Songbird presumed to be age‐limited learner may change repertoire size and composition throughout their life

Abstract

Songbirds learn to sing by imitating their conspecific songs through social learning. It is commonly thought that in species with small repertoires, so‐called crystallization of the song repertoire takes place before the first breeding attempt and afterwards their repertoires remain unchanged. However, the number of studies in which individual song repertoires have been tracked longitudinally under natural conditions is still small. The ortolan bunting (Emberiza hortulana) is a small Eurasian passerine species. Studies on this species have shown that males have small song repertoires (usually 2–3), share the same final phrase within a local dialect area, and their repertoires remain unchanged during their lifetimes. We studied the whole, isolated Norwegian population of this species with 100–150 individually marked males. We compared repertoire sizes and contents using cross‐sectional and longitudinal approaches. We focused on marked males aged 2–10 years and recorded in up to five breeding seasons between 2001 and 2006. There was no local dialect because songs with different final phrases occurred both within and between males. Repertoire size varied between 1 and 24 (4.7 ± 3.4) song types per male. Longitudinal analysis showed an increase in repertoire size in 29% and a decrease in 21% of males. Males whose repertoires remained the same in size between years often substantially changed in contents. New song types appeared in almost 70% of males, and over 30% of males started singing new syllable types after the second calendar year. In almost 50% of males, new song types appeared that were built as new combinations of syllables shown in previous years. In 30% of males, the song complexity increased with age. Simultaneously, over 60% of males selectively ceased singing some song types. We suggest that these repertoire alterations are linked to the isolation and fragmentation of this population, which may affect song learning patterns through increased breeding dispersal and a strongly male‐biased sex ratio. Similar studies from abundant and continuous populations of the species are needed to test this idea.

Maturational changes in song sparrow song

“…In swamp sparrows, for example, song rate, song length, song consistency and vocal performance change between a male's first and second year of life (Ballentine 2009, Zipple et al 2019). Other species exhibiting delayed maturation include willow warblers ( Phylloscopus trochilus ; repertoire size, element rate; Gil et al 2001), pied flycatchers ( Ficedula hypoleuca ; repertoire size, song versatility; Motes‐Rodrigo et al 2017), American redstarts ( Setophaga ruticilla ; repeat song structure; Germain 2011), banded wrens ( Thryophilus pleurostictus ; song consistency; de Kort et al 2009), great reed warblers ( Acrocephalus arundinaceus ; syllable switching, song repertoire, whistle duration and consistency; Forstmeier et al 2006, Węgrzyn et al 2010), barn swallows ( Hirundo rustica ; song length, uniqueness; Galeotti et al 2001), great tits ( Parus major ; song consistency; Rivera‐Gutierrez et al 2012), ortolan buntings ( Emberiza hortulana ; song type distribution and composition; Osiejuk et al 2019) and Java sparrows ( Lonchura oryzivora ; song length and tempo; Ota and Soma 2014). The strongest effects have been most often detected between the first and second year of life, with mixed trends observed in subsequent years (Kipper and Kiefer 2010).…”

Song parameters, repertoire size and song sharing within and across age classes in the saffron finch

“…We use both cross‐sectional analyses (i.e. comparison of groups of individuals across age classes, Kipper and Kiefer 2010, Osiejuk et al 2019) as well as longitudinal analyses of marked individuals across different ages (Forstmeier et al 2006). We also investigate spatial patterns of syllable sharing in the repertoires of SY and ASY males breeding at the same site.…”