Rachel Buxton (Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, USA) will host a discussion on behalf on the World Seabird Union on Twitter (#seabirdersaturday) this coming Saturday, 18 July, from 1530-1730 GMT on acoustic monitoring in seabirds (including burrowing species – of which seven petrels and shearwaters are ACAP-listed) as described below.

“Seabirds are among the most threatened group of marine animals.  Accordingly, over the past few decades, seabird conservation efforts have increased; including the eradication of harmful introduced predators from breeding sites and implementation of fisheries by-catch mitigation.  Population monitoring has therefore become especially important, to inform adaptive management by measuring the outcome of conservation efforts and to provide estimates for trajectory models under predicted future conditions.  Despite their threat status and the importance of long-term monitoring, seabird population estimates remain scarce because of the financial and logistical challenges associated with accessing remote island breeding sites.  Moreover, many seabirds have cryptic nesting behavior, including below-ground nesting and nocturnal colony attendance, precluding the use of conventional monitoring techniques.

More recently, passive acoustic recorders and automated acoustic analysis have received wide attention as powerful tools to monitor vocalizing wildlife.  Colonial seabirds lend themselves to acoustic monitoring, as their aggregated distribution reduces the spatial coverage required for monitoring and the number of vocalizations have [sic] been linked to relative abundance.  Moreover, the burgeoning field of acoustic ecology examines the relationship between the soundscape (combination of sounds from an environment) and ecosystem functioning.  In this way, acoustic monitoring provides an opportunity to not only monitor seabird populations, but also the broader island landscape” (click here).

White-chinned Petrels, photograph by Dave Boyle

Selected Literature:

Borker, A.L., McKown, M.W., Ackerman, J.T, Eagles-Smith, C.A., Tershy, B.R. & Croll, D.A. 2014.  Vocal activity as a low cost and scalable index of seabird colony size.  Conservation Biology 28: 1100-1108.

Buxton, R.T. & Jones, I.L. 2012.  Measuring nocturnal seabird activity and status using acoustic recording devices: applications for island restoration.  Journal of Field Ornithology 83: 47-60.

Buxton, R.T., Major, H.L., Jones ,IL. & Williams, J.C. 2013.  Examining patterns in nocturnal seabird activity and recovery across the western Aleutian Islands, Alaska, using automated acoustic recording.  The Auk 130: 331-341.

Blumstein, D.T., et al. 2011.  Acoustic monitoring in terrestrial environments using microphone arrays: applications, technological considerations and prospectus.  Journal of Applied Ecology 48: 758-767.

Oppel, S., Hervias, S., Oliveira, N., Pipa, T., Silva, C., Geraldes, P., Goh, M., Immler, E. & McKown, M.W. 2014.  Estimating population size of a nocturnal burrow-nesting seabird using acoustic monitoring and habitat mapping.  Nature Conservation 7: 1-13.

Pijanowski, .B.C., Villanueva-Rivera, L.J., Dumyahn, S.L., Farina, A., Krause, B.L., Napoletano, B.M., Gage, S.H. & Pieretti, N. 2011.  Soundscape ecology: the science of sound in the landscape.  Bioscience 61: 203-216.

John Cooper, ACAP Information Officer, 14 July 2015

Elsa Bonnaud (Unité Ecologie, Systématique et Evolution, Université Paris-Sud, Orsay, France) and colleagues have published in the journal Biological Invasions on feral Domestic Cats Felis catus preying upon Yelkouan Shearwaters Puffinus yelkouan in the French Mediterranean.

The paper’s abstract follows:

“Domestic cats are one of the most widespread predators on islands worldwide and are responsible for numerous reductions and extinctions of species on islands.  The three main islands of the Hyères Archipelago house one of the largest colonies of the Mediterranean endemic Yelkouan shearwater Puffinus yelkouan that has recently been up-listed by the IUCN to ‘vulnerable’.  The main objectives of this study were to assess the diet of cats and to study the effect of cat predation on Yelkouan shearwater populations at the archipelago scale. The diet of cats was studied using scat analyses according to years and seasons for each island.  Simultaneously, Yelkouan shearwater breeding success was monitored during a period of 8 years on Port-Cros and Porquerolles, and 3 years on Le Levant.  Descriptive analyses and GLM were used to compare data gathered on each island.  At the archipelago scale, cats preyed strongly upon introduced mammals and shearwaters.  Surprisingly, large differences appeared in cats’ diet according to the island considered.  The Yelkouan shearwater was the primary prey of cats on Le Levant, but secondary on Port-Cros and Porquerolles.  Cat predation was mainly concentrated during the shearwater prospecting period, when birds arrive at the colonies and look for a mate (if they are not already paired) and a burrow before breeding.  Consequently cat impact was low on shearwater breeding success.  However, this study demonstrates that the cat management conducted on Port-Cros was positive for fledging success.  The successful cat eradication on Port-Cros supports the need to continue working for Yelkouan shearwater conservation with Le Levant as a priority, because this is where the colonies are largest and predation on Yelkouan shearwaters is very high.”

At risk to cats: a Yelkouan Shearwater in its burrow, photograph by Jerome Lagrand 

Reference:

Elsa Bonnaud, E., Palmas, P., Bourgeois, K., Ollier, S. Zarzoso-Lacoste, D. & Vidal, E. 2015.  Island specificities matter: cat diet differs significantly between islands of a major breeding archipelago for a vulnerable endemic seabird.  Biological Invasions DOI 10.1007/s10530-015-0921-4.

John Cooper, ACAP Information Officer, 13 July 2015

Jim Roberts and colleagues (National Institute of Water & Atmospheric Research Ltd, Christchurch, New Zealand) have tabled a draft background report to last month’s meeting of the Conservation Services Programme (CSP) of New Zealand’s Department of Conservation that considers estimating demographic rates for White-capped Albatrosses Thalassarche steadi.

