Sounds

Development

No information on vocal learning or sensitive periods for learning. Chicks emit peeping sounds (Adams and Quay 1958, WRE). Also capable of short squeals if exposed to sun or chills until age 6 wk (Adams and Quay 1958). Six-week-old young utter soft chitty-chitty-chitty sound when near parents (Meanley 1985). Seven-week-old young use both chick calls and adult call notes (Adams and Quay 1958). Fledged young capable of emitting most adult call notes, suggesting a mode of vocal development that does not involve imitation (D. E. Kroodsma pers. comm.). First evidence of Clapper vocalization (see below) at 6 mo of age (Meanley 1985).

Vocal Array

Has large and varied vocal repertoire, although many vocalizations are subtle and rarely heard. As with most other rails, study of vocalizations complicated by inconsistent terminology and confusion over names of vocalizations. Most advertising and territorial vocalizations are based on 1 note that shows on a sonogram as a vertical bar with series of harmonic bands above a weak fundamental (Massey and Zembal 1987). Three sound types derived from these, including kek, Clapper, and burr . These sounds further serve as basis for most calls; differences are due to changes in intensity, duration, length of intervals between notes, and pitch. Low frequencies and buzzes of these sounds carry well through dense vegetation (Massey and Zembal 1987).

Male primary advertising call, kek, is simplest vocalization of Clapper Rails, consisting of 1 short, repeated note described as kek-kek-kek, kik-kik-kik, or bup-bup-bup (Meanley 1985, Massey and Zembal 1987). Pitch of notes varies, and call may be heard for 1–2 km. Sometimes confused with kek call of grackles (Quiscalus spp.), Red-winged Blackbird (Agelaius phoeniceus), or Common Moorhen (Gallinula chloropus; WRE). Sound spectrogram is given in Massey and Zembal 1987 .

Clapper. Primary vocalization given by paired birds during breeding season is Clapper, or Clatter (Massey and Zembal 1987). Composed of rapidly repeated chock-chock-chock-chock-chock-chock-chock-chock (Simmons 1914), cac-cac-cac series, or slower jupe-jupe-jupe series; variable in pitch and speed of delivery (Meanley 1985). Delivered as single, repeated notes (numbering 12–100), complete vocalization lasts up to 10 s (Massey and Zembal 1987). Call starts at higher pitch and volume; intervals between notes stay about the same in duration. Often given as antiphonal duet by pair or by single member of pair. Sound spectrograms of single and duet Clapper are given in Massey and Zembal 1987 . The Kek-hurrah is similar in pattern to Clapper, consisting of 2–6 drawn-out kek s and a trilled, descending krrrr (Eddleman 1989; see Fig. 3A).

Kek-burr. Given by female. Differs from Kek-hurrah (see above) in consisting of ≥1 evenly spaced, distinctive kek s followed by a trilled brrrr; or the brrrr may be given without introductory note(s) (Zembal and Massey 1985). Sound spectrogram is given in Zembal and Massey 1985 . Has been described or noted in Clapper Rails from California, Arizona, and Florida, and in King Rail (Bailey 1977, Zembal and Massey 1985, Eddleman 1989, WRE). Descriptions of Kek-burr and Kek-hurrah in Todd (1986) are reversed.

Rapid series of wyeek or wheet sounds (Eddleman 1989, see Fig. 3B); rarely heard.

Members of both sexes of pairs emit purr vocalization during nesting season (Smith 1974, Meanley 1985, Massey and Zembal 1987, Eddleman 1989). This is a low-pitched, low-volume call that sounds much like purr of a cat. If intruder or member of other pair is nearby, louder version of vocalization—Agitated Purr—may be given (Tomlinson and Todd 1973, Massey and Zembal 1987, Eddleman 1989; see Fig. 3C). Low-pitched, soft trill (churr) rarely given (Massey and Zembal 1987).

