North Island saddleback

The North Island saddleback (Philesturnus rufusater) is a forest-dwelling passerine bird, endemic to the North Island of New Zealand. It is also known in Māori as the tīeke.[2] It was formerly considered conspecific with the South Island saddleback.[3] The IUCN lists the species as Near Threatened, while it is listed as a "recovering" species in the New Zealand Threat Classification System.[1][4]

North Island saddleback
North Island saddleback, Zealandia (wildlife sanctuary)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Callaeidae
Genus: Philesturnus
Species:
P. rufusater
Binomial name
Philesturnus rufusater
(Lesson, 1828)
  Islands and sanctuaries where North Island saddlebacks are present
Synonyms

Philesturnus carunculatus rufusater

Taxonomy and systematics

René Lesson first described the species in 1828 from a specimen collected in the Bay of Islands four years earlier, using the binomial name Icterus rufusater.[5][6] The specific name rufusater refers to the saddleback's plumage - a combination of the Latin words rufus 'reddish-brown', and ater 'black'.[7] Their placement in the genus Icterus has since been revised, and the two saddleback species are now in their own separate genus, Philesturnus. This genus, created by Isidore Geoffroy Saint-Hilaire in 1832, comes from a portmanteau of two bird genera - Philemon (friarbirds) and Sturnus (starlings).[8]

Historically, there has been some uncertainty over the status of the North Island saddleback as its own species. North Island and South Island saddlebacks were formerly considered to be two subspecies of Philesturnus carunculatus, with the North Island subspecies being designated P. c. rufusater.[3] However, today they are generally considered to be separate species, with the North Island saddlebacks having the binomial Philesturnus rufusater.[9]

Description

The plumage of North Island saddlebacks is mostly black apart from the saddle, rump, and tail coverts, which are chestnut.[3] North Island saddlebacks are distinguished from South Island saddlebacks by a faint yellow lining on the superior edge of the saddle. The black bill is starling-like, with orange-red wattles hanging from its base.[10] North Island saddlebacks have an average length of 25 cm.[3] Males tend to be heavier (80 g) than females (69 g), and possess longer bills and larger wattles.[11] North Island saddlebacks produce calls described as "cheet, te-te-te-te" or "ti-e-ke-ke-ke-ke".[2][3] The Māori name for the bird, tīeke, is derived from the sound of this call.[2]

Distribution and habitat

North Island saddlebacks naturally occupy lowland broadleaf and coastal evergreen forests, though as a result of translocations, they are now also found in various other forest environments.[10] Before the arrival of humans, North Island saddlebacks were widespread on mainland North Island.[12] However, a combination of deforestation and introduced mammalian predators decimated these populations, and by the 1890s, the mainland population was eliminated, and the remaining North Island saddlebacks were only found on Hen Island, a small island off the coast of Northland.[10][12]

Translocations
An artificial nest box for North Island saddleback at Zealandia

Translocation efforts by the New Zealand Wildlife Service began in 1964, with birds being transported to Whatapuke Island. Further translocations have resulted in the North Island saddleback occupying various islands offshore (and onshore, at Lake Rotorua):[10]

North Island saddlebacks were first re-introduced to the mainland in 2002, at the Karori Wildlife Sanctuary (now known as Zealandia) in Wellington.[14] Some saddlebacks have since started breeding outside of the predator-proof sanctuary.[14][15] Saddlebacks have also been introduced at several other mainland sanctuaries.[13] The total population of North Island saddlebacks (as of 2013) is estimated to be at least 7,000.[1]

Behaviour and ecology

Breeding

North Island saddlebacks are monogamous and usually mate for life. The breeding season can vary from year to year and location to location, though clutches typically start appearing from August to April.[10] Fledgling saddlebacks are often seen until March and April.[10] Saddleback nests are mostly built in tree cavities, and will lay up to four eggs per clutch.[10]

Food and feeding
Saddleback feeding on nectar from a plant.

