NT
Shy Albatross Thalassarche cauta



Justification

Justification of Red List category
Although this species has a population size exceeding 10,000 mature individuals, it is suspected to undergo declines exceeding 20% within the next three generations. It is therefore classified as Near Threatened.

Population justification
The number of Shy Albatross pairs estimated to be breeding on Albatross Island was 5,150 ± 430 in 2018–2019, compared to 5,017 in 2008–2009. On Pedra Branca, 109 pairs were estimated to be breeding in in 2018–2019, compared to 130–170 pairs in 2008–2009 (DPIPWE 2019). On Mewstone, 9,988 ± 200 pairs bred in 2014–2015 (DPIPWE 2019), with 4,029 pre-fledging chicks estimated in 2018–2019, compared to 9,500 (7,600–12,400) in 2004–2005 (Alderman et al. 2011, DPIPWE unpublished). The population of this species is therefore estimated at 31,600 (29,800-33,400) mature individuals.

Trend justification
There is no evidence this species has declined over the past three generations (63 years; Bird et al. 2020). Numbers on Albatross Island declined from about 20,000 pairs in the late 18th century to 250–400 pairs in 1909 (Johnstone et al. 1975). Recovery started in the 1960s, and the 21-year trend for 1998–2018 was +0.74 ± 0.05% p.a. (DPIPWE 2019). On Pedra Branca, the 21-year trend in breeding pairs is negative (–5.9 ± 1.01% -p.a.). Due to interannual variability and the shorter time series of available data, the trend on Mewstone, based on pre-fledging counts, is currently uncertain, although appearing stable (DPIPWE 2019). Given the relative size of Albatross Island and Pedra Branca populations, the overall trend for the species appears to be stable. 
However, climate change effects are a suspected cause for future decline. Thomson et al. (2015) predicted a decline in the number of breeding females in the Albatross Island subpopulation of over 30% in three generations due to climate change effects, however discrepancies exist between the model’s predictions and the most recent empirical data. Thus while a future decline is suspected, there is uncertainty about when a decline may commence and consequently any rate of reduction. Breeding success of the Albatross Island population is also negatively affected by Avian pox virus (R. Woods and R. Gales in litt. 2008) and a phlebovirus carried by a tick Ixodes eudyptidis (Johnstone et al. 1975, Wang et al. 2014), while the small population breeding on Pedra Branca is being competitively excluded by Australasian Gannets Morus serrator. Overall, low breeding success on Pedra Branca and indications of decreased juvenile recruitment on Albatross Island suggest steep declines exceeding 20% are plausible in the next three generations (Garnett and Baker 2021).

Distribution and population

Thalassarche cauta is an endemic breeder in Australia, breeding on Albatross Island in Bass Strait and on the Mewstone and Pedra Branca south-west of Tasmania. At sea, adults largely remain in Australian waters, mostly remaining near nesting islands, as do juveniles from Albatross Island (Alderman et al. 2011). Juveniles from Mewstone and Pedra Branca travel further west, sometimes to South Africa, where they forage over shelf waters (Mason et al. 2018). There are genetic differences between the three subpopulations (Abbott and Double 2003).

Ecology

Shy Albatross breeds annually in colonies. Nests are a mound of soil, grass and roots, and are located on rock islands. Eggs are mostly laid in the second half of September (Brooke 2004). Chicks hatch in December and fledge mostly in April. Immature birds return to their breeding colony at least three years after fledging, mostly beginning breeding when at least five to six years old, nearly always in their natal colonies.
 
Thalassarche cauta
usually forage singly and have been observed taking prey from the surface during the day or occasionally making surface plunges or shallow dives, also feeding my moonlight. A study using time-depth recorders revealed T. cauta commonly plunge-dive within three metres of the surface and can swim down to over 7 metres (ACAP 2009). They feed mostly on fish, cephalopods, tunicates and crustaceans, with some food sourced from fisheries (McInnes et al. 2020). They often follow fishing boats (Hedd and Gales 2001, 2005).

Threats

Within the last three generations, the principal threat has been from fishing. Initially, pelagic longline fishing killed many birds, but this largely ceased in Australian waters by the early 2000s (Baker 2016, Baker and Robertson 2018, Commonwealth of Australia 2018); estimated annual captures in pelagic longline fisheries are now lower than the population productivity within Australian waters (Abraham et al. 2019). Ongoing losses of immature birds from Mewstone while in South Africa is currently unquantified but likely to be low (c. 60 birds per year; Baker 2016). More recently, large numbers have been killed through striking warps (cables) in trawl fisheries (Baker et al. 2007, Alderman et al. 2011, Baker 2016) but this is being reduced in Australian waters through the application of mitigation measures (e.g. Koopman et al. 2018).

On land, 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). A phlebovirus carried by the tick Ixodes eudyptidis periodically causes chick mortalities on parts of Albatross Island (Johnstone et al. 1975, Wang et al. 2014) with tick control increasing survivorship of chicks by 10% (Alderman and Hobday 2017).
The small population breeding on Pedra Branca is being competitively excluded from the limited space by Australasian Gannets Morus serrator (Alderman et al. 2011), and is also affected by storms associated with rough weather. Poor competitive abilities for nesting space appeared to reduce reproductive success on Pedra Branca by approximately 9% per year between 1993 and 2007 (ACAP 2009). Australian Gannets appear to be increasing in abundance and extent (Alderman et al. 2011) and may pose an increasing threat.

 There are no land-based threats to Mewstone, but some models suggest that warming seas will reduce productivity (Thomson et al. 2015). 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 (Thomson 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 (Thomson et al. 2015).

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). All breeding islands are strictly protected with stringent quarantine applied. Longline fisheries within its Australian range are monitored and managed under the TAP. Effective means of mitigating losses in trawl fisheries have been developed. Trials have successfully controlled ticks on Albatross Island.

Conservation Actions Proposed
Determine demographic trends on Mewstone. Identify demographic and mobility responses to changes in oceanographic conditions affected by climate change. If considered necessary, treat tick/virus affected birds on Albatross Island. Ensure compliance with the TAP. Work with non-breeding range states and fishing fleets to improve fishing regulations, and expand their influence to the high seas.

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
Berryman, A., Vine, J.

Contributors
Alderman, R., Anderson, O., Butchart, S., Calvert, R., Croxall, J., Fjagesund, T., Gales, R., Martin, R., Nel, D., Robertson, C., Small, C., Stattersfield, A., Stuart, A., Sullivan, B., Symes, A. & Woods, R.W.


Recommended citation
BirdLife International (2024) Species factsheet: Thalassarche cauta. Downloaded from https://datazone.birdlife.org/species/factsheet/shy-albatross-thalassarche-cauta on 25/02/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org on 25/02/2024.