NT
Shy Albatross Thalassarche cauta



Justification

Justification of Red List Category
This species breeds on just three islands. It may be susceptible to stochastic events and human activities, although one nesting site is moderately widely separated from the other two. For this reason it is treated as Near Threatened.

Population justification
The global population of Shy Albatross was estimated to be 12,000 to 19,000 pairs in 2009 (Alderman et al. 2011). Data submitted to ACAP estimated a total population of 15,350 pairs, made up of 5,200 pairs on Albatross Island (in 2010) (Alderman et al. 2011), 7,600-12,400 pairs on Mewstone (in 2005) (Alderman et al. 2011), and 130-170 pairs on Pedra Branca (in 2009) (Alderman et al. 2011). The number of mature individuals is therefore estimated at c.30,700. The global population including non-breeders is now estimated to be 60,000-70,000 individuals.

Trend justification
Without knowing the population trend on Mewstone, or the historic population size on Pedra Branca, overall trend over a three generation period (66 years) cannot be accurately assessed.

Distribution and population

Thalassarche cauta is an endemic breeder in Australia, with colonies on three islands off Tasmania. Data submitted to ACAP estimated the total breeding population to be approximately 15,350 breeding pairs, with the largest colonies being Albatross Island (5,200 pairs), Pedra Branca (130-170 pairs) and the Mewstone (7,600-12,400 pairs). T. cauta was historically killed for the feather trade and the Albatross Island population was reduced to c.300 pairs in 1909 (Johnstone et al. 1975, Brooke 2004). Since then, the population on Albatross Island has been slowly recovering (Brooke 2004), reaching approximately 25% of the pre-exploited population in 2004 (ACAP Species Assessment draft). The historical population size and trend of Mewstone and Pedra Branca are unknown. The population on Pedra Branca may have always been small but it appears competition for nesting space with Australasian Gannets Morus serrator may steadily be reducing the number of fledglings produced on the island each year. Chick production on Pedra Branca dropped from over 100 to 31 between 1993 and 2007, representing a decrease of approximately 9% a year (ACAP 2009). Understanding the at-sea distribution of T. cauta is confounded by its similar appearance to other 'shy-type' albatrosses, particularly T. steadi (Double et al. 2003, ACAP 2011). During the breeding season, adults are relatively sedentary and are concentrated around Tasmania and southern Australia (Garnett and Crowley 2000, Hedd et al. 2001, BirdLife International 2004, Baker et al. 2007). However, juvenile birds from Mewstone (Tasmania) are known to migrate to South Africa (BirdLife International 2004, Baker et al. 2007). One banded bird from Albatross Island has been recovered in northern New Zealand (C.J.R. Robertson in litt. 2008).

Ecology

Behaviour Shy Albatross breeds annually in colonies. Eggs are mostly laid in the second half of September (Brooke 2004). They hatch in December and chicks fledge mostly in April. Immature birds return to their breeding colony at least 3 years after fledging, mostly beginning breeding when at least 5 to 6 years old, nearly always in their natal colonies. Thalassarche cauta usually forage singly and have been observed taking prey from the surface or occasionally making surface plunges or shallow dives. However, a study using time-depth recorders revealed T. cauta commonly plunge-dive within 3 m of the surface and can swim down to over 7 metres (ACAP 2009). Habitat Breeding Nests are a mound of soil, grass and roots, and are located on rock islands. Diet The main foods are fish and cephalopods (Hedd and Gales 2001), with crustaceans and tunicates also forming a part of the diet. It is a ship-follower and fish discharge comprises a significant proportion of its diet.

