Since my last Nature Notes on 18th May I have received enthusiastic confirmation that cuckoos have arrived on Ilkley Moor albeit slightly later than usual. This is especially reassuring as we know cuckoo numbers are declining in England – though holding up in Scotland, apparently. It’s difficult to pinpoint reasons for decline of long-distance migrants; there are so many dangers en route – weather conditions, climate change causing serious alterations in already challenging terrain, human interference through agriculture, building or direct persecution like hunting or trapping – all across vast swathes of sparsely populated land and, of course, sea. Few eager bird spotters!
Some encouraging news reached me last week from the British Trust for Ornithology. In 2011 a research project was set up whereby tiny radio transmitters were fitted to young male cuckoos. This enabled them to be tracked on their journeys to the Congo rain forest where they spend our winter and back here again. It’s salutary to be reminded that “our” cuckoos actually spend only 15% of the year here. They spend 38% in their African home and the rest of the time in travelling. Interestingly, while it takes them 2 months to get here in Spring, they spend 4 months on the return trip. All that rush to breed is over and they can take their time! It still amazes me that each youngster has to find its own way – no reassuring flock to follow or parent to teach how to do it. Parents are long gone – some leaving as early as the end of June – well before the nestling is ready to fly We may be finding out lots about the “where” of cuckoo migration: the “how” remains more mysterious. And it’s not an exact science, the BTO newsletter reported that of the five named cuckoos you could follow on the internet, four had returned to their home range and one (David) had been lost. Disaster may have struck poor David, or, perhaps, his transmitter battery had given out. Let’s hope it was the latter. Meanwhile, even smaller transmitters have been developed, each weighing less than a 5p piece, and it’s planned to tag an additional 50 new birds this season.
New technology is being used to find answers to many vital questions, and it’s not a one-way street. Narwhals are being recruited to assist in research into ice melt and ocean temperatures around Greenland. Fitted with thermometers, they will transmit data via satellite as they feed around the calving ice caps: information vital for our understanding of global warming and all our futures.