Like humans, birds develop regional dialects. By imitating their parent’s song, birds in the same geographic area tend to whistle out the same formulaic tune to attract a mate. But new research suggests that the presence of wildfires can put a stop to the uniform chorus of Hermit Warblers across their summer range in California. As when fires force one group to leave an area, another flock can enter and diversify the local song.
This conclusion was reached by scientists who between 2009 and 2014 recorded the songs of 1,588 male Warblers across 101 study sites. In total, they could distinguish 35 dialects, which were separated according to forest type.
“Our surveys suggest that song dialects arose in sub-populations specialized to different forest types,” Brett Furnas from California’s Wildlife Investigations Laboratory said in a statement.
But Furnas and colleagues were interested in how other factors, such as the prevalence of local wildfires, effected the bird’s dialects. To do so, they revisited 10 of their previous study areas in 2019, some 5 to 10 years after their initial research. In areas that had been burned by wildfires in the interim period, they found that the Hermit Warbler’s songs had greatly diversified – more so than in unaffected regions.
“Over the longer term, fire caused some birds to flee and created a vacuum for other birds to fill,” Furnas explained. “The net result is that some areas now have birds singing more than one dialect resulting in a complex diversity of songs throughout California.”
The team’s paper, published in the journal The Auk: Ornithological Advances, adds to the perhaps little-known field of bird dialect. The changing song of a chorus can spell out the impact of a bird’s changing environment. For example, birds whose habitats have been encroached on by cities have begun singing at higher pitches to be heard over the hum of traffic and construction.
One powerline could be enough to split a population of birds and lead to the creation of new dialects, American ornithologist Donald Kroodsma told CNN. It's worth thinking about how we are shaping – and destroying – bird dialects generally, he warned.
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