Tuesday, 25 January 2011

Winter gatherings

Spring-like weather last week has given way to bitingly cold easterly winds. Despite there being clumps of wild narcissus in flower in sheltered places and some almond blossom, we are still in winter here. Despite the arrival of House Martins and some Swallows, and even a Great Bustard starting some tentative paces in its courtship display, the birds too still have a winter feel about them. Hard weather in central Europe has brought an invasion of Goosanders to Spain and two have even reached Extremadura, for the first time ever. I saw a female swimming on the river running through the Monfragüe National Park last Sunday. But the most striking feature of birds in winter are the sheer numbers. Yesterday we watched a big flock of two or three hundred Corn Bunting rising from a stubble field as a male Merlin attacked. It had arrived almost un-noticed, mimicking a Mistle Thrush with a low gliding flight interspersed with rapid flaps. Then it accerated and dashed through the rising buntings,twisting and turning, swerving upwards. It did not manage to take a bunting - I am sure had we not been there, it would have dived for a second attempt. At the weekend I took part in a national survey of winter roosts of Herons and Egrets. A tiny clump of rather undistinguished willows in a tiny gravel pit, beside a road has been a roosting site for Cattle Egret, close to one of my favourite birding routes. I arrived late afternoon. There was nothing in the trees and just half a dozen egrets were feeding around some sheep. As the sun set, parties of Cattle Egrets started to arrive from all directions, mostly flying low and direct, some coming in from greater height and then tumbling down to land. They gathered on a small hummock next to the trees (see the photo) before taking some mysterious cue which made them take off and then literally stream into the trees, which become something of a swarming white, squawking mass. I estimated somewhere between 2250 and 2400 Cattle Egrets had arrived, along with over a hundred Little Egret and a single Glossy Ibis, which is a very unusual winter record. As the results came in from across the province, it became clear that this roost was by far and away the largest.

Wednesday, 12 January 2011

Le grand duc

There is something magnificently apt in the French name for the Eagle Owl - the Grand Duke - an aristocratic aloofness, mystery and power. I certainly sensed this yesterday evening, in the dusk after sunset, in a perfect still calm with the moon and Jupiter starting to shine above me. The first bats had emerged and the last vultures had reached their roost. There was silence. Then, almost inaudible, a muffled "oohu". The next call was louder, more resonent, appearing to come from the dark rocky massif in front of me, the gorge creating a perfect acoustic arena. Then another call, quickly followed by another. Clearly I was now listening to two birds calling to each other. Instinct told me to scan the top of the cliff, where the sharp crisp boundary between the dark rock and the evening sky was visible. And there it was, close to the highest point of all, a new shape that had not been there a few minutes earlier: a large body, rounded head and long "ear-tufts" sometimes sticking out horizontally, sometimes just catching the slightest wisp of a breeze. It slowly moved its head. Its mate was not visible perched, but obviously had been nearby because as I watched, the second bird appeared in flight and headed due south, making a long silent glide into the distance, its wingspan as large as a Grey Heron's. Its mate stayed put and was silent for a few minutes, before it gave a more nasal barking call, its body tilting forward as it did so. This told me that this was the female. She stopped and then took off, but unlike the her mate, flying in my direction, overhead and then landing on the rocks behind me. There she stood for a short while before taking off again and gliding off to the east.

Eagle Owls are top predators with a huge variety of prey including hares, Roe Deer fawns and buzzards. Here in Extremadura they are quite common and widespread, although no one really has a good idea of the population size, which is estimated at anywhere between 400 to 800 pairs. Although the call can be quite far-carrying, it is also easily swamped by other sounds such as traffic and the calling each winter evening does not usually last very long, so detecting Eagle Owls is not as easy as one might imagine. The attached photo was taken in the spring by a guest of ours,David Irven.

Yesterday evening there was no doubt, however, who the Le Grand Duc of the terrain was, staking out its territory from its lofty vantage point and challenging the silence with its haunting call.

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.