Cuckoos missing off the map24 Feb 2015
From time to time we ‘lose’ one or two of our Cuckoos only for them to reappear several days, or even weeks, later. We are never entirely sure why this might be at the individual level but during the course of the project we have noticed similarities between some of the ‘lost’ birds.
We have lost some of our birds just prior to them making a large movement and we think that this might be because they move into denser vegetation in order to feed up before embarking on a long flight. Moving into denser vegetation may mean that the solar panel that recharges the battery for the tag is in shade for periods of time and the battery receives a poorer charge, which in turn results in poorer performance from the satellite tag.
Once the birds have put on enough weight to begin their journey they move into the open and the tag begins charging again and the birds ‘reappear’. We also see the same thing happen, although to a lesser extent, when birds complete a long movement and presumably move into denser vegetation to rest and feed up