Ki-Baek Nam (Korea Institute of Ornithology, Kyung Hee University, Seoul, Korea) and colleagues write in Korean in the journal Ocean and Polar Research on the effects of predation by Norway Rats Rattus norvegicus on Streaked Shearwaters Calonectris leucomelas when breeding.

http://www.dbpia.co.kr/Journal/IssueList/1537

The paper’s English abstract follows:

“The seabird plays an important role as one of the indicator species for the status of and changes within marine ecosystems.  Therefore, the conservation of seabirds and their habitats is important for maintaining the structure and function of marine ecosystems.  Biological invasions affect most ecosystems on oceanic islands.  In particular, Rattus spp. is the invasive species with the greatest impact on the seabird population.  Introduced predators, like rats, severely affect seabirds and endanger them worldwide.  The breeding population of Streaked Shearwaters Calonectris leucomelas in Sasu Island is one of biggest seabird colonies in Korea, and the Norway Rat Rattus norvegicus is known as an alien predator in this island.  In this study we investigated rates of burrow occupancy and breeding success of Streaked Shearwaters for 7 years, and the impact of Norway Rats on the breeding success of Streaked Shearwaters breeding in Sasu Island for 4 years.  Our results show that the percentage of breeding burrows decreased according to breeding stage during several years in the monitoring period, and that predation by the Norway Rat was the main cause in hatching failures.  Consequently, although our results indicate that their breeding population is not likely to decline, Norway Rats have been affecting the breeding status of Streaked Shearwaters on Sasu Island during the last decade.”

Reference:

Nam, K.-B., Lee, K.-G., Hwang, J.-W. & Yoo, J.-C.  2014.  Variation in breeding burrows of Streaked Shearwaters breeding in Sasu Island, and predation rates by Norway Rats.  Ocean and Polar Research 36: 49-57.

John Cooper, ACAP Information Officer, 10 May 2014

R.J. Spivey (Department of Biological Sciences, Bangor University, U.K.) and colleagues have published in the journal Progress in Oceanography on the intermittent flapping flight of the Manx Shearwater Puffinus puffinus.

The paper’s abstract follows:

“Flights of Manx Shearwaters over the Irish Sea were investigated using GPS (n=6) and simultaneous high sample rate triaxial accelerometry (n=1).  This pelagic species executes flight through intermittent bursts of flapping flight interspersed with gliding phases while meandering low over the waves.   To facilitate the analysis and interpretation of body-mounted accelerometry in these challenging circumstances we introduce a combined time and frequency domain technique allowing accurate separation of flapping from gliding, measurement of wing-beat frequency and determination of flapping duty cycle.  Considerable fluctuations in cycle period and time-averaged flapping duty cycle were found.  Our approach offered high temporal precision, which was crucial as half the flapping bursts were briefer than 0.8s and half the cycle times shorter than 2.55s.  Flapping duty cycles exceeding 38% were likeliest for short range flights and ascending flights.  At higher duty cycles, cycle time decreaased and wing-beat frequency and amplitude was only moderately elevated.  Near-continuous flapping was only observed during steep ascents and strong headwinds.  During a long-range foraging flight with good GPS coverage duty cycles between 7% and 63% were observed.  We posit that flapping was modulated in order to maintain a steady airspeed in somewhat variable wind and wave conditions as part of a complex wave-meandering wing-sailing flight strategy that was often effective in reducing locomotion costs.  Periods of very low duty cycle flight appear to have benefited from instantaneous crosswinds exceeding 10 m·s^-1with an estimated three-fold reduction in biomechanical power.  Accelerometry offers a very practical tool for studying flight performance and the methods herein described can be readily adapted to other species that intermittently beat their wings.”

Manx Shearwater, photograph by Nathan Fletcher

Reference:

Spivey, R.J., Stansfield, S. & Bishop, C.M. 2014.  Analysing the intermittent flapping flight of a Manx Shearwater, Puffinus puffinus, and its sporadic use of a wave-meandering wing-sailing flight strategy.  Progress in Oceanography doi.org/10.1016/j.pocean.2014.04.005.

John Cooper, ACAP Information Officer, 09 May 2014

Bronwyn Maree (Albatross Task Force, BirdLife South Africa, Cape Town, South Africa) and colleagues have published in the journal Animal Conservation on reductions in seabird mortality that occurs when trawl trail bird-scaring lines.

