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Types of song birds11/15/2023 In either case, song selection during crystallization is based on functional significance to maximize reproductive output.īirdsong is controlled by discrete brain regions that are interconnected. Cowbirds, on the other hand, attain songs that are more effective in triggering mating-like behaviors in females (West & King 1988). This can be advantageous because males that sing local dialects have a higher reproductive success than those that sing foreign dialects (MacDougall-Shackleton et al. White-crowned sparrows, for instance, integrate songs that match the dialects of neighboring males into the crystallized song (Nelson & Marler 1994). As you might expect, this selection is not random. This means that during song crystallization, those species select which sounds are incorporated into the crystallized song. If juveniles are deafened after the sensory phase but before the sensorimotor phase, they develop aberrant songs (Konishi 1965).īirds of certain species produce more sounds during the sensorimotor phase than the sounds they will produce in adulthood. During the sensorimotor phase, birds need to hear their own vocalization in order to develop normal songs. Songs finally crystallize to stable stereotyped songs that are similar to the songs they memorized. They then produce louder, more structured songs called plastic songs, which are still variable but contain some elements of the tutor song. Interestingly, if birds are raised in acoustic isolation, the sensory phase can be extended even into adulthood in some species.Īt the beginning of the sensorimotor phase, young birds first produce generic, variable, and quiet vocalizations called subsong, which is similar to human baby babbling (Brenowitz et al. If young are raised only with heterospecific songs, birds can learn conspecific songs later than those raised hearing conspecific songs (Brainard & Doupe 2002). When the sensory phase ends varies among species, but this timing depends partly on experience. Thus, together with the genetic predisposition for recognizing and learning species-specific songs, this minimizes the risk of learning wrong songs. Timing of the sensory phase varies among species, but this window aligns with when adults of the species sing the most (Zeigler & Marler 2008). If given a choice, young birds preferentially learn conspecific over heterospecific songs, and if birds are raised in acoustic isolation, they sing abnormal songs yet still with species-specific elements. So why don't they learn the songs of multiple species? Studies have shown that even without prior experience in hearing their own species' songs, young birds still increase their heart rate and beg more when they hear conspecific songs, indicating that they are born with an innate ability to discriminate their species-specific songs (Brainard & Doupe 2002). In the wild, birds grow up listening to the songs of a variety of different species. This is because most young birds learn the species-specific songs during the first year of their lives. With some exceptions (e.g., gray catbirds, sedge warblers, brown-headed cowbirds ), birds raised in acoustic isolation during the sensory phase produce atypical songs as adults. Territorial conflicts are energetically costly, and the song of a local population, or dialect, is thus thought to be favored as it can serve as an indication of regional origin, minimizing physically demanding defense measures. When maintaining a breeding territory, familiar neighbors are preferred over newcomers because newcomers, who do not yet have a territory, are more likely to expand their territories than established neighbors. On the other hand, the "song-sharing hypothesis" suggests that male-male competition selects for simpler, more homogenous songs (Beecher & Brenowitz 2005). In fact, in some species females prefer males with large repertoires, and males with larger repertoires have a higher reproductive success (i.e., they produce more offspring) than those with a smaller repertoire (Catchpole & Slater 2008). So what favors large and small repertoire size? According to the "repertoire hypothesis," a large repertoire is thought to be under directional sexual selection (Catchpole & Slater 2008, Beecher & Brenowitz 2005) where the choosy sex (often the females) favors one extreme end of a heritable, sexual trait. As we already learned, variation in repertoire size among species is extensive, and the characteristic of having a repertoire with multiple song types likely evolved more than once in songbirds (MacDougall-Shackleton 1997).
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