The satellite tracking program still continues. Currently we focus on obtaining more detailed tracks by combining satellite telemetry with GPS technology. Nowadays we can follow migrating Ospreys in such detail that we can see exactly where they catch their fishes! A consequence of tracking only raptor birds is that one might get a somewhat biased view on migrating birds, as raptor birds only represent one type of migrant. One very typical aspect of raptor birds is that they frequently soar in thermals, a very energy efficient way of travelling. Even the small Hobby might be able to profit from these columns of raising air, although it is unknown to what extent. It would therefore be very interesting to track a species that does not soar, but still flies during the day. A species that is big enough to carry a 22g transmitter. That is how we ended up with Wood Pigeons.
The Wood Pigeon is a strong flyer that only flies during the day. They make considerable migrations; birds ringed in Sweden were recovered from wintering sites in France and Spain. In October, one can witness an impressive Wood Pigeon migration at Falsterbo, where flocks of sometimes thousands of birds congregate before the water crossing.
So the task was to catch 4 Wood Pigeons for GPS satellite transmitters. We decided to focus on birds breeding outside towns and villages as this presumably reduced the risk that we tag a bird that stays the winter in Sweden (small numbers of Wood Pigeons can be found in towns in the winter). The idea was catch them near the nest using mistnets. As we cannot easily raise the nets very high above the ground we were searching for nests in bushes or low in the trees. Early in the season a considerable number of suitable nests was found. However, at the time the transmitters had arrived all these ‘low nests’ had disappeared, and the pigeons were laughing at us from their safe nests high in the trees...
Marten on the pigeon nest, looking anxiously at frustrated pigeon catcher.
As the breeding season progressed it became more and more challenging to obtain birds. No birds were caught despite several attempts in Skåne and even near Grimsö. When we were visiting the bird observatory on Öland we explained for the young but experienced bird catchers that we were in need of Wood Pigeons. They unanimously reported that the Wood Pigeon is a very difficult species to catch. The last time Wood Pigeons were ringed at the station was almost 2 years ago... The next day we were out in the field, when we received a phone call that they had just caught two Wood Pigeons at the ringing station! We thus rushed back to apply transmitters on these birds. We are very grateful to the staff that they remembered us talking about pigeons and thus not had released the birds directly after ringing!
A happy researcher with the first Wood Pigeon with a satellite transmitter.
The very first results are already very interesting. The birds are commuting between some resting place at Ottenby and foraging fields just northeast of the area. The flight speeds are different from what we observe in raptor birds. The pigeons regularly fly about 60 km/h, which is in the upper range of flight speeds as we have recorded for raptor birds.
GPS locations for a Wood Pigeon on Öland. The birds rest in the southern forested area and feed on field in the north.