Sound recordings reshape Yellow Rail distribution

The Yellow Rail is a notoriously difficult species to spot, but recording devices have revealed a previously unknown stronghold for the elusive rallying.

North America’s boreal zone is vast and relatively untouched, which means it’s a haven for birds, but a challenge to study. The marshes and bogs of this ecosystem are particularly difficult to monitor, but birders have found a new way to map this tiny, inconspicuous bird of wetlands.

Until recently the best way to investigate Yellow Rails was to play recordings of calling males in suitable habitat and listen for any response, but this requires people in the field and it is not clear how. bird behavior can be affected by reading. .

Passive acoustic monitoring has revolutionized ornithology in recent years in many environments. The method involves leaving the sound recording devices for an extended period of time and then picking them up later to start analyzing the audio files.

The Edéhzhíe Dehcho Protected Area in the Dehcho region of the Northwest Territories of Canada lies some 150 km beyond the known range limits of the Yellow Rail.

However, recent eBird reports from the Northwest Territories and swathes of suitable habitat have prompted researchers to investigate.

Self-contained recording devices were placed at 199 positions within Edéhzhíe, where they collected audio recordings for a week in mid-May 2016 and were recovered two months later.

A machine learning algorithm was trained to recognize the distinctive “clicking” call of male Yellow Rails and helped researchers distill many hours of sound recordings and determine the number of birds at each position. investigation.

The results were astounding. Yellow Rails were recorded at 16% of sampling positions during the survey, with an average of 1.3 birds at each position producing a positive result, redrawing the distribution map of the species.

Marshes had the highest densities of birds, although rails were also detected in bog and bog habitats. The researchers estimated a population of 906 breeding pairs of Yellow Rails in Edéhzhíe, an area previously thought to be well beyond the species’ range.

Even the northernmost sites surveyed had Yellow Rails, pushing the known range north by about 350 km.

It is likely that the Yellow Rail was simply not detected in the area prior to the work, the distribution of most boreal birds being considered underestimated, but it remains possible that the results indicate a significant expansion of the distribution area.

Mills Lake, which has proven to be a key area in Edéhzhíe for Yellow Rails, is also important for other wetland birds such as American Bittern and Nelson’s Sparrow, and could therefore serve as an important stepping stone for birds that spread from the south.

Acoustic monitoring studies such as this could play a crucial role in anticipating and tracking avian responses to climate change and habitat loss in the future, especially for inconspicuous species like the Yellow Rail that are not effectively detected by traditional methods.

Reference

McLoad, LJ T, Haché, S, Pankratz, RF and Bayne, E M. High density yellow rail (Coturnicops noveboracensis) Population beyond putative range limits in Northwest Territories, Canada. water birds 44(2): 175-184. DOI: https://doi.org/10.1675/063.044.0204


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