Friday, 7 January 2011
Discovering more migration wonders
It is a pretty wet and windy start to the year here in Extremadura. Traditionally in Spain children receive their Christmas presents on the morning of 6th January, having left out milk and biscuits the previous evening for the Three Kings of the Orient (Los Reyes Magos). Many families will have congregated in town squares across Spain on the evening of the 5th to watch the horseback procession, along with decorated floats, accompanying the arrival of the Magi to the town. In nearby Trujillo, the Three Kings bring gifts to a Nativity Scene where children portray the roles of Mary, Joseph and shepherds, with Mary carrying a real baby. After a welcome from the mayor, the Kings give a short speech and then the children from the town line-up to receive bags of sweets, before heading back home looking forward to their presents the following morning. This year a downpour soaked everyone in the square just as the Three Kings arrived.
I have been making best use of the bad weather to catch-up on lots of chores in-doors, paperwork and enjoying some reading by the log fire. Yesterday I came across a fascinating article about one of our most enchanting birds here, the Lesser Kestrel. Apart from the occasional bird which stays here in the winter, Lesser Kestrels are now all south of the Sahara, on their wintering grounds in Senegal, Mali and Mauritania. They are an early migrant back here in the spring. By February one can hear their soft "chi-chi-chi" call as they drift over the rooftops in Trujillo. In the most recent issue of Ibis, the journal of the British Ornithologists Union (2011. 153: 154-164), an international team of scientists describes a study of Lesser Kestrels which breed in southern Portugal. They attached light-weight devices onto some of the birds in the summer which record the daylight pattern everyday. Using this information, the researchers are able to determine the daily location of each marked individual. This information is retrieved when the birds are recaptured on their return the following spring. These devices are cheaper and smaller than those used for tracking by satellite, and so much more appropriate for small and medium-sized birds.
The results were very interesting. We knew that there was some dispersal of juvenile birds from colonies after the breeding season, with some birds moving northwards into Spain in search of food, but this study showed that some adults too travel as far as north-east Spain from southern Portugal. Most amazing was the information on journey time for their main migration. These birds were taking on average 4.8 days to travel from the Iberian peninsular to West Africa in the autumn (an average of 600kms a day!) whilst in the spring, they return from West Africa to southern Portugal in just over four days (4.1 days on average), clocking up 650 kms per day! In the winter they are known to form large roosts and the article cited the discovery by French ornithologists of a roost in Senegal holding no fewer than 28,000 Lesser Kestrels. This represents somewhere between 30% and 50% of the entire Western Europan population! I remember visiting a much smaller roost of Lesser Kestrel in southern Ethiopia a few years ago, watching the birds seemingly appear out of nowhere out of the sky as the sun was setting.
We certainly live in interesting times regarding the discoveries being made thanks to the tracking of individual birds on migration. This new techology is making us revise many of our assumptions on the way in which birds behave on migration and make us marvel at the extraordinary journeys they make. I will certainly welcome back our Lesser Kestrels in a few weeks time with a sense of wonder.