several minutes, but each phrase is slightly different. Ventriloqual, seems to come from a great distance. Whisper song in closely related Bachman's Sparrow is directed by male at female mate (JBD).
Chitter Call. Also called the Tzee-tzee-tzee or Twitter call. Variable; many versions are a series of short, very high-pitched (9 kHz) seet-like notes given in a rapid twitter. Some versions transition into a lower-pitched (2–3 kHz) series of slightly nasal chip-like notes, apparently especially in high agitation. Given by male in courtship chases, by young chasing parents, and by overwintering birds when flushed (78, 3). Also given by highly agitated birds on overwintering territories in response to playback of recorded song (RKB).
Psit. A very high-pitched (8.5–9 kHz), slightly upslurred note that is the most common call of the species. Given by male joining mate after short separation, or in response to female Alarm Call (78). Given by adult when observer is near young or other alarm situations (3). Dependent young give soft version, ship. Most common response of wintering birds to recorded song (S. M. Russell, personal communication; RKB). At 10 grassy patches in West Turkey Creek Canyon, Chiricahua Mountains, Arizona, on 12 January 1978, a range of 0–4 individuals per location responded to recorded song (S. M. Russell, personal communication). Of the 18 birds that responded, all gave Tsip, some flew to a perch near the observer, and most responded by the time 4–6 songs had been played. In these same patches, only one individual was flushed without use of the song broadcast.
Borror (8) sampled birds from Texas and southeastern Arizona, and described some differences. Schnase (29) found several variants of song phrases in a west-central Texas sample that were not described in Borror (8). Unpublished analysis of small sample of songs from Arizona and Texas found that songs were “very distinctive” (S. M. Russell, personal communication).
Schnase et al. (7) quantified patterns of song delivery and activity: Prior to arrival of females on breeding grounds, male sings from prominent, exposed perches. Skylarking is infrequent, but countersinging between neighboring males common. Percentage of songs delivered as Flight Songs increases markedly with arrival of females. It is not unusual for 100% of songs to be delivered in flight during periods of intense singing. Female presence on territories invokes intense skylarking. Male pursues females in long flights giving Complex Songs (see above).
Male spends little time singing or skylarking while females are incubating. Male resumes skylarking 2–3 d after young fledge from nest, perhaps because female may be fertile again in preparation for second brood.
In Texas, male may sing on warm days in early February; while first-year male may sing in March before losing breast streaks (78). “From April to July their songs are heard incessantly, night and day” (78: 988). Primary Song not sung from mid-July to mid-September in north-central Texas. In September, songs quiet, less frequent, not always typical in structure (78).
In Arizona, singing is heard primarily after the onset of monsoon rains in early July. Occasionally song is heard in March–late April, especially following springs with unusually heavy rains (110). Skylarking is most common during late summer (JBD, RKB).
In El Paso, Texas area (J. Donaldson and B. Zimmer, personal communication): singing also concentrated in two periods (Table 1). Singing common March to first week of May, and again from mid-July to mid-August. Singing after latter period drops off in intensity from mid-August through September. Few records outside active singing periods.
From Schnase et al. (7): Prior to arrival of females, most songs delivered in early morning. Little song activity in afternoon as male forages on ground and rests. Singing activity resumes briefly in evening before sunset.
After females arrive but before incubation begins, male begins singing about 1 h before sunrise. Male sings at rate of 3.9 songs/min ± 0.4 SD (range 3.0–4.5, n = 10 males) during morning period (06:00–10:00) in the first 2 weeks of April (7). Decrease in song frequency after 10:00, singing usually ceasing after noon. Evening singing resembles morning activity. Frequency of Complex Song declines after pair bonding. Borror (8) recorded an average song rate of 4.1 songs/min in Texas, and 4.5 songs/min in Arizona. Schnase (29, 7) did not report singing after dusk, but nighttime singing was reported to be common by Williams and LeSarrier (78).
Places of Vocalizing
Primary Song usually given from exposed perch (often shrub or fence post) or during flight display. Complex Song can also be given either while perched or in flight, but appears to average more often while perched than Primary Song.
Repertoire and Delivery of Songs
Individual males sing 1–3 variations of Primary Song (8, 9). Male typically sings 2–4 songs of one pattern, then switches to another pattern. Variations are subtle, but most are detectable audibly by observers; 3 of 40 variations detectable only on sonograms in Schnase and Maxwell (9) study. Identical song patterns are rarely sung by different males; therefore song patterns can be used to identify individual, unmarked males throughout breeding season (9). Fourteen males averaged 2.9 songs ± 0.9 SD (range 2–5) in repertoire (29). Full repertoire usually sung by an individual male during a song bout of ≥ 15 songs.
Spectral analysis of sparrow trills by Podos (111) included samples of 24 Cassin's Sparrow. Within the genus Aimophila (sensu lato), Cassin's showed very small range of frequency band width (all trills near 1 kHz), but wide range of trill rates used (5–50 Hz). Schnase (29) reported somewhat wider range of frequency: 2.1–9.2 kHz and average song duration of 2.52 s ± 0.18 SD (range 2.15–3.05, n = 40). In a study by Podos (111), Bachman's Sparrow showed a frequency bandwidth (1.0–5.5 kHz) similar to that shown by Schnase (29) for Cassin's Sparrow.