Fairy tern
| Fairy tern | |
|---|---|
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Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Charadriiformes |
| Family: | Laridae |
| Genus: | Sternula |
| Species: | S. nereis
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| Binomial name | |
| Sternula nereis Gould, 1843
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| Subspecies | |
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Sternula nereis davisae | |
| Synonyms | |
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Sterna nereis | |
The fairy tern (Sternula nereis) is a small tern which is native to the southwestern Pacific. It is listed as "Vulnerable" by the IUCN and the New Zealand subspecies is "Critically Endangered". Fairy terns live in colonies along the coastlines and estuaries of Australia, New Zealand, and New Caledonia, feeding largely on small, epipelagic schooling fishes, breeding in areas close to their feeding sites. They have a monogamous mating system, forming breeding pairs in which they mate, nest, and care for offspring together.
There are three subspecies:
- Australian fairy tern, Sternula nereis nereis (Gould, 1843) – breeds in Australia
- New Caledonian fairy tern, Sternula nereis exsul (Mathews, 1912) – breeds in New Caledonia
- New Zealand fairy tern, Sternula nereis davisae (Mathews & Iredale, 1913) – breeds in northern New Zealand
Description
[edit]The fairy tern is a small tern with a white body and light bluish-grey wings. A small black patch extends no further than the eye and not as far as the bill. In the breeding plumage both the beak and the legs are yellowish-orange. During the rest of the year the black crown is lost, being mostly replaced by white feathers, and the beak becomes black at the tip and the base. The sexes look alike and the plumage of immature birds is similar to the non-breeding plumage. The total length of the fairy tern is about 25 cm (10 in).[2]
Status
[edit]Formerly classified as a Species of Least Concern by the IUCN,[3] recent research shows that its numbers have been decreasing rapidly throughout its range; the New Zealand subspecies has been on the brink of extinction for decades. The fairy tern was consequently uplisted to Vulnerable status in 2008.[3] The New Zealand fairy tern has numerous breeding areas, largely incorporating the upper-north region of the North Island. In 2011, there were only about 42 known individuals. With a breeding program in place by the New Zealand Department of Conservation, the population was estimated in 2020 at 40.[4]
Behaviour
[edit]Feeding
[edit]Fairy terns are surface plungers, feeding on fish that shoal just under the water surface. To forage, fairy terns hover between five and fifteen metres above the water to search for prey, then carrying out a descending aerial dive beak-first towards the water.[5] They then spread their wings and tails just above the water surface, submerging only their bills and heads to catch their prey.[5] This foraging technique means that they catch prey no deeper than around eight centimetres under the water surface, allowing them to make use of shallow waters such as tidal pools[5]. Fairy terns seldom go far out to sea but are often to be seen where predatory fish are feeding on shoals of small fish.
Fairy tern diets consist predominantly of pelagic schooling fishes.[6][7] For instance, Australian fairy terns mostly eat blue sprat, hardyheads, and garfishes.[7] Similarly, New Zealand fairy terns have a diet made up of common estuarine fish, namely gobies and flounders, responsible for most of their consumed biomass, as well as shrimps, comprising up to 21% of their diet.[5] Little research has been done on the diet of New Caledonian fairy terns, but given their foraging technique, it is likely that they too forage for small marine fish that school just below the water surface. Fairy terns also consume crustaceans, molluscs and some plant material.[2]
Breeding
[edit]Breeding takes place in the spring in colonies on sheltered beaches on the mainland or on offshore islands. The nest is just above high-water mark and is a scrape in the sand. One or two eggs are laid and both parents share the incubation and care of the chicks and have occasionally been seen providing post-fledging parental care.[3]
Threats
[edit]Predation
[edit]Fairy terns are predated on by small mammals, which may eat adults, chicks and eggs[8][9][10]. In Australia, the presence of semi-wild cats threatens the already declining population of Australian fairy terns[9]. Likewise, in New Zealand, non-native invasive mammalian species including rats, mustelids, hedgehogs and cats, predate on fairy terns[8][10]. As with fairy terns, non-native mammalian predation is a common issue for vulnerable endemic birds in New Zealand, and is a key focus for conversation.
Fairy tern chicks and eggs are also at risk of avian predation[11][12]. Specifically, birds including harrier hawks and black backed gulls will eat chicks and eggs[8][10]. The only defence against predation for fairy tern chicks is their cryptic colouration, which allows them to camouflage with seashells that surround their nests[10][13]. This contributes to a high level of chick mortality that threatens the decreasing population of fairy terns, particularly for the endangered New Zealand and New Caledonian subspecies[14].
