Osprey Migration Update – 6th December 2012

Blue YD continues to overwinter in Senegal and is enjoying the area of Doue, making regular trips to the river for some fresh fish and roosting assiduously in his favourite spots. But he is not the only British bird choosing Senegal as you can see in the map below. Roy Dennis currently has eight satellite-tracked ospreys: five of them are in Senegal (in red on map: Red 8T, Rothiemurchus, Fiddich, Fearna and Aigan); as well as Beatrice, wintering in the southeast of Spain, near Gibraltar; Stan, who is thought to have set off over the ocean from the Cape Verde Islands and failed to make landfall at the beginning of October; and Morven, a female Roy has been tracking since 2009 and whose transmitter is only working sporadically now. The last data received showed her flying over Morocco at the beginning of September. Dyfi Osprey Project  has two satellite-tracked ospreys: (in green on map)  Leri, a 2011 female with whom contact has been lost since October 2011; and Ceulan, this year’s juvenile holding the Guinness World Record for the fastest osprey migration to date (12 days!). And last but not least, our own at Loch of the Lowes (in blue on map) Blue YD, who currently winters in Senegal, and Blue 44, who we hope is currently wintering somewhere in Spain.

UK Ospreys in Africa 2012

Also satellite-tagged but not on this map are : Rutland Water’s  two ospreys from last year; one of them (AW) was lost last year in Africa, and the other one (09) died on migration in the Sahara Desert this year; Loch Garten had chicks Alba and Caledonia: the first is thought to be dead since they have received multiple data from the same point, and the latter is currently in Seville, Spain. The Lake District Osprey Project had Lucky 13 this year, whose transmitter stopped working at the beginning of September this year in Alicante, Spain.

If we take a closer look at the map, five of these birds have decided to winter in the River Senegal. Senegal is centrally located within the West African Marine Ecoregion (WAMER) which is the most important breeding site in the world for the highly endangered monk seal. Both Senegal and Gambia’s river basins are closely related and tend to be combined into a single ecoregion known as the Senegal-Gambia Catchment, sharing high species richness with three species of frogs and one species of fish endemic to the region. In the rainy season (June-October) the river has traditionally experienced devastating flooding, causing famine within the region and changed the ecology of the riparian system. In the dry season saltwater moves into the deltas of the Senegalese lowland coastal rivers forcing on the one hand strictly freshwater species to move inland, but supporting large migrant bird populations on the other. The fact that seawater penetrates far inland allows the growth of mangrove forests which also provide a great habitat for bird species.

West African Marine Ecoregion (Source WWF-WAMER, 2003)

As we have previously mentioned in the blog, in the 1970s and 80s an irrigation agricultural plan in the Senegal River Valley was developed by a partnership of three countries (Senegal, Mali and Mauritania) to minimise the negative impacts of flooding on the surrounding population by building two dams. Manantali Dam was built in 1988, located on the Mali branch of the Senegal River and controls 40-60% of the water flow. The intention was to expand irrigation and produce electricity in the Senegalese and Mauritania river valleys, but due to political and economic disagreements the dam only started producing electricity for Senegal, Mali and Mauritania in 2001. Diama Dam was built in 1986, located at the mouth of the Senegal River at St. Louis.  Although highly criticised due to its lack of planning and realistic development, the irrigation farming system created by both dams is an alternative to past practices. Nonetheless, a large amount of villages in the middle and upper river valley still depend on traditional flood recessions agriculture.

This continuous irrigation also brought a significant increase in waterborne diseases affecting both livestock and population, with the most appalling one being intestinal shistosomiasis (its host thrived in pools of freshwater newly created by the dams). Freshwater pools also brought along malaria and cholera and depletion of food resources, decimating native fish along the way. Other freshwater fish have gradually replaced the native fish species and fishing is the most important economic activity in Senegal. FAO estimated in 2011 that there were a total of 16,000 small fishing boats in Senegal.

West Africa’s high diversity of water related habitats (lagoons, high discharge rivers, hypersaline estuaries) results in a high diversity of estuarine fish species where the species richness (number of different species) mainly relies on the balance between marine-freshwater levels. Estuarine species are a main food source for local populations through the extended practice of artisanal fishery. Considering local consumption of fish is 28kg per person per year, twice the world average, and 75% of protein in the Senegalese diet comes from fish, it is not surprising ospreys tend to favour its grounds. It is an abundantly stock place to be! On a sad note though we should highlight the fact that Senegal stopped renewing agreements allowing European vessels into their waters in 2006. Thus, Senegalese fishermen (artisanal fishing boats in particular which account for 90% of Senegal fishing industry nowadays) enjoy exclusive fishing rights under lax regulations, which has led to habitat destruction and the disappearance of many species.

And with this, my last post of the year, my time at Loch of the Lowes comes to an end (at least for this year!). I have had a great time surrounded by lovely volunteers and very helpful staff that have helped me learn a lot about Lowes and other reserves, Scottish wildlife and history altogether. Thanks to everyone and hasta la vista!

Ainoa

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Blue YD continues to overwinter in Senegal and is enjoying the area of Doue, making regular trips to the river for some fresh fish and roosting assiduously in his favourite …

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