Long-tailed Cuckoo – Part 1

Gerald McCormack, CINHT

The Long-tailed Cuckoo (Karavia, Urodynamis taitensis) winters in tropical Polynesia and migrates to New Zealand in October and November to breed by duping other birds to incubate its eggs and raise its young. This post explores its behaviour in the Cook Islands and New Zealand and the discovery that it is a migrant.

Tropical behaviour

Long-tailed Cuckoo, adult on branch and in flight – Cook Islands, Ātiu – Gerald McCormack 2010-04

The Long-tailed Cuckoo is dark brown with pale brown spots topside and white with brown streaks below; its conspicuously long tail is dark brown with pale brown bars.

In the tropics the cuckoo is solitary, secretive and inconspicuous except for the occasional loud screeching “wrrrrisssSST” call from high in trees. They are sometimes seen in fast direct flight between trees or slinking along tree branches in search of insects and lizards.

On Ātiu, twice in March and once in November, I have seen gregarious behaviour of small groups with much chasing associated with a rattling “chi-chi-chi-chi-chi-chi” call. The significance of this behaviour is unknown.

Nesting birds in the Cook Islands, such as the Rarotonga Flycatcher (Kākerōri, Pomarea dimidiata) and the Rimatara Lorikeet (Kura, Vini kuhlii) react very strongly to the presence of a cuckoo and chase it away. In New Zealand the cuckoo is a well-known predator on the eggs and nestlings of other birds and presumably they do the same here when the chance arises.

New Zealand behaviour

Each year the Long-tailed Cuckoo is first noticed in New Zealand in October and November. Although generally inconspicuous, they make their presence known with an occasional “wwrrrrissST” call while perched high in a tree or when flying. Around mid-November the males start to gather in small choral groups singing “wwwrrrissST” and “chi-chi-chi-chi-chi”  to attract females which are receptive from mid-November to mid-December. After mating the females go their own way, in search of food and a suitable nest into which they can lay an egg.

In the North Island the cuckoo lays exclusively in the cup-nest of the common Whitehead (Pōpokatea/ Pōpokotea, Mohoua albicilla), while in the South Island they lay mainly in the cup-nest of the common Brown Creeper (Pipipi, Mohoua novaeseelandiae) and also into the tree-hole-nest of the endangered Yellowhead (Mōhua, Mohoua ochrocephala). These closely-related bush birds are tiny compared to the cuckoo – a mere 15cm long and 20g versus 40cm long and 130g.

The cuckoo approaches the nest of prospective adoptive parents with stealth, for if they detect her they are alarmed and chase her away – only to have her sneak back again and again. The host nest usually has 2-4 eggs; the cuckoo lays directly into the nest and its egg is usually not noticed because it is similar in colour, even if significantly larger (23x17mm compared to 20x15mm). It is not known if the Long-tailed Cuckoo uses its beak to remove one of the host’s eggs before laying, as is known for some other species of cuckoo.

The cuckoo egg hatches in 16 days and the nestling is an aggressive beggar for food and grows rapidly. As soon as possible it pushes the host’s eggs or hatchlings out of the nest. The adoptive parents struggle to keep up with its demand for food. They must be relieved when after three weeks the nestling leaves the nest, only to discover that it will sit on a nearby branch demanding to be fed for another month. At this stage it is six times the size of its foster parents and it is ready to fly away to find its own food. In total, the small birds worked for nine weeks to get rid of their super-sized foster child and it is then too late in the season to have a family of their own.

The mystery bird

Māori and early naturalists in New Zealand were very aware that the two cuckoos – the Shining Cuckoo (Pīpīwharauroa, Chalcites lucidus) and Long-tailed Cuckoo – appeared in Spring and disappeared for the winter.

The cuckoos were well-known to Māori as the  joyful harbinger of Spring. But where they went for winter was a mystery. There was a widespread belief that the cuckoos buried themselves for the winter – in riverbed mud, in holes in Puriri (Vitex lucens) trees, or in rock crevices. Some believed that when buried they transformed into lizards and they reversed the process in Spring. There was no suggestion that the cuckoos arrived and departed over the ocean.

By the 1850s, New Zealand ornithologists increasingly believed that the cuckoos were tropical migrants. In contrast, overseas biologists were less convinced as we see in 1876 when the great Alfred Wallace, cofounder of the theory of evolution with Darwin, wrote that New Zealand ornithologists had “insufficient evidence” to prove that the cuckoos migrated over a thousand miles of open ocean, which he thought was “extremely improbable”. Undaunted, two years later, in 1878 Walter Buller declared in his Royal Society paper that the Long-tailed Cuckoo “migrates every winter to the Society Islands”. In the 1888 classic “The History of the Birds of New Zealand”, Buller mentioned the cuckoo in Fiji, Samoa, Tonga, Societies and Marquesas and declared that it migrated to New Zealand.

Hutton in 1901 and Fulton in 1903 both presented a wide range of scientific evidence before the Royal Society and established beyond reasonable doubt that the Long-tailed Cuckoo migrates between New Zealand and the islands of the tropical Pacific.

Meanwhile on islands in the tropical Pacific some of the collectors of cuckoo specimens, including immatures, were claiming the bird bred in the tropics. As late as 1917, the renowned American ornithologist Alfred Wetmore accepted the claims that the cuckoo bred in the tropics, and with further support from a difference of plumage colour he proposed two subspecies: Urodynamis taitensis taitensis breeding in the tropical Pacific islands, and Urodynamis taitensis pheletes breeding in New Zealand.

Figure 1: Winter and summer ranges for the Long-tailed Cuckoo throughout the Pacific

Finally, in 1937 Bogert undertook an extensive study of specimens and established the modern understanding of the migration and wintering distribution of the Long-tailed Cuckoo.

After breeding in New Zealand the adult cuckoos leave during January and February to migrate to the tropical islands of the Pacific, mainly to the islands of Fiji, Samoa, Tonga, Cook Islands, the Australs and Societies which are 3000 to 4000km from North Island. In many cases they are thought to undertake a direct overwater flight – the longest of any landbird.

The cuckoo has been recorded in New Zealand flying 80km/hr and if we assume it can sustain a modest 50km/hr during migration, it would take two-and-a-half days to fly the 3,000km to Rarotonga. With the initial support of the common westerlies it probably transits in less than two days.

Some cuckoos migrate much further afield to Micronesia in the west and the Marquesas and Pitcairn in the east, 5,000 to 6,000km from New Zealand. Future satellite tracking would show if they island-hop or fly direct.

The young cuckoos leave New Zealand in March and April and migrate by themselves northward to the tropical islands using inherited knowledge. Recent evidence shows that young cuckoos do not just fly north and stop at the first island. Their knowledge enables them to migrate to the full adult wintering distribution from Micronesia to French Polynesia.  Amazing.

The juvenile birds have conspicuous cream spots above and a pale brown underside; by September most have changed into adult plumage. It is not known how many first year birds accompany the breeding adults south in October and November, but it is thought that the adults in the tropics during the summer are first-year birds which will migrate to breed in their second year.

The migration story took a surprising twist in 2012 when Gill and Hauber undertook a new study of specimens and observations. They concluded that many cuckoos in tropical Eastern Polynesia, such as the Cook Islands, do not migrate directly southwest to New Zealand. Beginning in June they use the persistent Southeast Trades to move westward to Samoa, Tonga and Fiji and it is from there that they migrate to New Zealand in October and November thereby avoiding the unfavourable westerlies below 30°S.