Nature Studies by Michael McCarthy: Cuckoo-style decision-making is a thing of wonder

On his way to Africa, Indy did something astonishing

Imagine this. You're piloting, solo, a light plane from Italy to Africa, over the Mediterranean, during the night, and when dawn comes up you still can't see the African coast which is nearly 100 miles away, and you check your fuel supply and realise you may not have enough left to make it… so what do you do?

Such was the dilemma faced 10 days ago by Indy, the cuckoo adopted this summer by The Independent, on his 5,000-mile migratory journey to his African wintering grounds; and what he did was astonishing.

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Ringed in Central Wales on 30 May and fitted with a lightweight satellite transmitter by scientists from the British Trust for Ornithology, as part of BTO research into the cuckoo's decline in Britain, Indy subsequently left for Africa via France, and in early July he reached the wooded valley of the River Po in northern Italy, where he spent the next three weeks feeding. He was taking on fuel to get him over the really testing bits of his journey, the crossing-in-one-go of the Mediterranean, and then the similar traverse of the Sahara. But he may not have taken on enough.

For when dawn broke on 23 July, Indy was Africa-bound over the sea, 200 miles out from Sicily and still nearly 100 miles from the Libyan coast, when he did something, as his satellite tag showed, which amazed the BTO scientists: he turned back.

High above the waves, about 5am BST, he did a 180-degree U-turn, and headed back the way he had come, eventually making landfall north of Rome, where he rested for a day; then he flew all the way back to his previous "pit-stop" in the Po valley, completing a round trip to nowhere of 1,700 miles. And he's still there, taking on fuel once again, because he's got to get to Africa: no food for cuckoos in a European winter.

To me as a non-scientist, Indy's U-turn, two-thirds of the way across the Med, looks like something scarcely believable: a rational choice, as if thought-processes were involved. He took a decision and suddenly said to himself: sod this, I'm going back.

The BTO's Dr Chris Hewson doesn't believe reason was involved. He thinks Indy sensed his strength failing, and about-turned in a survival response conditioned by millions of years of evolution. The astounding thing for Dr Hewson is that Indy then flew the 850 miles all the way back to the Po. "That was completely gobsmacking, to be honest," Dr Hewson said. "But it may be an evolutionary rule for these circumstances, such as 'go back to last good feeding place'. Even all that distance away, it may be a better survival strategy than looking for a new one. At any rate, we will know if it was the right decision, if he makes it back to Africa in the end."

Tough life, isn't it, for migratory birds? Fill up, Indy. Fill up till the dial says Full.

m.mccarthy@independent.co.uk; twitter.com/@mjpmccarthy