Trialling camera traps to determine occupancy and breeding in burrowing seabirds

Abstract

Burrowing seabirds are important in ecological and conservation terms. Many populations are in flux due to both negative and positive anthropogenic impacts, but their ecology makes measuring changes difficult. Reliably recording key metrics, the proportion of burrows with breeding pairs and the success of breeding attempts requires burrow-level information on occupancy. We investigated the use of camera traps positioned at burrow entrances for determining the number of breeding pairs in a sample to inform population estimates, and for recording breeding success. The performance of two cameras makes we tested differed markedly, with Spypoint Force 10 trail cameras prone to malfunction while Reconyx HC600 Hyperfire cameras performed well. Nevertheless, both makes yielded season-long activity patterns for individual burrows, eliminating uncertainty around successful fledging attempts. Dimensionality reduction of activity metrics derived from camera time series suggests breeding and non-breeding burrows may be identifiable using linear discriminant analyses but sample sizes from our trial were low and group means were only significantly different during certain breeding stages (permutational multivariate analysis of variance: early chick-rearing f = 3.64, P = 0.06; late chick-rearing f = 8.28, P = 0.009). Compared with traditional techniques for determining burrow occupancy (e.g. manual burrow inspection and playback of conspecific calls at burrow entrances), camera traps can reduce uncertainty in estimated breeding success and potentially breeding status of burrows. Significant upfront investment is required in terms of equipment and human resources but for long-term studies, camera traps may deliver advantages, particularly when unanticipated novel observations and the potential for calibrating traditional methods with cameras are factored in.

Patterns of recovery in extant and extirpated seabirds after the world's largest multipredator eradication

“…In the 20 years since blue and gray petrels recolonized the main island, both species have established new colonies on north, south, east, and west coasts. Over the same period, neither Antarctic prions nor white‐headed petrels have established colonies discrete from their former 1970s distribution, although we did record for the first time Antarctic prions visiting blue petrel colonies and a white‐headed petrel at a gray petrel burrow outside their current breeding distribution (Bird, Fuller et al., 2021).…”

“…With a population of <1000 mature individuals, gray petrels still meet the criteria for vulnerable in Australia (EPBC), irrespective of their increasing population trend. However, based on current rates of population growth and a population of 252 breeding pairs (∼500 mature individuals) in 2018, we project they will exceed this threshold by 2026, possibly sooner if breeding starts to occur in the high proportion of nonbreeding birds recorded during recent surveys (Bird et al, 2022;Bird, Fuller, et al, 2021). Vulnerability to invasive species impacts is not uniform, but it can be predicted from species' physiology and life histories, especially if quantitative data are lacking.…”

“…We used a burrow scope or digital camera to manually inspect all gray and white‐headed petrel burrows and used burrow scope and playback to determine occupancy in Antarctic prion burrows (full methods in Bird, et al. [2021]). In total, monitoring data from 12 Antarctic prion, 13 white‐headed petrel, and 10 gray petrel seasons were combined for trend analysis.…”