Fairy tern

Sternula nereis Gould, 1843

Order: Charadriiformes

Family: Sternidae

New Zealand status: Native

Conservation status: Nationally Critical

Other names: tara iti

Geographical variation: Three subspecies: nominate nereis in Australia, exsul in New Caledonia, and davisae in New Zealand

Fairy tern. Adult breeding plumage. Pakiri Beach, October 2012. Image © Glenda Rees by Glenda Rees Glenda Rees (http://www.flickr.com/photos/nzsamphotofanatic/)

Fairy tern. Adult breeding plumage. Pakiri Beach, October 2012. Image © Glenda Rees by Glenda Rees Glenda Rees (http://www.flickr.com/photos/nzsamphotofanatic/)

This small, dainty coastal tern is the most threatened of New Zealand’s endemic birds. The relict population of fewer than a dozen pairs survives between Whangarei in the north and Auckland to the south. The tiny population is gravely threatened by introduced predators and human disturbance and encroachment. They are intensively managed during the breeding season.

Identification

The fairy tern is a small tern with pale grey upperparts and white underparts, with the rump and forked tail also white. The wings have black on the outer primary only. Breeding adults have a completely yellow-orange bill, and a black cap covering the crown and nape. The cap extends forward to surround the eye, forming an irregular patch in front of it, but never reaching the bill. A rounded white ‘notch’ projects into the black cap above the eye, and is contiguous with the white forehead. The legs are bright orange. In late summer, black appears on the base of the bill, nostrils then tip, whilst the black cap recedes, leaving the forecrown mottled. The black feathering forward of the eye reduces in extent, and the legs and bill become duller. Breeding plumage is regained from June onwards. The sexes are alike. Immature birds are similar to non-breeding adults. First winter birds have a pale grey crown and a black band from eye to eye around the back of the head. The bill is brown-black initially, with yellow-orange emerging before their first summer. The leading edge of the wing is dark, visible in flight and as a ‘carpal bar’ when the wings are folded. The legs are brown. This first winter plumage is easily confused with non-breeding little tern because, in addition to the above, first-year fairy terns have dark webs on several outer primaries, a feature shared with little tern.

Voice: high-pitched calls, often repeated, which render as ‘tiet, tiet’ or ‘kek, kek’. An alarm call, ‘zipt-zipt-zipt’ accompanies dive-bombing and defecation when nests or chicks are threatened.

Similar species: the fairy tern is very similar to the migratory little tern. Compared to little terns, fairy terns are stouter, with sturdier, relatively shorter legs and a more conical bill. The white ’notch’ above the eye in little tern breeding plumage is acutely angled, not rounded. Only in little tern breeding plumage does the black in front of the eye taper to the base of the chrome-yellow, black-tipped bill.

Distribution and habitat

Fairy terns are confined to Australia, New Zealand and New Caledonia, with endemic subspecies in each country. Fairy terns breed successfully at four sites only in New Zealand: Waipu sandspit, Mangawhai sandspit, Pakiri River mouth (one pair since 2003), and Papakanui sandspit on the southern headland of the Kaipara Harbour. They nest on exposed sand spits, clear of vegetation and large debris, and where shell accumulates above spring high water. Birds forage in adjacent estuaries or a short distance out to sea. Immediately post-breeding, east coast birds are known to forage over Slipper and Spectacle Lakes and regularly roost at Te Arai Stream-mouth, just south of Mangawhai. Birds of all ages frequent sheltered estuaries and harbours between Whangarei and Auckland, but mainly the Kaipara Harbour, where autumn and winter flocks can number 20 birds.

Population

There are currently c.40 fairy terns in New Zealand, with fewer than a dozen breeding pairs. A lack of breeding-age females is currently limiting the breeding population.

Threats and conservation

Fairy terns were once widespread around the North Island coast and at river mouths in the South Island. Some historical records are doubtful, as little terns were not recognised in New Zealand until the 1950s. Fairy tern range contracted during the 19th and 20th centuries due to introduced predators, modification of coastal habitats and human disturbance during breeding. These factors continue to threaten the remnant population. Conservation effort at breeding sites concentrates on predator control (including gulls and harriers), cordoning off nests to avoid human disturbance, and minimising development impacts. Breeding success is also frequently affected by environmental factors. High tides backed by onshore wind can inundate nests. Adverse weather can diminish foraging ability, causing desertion of eggs or death of chicks, and mobile sand dunes can cover nests.  When necessary, nests are intensively managed by gradual repositioning or by elevation or by sandbagging, to protect them from rapid sand movement in high winds or spring tides or storm surges. Pro-active enhancement of nest sites by removing vegetation and/or adding appropriately coloured shell, is increasingly undertaken prior to the breeding season, to encourage nesting in the safest possible locations. Some eggs are cross-fostered between pairs (via artificial incubation at Auckland Zoo) as an intervention for vulnerable nests. Public awareness and education is ongoing, especially among communities adjacent to fairy tern nesting areas. All sites are increasingly popular recreational destinations, and new recreational activities (e.g. kite-surfing) are reducing the area of undisturbed coastal waters available for fairy terns to forage. Pre-fledging chicks are individually colour banded to facilitate population monitoring and management. Supplementary feeding assisted with the full fledging of two chicks in 2014, following the loss of their male parent just before fledging.

