7.5 As larks sing songs, researchers hear population health

http://arstechnica.com/journals/science.ars/2008/10/22/what-can-we-learn-from-a-birdsong

As larks sing songs, researchers hear population health

By Yun Xie | Published: October 22, 2008 - 11:35AM CT

Biologists and ecologists have long known that animal behavior reflects environmental factors like habitat loss. For example, disruption in the populations of wild dogs in Africa negatively affected cooperative behavior in the packs, causing problems with defense, pup rearing, and hunting. Habitat destruction also influences the repertoire of bird songs. Paola Laiolo, a conservation biologist from Spain, and her colleagues have seen that Dupont's lark had less variation in its songs when populations decreased because there were fewer birds from which to learn new notes. This loss of musical range was detrimental to the sexual appeal of male larks.

Dupont's Lark: SEO/BirdLife. 

From a conservation perspective, Laiolo proposes that valuable information can be gathered by quantifying the behavioral processes of animals. Research groups have tried to measure animal behavior in the past with variable degrees of success—it can be tricky to create statistical tools to account for behavioral patterns.

Laiolo chose to work with the songs of Dupont's lark, as they are well understood. By using computer software to differentiate songs and fitting the song variations to a piecewise and exponential model, she hoped to correlate song diversity and population viability. In essence, she wanted to see if it was possible to use the song repertoire of individual birds as an indicator of population problems. She was also interested to find a minimum threshold of habitat size.

From 2004 to 2007, Laiolo recorded songs from 385 male larks in 51 steppe patches across Spain. The patches were anywhere from 20 to over 5000 ha in size, and some patches contained as few as one male lark, while others had over 250. According to Laiolo, the variability in patches "is largely due to human-driven habitat transformations, which is threatening the species’ persistence in many small and isolated areas." During the course of her study, three out of the 51 Dupont’s lark populations went extinct.

Laiolo ended up isolating 253 different songs and found that at least two lark populations shared 169 songs. Well situated larks would sing as many as 12 types of songs. She discovered that "individual song diversity is linked to population viability because of its positive association with population size." Average repertoires of less than five songs indicated populations that were at risk. It also appeared that a minimum threshold size of 100 ha is necessary for population sustainability, as habitats smaller than that contained larks that sang only a few songs.

Laiolo suggests that we can do more than simply enjoy the beauty of a lark’s song. Carefully listening to the full repertoire of individual larks might clue us in on their viability in a particular habitat.

Ecological Applications, 2008. DOI: 10.1890/07-1433.1 

 

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