Threats

Incidental mortality in fishing gear is thought to pose the greatest threat to this species. Morphological similarity to White-capped Albatross Thalassarche steadi confounds accurate quantification of bycatch. Yet, the Shy Albatross is considered vulnerable to mortality associated with commercial longlining and trawling (e.g. Baker et al. 2007, Alderman et al. 2011, Phillips et al. 2010), even if overlap with White-capped Albatross is accounted for (Abbott et al. 2006, AFMA 2007, Brothers et al. 2010). 'Shy-type' albatrosses, (thought largely to be T. cauta) comprised over 12% of seabirds caught by Japanese tuna longliners in Australian waters during 1989-1995 (up to 900 birds per year) (Gales et al. 1998), Japanese fishing effort ceased in 1997 and the current domestic effort is concentrated in northern waters where the likelihood of encountering albatrosses is much lower (Baker et al. 2007). Juvenile birds from the Mewstone population are known to traverse the Indian Ocean and forage in waters off South Africa, which brings them into contact with several fisheries that pose a greater bycatch threat (Baker et al. 2007).

Threats due to climate change are becoming evident and local environmental conditions (rainfall, air temperature, and sea-surface height) during the chick-rearing stage, have been shown to be significantly correlated with breeding success (Thompson et al. 2015). The Pedra Branca colony may be exposed to significant wave action from storms, potentially impacting the species (ACAP 2009) and increased rainfall events have led to reduced reproductive success at Albatross Island and is a suspected cause for decline at the Mewstone colony (Thompson et al. 2015). While recent climate models predict little change in future local average rainfall, increases are forecast in both temperature and upwelling, with detrimental and beneficial effects respectively on breeding success (Thompson et al. 2015). An estimated 50% reduction in bycatch would be required to offset the negative impact of temperature increases, even in the scenario of increased upwelling (Thompson et al. 2015).

Poor competitive abilities for nesting space against Australasian Gannet Morus serrator appears to be reducing reproductive success on Pedra Branca by approximately 9% per year between 1993 and 2007 (ACAP 2009). This is thought to be the primary cause of the observed local rapid declines in the number of chicks produced each year and likely contributed to the number of breeding pairs on Pedra Branca declining from about 350 in 2005 to about 140 in 2015 (ACAP 2016 unpublished data). Australian Gannets appear to be increasing in abundance and extent (Alderman et al. 2011) and may pose an increasing threat.

Avian pox virus has been recorded in chicks on Albatross Island and has the potential to impact population trends through negative impacts to breeding success (R. Woods and R. Gales in litt. 2008).

Conservation actions

Conservation Actions Underway
CMS Appendix II and ACAP Annex 1. Currently disturbance and access issues prevent studies on Pedra Branca and the Mewstone. These two sites are also internationally designated protected sites, being part of the Tasmanian Wilderness World Heritage Area (UNEP/CMS 2008).

Conservation Actions Proposed
Analysis of aerial census data and maintenance of current programme for Pedra Branca and the Mewstone (due to logistic difficulties demographic studies of populations on Pedra Branca and the Mewstone population are not feasible). Promote the adoption of a) monitoring of seabird bycatch associated with longline and trawl fishing and b) best-practice mitigation measures in all fisheries within the species's range, including via intergovernmental mechanisms such as ACAP, the Indian Ocean Tuna Commission and FAO. Mewstone birds appear to travel more extensively than Albatross Island birds and are therefore exposed to interactions with a range of fishing fleets.

Identification

90 cm. Medium-sized black, white and slate-grey albatross with characteristic black thumb mark at the base of the leading edge of the underwing characteristic of the 'shy-type' albatrosses. Adult has forehead and crown white bordered below by dark eyebrow and pale grey face. Grey-black mantle, upperwing and tail. The remainder is white. Bill grey-yellow, with more prominent yellow culmen, and yellow tip. Similar spp. the very similar White-capped albatross T. steadi is slightly larger and has a paler face and less yellow on the culmen of the bill.

Acknowledgements

Text account compilers
Stattersfield, A., Stuart, A., Sullivan, B., Symes, A., Fjagesund, T., Calvert, R., Hermes, C., Butchart, S., Martin, R., Anderson, O., Nel, D., Small, C.

Contributors
Croxall, J., Gales, R., Robertson, C., Alderman, R.


Recommended citation
BirdLife International (2019) Species factsheet: Thalassarche cauta. Downloaded from http://www.birdlife.org on 20/05/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 20/05/2019.