Akiko Shoji (Department of Zoology, University of Oxford, UK) and colleagues have published in the journal Ibis on diving in the Manx Shearwater Puffinus puffinus to “nearly” 55 m.

The paper’s abstract follows:

“The diving capabilities of the Procellariformes [sic] remain the least understood component of avian diving physiology.  Due to their relatively small size, shearwaters may have high oxygen consumption rates during diving relative to their available oxygen stores.  Dive performance in this group should be strongly limited by the trade-off between oxygen consumption and oxygen stores, and shearwaters could be a good model group for testing predictions of dive theory.  Many earlier measurements of shearwater dive behaviour relied on observations from the surface or potentially biased technology, and it is only recently that diving behaviour has been observed using electronic recorders for many of the clades within the family.  The diving behaviour of Manx Shearwaters Puffinus puffinus breeding in Wales, United Kingdom, was studied on a large sample of birds using time-depth-temperature recorders deployed on chick-rearing shearwaters in July and August over three years (2009-2011).  Light availability apparently limited diving as dives only occurred between 04:00 and 19:00 GMT.  All individuals routinely dived deeper than traditionally assumed, to a mean maximum depth of 31 m and occasionally down to nearly 55 m.  We compiled all available data for a comparison of the dive depth across shearwater species.  There was a positive allometric relationship between maximum dive depth and body mass across Puffinus and Ardenna shearwater species, as expected, but only if samples of fewer than two individuals were excluded.  The large intra-specific range in maximum dive depth in our study illustrates that apparent diversity in diving performance across species must be interpreted cautiously.”

Manx Shearwater at sea, photograph by Nathan Fletcher

Reference:

Shoji, A., Dean, B., Kirk, H., Freeman, R., Perrins, C.M. & Guilford, T.C. 2016.  The diving behaviour of the Manx Shearwater Puffinus puffinus.  Ibis doi: 10.1111/ibi.12381.

John Cooper, ACAP Information Officer, 08 May 2016

The Albatross and Petrel Agreement has produced a number of conservation guideline documents that are available on its web site (click here).  Subjects covered to date include biosecurity, eradication of introduced vertebrates, translocations of albatrosses and petrels, conducting censuses, and removing hooks from birds brought aboard fishing vessels.

A new conservation guideline document has recently been added to the series, written by Graham Parker and Kalinka Rexer-Huber (Parker Conservation, New Zealand), which advises on designing surveys for burrowing petrels.

The guidelines’ 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) availability bias, (4) burrow detection probability, and (5) observer bias. 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. The timing of burrow occupancy checks can help avoid assumptions about what proportion of breeding birds has not yet laid or has already failed. If sampling sites are not representative, or if some part of a petrel’s burrowing range is not accessible, this availability bias can affect extrapolation. Extrapolation errors occur when the area sampled is not representative of the area that the samples are extrapolated to. 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. 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 in burrows. If a proportion of occupants is missed, further error is introduced to the population estimate, so it can be valuable to check occupant detection probability. 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. For reference, we summarise the key problems associated with extrapolation of burrowing petrel surveys, and the implications if these error sources are not addressed (Table 2).”

ACAP’s Seabird Bycatch and Population and Conservation Status Working Groups that met this month in La Serena, Chile heard of plans for further ACAP Conservation Guidelines, as well as of the updating of existing ones.

Graham Parker surveys Grey Petrels on Campbell Island

Grey Petrel in its burrow on Gough Island, photograph by Kalinka Rexer-Huber 

Reference:

Parker, G. & Rexer-Huber, K. 2016.  Guidelines for designing burrowing petrel surveys to improve population estimate precision.  ACAP Conservation Guidelines Series.  19 pp.

John Cooper, ACAP Information Officer, 07 May 2016

On behalf of a group of Australian and Chilean marine ornithologists Javier Arata reported this week to the Third Meeting of ACAP's Population and Conservation Status Working Group (PaCSWG3) in La Serena, Chile on a recent survey of Black-browed Thalassarche melanophris and Grey-headed T. chrysostoma Albatrosses on the Diego Ramirez Islands.

