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June 01, 2013

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Birdsong changes much like language, study finds

Jan. 29, 2013
Courtesy of the University of Guelph
and World Science staff

Changes in bird “cul­ture” ex­plain why male Sa­van­nah spar­rows have al­tered their mat­ing song over three dec­ades, sci­en­tists say.

The re­search­ers, who stud­ied over 30 years of bird­song record­ings, said these changes are passed from genera­t­ion to genera­t­ion. It’s “the re­sult of cul­tur­al trans­mis­sion of dif­fer­ent song el­e­ments through many genera­t­ions,” said Ryan Nor­ris, a bi­ol­o­gist at the Uni­vers­ity of Guelph in Can­a­da, who co-led the stu­dy.

Male Savannah sparrow. (Courtesy U. of Guelph)


The modifica­t­ions re­sem­ble changes in hu­mans' word choice and lan­guage, he went on. “If you lis­ten to how peo­ple used to talk in the 1890s and how we talk to­day, you would no­tice ma­jor dif­fer­ences, and this is the re­sult of shifts in cul­ture or the pop­u­lar­ity of cer­tain forms,” he ex­plained. “The change in spar­row songs over time has oc­curred much the same way.”

The spar­rows in the study, which live on Kent Is­land in the Bay of Fun­dy, in New Bruns­wick, can gen­er­ally sing only one song type that con­sists of sev­er­al parts. Male spar­rows learn that song early in their first year and con­tin­ue to sing the same tune for the rest of their lives.

“Y­oung male spar­rows learn their songs from the birds around them,” said Nor­ris. “It may be their fa­thers, or it could be oth­er old­er male birds that live near­by.”

Each male spar­row has his own un­ique sound, said Amy New­man of the uni­vers­ity, who co-led the study with Nor­ris. “While the is­land's spar­rows all sing a char­ac­ter­is­tic 'sa­van­nah spar­row song’ ... there are dis­tinct dif­fer­ences be­tween each bird,” she said. It's bas­ic­ally “like karaoke ver­sions of pop­u­lar songs. It is the rise and fall in pop­u­lar co­ver ver­sions that has changed over time.”

The re­search­ers found that each song gen­er­ally has three main el­e­ments. The first iden­ti­fies the bird as a Sa­van­nah spar­row, the sec­ond iden­ti­fies which in­di­vid­ual is sing­ing, and the third com­po­nent is used by females to as­sess ma­les.

Us­ing graph­i­cal rep­re­senta­t­ions of the songs from males each breed­ing sea­son, the re­search­ers de­ter­mined that, while the in­tro­duc­to­ry notes had stayed gen­er­ally con­sist­ent for the last 30 years, the spar­rows had added a se­ries of clicks to the mid­dle of their songs. The birds had al­so changed the end­ing trill: once long and high-pitched, it's now shorter and low­er. Evidently “female spar­rows pre­ferred this, be­cause males with shorter trills had high­er re­pro­duc­tive suc­cess,” Nor­ris said.

Kent Is­land has been home to the Bow­doin Sci­en­tif­ic Sta­t­ion since 1932, and the birds have been recorded since the 1980s. In­di­vid­ual birds are al­so mon­i­tored life­long. “We know the ident­ity and his­to­ry of eve­ry sin­gle spar­row in the study popula­t­ion,” said Nor­ris. “To have 30 years of record­ings is very rare, and it was def­i­nitely sur­pris­ing to see such dras­tic changes.” The study ap­pears in the Jan­u­ary is­sue of the jour­nal An­i­mal Be­hav­iour.


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Changes in bird “culture“ explain why male Savannah sparrows have altered their mating song over three decades, scientists say. Changes passed from generation to generation explain why the tunes keep changing, said researchers who studied over 30 years of birdsong recordings. “The change is the result of cultural transmission of different song elements through many generations,“ said Ryan Norris, a biologist at the University of Guelph in Canada, who co-led the study. The modifications resemble changes in humans' word choice and language, he went on. “If you listen to how people used to talk in the 1890s and how we talk today, you would notice major differences, and this is the result of shifts in culture or the popularity of certain forms,“ he explained. “The change in sparrow songs over time has occurred much the same way“ The sparrows, which live on Kent Island in the Bay of Fundy, in New Brunswick, can generally sing only one song type that consists of several parts. Male sparrows learn that song early in their first year and continue to sing the same tune for the rest of their lives. “Young male sparrows learn their songs from the birds around them,“ said Norris. “It may be their fathers, or it could be other older male birds that live nearby.“ Each male sparrow has his own unique sound, said Amy Newman of the university, who co-led the study with Norris. “While the island's sparrows all sing a characteristic 'savannah sparrow song,' with the same verses and sound similar, there are distinct differences between each bird,“ she said. It's basically “like karaoke versions of popular songs. It is the rise and fall in popular cover versions that has changed over time.“ The researchers found that each song generally has three main elements. The first identifies the bird as a Savannah sparrow, the second identifies which individual is singing, and the third component is used by females to assess males. Using graphical representations of the songs from males each breeding season, the researchers determined that, while the introductory notes had stayed generally consistent for the last 30 years, the sparrows had added a series of clicks to the middle of their songs. The birds had also changed the ending trill: once long and high-pitched, it's now shorter and lower. “The ending trill of the song has become shorter, likely because female sparrows preferred this, because males with shorter trills had higher reproductive success,“ Norris said. Kent Island has been home to the Bowdoin Scientific Station since 1932, and the birds have been recorded since the 1980s. Individual birds are also monitored lifelong. “We know the identity and history of every single sparrow in the study population,“ said Norris. “To have 30 years of recordings is very rare, and it was definitely surprising to see such drastic changes.“ The study appears in the January issue of the journal Animal Behaviour.