The report’s Executive Summary follows:

“Disappointment Island, within the Auckland Islands group, supports over 70,000 breeding pairs of white-capped albatrosses Thalassarche cauta steadi annually, the largest colony of New Zealand’s most abundant albatross species.  This species interacts with commercial fisheries and ranks highly within the Level 2 Seabird Risk Assessment process, but with a relatively high level of uncertainty around the estimate of adult survival.  A study was undertaken to assess the effect of alternative mark-recapture sampling approaches to a potential mark-resighting study of white-capped albatross on the estimation of demographic rates.

A data simulator was used to create dummy mark-resighting observations for a single banding year with alternative scenarios of: banded sample size (150, 300 or 600 breeding individuals); number of subsequent consecutive resighting years (2, 3, 4, 5 or 10 years); and resighting probability of breeders (0.6 or 0.4) and non-breeders (0.0 or 0.1).

The SeaBird demographic modelling software was then used to determine variability in the estimates of survival and breeding rate using the dummy mark-resighting observations.  This assessment assumed that demographic rates were constant with respect to year and age and variability of demographic rates of wild populations are likely to be greater than those obtained by this assessment.  Increasing the banded sample size from 150 to 600 individuals led to an increase in the precision (c.v.) of annual survival breeding rate estimates.

With an input survival rate of 0.95 and a banded population of 150 individuals, the range of survival estimates was wide with 5 years of resighting effort (range from 0.91-0.99, x̅ = 0.95), though was much narrower with 10 years of resighting effort (0.93-0.96, x̅ = 0.95).  With a banded sample size of 600 individuals, the range of survival estimates was narrow with 5 years of resighting effort (0.93-0.97, x̅ = 0.95).

The precision of demographic rate estimates was not greatly affected by reducing the resighting probability of breeders from 0.6 to 0.4, though reducing the resighting probability of non-breeders from 0.10 to 0.00 produced imprecise estimates that were for some samples very different from input values.

To produce estimates of demographic rates that would be suitably precise for risk assessment purposes, this data simulation approach indicates that resighting effort over 5-10 years would be required subsequent to banding of a population between 150-600 individuals.  In a wild population, demographic rates are likely to change through time, so that greater sampling effort (in terms of banded individuals, number of resighting years or even resighting effort) may be required.”

White-capped Albatross, photograph by Graham Parker

Reference:

Roberts, J., Doonan, I. & Thompson, D. 2015.  Demographic Rate Estimation of White-capped Albatross Simulation Modelling.  Draft Copy Prepared for Department of Conservation June 2015.  Wellington: National Institute of Water & Atmospheric Research Ltd.  12 pp.

John Cooper, ACAP Information Officer, 12 July 2015

Graham Parker and Kalinka Rexer‐Huber (Parker Conservation, Dunedin, New Zealand) have submitted a draft literature review of methods for estimating population sizes of burrowing petrels (including ACAP-listed Procellaria petrels and Puffinus shearwaters) to last month’s meeting of the Conservation Services Programme (CSP) of New Zealand’s Department of Conservation.

The report’s Executive Summary follows:

“Robust population estimates are needed for conservation management of burrowing petrel populations.  Estimates of population size for burrowing petrels are often obtained by extrapolation of burrow surveys to a population- or island-wide scale.   However, extrapolation will also extrapolate bias or error, giving rise to potentially large error bounds reflecting imprecise estimates of population size.  This hinders species risk assessment and limits the ability to detect trends in population size over time.   We review methods for estimating the breeding population size of burrowing petrels by extrapolation from surveys, focusing in particular on the error associated with population estimates of the larger Procellaria petrels.  Sources of error in extrapolation of survey data are divided into five key areas: (1) uncertainty of burrow contents, (2) timing, (3) burrow detection probability, (4) availability bias and (5) observer bias.  We reviewed 87 relevant studies.  Of these, 45 published and unpublished studies deal specifically with quantitative surveys of burrowing petrels.  The review highlights that there is no single-best method for minimising error levels in population estimates.  Rather, the most accurate and precise studies are those designed according to the specifics of the study resources, species and site, and we discuss a range of the factors that are important to consider.  To produce an accurate and precise population estimate from burrow counts, it is important to determine burrow contents and to distinguish between breeding and non-breeding birds.  If a proportion of occupants are missed, further error is introduced to the population estimate, so it can be valuable to check occupant detection probability.  The timing of burrow occupancy checks can help avoid assumptions about what proportion of breeding birds has not yet laid or has already failed.  Extrapolation errors occur when the area sampled is not representative of the area that the samples are extrapolated to.  If sampling sites are not representative, or if some part of a petrel’s burrowing range is not accessible/available to sample, this availability bias can affect extrapolation.  Burrow detection rates can also affect the accuracy of extrapolation, so the assumption that every burrow in the sampled area was detected should be checked.  Whether planar map area or true surface area is used for extrapolation can be a further source of error.  Observers may differ in their ability to detect burrows or burrow contents and this observer bias should be tested for.  Several key points are relevant to all studies: the need for a good pilot study to minimise error sources in the main survey; the need for sufficient time to cover enough ground while including contingency for weather; and the need to document burrowing petrel survey methods in enough depth to be repeatable.”

Black Petrel, photograph by David Boyle

Click here for a visual presentation on the literature review.

Reference:

Parker, G.C. and Rexer-Huber, K. 2015.  Literature Review of Methods for Estimating Population Size of Burrowing Petrels based on Extrapolations from Surveys.  Department of Conservation, Conservation Services Programme Objective 7, Project POP2014-02.  Dunedin: Parker Conservation.  28 pp.

John Cooper, ACAP Information Officer, 11 July 2015