Report co-authors Javier Arata from Chile and Barbara Wienecke from Australia at PaCSWG3

Photograph by John Cooper

Grey-headed Albatrosses on Diego Ramirez, photograph by Graham Robertson 

The report’s summary follows:

“Black-browed albatrosses are killed incidentally in commercial fishing operations.  Aerial surveys in 2002 and 2011 revealed the number of black-browed albatrosses at the Diego Ramirez and Ildefonso islands, Chile, increased by 52% and 18%, respectively.  The increases were attributed to reduced mortality in the longline fishery for Patagonian toothfish following fleet conversion to a new gear configuration with much higher average hook sink rates.  A new survey in 2014 revealed the number of black-browed albatrosses at Ildefonso was about the same as in 2011, but the number at Diego Ramirez had increased by a further 29% (8.8%/year).  The number of grey-headed albatrosses at Diego Ramirez also increased, by 23%, in the same time period.  In 2014 Ildefonso held an estimated 54,284 breeding pairs of black-browed albatrosses.  The populations of black-browed albatrosses at two more northern sites, the Evangelistas and Leonard islets, stood at 4,818 and 545 breeding pairs, respectively.  The number of breeding pairs of both albatross species at Diego Ramirez could not be determined because not all islands in the archipelago were surveyed.”

Reference:

Robertson, G., Wienecke, B., Suazo, C.G., Lawton, K., Arata, J.A. & Moreno, C. 2016.  Continued increase in the number of Black-browed Albatrosses at Diego Ramirez, Chile.  Third Meeting of the Population and Conservation Status Working Group, La Serena, Chile, 5 – 6 May 2016.  PaCSWG3 Inf 12 Rev 1.  14 pp.

[Note that the report is password protected].

John Cooper, ACAP Information Officer, 06 May 2016

Stefan Schoombie (FitzPatrick Institute, University of Cape Town, South Africa) and colleagues have published in the African Journal of Marine Science on the changing population trends in Sooty Phoebetria fusca and Light-mantled P. palpebrata Albatrosses at South Africa's Marion Island.

The paper’s abstract follows:

“Sub-Antarctic Marion Island is one of the few islands where both species of Phoebetria albatrosses breed sympatrically.  The last published assessment of their population trends, which reported counts up to 2008, concluded that the numbers of breeding pairs of sooty albatrossP. fusca (Endangered) were decreasing, whereas numbers of light-mantled albatrossP. palpebrata (Near Threatened) were increasing.  Extending the counts to 2014 reversed these trends, with numbers of sooty albatrosses increasing from 2006 to 2014, and numbers of light-mantled albatrosses decreasing from 2007 to 2014.  Confidence in island-wide counts is low due to the cryptic nature of the albatrosses on their largely inaccessible cliff-side nest sites, as well as counts for sooty albatrosses taking place late in the incubation period when 10−20% of nests have already failed.  Given the greater conservation concern for the sooty albatross, we recommend that dedicated annual counts be conducted during the early incubation period, and be repeated shortly after the chicks hatch (late December), mid-way through the nestling period (late February) and prior to fledging (late April), to give a better idea of breeding success.  Count zones also should be revised to facilitate more accurate counts, ensuring more reliable estimates of sooty albatross population trends at Marion Island.”

Sooty Albatross chick on Marion Island, photograph by Marienne de Villiers

The paper will be discussed at the Third Meeting of ACAP's Population and Conservation Status Working Group, being held today and tomorrow in La Serena, Chile (click here).

With thanks to Rob Crawford and Susan Mvungi. 

Reference:

Schoombie, S., Crawford, R.J.M., Makhado, A.B., Dyer, B.M. & Ryan, P.G. 2016.  Recent population trends of sooty and light-mantled albatrosses breeding on Marion Island.  African Journal of Marine Science 38:  119-127.

John Cooper, ACAP Information Officer, 05 May 2016