Sounds

Extensive description of tern calls by Marples and Marples (1934) is basis for much discussion of Least Tern calls. Distinctions in the basic 4-figure call as described by Massey (1976) were the primary basis for recognition by Am. Ornithol. Union (1983) of Least and Little terns as separate species. Although some calls of Least Tern are considered deeper and less sharp than corresponding calls of Little Tern, several others are considered identical (Alström and Colstrom 1992, K. Beylefeld and C. Wilds pers. comm. cited in Olsen and Larsson 1995).

Development

Juveniles begin vocalizing with cheep begging calls. After fledging, juvenile calls are distinguished from those of adults as being higher-pitched and consisting of 2 or 3 distinct parts (Massey 1974).

Vocal Array

Calls only; no song. Although mnemonics (phonetic or word equivalents) vary, most authors agree on the nature and function of the following calls:

Male’s Contact Call. Typically a 2-toned ki-dik (Olsen and Larsson 1995), given by males carrying fish to feed mate or young. Adult male may give soft version while watching young swallow food (Wolk 1974).

Alarm Calls. At least 3 related Alarm Calls described (Massey 1974, Wolk 1974) representing increasing levels of alarm by male and female. The least of these, zwreep is given in the air after an adult has been flushed from its nest; a signal of imminent danger that elicits motionless hiding by young. With greater alarm, zwreep mixed with high-pitched tsip tsip tsip or a staccato kit-kit-kit-kit . A deeper, more guttural krowkgh is given at the bottom of an aggressive dive, apparently a more intensive threat call.

Recognition Call. Well-known 4-note call seems primarily to allow recognition between pair members or between a parent and its young. Given in flight primarily at or near the colony in group situations when not visibly disturbed. Adult returning to colony may begin giving this call 1 km away (Massey 1974). The most musical call of the repertoire; variously described as k’ee-you-hud-dut (New York; Wolk 1974), keedee-cui, keedee-cui (Mississippi River; Hardy 1957), or kee-zink, kee-zink (California; Davis 1968). Massey (1974) provided sonograms of California birds. Wolk (1974) suggested that the Recognition Call is given in circumstances similar to the aerial long call or landing call (Moynihan 1955) of other larids.

Summons Call to Young. K’ee-you, given by adult male or female flying to feed or brood its young; young respond by running to parent and giving begging cheeps or later a ti-seep call, which is an apparent developmental stage of the young call of adults (Wolk 1974). Call varies among individuals, and chicks learn to recognize and respond to the calls of only their own parents.

Brooding Call. Soft, throaty contentment call given by adult male and female during brooding. Massey (1974) referred to the call as crooning and provided a sonogram showing a 6-figure construction.

Begging Call. Given by chicks begging from parents; basic 3- to 5-note pattern that varies with intensity of begging. Described as twee-dididi-twi; initial note longer than the last (Wolk 1974).

Phenology

Knowledge of vocalizations is limited to breeding season. Calls related to courtship and tending nest or young wane as breeding season progresses; Alarm and Recognition calls prevalent throughout.

Daily Pattern Of Vocalizing

No pattern described, but vocalizations continue at lesser level in large colonies through the night.

Places Of Vocalizing

Calls given variably from ground or in flight.

Repertoire And Delivery Of Songs

As described above.

Social Context And Presumed Functions Of Vocalizations

Calls associated largely with announcing approach to colony, communication between paired birds, tending young, and individual or group aggression toward colony intruder.

During a diving attack on an intruder near the nest site, the rush of air through wings and tail, although perhaps just a by-product of the behavior, may deter the intruder.