The paper’s abstract follows:

Globally, many thousands of seabirds are killed accidentally in demersal trawl fisheries through cable interactions and net entanglements.  However, multi-year datasets for estimating seabird–trawl interactions robustly are scarce.  In 2004/2005, an estimated 15 500 (7000–26 000) seabirds were killed annually through cable strikes in the South African deep-water hake trawl fishery; the majority were albatrosses.  We reanalysed those data using fishing effort from vessel logbooks (previously unavailable).  The new estimates are ∼40% lower across all taxa: ∼9300 birds in 2004, of which ∼7200 were albatrosses.  We compare these figures to data from 2006 to 2010, when vessels used a single measure (bird-scaring lines) to reduce seabird mortality.  From 64 trips and 690 hours of observation, 41 seabirds were confirmed killed due to cable strikes, of which 22% were albatrosses.  Fatal cable interactions occurred overwhelmingly when vessels discarded offal, with the highest rates (birds killed per hour of observation) in winter and during setting.  Comparing rates shows that bird-scaring lines alone resulted in 73–95% lower mortality in the winter/discard strata (all seabirds: 0.56 birds per hour before, 0.15 birds per hour after, P < 0.001; albatrosses: 0.44 birds per hour before, 0.02 birds per hour after, P < 0.001).  Estimated total mortality [mean and 95% confidence intervals (CIs)] in this fishery in 2010 was 990 (556–1633) seabirds, including 83 (38–166) albatrosses, a reduction in mean albatross deaths of > 95%, reflecting both bird-scaring line effectiveness (accounting for > 90%) and annual fishing effort reduced by 50% from 2004–2005 to 2010.  Bird-scaring lines cost < US$200 each in South Africa, a trivial expense per vessel for a measure that reduces fatal interactions with threatened seabirds so effectively.  Our results provide a strong case for the mandatory adoption of bird-scaring lines in trawl fisheries with high densities of scavenging seabirds.”

Black-browed Albatrosses gather behind a South Atlantic trawler

Photograph by Graham Parker

Click here to find BLSA's press release on their recently published research on bird-scaring lines for trwalers.

With thanks to Bronwyn Maree for information.

Reference:

B.A. Maree, B.A., Wanless, R.M., Fairweather, T.P., Sullivan, B.J. & Yates, O. 2014.  Significant reductions in mortality of threatened seabirds in a South African trawl fishery.  Animal Conservation doi:10.1111/acv.12126.

John Cooper, ACAP Information Officer, 08 May 2014

Steffen Oppel (Royal Society for the Protection of Birds, Sandy, U.K.) and colleagues have published open-access in the journal Nature Conservation on estimating population size of the Cory’s Shearwater Calonectris borealis.

The paper’s abstract follows:

Population size assessments for nocturnal burrow-nesting seabirds are logistically challenging because these species are active in colonies only during darkness and often nest on remote islands where manual inspections of breeding burrows are not feasible.  Many seabird species are highly vocal, and recent technological innovations now make it possible to record and quantify vocal activity in seabird colonies.  Here we test the hypothesis that remotely recorded vocal activity in Cory’s shearwater (Calonectris borealis) breeding colonies in the North Atlantic increases with nest density, and combined this relationship with cliff habitat mapping to estimate the population size of Cory’s shearwaters on the island of Corvo (Azores).  We deployed acoustic recording devices in 9 Cory’s shearwater colonies of known size to establish a relationship between vocal activity and local nest density (slope = 1.07,R2 = 0.86,p < 0.001).  We used this relationship to predict the nest density in various cliff habitat types and produced a habitat map of breeding cliffs to extrapolate nest density around the island of Corvo.  The mean predicted nest density on Corvo ranged from 6.6 (2.1–16.2) to 27.8 (19.5–36.4) nests/ha.  Extrapolation of habitat-specific nest densities across the cliff area of Corvo resulted in an estimate of 6326 Cory’s shearwater nests (95% confidence interval: 3735–10,524). This population size estimate is similar to previous assessments, but is too imprecise to detect moderate changes in population size over time.  While estimating absolute population size from acoustic recordings may not be sufficiently precise, the strong positive relationship that we found between local nest density and recorded calling rate indicates that passive acoustic monitoring may be useful to document relative changes in seabird populations over time.

Cory's Shearwater, photograph by Paulo Catry

Reference:

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

John Cooper, ACAP Information Officer, 07 May 2014