Alarm Calls. Several alarm or agitation calls given by either sex in different contexts. Agitated Kek (also termed Jeer-kek [Todd 1986], gip-gip-gip, or gup-gup-gup [Meanley 1985]) is higher pitched and faster than kek (Tomlinson and Todd 1973, Smith 1974, Massey and Zembal 1987, Eddleman 1989). Chase Squeal, or kak, resembles squawk of a chicken and is given by birds involved in territorial disputes (Massey and Zembal 1987, Eddleman 1989). Flushed birds or birds in traps, in situations where behavior alternates between aggression and flight, may emit Screech, or Shriek (Massey and Zembal 1987).

Other Vocalizations. Birds in hand or (presumably) seized by predator give raucous rack vocalization, sounding like rack-k-k-rack-k-k, and repeated incessantly (Meanley 1985, Eddleman 1989, Fig. 3D). Bird under extreme duress may combine this vocalization with Tremolo Call: rack-k-k, rack-k-k, raa-ha-ha-ha-, speeding up with the end phrases (Eddleman 1989, Fig. 3E). Birds in traps may emit Burp Call, which sounds like low kek (Eddleman 1989).

If disturbance occurs within 15 m of bird, both sexes may give Hoo Call, sounding like oom-oom-oom, and similar to sound of a distant Great Horned Owl (Bubo virginianus; Tomlinson and Todd 1973, Smith 1974, Holliman 1978, Meanley 1985, Eddleman 1989). Adults with young produce calls that sound like cluck of chicken, or woof-woof-woof (Meanley 1985, Duhsé 1988).

Phenology

Exact phenology variable among sites and years (Eddleman 1989). Vocalizations involved with breeding are highly seasonal. Kek calls peak in Virginia between second week of Apr and second week of May; heard less often thereafter (Meanley 1985). Peak in Mar in Texas, then tapering off at start of nesting season (Simmons 1914). Kek given mostly Feb–Jun, kek-burr heard only in May–Jun, and purr in Apr–late May in Arizona (Smith 1974). Peak of spring vocalization at 2 Arizona sites in 1985–1987 varied from late Feb to mid-Jul among years (Eddleman 1989). Peak of kek vocalization in Mar–Jun and Clapper vocalization in mid-Feb–mid-Apr in California (Zembal and Massey 1987). In autumn, peak of vocalizations (mainly Clapper and Kek-hurrah) from mid-Jul to mid-Oct in Arizona and in Sep–Oct in California (Zembal and Massey 1987, Eddleman 1989); may represent addition of calling juveniles or gonadal recrudescence. Calls associated with aggression (Agitated Kek, Chase Squeal) increase at end of breeding season and in autumn because of frequent interactions among juveniles (Zembal and Massey 1987). Response to tape playback highly seasonal in Arizona, averaging 40% of birds during Mar–Apr, 20% May–Jul, 7% Aug–Oct, and 10% Nov–Feb (Conway et al. 1993). However, these estimates are from populations that had been repeatedly presented with playback recordings; response rate is probably higher when birds are not habituated to recordings. Other estimates of 70–95% response rate are based on estimates of calling by unknown numbers of birds (Smith 1974, Bennett and Ohmart 1978).

Daily Pattern Of Vocalizing

Depends on call type and weather. Generally, most calling occurs in evening and early morning (Smith 1974, Zembal and Massey 1987, WRE). In morning, calling period shorter, individual birds do not call as often, and more difficult to distinguish pairs and individuals (Zembal and Massey 1987). Heavy rain, high winds (>16 km/h), and extreme high tides depress vocalizing activity (Smith 1974, Zembal and Massey 1987). In spring in Arizona, responds well to tape playback for only 0.5 h after sunrise, especially when temperature is <21°C (Smith 1974). As temperatures warm in summer, birds respond best to tape playback for about 3.5 h after dawn. Kek vocalization given mostly in late afternoon and evening, but may be given all night when single males are attempting to attract mates in spring (Todd 1986, Massey and Zembal 1987, WRE). Clapper vocalization given at any time of day, but especially in evening (Massey and Zembal 1987). More calling at night in late summer and early fall in Virginia (Meanley 1985).

