Gonzalo Arroyo (Fundación Migres, Cadiz, Spain) and colleagues have come up with a new estimate of the numbers of ACAP-listed  Shearwaters Puffinus mauretanicus based on counts of migrating birds, publishing in the journal Bird Conservation International.

“The Balearic Shearwater Puffinus mauretanicus is considered one of the most threatened seabirds in the world, with the breeding population thought to be in the range of 2,000–3,200 breeding pairs, from which global population has been inferred as 10,000 to 15,000 birds.  To test whether the actual population of Balearic Shearwaters is larger than presently thought, we analysed the data from four land-based census campaigns of Balearic Shearwater post-breeding migration through the Strait of Gibraltar (mid-May to mid-July 2007–2010).  The raw results of the counts, covering from 37% to 67% of the daylight time throughout the migratory period, all revealed figures in excess of 12,000 birds, and went up to almost 18,000 in two years.  Generalised Additive Models were used to estimate the numbers of birds passing during the time periods in which counts were not undertaken (count gaps), and their associated error.  The addition of both counted and estimated birds reveals figures of between 23,780 and 26,535 Balearic Shearwaters migrating along the north coast of the Strait of Gibraltar in each of the four years of our study.  The effects of several sources of bias suggest a slight potential underestimation in our results.  These figures reveal the urgent need to reformulate the population viability analysis for the species, and then if necessary reconsider its conservation status.”

Balearic Shearwater at sea

Reference:

Arroyo, G.M., Mateos-Rodríguez, M., Muñoz, R., De La Cruz, A., Cuenca, D.& Onrubia, A. 2014.  New population estimates of a critically endangered species, the Balearic Shearwater Puffinus mauretanicus, based on coastal migration counts.  Bird Conservation International  DOI: http://dx.doi.org/10.1017/S095927091400032X http://dx.doi.org/10.1017/S095927091400032X.

John Cooper, ACAP Information Officer, 27 December 2014

Takashi Yamamoto (Arctic Environment Research Center, National Institute of Polar Research, Tokyo, Japan) and colleagues have a recent paper in the journal Marine Biology that reports on Short-tailed Shearwaters Puffinus tenuirostris visiting Arctic waters.

The paper’s abstract follows:

"The marine ecosystems of the Bering Sea and adjacent southern Chukchi Sea are experiencing rapid changes due to recent reductions in sea ice.  Short-tailed shearwaters Puffinus tenuirostris visit this region in huge numbers between the boreal summer and autumn during non-breeding season, and represent one of the dominant top predators.  To understand the implications for this species of ongoing environmental change in the Pacific sub-Arctic and Arctic seas, we tracked the migratory movements of 19 and 24 birds in 2010 and 2011, respectively, using light-level geolocators.  In both years, tracked birds occupied the western (Okhotsk Sea and Kuril Islands) and eastern (southeast Bering Sea) North Pacific from May to July.  In August–September of 2010, but not 2011, a substantial proportion (68 % of the tracked individuals in 2010 compared to 38 % in 2011) moved through the Bering Strait to feed in the Chukchi Sea.  Based on the correlation with oceanographic variables, the probability of shearwater occurrence was highest in waters with sea surface temperatures (SSTs) of 8–10°C over shallow depths.  Furthermore, shearwaters spent more time flying when SST was warmer than 9°C, suggesting increased search effort for prey. We hypothesized that the northward shift in the distribution of shearwaters may have been related to temperature-driven changes in the abundance of their dominant prey, krill (Euphausiacea), as the timing of krill spawning coincides with the seasonal increase in water temperature.  Our results indicate a flexible response of foraging birds to ongoing changes in the sub-Arctic and Arctic ecosystems.”

With thanks to Richard Phillips for information.

Short-tailed Shearwater, photograph by Kirk Zufelt

 Reference:

Yamamoto, T., Hoshina, K., Nishizawa, B., Meathrel, C.E., Phillips, R.A. & Watanuki, Y. 2014.  Annual and seasonal movements of migrating short-tailed shearwaters reflect environmental variation in sub-Arctic and Arctic waters.  Marine Biology DOI 10.1007/s00227-014-2589-1.

John Cooper, ACAP Information Officer, 26 December 2014

Photograph by Ross Wanless

ACAP Secretariat, 25 December 2014

A single pair of Vulnerable Short-tailed Albatrosses Phoebastria albatrus has bred successfully in three of the four seasons since 2010/11 on the USA’s Midway Atoll, one of the North-Western Hawaiian Islands, as regularly reported in ACAP Latest News (click here).

The immediate end of breeding by Short-tailed Albatrosses on Midway now seems likely with the discovery of the corpse of an adult male on 13 December on Eastern Island within the Midway Atoll National Wildlife Refuge, part of the Papahanaumokuakea Marine National Monument.  The bird was found by a U.S. Fish and Wildlife Service volunteer in an area containing Short-tailed Albatross decoys and where the male and female pair had successfully bred (click here).

The dead Short-tailed Albatross as discovered on 13 December, photograph by Dan Clark/USFWS

Refuge Biologist Meg Duhr-Shultz takes measurements and acquires tissue samples from the seemingly freshly-dead corpse

Photograph by Penny Knuckles/USFWS

Midway staff believes the dead bird was paired with the female that produced three chicks at the same site.  How it may have died is currently unknown. Tissue samples will be transported from Midway Atoll to the U.S. Geological Survey’s National Wildlife Health Center Honolulu Field Station for analysis with the hopes of shedding light on the cause of death.

Midway Atoll National Wildlife Refuge Manager Dan Clark stated, “It is always difficult and a bit heart-wrenching to discover such an important and highly endangered bird deceased."

This male bird was first sighted in late October and was settled in amongst the decoys on Eastern Island, giving staff the impression it was one of the adults that had successfully reared chicks in previous years. His female mate has not been observed at Midway Atoll this year, although it is not unusual for Short-tailed Albatrosses to skip a breeding year.

Happier times.  The male Short-tailed Albatross incubates on Midway's Eastern Island

Photograph by Pete Leary

The first documented Short-tailed Albatross record on Midway Atoll was of a single individual in 1938.  After Midway Atoll became a national wildlife refuge in 1988 a “social attraction project” was implemented with the support from Japanese researchers involving placement of decoys and installation of a solar-powered calling system.  By 2007, one or two Short-tailed Albatrosses were observed and another four birds were observed in 2008.  Two years later, a female arrived and mated with a male who had been returning once a year for four consecutive years. Their chick hatched on 14 January 2011 and by 7 June the chick took flight, marking the first time a Short-tailed Albatross chick has fledged outside of islands near Japan in recorded history.  Since that time, the pair skipped the 2012 hatch year but returned and reared a chick during the 2013 and 2014 hatch years.

With acknowledgement to the Friends of Midway Atoll National Wildlife Refuge.

John Cooper, ACAP Information Officer, 24 December 2014