We know that cuckoos nest over winter in the Congo and breed in Europe. UK cuckoos arrive in the latter part of April and lay their eggs in another bird’s nest. The common host of cuckoos are Reed warblers, Meadow pipits and even non-migratory Robins. The juveniles a month later in May. The fledgling casts out the other hatchlings and the hapless host continues to feed the cuckoo until it too flies away.
They fly individually with no parent to guide them all the way to the Congo (Cloud Cuckoo land?) for the winter.
There has been some great work done by the BTO tracking cuckoos from Norfolk. There are two principle routes: one goes down through Spain and across the Sahara and another down Italy.
It appears that the 4000 km journey down to the Congo is slower with stops off for food etc. The journey back is faster and more direct although a refuelling stop has been found in Ghana
How do they do this?
Quantum Mechanics is very happy that there has been a quantum data base recording everything since the beginning of time, a cosmic Google if you like. So, navigational information is stored there along with everything else.
Imagine that over the years cuckoos lay down their navigational routes linking their breeding grounds and wintering grounds. The more that these are used the stronger they become. Incidentally, any dowser would say that this is so because you can dowse these paths.
Now imagine this young fledgling gets fit enough to fly and rises into the air to go to Africa. Each starts from a different place but each must find out which way is the right way to go.
Now imagine the bird casting about for one of these imprinted ancestral routes. It finds one going the right way and follows it. There are turnings and places to stop and even if they get lost they cast around again and find the route again or find the one that they have lost again. Dowsers can do this too and when they are trained they can feel tracks.
An analogy might help here. You are a student, who has lost your maps and have no GPS. You live near London and must get to a wedding you have been invited to attend up North. You get into you car and cast around for a road that goes North. As you go along sometimes you get lost but you keep going, always looking for others who are dressed up for wedding. After a bit you dimly remember that the wedding is near York, you look for some way points and landmarks, meanwhile, you really start looking out for wedding goers. If you see one you follow them and hopefully get to the right wedding if not you circle again until you are lead to the right wedding
Obviously in this analogy the student is the cuckoo and the wedding is Cuckoo land (the Congo) and the others in wedding dress are other cuckoos who become more obvious the nearer you get to their winter home
The interesting bit is that Cuckoos like many migratory birds do not use the route that they took to arrive at their wintering grounds to go back to their breeding grounds. I feel that this is because they do exactly what they did on the way down to Africa and cast around for a ancestral route north again. When they find one, they follow it.
However, on the spring journey north, they are adults are returning to somewhere they know. When they get near where they will breed they remember this location, just like coming home and can be very accurate as to where they are going. This last part is neighbourhood knowledge probably encoded in the hippocampus area of the brain.
It is important to note that the cuckoos like other species rush to get to their breeding grounds in the spring to mark out territories and find breeding partners.