Passive acoustic monitoring: can it help measure nest density in Manx Shearwaters?

Gavin Arneill (School of Biological, Earth and Environmental Sciences, University College Cork, Ireland) and colleagues have written for the journal Ibis on the use of recording sound to monitor Manx Shearwaters Puffinus puffinus.

The paper’s abstract follows:

“Passive acoustic monitoring is increasingly used as a cost‐effective way to study wildlife populations, especially those that are difficult to census using conventional methods.  Burrow‐nesting seabirds are amongst the most threatened birds globally, but they are also one of the most challenging taxa to census, making them prime candidates for research into such automated monitoring platforms.  Passive acoustic monitoring has the potential to determine presence/absence, or quantify burrow‐nesting populations, but its effectiveness remains unclear.  We compared passive acoustic monitoring, tape‐playbacks, and GPS tracking data to investigate the ability of passive acoustic monitoring to capture unbiased estimates of within‐colony variation in nest density for the Manx Shearwater Puffinus puffinus.  Variation in acoustic activity across twelve study plots on an island colony was examined in relation to burrow density and environmental factors across two years. As predicted fewer calls were recorded when wind speed was high, and on moon‐lit nights, but there was no correlation between acoustic activity and the density of breeding birds within the plots as determined by tape‐playback surveys. Instead, acoustic indices correlated positively with spatial variation in the in‐colony flight activity of breeding individuals detected by GPS. Though passive acoustic monitoring has enormous potential in avian conservation, our results highlight the importance of understanding behaviour when using passive acoustic monitoring to estimate density and distribution.”

Reference:

Arneill, G.E., Critchley, E.J., Wischnewski, S., Jessopp, M.J. & Quinn, J.L. 2019.  Acoustic activity across a seabird colony reflects patterns of within‐colony flight rather than nest density.  Ibis doi.org/10.1111/ibi.12740.

John Cooper, ACAP Information Officer, 25 June 2019