The diet of North Island saddlebacks mostly consists of insects, berries, invertebrates, and nectar.[10] Their bill allows them to force open dead wood to expose insects such as grubs.[16] In forests, saddlebacks forage at all heights, but tend to spend most of the time on the forest floor browsing in leaf litter.[3][10]

Threats

Introduced mammalian predators, particularly brown rats, were the primary cause of the North Island saddleback's extinction from mainland New Zealand.[10] Saddlebacks are particularly susceptible to predation because of their tendency to roost and nest in low-lying areas.[17] Several translocations of North Island saddlebacks were made to Kapiti Island between 1981 and 1990, but the population suffered high mortality due to rat predation (rats were not eradicated until 1998).[17] Today, North Island saddleback populations are usually found on predator-free islands and in sanctuaries protected by pest fences, affording the birds protection from these predators. North Island saddlebacks appear to be capable of co-existing with some predators such as the kiore, possibly because they have had a longer history of cohabitation than with brown and black rats.[18] Current efforts are focused towards exterminating pests surrounding mainland sanctuaries, to allow the saddlebacks to successfully expand outside of the sanctuaries.[14]

South Island saddlebacks have been affected by avian malaria and avian pox; this has not yet spread to the North Island saddlebacks, but there are concerns that it may do so in the future.[19][1]

References
  1. BirdLife International (2016). "Philesturnus rufusater". IUCN Red List of Threatened Species. 2016: e.T103730503A104102989. doi:10.2305/IUCN.UK.2016-3.RLTS.T103730503A104102989.en.
  2. "Tīeke / North Island saddleback". Auckland Zoo. Retrieved 1 February 2018.
  3. Heather, Barrie & Robertson, Hugh (1996). The Field Guide to the Birds of New Zealand. Viking. pp. 418–419. ISBN 0-670-86911-2.
  4. Robertson, Hugh A.; Baird, Karen; Dowding, John E.; Elliott, Graeme P.; Hitchmough, Rodney A.; Miskelly, Colin M.; McArthur, Nikki; O'Donnell, Colin F. J.; Sagar, Paul M.; Scofield, R. Paul; Taylor, Graeme A. (2017). New Zealand Threat Classification Series (PDF) (Report). 19. Wellington, New Zealand: Department of Conservation.
  5. Watola, George V. (2011) [2008]. The Discovery of New Zealand’s Birds (PDF) (2nd ed.). Orewa, New Zealand: Arun Books. p. 196.
  6. "North Island Saddleback (Philesturnus rufusater)". Handbook of the Birds of the World Alive. Lynx Edicions. Retrieved 1 February 2018.
  7. Jobling, James A. "Rufusater". Handbook of the Birds of the World Alive. Lynx Edicions. Retrieved 1 February 2018.
  8. Jobling, James A. "Philesturnus". Handbook of the Birds of the World Alive. Lynx Edicions. Retrieved 1 February 2018.
  9. Holdaway, Richard N.; Worthy, Trevor H.; Tennyson, Alan J. D. (2001). "A working list of breeding bird species of the New Zealand region at first human contact". New Zealand Journal of Zoology. 28 (2): 119–187. doi:10.1080/03014223.2001.9518262.
  10. Higgins, P. J.; Peter, J. M. & Cowling, S. J., eds. (2006). Handbook of Australian, New Zealand & Antarctic Birds. 7: Boatbill to starlings. Oxford University Press. pp. 986–1013. ISBN 9780195530681.
  11. Jenkins, P. F.; Veitch, C. R. (1991). "Sexual dimorphism and age determination in the North Island saddleback (Philesturnus carunculatus rufaster)". New Zealand Journal of Zoology. 18 (4): 445–450. doi:10.1080/03014223.1991.10422851.
  12. "Saddleback/tīeke: New Zealand native land birds". Department of Conservation. Retrieved 1 February 2018.
  13. "North Island saddleback". New Zealand Birds Online. Retrieved 1 February 2018.
  14. Swinnen, Lucy (26 May 2017). "Moment of truth for tieke reintroduced to Wellington's urban environment from Zealandia". Stuff.co.nz. Retrieved 1 February 2018.
  15. "Rare saddleback chicks found in Polhill Gully". Wellington City Council. 10 November 2014. Retrieved 1 February 2018.
  16. Troup, Christina. "Small forest birds - Saddlebacks and stitchbirds". Te Ara. Retrieved 1 February 2018.
  17. Lovegrove, T. G. (1996). "A comparison of the effects of predation by Norway (Rattus norvegicus) and Polynesian rats (R. exulans) on the Saddleback (Philesturnus carunculatus)". Notornis. 43 (2): 91–112.
  18. Hooson, Scott; Jamieson, Ian G. (2003). "The distribution and current status of New Zealand Saddleback Philesturnus carunculatus". Bird Conservation International. 13: 79–95. doi:10.1017/S0959270903003083.
  19. Hale, Katrina A. (2008). Disease outbreak amongst South Island saddlebacks (Philesturnus carunculatus carunculatus) on Long Island (PDF) (Report). Wellington, New Zealand: Department of Conservation. Archived from the original (PDF) on 2018-02-01. Retrieved 2018-02-01.
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