Aotearoa New Zealand is a long way from anywhere. Despite being 2,000 km from the nearest continent, vagrant land birds regularly find their way across the Tasman Sea – though some don’t quite make it. Bird curator Colin Miskelly describes the latest new species to come to grief on our shores.
Beach patrolling for dead seabirds
New Zealand has a great diversity and abundance of seabirds. Most spend their lives well away from mainland shores, breeding on remote islands and feeding over the open ocean. The only opportunity most of us have to see these birds up close is when they expire and wash ashore on beaches.
Birds New Zealand members regularly patrol sections of the coastline looking for dead seabirds, and contributing data to the long-running Beach Patrol Scheme.
The scheme provides information of patterns of mortality between seasons and over longer timeframes, as well as evidence of causes of mortality (including fisheries impacts), and occasional band recoveries or remains of rare species.
The Auckland west coast is a productive area for beach patrolling, and Birds New Zealand Auckland branch members aim to patrol a section of Muriwai Beach every month.
On 16 March last year, local organiser Ian McLean led a team of six members and friends on a patrol at the south end of Muriwai Beach, finding four dead seabirds of three species (white-capped mollymawk, fluttering shearwater | pakahā, and Australasian gannet | tākapu).
Remains of a mystery bird
On their return back down the beach, Ariel-Micaiah Wijaya and Miguel Mejias found the remains of an unusual small bird that had washed ashore on the receding tide – and it clearly wasn’t a seabird.
The reddish feathering initially led the team to suspect they had found a rufous fantail (an Australian species not known from New Zealand). However, closer inspection revealed it was a small cuckoo – and apparently a species previously unknown to New Zealand.
Two species of cuckoo breed in New Zealand (shining cuckoo | pīpīwharauroa and long-tailed cuckoo | koekoeā), and another four species occasionally find their way across the Tasman Sea (oriental cuckoo, pallid cuckoo, fan-tailed cuckoo, and channel-billed cuckoo). All four of these vagrant cuckoo species are much larger than the Muriwai bird, which appeared to be one of the bronze cuckoo group (of which the shining cuckoo is a member).
Forensic examination
Ian delivered the remains to Auckland Museum, where Brian Gill and Josie Galbraith compared it to specimens held there, and compared its measurements with published measurements of Australian species of bronze cuckoos (including little bronze-cuckoo, Gould’s bronze-cuckoo, and Horsfield’s bronze-cuckoo).
Several features of the Muriwai bird indicated it was a fledgling that had only recently left its host nest, including the presence of fleshy yellow flanges at the corner of the bill. This clarified why the bird lacked barring on the underparts (juvenile cuckoos are not as boldly patterned as adults) and why some of the bird’s measurements were smaller than expected.
Mystery solved
Measurements and plumage details revealed that the Muriwai cuckoo was a juvenile Horsfield’s bronze-cuckoo. A key difference from the similar little bronze-cuckoo was the presence of six white spots on the outer tail feathers (viewed from the underside). Little bronze-cuckoos have fewer (and larger) white spots.
Ian assembled the information on the Muriwai cuckoo into an Unusual Bird Report, and submitted it to the Birds New Zealand Records Appraisal Committee. Based on the images and measurements provided, the Records Appraisal Committee unanimously agreed that Horsfield’s bronze-cuckoo should be added to the New Zealand list.
Heading the wrong way
Horsfield’s bronze-cuckoos breed in southern Australia (including Tasmania), and migrate north in autumn. It is likely that this young bird got caught in westerly winds while attempting to migrate, possibly while crossing Bass Strait.
Other Australian land birds that have so far been recorded in New Zealand on a single occasion include white-winged triller (1969), black-faced monarch (1996), willie wagtail (1999), Australian reed warbler (2004), magpie-lark (2008), and rose-crowned fruit dove (2019).
Congratulations to Ian, Ariel-Micaiah and Miguel for their addition to this exclusive list.
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