Due to some international aspirations on my end, this new blog-post is written in English. As it is not my native language, please bear with me on this one.
During our research in Amsterdam on breeding locations of the Common swifts (Apus apus), I always found the wintering stays of these migratory birds fascinating. During warm summer evenings, some streets seem packed with these fast screaming birds. Their departure at the end of July is very abrupt; more than half of the birds will not return overnight. Instead of returning to the breeding grounds, they fly Southbound in great groups. As of that point, the fieldwork season ends. Both a relieving and frightening moment for us as ecologists. I can imagine it feels the same for these birds, but let’s not anthropomorphize.
The global population of Common swifts is under pressure by several factors. I’ve el Policy and legislation on conserving this species in the breeding areas in Europe are now stricter than ever. However, the pre-existence of this species (and many other palearctic migrants) also depends on the habitat quality of the wintering areas. After spending the breeding season in Eurasia, the Swifts fly an average of 10.000 kilometres to the tropical forests in Africa to spend the winter. As geolocator research has revealed, the trajectory of these birds is somewhat straight to Western Africa. After reaching the tropical forests in Liberia, Ivory Coast and Ghana they gradually ‘descend’ to the Congo basin. Some even go as far as Mozambique, see figure 1.
During the beginning of April, the Swifts abruptly leave the Congo basin and fly in a straight line towards Western Africa. The dependency of this area is clear; the birds come here during their spring migration as a stopover to fatten-up before finishing their journey to the breeding grounds in Europe. As Wulf Gatter has observed, this stopover happens to coincide with an explosion of several species of termites. These insects are high in protein, and would be a perfect pre-migration snack so they can safely cross the Sahara towards the breeding grounds. After being fattened-up by the local cuisine, the Swifts leave Western Africa and fly with an astonishing average fly speed of 782 km a day.
So, Liberia, Ivory Coast and Ghana play a key role in the migratory strategy of these birds. However, these areas suffer from habitat degradation by deforestation and wrongful use of pesticides. This loss of habitat results in a lowered insect abundance, which in turn could negatively influence the survival of many migratory birds. Bottlenecks and threats need to be identified together with local authorities, so management can be applied to important bird areas. In March and April, I will visit Ghana where I hope to see Swifts. ‘My’ Common swifts should be in Ghana by then. But also several other species are present in Ghana. Like the Mottled swift (Tachymarptis aequatorialis), not member of the Apus genus, but closely related to the Alpine swift (T. melba). This is a huge swift, and supposed to be very fast. I will also meetup with some colleagues at the Ghana Wildlife Society in Accra, and talk about conservational issues.
I’ll try to keep you guys posted!