Birds sing different songs after wildfires

Birds alter the way they communicate in new habitats in order to exploit the acoustic properties of their surroundings. Thicker vegetation, the size of tree branches, or even the wind can influence the vocalizations of birds.

In a recent study published by Oxford University Press, experts have found that wildfires also alter the way birds communicate. The researchers discovered that fires cause birds in nearby forests to sing new songs.

Hermit warblers have a collection of complex songs they use to defend their territory, but they have a fixed song to attract mates. The birds usually rely on a single dominant song across the same geographic area.

In the United States, the summer range of the hermit warblers is limited to the Pacific Coast states of California, Oregon, and Washington.

Hermit warblers are particularly sensitive to fire and other disturbances. But while the birds are negatively impacted after wildfires in the short-term, they show positive changes in response to larger shifts in the forest structure over the long-term.

The researchers recorded the dominant songs of 1,588 males across 101 study sites between 2009 and 2014. The songs were analyzed and classified into 35 dialects. 

To investigate the factors that influence bird song diversity, the team modeled the effects of recent fire history at the local scale, the amount of breeding habitat on a regional scale, and the distance between territories.

The study revealed that local bird song diversity increased in correspondence with the extent of local fires and the amount of regional habitat. 

The analysis of data from ten study areas revisited in 2019 confirmed the influence of wildfires on bird songs. The researchers noted that song structure had changed since the initial visits five to ten years earlier. They also found that song diversity had substantially increased at locations that had endured wildfires between the two visits. 

“Our surveys suggest that song dialects arose in sub-populations specialized to different forest types,” said study lead author Brett Furnas. 

“Over the longer term, fire caused some birds to flee and created a vacuum for other birds to fill. 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 research is published in The Auk: Ornithological Advances.

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By Chrissy Sexton, Earth.com Staff Writer