Our strange winter visitor, the cuckoo (aleva)
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| Used with permission from Dick Watling from “Birds of Fiji, Tonga and Samoa” and “Birds of Fiji and Western Polynesia” (Pacificbirds.com). |
The aleva or Long-tailed Cuckoo is a very odd bird, no doubt about it. For one thing, when the weather starts to get cold in its summer home, the aleva migrates north for the winter. For another, it has a highly unusual home life: it doesn't build its own nest or care for its own young, but abandons its eggs in the nests of other birds, to be raised not only by strangers, but by completely different kinds of birds. The aleva lives and breeds in New Zealand for half of the year. But when winter approaches, around March or April, the aleva leaves its chilly home islands, and flies north into sunny Polynesia. In fact, it is the only land bird to migrate north to spend the winter with us (although a few aleva may be found here year-round). The aleva's winter range extends all the way from Palau on the west to Pitcairn Island on the east, but the largest numbers winter in Fiji, Samoa, and Tonga. Here it can be found on any island, from the mountainous interiors of the largest high islands to the coastal vegetation of tiny atolls. Wherever it ends up, the aleva feeds mostly on large insects, including caterpillars and stick insects, but also small lizards.
The aleva is a hard bird to see, usually creeping without a sound through dense foliage. In fact, we most often see aleva because they are being chased by other birds, especially the iao (Wattled Honeyeater). Iao seem to hate aleva, and chase them vigorously, with loud scolding cries. It is very interesting to try to figure out why they do this. There are at least three possibilities. It may be that aleva will eat eggs if they get the chance; however, this has never been observed. Second, in flight the aleva looks much like a hawk, with its pointed wings and long tail. Perhaps iao mistake the aleva for a hawk, and think they are chasing a dangerous predator away. But there are no hawks in Samoa. Therefore, this explanation would mean that iao still have an instinctive fear of hawk-like birds thousands of years after they last saw a hawk (which was probably when the ancestors of our iao came here from Fiji). The last explanation seems even more far-fetched. This is that the iao chases the aleva because it is afraid that the cuckoo will lay its eggs in the iao's nest. To understand this possibility, we must discuss the strange breeding behavior of the aleva.
Like many other members of the cuckoo family, the aleva is a nest parasite. This means that it secretly lays its eggs in other birds' nests. The unlucky host birds think that the cuckoo egg is their own, and raise it alongside their own babies. Usually the baby cuckoo is much larger than the babies of its hosts, who are unable to compete and starve to death. Many New Zealand birds, including honeyeaters related to the iao, recognize the aleva and chase it away. This makes a lot of sense in New Zealand, where the aleva breeds. But the aleva never breeds on its wintering grounds in Polynesia. Therefore, the iao has no reason to fear that the aleva will lay eggs in its nest. Could there be an instinctive hatred of cuckoos in all members of the honeyeater family? Like many questions in biology, this one would be hard to answer, but it's still fun to think about.
Many older Samoans say that aleva used to be much more common than they are today. The aleva is now a rare sight on Tutuila. It's hard to know just how rare the bird really is because of its secretive habits. If you see one, consider yourself lucky, and take a moment to think about the many mysteries in the life of this strange visitor to our shores.
Pepper Trail, DMWR