Development
Young begin vocalizing at least by 5–6 days of age. The call of each chick becomes uniquely recognizable by day 15 and is pure and consistent in structure by day 18–21 (Stoddard and Beecher 1983). Calls of siblings are structurally similar. Sib-sib similarity is genetically based, rather than reflecting vocal imitation among nest mates (Medvin et al. 1992). There is no evidence for vocal learning, sensitive periods, or vocal mimicry. The juvenile’s Begging Call (see below) develops into the Chur Call of adult. A call resembling the Purr Call (alarm) was given by juveniles that were about 6 weeks old (CRB, MBB).
Vocal Array
Limited vocal repertoire. Five vocalizations: the Begging Call (Stoddard and Beecher 1983), used by juveniles when soliciting food from adults; the Purr Call, used as alarm call when predators approach; the Chur Call, commonly used in many contexts (Brown 1985); the Twitter-squeak Song, up to 6 s in typical duration, composed of many guttural gratings, and used primarily during courtship and nest establishment; and the Squeak Call, used as a food-finding signal (Brown et al. 1991). The Squeak Call is structurally similar to the much longer Twitter-squeak Song and may be derived from that song. Both sexes give the Begging Call, the Purr Call, the Chur Call, and the Squeak Call; presumably only males give the Twitter-squeak Song, but no study of singing with marked birds has been done. Apparently there is little geographic variation. Descriptions of vocalizations were similar for birds from W. Virginia, Texas, and Nebraska (Samuel 1971a, Brown 1985), although the rarely used tseer call of birds in the Pacific Northwest does not apparently occur in the Great Plains.
Young begin vocalizing at least by 5–6 days of age. The call of each chick becomes uniquely recognizable by day 15 and is pure and consistent in structure by day 18–21 (Stoddard and Beecher 1983). Calls of siblings are structurally similar. Sib-sib similarity is genetically based, rather than reflecting vocal imitation among nest mates (Medvin et al. 1992). There is no evidence for vocal learning, sensitive periods, or vocal mimicry. The juvenile’s Begging Call (see below) develops into the Chur Call of adult. A call resembling the Purr Call (alarm) was given by juveniles that were about 6 weeks old (CRB, MBB).
Vocal Array
Limited vocal repertoire. Five vocalizations: the Begging Call (Stoddard and Beecher 1983), used by juveniles when soliciting food from adults; the Purr Call, used as alarm call when predators approach; the Chur Call, commonly used in many contexts (Brown 1985); the Twitter-squeak Song, up to 6 s in typical duration, composed of many guttural gratings, and used primarily during courtship and nest establishment; and the Squeak Call, used as a food-finding signal (Brown et al. 1991). The Squeak Call is structurally similar to the much longer Twitter-squeak Song and may be derived from that song. Both sexes give the Begging Call, the Purr Call, the Chur Call, and the Squeak Call; presumably only males give the Twitter-squeak Song, but no study of singing with marked birds has been done. Apparently there is little geographic variation. Descriptions of vocalizations were similar for birds from W. Virginia, Texas, and Nebraska (Samuel 1971a, Brown 1985), although the rarely used tseer call of birds in the Pacific Northwest does not apparently occur in the Great Plains.
Phenology
The Begging Call is used only until juveniles become independent of their parents in midsummer, then changes to the Chur Call. Purr and Chur calls are used at all times of the breeding season; birds seem rarely to vocalize in winter (A. Jaramillo pers. comm.). The Twitter-squeak Song is used primarily in spring while birds are establishing pairs, declines in usage when parents are feeding nestlings, and then is used again during a brief period in late summer while postbreeding birds are defending nests and assessing colony sites (Brown and Brown 1996). Songs presumably are not used on migration or during the winter. The Squeak Call is used from the time of birds’ arrival on the breeding grounds until midsummer; it is unknown if this call is used at other times of the year (Brown et al. 1991).
Time and Places of Vocalizing
Time of day has little influence on the pattern of vocalizing. The Begging Call, the Chur Call, and the Twitter-squeak Song are given by birds at night (2200–0400 h; MDT) while inside their nests (CRB, MBB).
The Begging Call is given by juveniles inside nests and when assembled away from a colony in creches. The Purr Call is usually given in flight, although occasionally a bird in a nest uses a Purr Call upon approach of a terrestrial predator. The Chur Call is used at nests and in flight. The Twitter-squeak Song is given by birds at nests and occasionally in flight as 1 or more birds (males?) chase another (female?). The Squeak Call is given only in flight.
Repertoire and Delivery of Songs
The Begging Call of the juvenile is individually distinctive enough to represent a “signature” that parents use to identify their own chicks (Stoddard and Beecher 1983, Medvin et al. 1993). The Chur Call of the adult may also be distinctive enough to allow juveniles to recognize their own parent (Beecher et al. 1985).
