Some birds can’t wait to get back to Africa, and it seems the cuckoos are leading the race. Unfortunately, the reality here is that many species have advanced their migration departure dates due to climate change; it’s warmer, so it seems like the season is more advanced, so off they go.
A couple of years ago I happened upon an amazing website that tracks Common Cuckoos via GPS. Micro-transmitters are attached to the birds and their daily movements are logged. The website uploads daily updates on the cuckoos’ migration progress, providing fascinating insights into the mechanisms of migration.
The crux of the route for many bird species is that rather large tract of inhospitable land known as the Sahara Desert. Barren, to say the least, it’s imperative that birds like cuckoos spend as little time as possible moving through this area of limited resources, and the cuckoos get around the problem by simply flying across the whole thing in as little as 24 hours. A two or three day hop at the most sees them south of the desert lands and into areas of higher resources where they can replenish what can only be severely depleted energy reserves after such a taxing flight. This is an absolutely staggering feat when you consider that the Sahara is wider than 2000km along its western edge, where the majority of these cuckoos are flying.
Studies have shown that cuckoos favour one of two routes down to Africa; the western route which brings them down through Spain and further south through Morocco or Algeria, and an eastern route which has them descending through Italy and the Balkans and then making a slightly longer hop across the Mediterranean into Libya before heading further south across the desert.
Owing to declines in the cuckoo population in the UK, the study aimed to determine which route was more dangerous for the birds, and where most fatalities were occurring. Interestingly enough, it was before the hazardous desert crossing that most deaths were recorded, which pointed strongly towards changing conditions in the areas in which the cuckoos were stocking up on food supplies before the big leg to West Africa. The main food source of cuckoos is the caterpillars of certain moth species, and it may well be a decline in these numbers that is having a knock-on effect on the cuckoo populations.
I’m a bit irritated with myself, as every year I try to remember to start tracking the individuals before they begin their arduous journey, but I keep missing it. I’ll give myself a little leeway by assuming it’s because they are leaving earlier, but in fact I just assumed they would only be departing around the northern hemisphere Autumn (September). If you visit the website you will see that there are still a fair number of birds that are still in Europe, so we’ll be following their progress with interest.
Down at the opposite end of Africa, we’ve already had the first wave of migrants start to pop up at Londolozi.
It’s usually the Wahlberg’s Eagles and Yellow-Billed Kites that are the first to arrive here, but this year we’ve seen a slight change up with Lesser Striped Swallows, Greenshanks and some Sandpipers already being recorded. Maybe they’re also starting their migrations early.
The cuckoos will still take a couple of months to get here, but given their unbelievable cross-Sahara prowess, maybe we should expect some of them next week…