Places Of Vocalizing

Poorly described. Usually vocalize from the ground in dense vegetation, but a few birds vocalize from sites up to 3 m above ground or above water level in tall emergent plants (WRE). Advertising males vocalize from small area at sites with high density of conspecifics; but vary their location frequently in low-density populations, suggesting that unmated males move in and out of substandard habitats (Zembal and Massey 1987). Single males that do not attract mates call from 1–3 sites for periods of up to 4 wk before moving to other areas (WRE).

Repertoire And Delivery Of Songs

No information, because of difficulty of making repeated observations on individuals. Delivers Clapper vocalization with bill open, and entire body shakes during vocalization (Todd 1986). Vocalizing birds hold body in varied postures. Rate of delivery of kek 70–125/min.

Social Context And Presumed Functions

In general, more vocalizations given by birds in populations of higher density, indicating increased interactions among birds (Zembal and Massey 1987).

Delivered by unmated males, presumably to attract females (Massey and Zembal 1987, Eddleman 1989). Often given incessantly for many hours during spring. Tempo increases in response to external stimuli such as other calling birds, tape playback, or presence of humans. Ceases when male is mated.

Clapper. Given by both sexes; appears to function as greeting when separated members of pair meet, as means of communicating location of mate in dense vegetation, as nest exchange vocalization, during precopulatory period, or in response to loud noises or vocalizations of other pairs (Zembal and Massey 1985). May function for territorial defense.

Kek-hurrah. May be abbreviated version of Clapper, given by single birds of either sex, possibly given by unmated males in summer, or may be “subsong” given by maturing juveniles. Heard more often in some populations than in others (Todd 1986). Wheet always followed by Clapper or Kek-hurrah; possibly an indication of a high level of agitation (Eddleman 1989).

Kek-burr. Primary advertising call of female; functions to attract males (Zembal and Massey 1985). May be given by unmated females, females that have lost their mates, or females calling to straying males (Zembal and Massey 1985). Playback of Kek-burr attracts both mated and unmated males (Eddleman 1989).

Serves as contact call between members of pair; given by both sexes, especially near nests or when pair responds to minor disturbances (Massey and Zembal 1987). Agitated Purr given in response to disturbance when adult is close to nest. Churr heard rarely; function unknown, possibly given by female calling to nearby mate (Zembal and Massey 1987, WRE).

Other Vocalizations. Several calls indicate agitation or alarm, possibly given in different contexts. Agitated Kek is emitted by disturbed individuals or birds under stress (Massey and Zembal 1987). Examples include juveniles involved in chase sequences as they leave natal territories, and adults when humans are detected near nest (Simmons 1914, Meanley 1985, Massey and Zembal 1987). Chase Squeal is given by bird initiating chase; sometimes followed by Clapper if mate appears or Agitated Kek if an unrelated bird is being chased (Massey and Zembal 1987). Rack and Tremolo Call is given only by birds in the hand; indicate very high level of distress (Eddleman 1989).

Single sharp kek given by adult in Florida caused chicks to stop moving (Duhsé 1988). Low clucking sound given by brooding parents may function to keep brood together. Function of Burp Call unknown, but may be for pair contact (Smith 1974) or alarm or agitation call (Eddleman 1989). Hoo Call given by startled birds, as low-level agitation call, or as investigatory vocalization (Bennett and Ohmart 1978, Todd 1986, Eddleman 1989). May also be used by young birds to keep family unit together (Holliman 1978).

Adults sometimes communicate with young using a low clicking or shirring sound apparently made by snapping bill (Nicholson 1927, Duhsé 1988). These sounds are barely audible, but they travel 5–7 m through dense vegetation and are used to call chicks for feeding or for safety.