Presumed Functions of Vocalizations
The Begging Call probably reflects food needs of chicks, as hungrier nestlings call more loudly and more readily when adults pass by. Primary function of the Begging Call may be to allow parents to recognize their offspring. Parents learn their chicks’ calls as they develop, so that parental recognition of offspring is well developed by the time nestlings fledge (Stoddard and Beecher 1983, Medvin et al. 1993). Parents in small colonies in Washington discriminate among chicks of similar age and evict intruding ones from their nest (P. Stoddard pers. comm.); eviction of intruders has not been observed in Nebraska colonies which tend to be larger (Brown and Brown 1996). Parents locate their own offspring in a creche (see Breeding: fledgling stage) by the juveniles’ Begging Calls, although the parents’ efficiency at discriminating their own chicks’ voices from others declines in large groups (Medvin et al. 1993, Brown and Brown 1996).
The Purr Call is the Cliff Swallow’s alarm call, used whenever an aerial or terrestrial predator approaches a colony. The call often seems directed at the predator, with birds typically swirling directly above a predator and emitting barrages of Purr Calls. Other colony members respond by exiting their nests. The Purr Call is occasionally given when no apparent predator is present, causing some birds to flush from their nests, whereupon others in the colony use the opportunity to intrude into neighboring nests (Brown and Brown 1996). Such circumstances might represent a deceptive use of alarm calling (Brown and Brown 1989). The Chur Call is a multipurpose vocalization used widely, most often when birds are undisturbed, and may be used for individual recognition between members of a pair, parents and offspring (Beecher et al. 1985), and perhaps neighboring residents within a colony. The Twitter-squeak Song may serve to attract a female to a male’s partially or completely constructed nest and allow her to assess male quality. The Squeak Call and tseer call (Brown et al. 1991, Stoddard 1988) are used by foragers to signal the location of a food patch (see Food Habits).
The Begging Call is used only until juveniles become independent of their parents in midsummer, then changes to the Chur Call. Purr and Chur calls are used at all times of the breeding season; birds seem rarely to vocalize in winter (A. Jaramillo pers. comm.). The Twitter-squeak Song is used primarily in spring while birds are establishing pairs, declines in usage when parents are feeding nestlings, and then is used again during a brief period in late summer while postbreeding birds are defending nests and assessing colony sites (Brown and Brown 1996). Songs presumably are not used on migration or during the winter. The Squeak Call is used from the time of birds’ arrival on the breeding grounds until midsummer; it is unknown if this call is used at other times of the year (Brown et al. 1991).
Time and Places of Vocalizing
Time of day has little influence on the pattern of vocalizing. The Begging Call, the Chur Call, and the Twitter-squeak Song are given by birds at night (2200–0400 h; MDT) while inside their nests (CRB, MBB).
The Begging Call is given by juveniles inside nests and when assembled away from a colony in creches. The Purr Call is usually given in flight, although occasionally a bird in a nest uses a Purr Call upon approach of a terrestrial predator. The Chur Call is used at nests and in flight. The Twitter-squeak Song is given by birds at nests and occasionally in flight as 1 or more birds (males?) chase another (female?). The Squeak Call is given only in flight.
Repertoire and Delivery of Songs
The Begging Call of the juvenile is individually distinctive enough to represent a “signature” that parents use to identify their own chicks (Stoddard and Beecher 1983, Medvin et al. 1993). The Chur Call of the adult may also be distinctive enough to allow juveniles to recognize their own parent (Beecher et al. 1985).
Presumed Functions of Vocalizations
The Begging Call probably reflects food needs of chicks, as hungrier nestlings call more loudly and more readily when adults pass by. Primary function of the Begging Call may be to allow parents to recognize their offspring. Parents learn their chicks’ calls as they develop, so that parental recognition of offspring is well developed by the time nestlings fledge (Stoddard and Beecher 1983, Medvin et al. 1993). Parents in small colonies in Washington discriminate among chicks of similar age and evict intruding ones from their nest (P. Stoddard pers. comm.); eviction of intruders has not been observed in Nebraska colonies which tend to be larger (Brown and Brown 1996). Parents locate their own offspring in a creche (see Breeding: fledgling stage) by the juveniles’ Begging Calls, although the parents’ efficiency at discriminating their own chicks’ voices from others declines in large groups (Medvin et al. 1993, Brown and Brown 1996).
The Purr Call is the Cliff Swallow’s alarm call, used whenever an aerial or terrestrial predator approaches a colony. The call often seems directed at the predator, with birds typically swirling directly above a predator and emitting barrages of Purr Calls. Other colony members respond by exiting their nests. The Purr Call is occasionally given when no apparent predator is present, causing some birds to flush from their nests, whereupon others in the colony use the opportunity to intrude into neighboring nests (Brown and Brown 1996). Such circumstances might represent a deceptive use of alarm calling (Brown and Brown 1989). The Chur Call is a multipurpose vocalization used widely, most often when birds are undisturbed, and may be used for individual recognition between members of a pair, parents and offspring (Beecher et al. 1985), and perhaps neighboring residents within a colony. The Twitter-squeak Song may serve to attract a female to a male’s partially or completely constructed nest and allow her to assess male quality. The Squeak Call and tseer call (Brown et al. 1991, Stoddard 1988) are used by foragers to signal the location of a food patch (see Food Habits).