Flying Without a Map

The British population of the European Cuckoo has declined by 65 percent over the past 25 years. In an effort to find out what has been happening to the Cuckoos, the British Trust for Ornithology (BTO) attached minute radio transmitters to five Cuckoos from southeast England so that scientists could track their movements and find out what has been causing the drop in numbers. Using the technology, the ornithologists could track the birds and find out what migration routes they were following and when. One of these was Clement.

 To the surprise of the BTO researchers, who were expecting their subjects to start their fall migration in fall, their gadgetry picked up Clement’s transmitter happily beeping away in Africa in early July, having left England on June 3. His companions in the study — named Martin, Lyster, Caspar and Chris — were not far behind. This is far, far earlier than predicted or expected and possibly a consequence of climate change. It does mean that I now get to write about Cuckoos a couple of months earlier than I expected. So much for the predictability of nature.

For me, the most extraordinary thing about Cuckoo migration is not its length — many thousands of miles — nor the obstacles the birds face, the featureless expanse of the Mediterranean and the vast tracts of the Sahara Desert. Many migrants face similar challenges, and many are smaller than the European Cuckoo. It is estimated that the diminutive Lesser Whitethroat, a waif of barely 12 centimeters, will make the same journey from Northern Europe to Sub-Saharan Africa in less than a week. Neither is it the migration of the adult Cuckoos such as Clement and his colleagues; after all, they have experience, they have done it before. For me, the truly remarkable feature of Cuckoo migration is that of the juveniles making the incredible journey for the first time completely unaided.

The European Cuckoo is a brood parasite. The parent Cuckoos play absolutely no role in their offspring’s life. Having arrived on his breeding grounds, the male Cuckoo, such as Clement, will attract a female with that enigmatic and onomatopoeic call. The pair will mate and in a blow to romance go their separate ways. The female Cuckoo will then look for the nest of another bird — often a Meadow Pipit or Reed Warbler, though dozens of species have been recorded — and lay her egg in the nest of the unwitting host. So highly evolved has the relationship between parasite and host become that the eggs of any individual Cuckoo are colored and patterned similar to those of the host species. The Cuckoo egg also hatches more quickly than the eggs of the victim, and the first task of the newly hatched baby Cuckoo is to evict the legitimate eggs of the host parents out of the nest. That done, it has no competition for parental attention, and more importantly the food, of the surrogates.

The young Cuckoo grows rapidly and is frequently far larger than its supposed ‘parents.’ A Reed Warbler for instance is 13 centimeters long, the Meadow Pipit just a couple of centimeters longer, while the young Cuckoo reaches 36 centimeters. However the parental drive is so strong that the unwitting hosts continue feeding their monstrous pseudo-offspring as though it was their own. It grows and grows and then, as summer draws to a close, the fledgling Cuckoo’s instinct to migrate sets in and it will leave the nest of its step-parents and head south for Sub-Saharan wintering grounds as yet unseen or experienced. And this is what I find so utterly incredible.

Scientists have known for years that adult cuckoos migrate earlier than the juveniles — the BTO’s study has shown just how much earlier the adult migration takes place. But in fall the young Cuckoos will leave Europe and undergo their first migration with absolutely no parental guidance whatsoever and without ever even encountering another Cuckoo, after having been raised by completely unrelated and quite possibly non-migratory foster parents. To me it is truly astonishing.

So watch out for adult European Cuckoos passing through Egypt as of now. Then later the juveniles will follow. Look out for them, look and then marvel about how on earth they do it. And truly marvel because scientists have yet to crack the mystery.

Such feats of navigation are not confined to the bird world. Three species of sea turtle breed in Egypt. The Loggerhead Turtle is largely restricted to the Mediterranean coast including North Sinai, while the Green Turtle is also found along the Red Sea and the Hawksbill Turtle is confined to the Red Sea. All three nest in summer, the female burying her eggs in the sand on specific beaches before heading back out to sea. The young hatch all at once, triggered by the lunar cycle. The juvenile turtles burrow their way out of the sand and head instinctively for the ocean where they will spend the next few years of their life. The females, having mated, will return unaided yet unerringly to the same beach of their birth to themselves nest and for the cycle to continue.

Sadly, sea turtles worldwide are threatened and Egypt’s populations are no exception. The adults are hunted for food and for traditional medicine (Alexandria’s fish market has seen sea turtles being sold in the recent past). Those that feed largely on jelly fish such as the Leatherback Turtle, a rare visitor to Egyptian waters, are choked as they ingest plastic bags that clog the ocean doing passable impressions of their natural prey. Others are maimed by boat propellers. Many juveniles, at their most vulnerable, are preyed on by natural predators.

But perhaps the single biggest threat to sea turtles is the development of coastlines for tourism. The beaches are destroyed and disturbed as the hotels go up, but there is a more insidious threat. Research carried out in Greece and Turkey has shown that when the eggs hatch the young turtles head towards the hotel lights rather than to the sea, mistaking the garish illuminations of a 70s-themed disco night for the natural glimmer of moonlight on ocean. I cannot imagine a worse introduction to the world.