Long-tailed cuckoo with grey warbler

Long-tailed cuckoo with grey warbler

The long-tailed cuckoo (its young being fed here by a grey warbler) winters over in the Pacific Islands and flies south in spring. Polynesians would have noted the seasonal arrival and departure of the bird. They would have known it was heading towards land somewhere. This may have fuelled speculation about undiscovered islands in the vast Pacific Ocean.