NT
White-fronted Tern Sterna striata



Justification

Justification of Red List Category
This species is considered to be declining at a moderately rapid rate, and as such is listed as Near Threatened.

Population justification

In New Zealand, S. s. striata has been considered to have a population size of 5,000-20,000 mature individuals, and S. s. aucklandorum was considered to have a population size of 1,000-5,000 mature individuals (Robertson et al. 2017). In Australia, (S. s. incerta) the breeding population is considered to be 120 mature individuals (Garnett et al. 2011). Therefore, the overall population size falls in the range 6,120-25,120 mature individuals.

Trend justification
Based on the subpopulation trends and subpopulation sizes from Garnett et al. (2011) and Robertson et al. (2017), the species may overall be expected to be in decline. The overall rate of decline depends highly on the population size, but would fall in the range 5.2-29.1% over 3 generations (30.3 years).

Distribution and population

The White-fronted Tern is native to south-west Australasia, breeding on the North and South Island of New Zealand, Stewart Island, the Chatham, Auckland and Snares Islands off the coast of New Zealand, and Flinders and Cape Barren Island off the north-east of Tasmania, Australia. It is also a winter visitor to Australia, from south Queensland to Tasmania and west to South Australia.

Ecology

This species can be found in coastal areas, nesting on rocky or sandy beaches and shingle islands in rivers, also on coastal cliffs and deserted barges, often close to the surf. It feeds along the shore and in bays, and over oceanic waters in winter. It feeds almost exclusively on fish, but will also take shrimp, feeding in the surf zone or several kilometres out to sea. It often feeds in flocks by plunge-diving from 7-10 metres with or without hovering, and by contact-dipping. Nesting takes place from October to December with most colonies containing 100-500 pairs, although solitary pairs are recorded at the edges of the range (del Hoyo et al. 1996).

Threats

The species's habit of nesting in densely packed colonies leaves it at considerable risk of predation by invasive predators including stoats, feral cats, hedgehogs and rats (Mills 2013). It is also vulnerable to predation by native species, with an entire colony at Kaikoura abandoned following chick predation by a single Northern Giant Petrel (Mills et al. 2013). There is also potentially a risk from the spread of the weed Sea Spurge Euphorbia paralias; however, this does not seem to be significant at present.

Conservation actions

Conservation Actions Underway
 In New Zealand, S. s. striata is listed as nationally At Risk and S. s. aucklandorum as nationally Vulnerable (Robertson et al. 2017). In Australia, S. s. incerta is currently listed as nationally Near Threatened (Garnett et al. 2011).

Conservation Actions Needed
Repeat censuses in New Zealand to update the population size estimate and population trend (H. Robertson in litt. 2018, G. Taylor in litt. 2018).  Map, count and monitor the breeding colonies in Australia, and manage access to any breeding sites (Garnett et al. 2011).

Acknowledgements

Text account compilers
Ekstrom, J., Calvert, R., Butchart, S., Martin, R., Stuart, A., Westrip, J.

Contributors
Taylor, G.A., Robertson, H.


Recommended citation
BirdLife International (2019) Species factsheet: Sterna striata. Downloaded from http://www.birdlife.org on 26/05/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/05/2019.