Breeding

Fairy terns have a high degree of fidelity to mates, nest sites and foraging areas. Courtship begins in September, and egg-laying occurs from late October until early January. Females will relay if clutches or young chicks are lost early in the season. The female is supplementary-fed by the male before laying. The 1-2 well-camouflaged eggs are placed in an unlined scrape well away from vegetation or flotsam. Nest sites are in areas with predominantly white, grey and orange shells on sand, thereby aiding concealment of eggs, chicks and incubating adults. Nests are often at least 1 km apart; intraspecific aggression reduces fledging success when pairs try to nest in close proximity, e.g. 10 m apart. Females tend to take longer incubation shifts than males. The chicks are mobile from day one. If parents utter alarm calls, chicks freeze in situ, blending into the beach. Both parents guard and feed the young, with the male providing most food. Chicks fully fledge at about 30 days, and are fed with reducing frequency by their parents for another month while they learn to forage for themselves. By this time, most family groups have vacated their breeding estuaries.

Behaviour and ecology

Fairy terns forage by working against the tidal flow in estuaries, periodically hovering 5-15 m above the water surface. They shallow dive for prey, not totally immersing the body.

Fairy terns’ high tide roost sites are open areas of mud, sand, shell or sparsely vegetated salt marsh, and are used by other roosting shorebirds. Tidal heights determine site usage. Roosts are abandoned or adopted in response to natural or human-induced changes, including vegetation encroachment and disturbance.

Food

Fairy terns catch juvenile flounder, gobies, elvers and other small coastal or estuarine fish and shrimps. A regurgitated pellet retrieved at a Kaipara roost contained juvenile kahawai ear bones (Tom Trnski pers. comm.).

Weblinks

www.omahashorebirds.co.nz

http://en.wikipedia.org/wiki/New_Zealand_Fairy_Tern

http://www.doc.govt.nz/conservation/native-animals/birds/sea-and-shore-birds/nz-fairy-tern-tara-iti/

References

Heather, B.D.; Robertson, H.A. 1996. The field guide to the birds of New Zealand. Viking, Auckland.

Higgins, P.J.; Davies, S.J.J.F. (eds) 1996. Handbook of Australian, New Zealand, and Antarctic birds. Vol. 3, snipe to pigeons. Oxford University Press, Melbourne.

Lagnaz, E. 2012. Monitoring and management of shorebirds, Pakiri River mouth, 2011/2012, Department of Conservation internal report, Warkworth.

McKenzie, H.R.; Sibson, R.B. 1957. Does the little tern (Sterna albifrons) reach New Zealand? Notornis 7:174-182.

Preddey, J.M. 2008. Post-fledgling care of a juvenile New Zealandfairy tern (Sterna nereis davisae). Notornis 55: 159-161.

Zimmerman, R. 2011. NZ fairy tern monitoring report, Mangawhai Wildlife Refuge 2010-11 breeding season, Department of Conservation internal report, Whangarei.

Recommended citation

Pulham, G.; Wilson, D. 2013 [updated 2015]. Fairy tern. In Miskelly, C.M. (ed.) New Zealand Birds Online www.nzbirdsonline.org.nz

Fairy tern

Social structure
monogamous
Breeding season
  • Jul
  • Aug
  • Sep
  • Oct
  • Nov
  • Dec
  • Jan
  • Feb
  • Mar
  • Apr
  • May
  • Jun
Nest type
scrape
Nest description
Shallow scrape in sand-shell substrate.
Nest height (mean)
0 m
Maximum number of successful broods
1
Clutch size (min)
1
Clutch size (max)
2
Mean egg dimensions (length)
35 mm
Mean egg dimensions (width)
25 mm
Egg colour
Creamy grey with diffuse dark toned spots and blotches
Egg laying dates
  • Jul
  • Aug
  • Sep
  • Oct
  • Nov
  • Dec
  • Jan
  • Feb
  • Mar
  • Apr
  • May
  • Jun
Interval between eggs in a clutch
1-2 days days
Incubation behaviour
shared
Incubation length (mean)
23 days
Incubation length (min)
22 days
Incubation length (max)
25 days
Nestling type
semi-precocial
Nestling period (mean)
4-5 days
Age at fledging (mean)
27 days
Age at fledging (min)
20 days
Age at fledging (max)
30 days
Age at independence (mean)
About 90 days
Age at independence (min)
60 days
Age at first breeding (typical)
3-4 years
Age at first breeding (min)
2 years
Maximum longevity
18 years and 10 months (banded)
Maximum dispersal
455 km

Fairy tern

Breeding season
  • Jul
  • Aug
  • Sep
  • Oct
  • Nov
  • Dec
  • Jan
  • Feb
  • Mar
  • Apr
  • May
  • Jun
Egg laying dates
  • Jul
  • Aug
  • Sep
  • Oct
  • Nov
  • Dec
  • Jan
  • Feb
  • Mar
  • Apr
  • May
  • Jun