Signature Versus Perceptual Adaptations for Individual Vocal Recognition in Swallows

Abstract

Field experiments have shown that parents in the colonially-nesting cliff swallow (Hirundo pyrrhonota) discriminate between their offspring and unrelated young whereas parents in the closely-related but noncolonial barn swallow (H. rustica) do not, and that discrimination is based on the chick begging call. In a laboratory experiment, we trained three cliff swallows, two barn swallows and a European starling (Sturnus vulgaris) to discriminate among chick begging calls of the two swallow species. All birds discriminated more easily among the calls of different cliff swallows than among the calls of different barn swallows, suggesting that cliff swallow calls are more individually distinctive, and may be adapted for a signature function. Moreover, cliff swallows discriminated among both cliff swallow and barn swallow calls faster than did the other birds, which is consistent with a perceptual adaptation for conspecific calls that incidentally facilitates the discrimination of similarly-structured heterospecific calls.

Cooperative bird differentiates between the calls of different individuals, even when vocalizations were from completely unfamiliar individuals

“…Differential responses arising from the 'dear enemy effect' are commonly cited as evidence of individual recognition, but may simply reflect classification of signals by receivers into categories that coincide with individual identity, such as familiarity [9]. Carefully designed playback studies can demonstrate fine-scale differentiation abilities [10], but not if responses are subtle [11] or influenced by other group members. Here, I adapt the habituation -discrimination paradigm (HDP) to avoid these issues [10,12] and, without training subjects, directly test the acoustic discrimination abilities of a highly social bird, the noisy miner (Manorina melanocephala).…”

Discrimination of individual vocalizations by black-capped chickadees (Poecile atricapilla)

“…Instead, the chickadees discriminated among heterospecific calls about as well as among conspecific songs. Also, the chickadees showed no differences in transferring their discriminations to degraded versions of either conspecific or heterospecific vocalizations.One might expect that birds have an evolutionary advantage in discriminating among conspecific vocalizations,but other results, even better discriminations among heterospecific vocalizations, are logically possible (see Loesche et al, 1991).…”

“…Also, in experiments using the same stimuli as the present work, Phillmore et al found that both chickadees and zebra finches discriminated the distance cues faster in chickadee songs than in zebra finch calls. In other words, the go/nogo methodology used here, in other studies of auditory perception in songbirds(e.g., Loesche et al, 1991), and in studies of visual cognition in other species, (e.g., Gottselig, Wasserman, & Young, 2001) are adequate to detect real differences in the learning and perception of songbirds.…”

“…In this stable protocol, researchers can study aspects of the recognition of individual vocalizations untestable in natural settings-for example, memory capacity, ability to discriminate heterospecific vocalizations, and transfer of training across song types. For example, operant go/no-go discrimination studies have demonstrated that barn and cliff swallows (Hirundo rustica and Hirundo pyrrhonota) can discriminate at least 10 pairs of individual vocalizations (Loesche, Stoddard, Higgins, & Beecher, 1991) and that song sparrows can discriminate among as many as 32 pairs of conspecific vocalizations (Stoddard, Beecher, Loesche, & Campbell, 1992). We need to distinguish between studies of the discrimination of individual vocalizations, as in the present study (also Loesche et al, 1991;Stoddard et al, 1992), and (much rarer) tests of the recognition of the voice characteristics of individualbirds, as in transfer across different vocalizations from the same bird (see Gentner & Hulse, 1998;Weary & Krebs, 1992).…”

Variable facial plumage in juvenile Cliff Swallows: A potential offspring recognition cue?

“…Although conspicuous juvenile coloration is used in lieu of vocalization during begging in nonvocal birds (Lyon et al 1994), juvenile swallows are very vocal while begging. The high level of plumage variability has led to suggestions that facial patterning in swallows could indicate individual identity (Loesche et al 1991). Stoddard and Beecher (1983) speculated that facial plumage may be a cue used by Cliff Swallows to recognize offspring.…”