Human Disturbance
[edit]Human disturbance poses a great threat to fairy terns. Particularly during the breeding season, human activity puts fairy terns at risk of further population decrease, disrupting nesting and breeding behaviours to ultimately reduce breeding success[10][12]. The New Zealand Department of Conservation warns of the danger of human activation including dog walking, drone use, bonfires, vehicular beach use, horse riding, and recreational beach activities in fairy tern breeding areas. These disturbances have been known to not only disrupt breeding behaviours, but to scare fairy terns away from their nests, causing fairy terns to abandon their eggs, leaving them vulnerable to predation as well as embryo death due to thermal exposure[8]. For this reason, conversation efforts are being made to reduce human disturbance towards fairy terns.
References
[edit]- ^ BirdLife International (2018). "Sternula nereis". IUCN Red List of Threatened Species. 2018: e.T22694691A132568135. doi:10.2305/IUCN.UK.2018-2.RLTS.T22694691A132568135.en. Retrieved 19 November 2021.
- ^ a b "Fairy Tern: Sterna nereis". Tasmania Parks and Wildlife Service. Retrieved 2013-12-17.
- ^ a b c "Species factsheet: Sterna nereis". BirdLife International. Retrieved 2013-12-17.
- ^ Smith, Anneke (23 August 2018). "Rarest bird in the country gets a helping hand". RNZ.
- ^ a b c d Ismar, Stefanie M. H.; Trnski, Tom; Beauchamp, Tony; Bury, Sarah J.; Wilson, David; Kannemeyer, Robyn; Bellingham, Mark; Baird, Karen (March 2014). "Foraging ecology and choice of feeding habitat in the New Zealand Fairy Tern Sternula nereis davisae". Bird Conservation International. 24 (1): 72–87. doi:10.1017/S0959270913000312. ProQuest 1611063475.
- ^ Greenwell, C.N.; Tweedley, J.R.; Moore, G.I.; Lenanton, R.C.J.; Dunlop, J.N.; Loneragan, N.R. (December 2021). "Feeding ecology of a threatened coastal seabird across an inner shelf seascape". Estuarine, Coastal and Shelf Science. 263: 107627. Bibcode:2021ECSS..26307627G. doi:10.1016/j.ecss.2021.107627.
- ^ a b Greenwell, Claire (2021). Life history, ecology, and population dynamics of the Australian Fairy Tern and implications for their conservation (Thesis).[page needed]
- ^ a b c d "New Zealand fairy tern/tara iti". www.doc.govt.nz. Retrieved 2024-10-12.
- ^ a b Greenwell, Claire N.; Calver, Michael C.; Loneragan, Neil R. (2019). "Cat Gets Its Tern: A Case Study of Predation on a Threatened Coastal Seabird". Animals, MDPI. 9 (7): 445. doi:10.3390/ani9070445. ISSN 2076-2615. PMID 31315191.
- ^ a b c d e Treadgold (2000). "Behavioural Ecology of the endangered New Zealand Fairy Tern (Tara-iti) Sterna nereis davisae: implications for management". Massey University.
- ^ Villard, Pascal; Hunt, Gavin; Coll, Jonathan; Cassan, Jean-Jérome (2020-10-01). "Breeding biology of Fairy Terns on Magone Islet, New Caledonia". Emu - Austral Ornithology. 120 (4): 360–364. Bibcode:2020EmuAO.120..360V. doi:10.1080/01584197.2020.1830705. ISSN 0158-4197.
- ^ a b Barré, Nicolas; Baling, Marleen; Baillon, Nathalie; Le Bouteiller, Aubert; Bachy, Pierre; Chartendrault, Vivien; Spaggiari, Jérôme (2012). "Survey of Fairy Tern Sterna Nereis Exsul in New Caledonia" (PDF). Marine Ornithology. 40: 31–38.
- ^ Greenwell, C.N.; Sullivan, D.; Goddard, N.; Bedford, F.; Douglas, T.K. (2021). "Application of a novel banding technique and photographic recapture to describe plumage development and behaviour of juvenile fairy terns". Australian Field Ornithology. 38: 49–55. doi:10.20938/afo38049055 – via Informit.
- ^ Baling, Marleen; Jeffries, Darryl; Barré, Nicolas; Brunton, Dianne H. (2009). "A survey of Fairy Tern ( Sterna nereis ) breeding colonies in the Southern Lagoon, New Caledonia". Emu-Austral Ornithology. 109 (1): 57–61. Bibcode:2009EmuAO.109...57B. doi:10.1071/MU08047. ISSN 0158-4197 – via Tandfonline.
External links
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