Measuring nocturnal seabird activity and status using acoustic recording devices: applications for island restoration

Abstract

Nocturnal burrow‐nesting seabirds breeding on isolated oceanic islands pose challenges to conventional monitoring techniques, resulting in their frequent exclusion from population studies. These seabirds have been devastated by nonnative predator introductions on islands worldwide. After predators are eradicated, recovery has been poorly quantified, but evidence suggests some nocturnal seabird populations have been slow to return. We evaluated the use of automated acoustic recorders and call‐recognition software to investigate nocturnal seabird recovery after removal of introduced Arctic foxes (Alopex lagopus) in the Aleutian Archipelago, Alaska. We compared relative seabird abundance among islands by examining levels of vocal activity. We deployed acoustic recorders on Nizki‐Alaid, Amatignak, and Little Sitkin islands that had foxes removed in 1975, 1991, and 2000, respectively, and on Buldir, a predator‐free seabird colony. Despite frequent gales, only 2.9% of 2230 recording hours from May to August of 2008 and 2009 were unusable due to wind noise. Recording quality and call recognition model success were highest when recording devices were placed at sites offering some wind shelter. We detected greater vocal activity of Fork‐tailed (Oceanodroma furcata) and Leach's (O. leucorhoa) storm‐petrels and Ancient Murrelets (Synthliboramphus antiquus) on islands with longer time periods since fox eradication. Also, by detecting chick calls in the automated recordings, we confirmed breeding by Ancient Murrelets on an island thought to be abandoned due to fox predation. Acoustic monitoring allowed us to examine the relative abundance of seabirds at remote sites. If a link between vocalizations and population dynamics can be made, acoustic monitoring could be a powerful census method.

Autonomous recording units in avian ecological research: current use and future applications

“…ARUs can be an effective method for tracking presence or absence of multiple taxa for monitoring and conservation. ARUs can monitor the success of conservation programs (e.g., activity at seabird colonies after invasive predator eradication; Buxton and Jones 2012). Monitoring can continue uninterrupted as long as ARUs are serviced and batteries and data storage are replenished.…”

Applying bioacoustic methods for long-term monitoring of a nocturnal wetland bird

“…However it was difficult to estimate the absolute number of animals because the call rate differs between species and even within a species, the call rate being strongly dependent on the particular environmental conditions (Farnsworth, 2005;Farnsworth et al, 2004;Hüppop and Hilgerloh, 2012). Buxton and Jones (2012) found that nocturnal call activity can at least provide information on the relative population density of cave breeding birds. Comparing different methods of bird surveys Buckland (2006) found that the census based on song activity delivered results with a rather poor precision.…”

Estimating population size of a nocturnal burrow-nesting seabird using acoustic monitoring and habitat mapping

“…On many islands the marking of seabirds or inspection of burrows is logistically not feasible, because birds nest on inaccessible cliffs. As a consequence of the various logistical constraints, the population sizes of many species of storm-petrels, petrels, shearwaters and alcids are very poorly known (Brooke 2004;Croxall et al 2012). The burrow-nesting habit of many species, which directly influences the complexity of population assessments, also contributes to their vulnerability to invasive alien predators, a key threat to seabirds (Croxall et al 2012;Jones et al 2008).…”