Fact 41
Many osprey populations around the world migrate. Those that breed in the northern countries across Europe, Russia, Canada and the US and migrate thousands of miles south for the winter.
Fact 42
Ospreys leave northern breeding grounds in case it gets too cold and the water they fish in freezes over. The Thames, The Volga, The Rhine, The Danube, Hudson Bay, Niagara Falls - all freeze over during severe winter weather and if they did while the ospreys were there, the osprey would vanish almost overnight.
Fact 43
Also, fish tend to be deeper in the water during the colder months and there are a lot less hours of daylight to try and catch them. In fact, in some of the most northerly osprey nesting sites the sun doesn't rise above the horizon for a few weeks in mid winter.
Fact 44
So why don't ospreys stay somewhere warm all year around? There are more ground and avian predators as well as much more competition for food. The soaring temperatures could kill chicks - for the first few days their thermoregulatory abilities are quite poor and they depend on their parents to keep them cool. There are also the extreme monsoon rains to contend with (we are convinced Dulas died in a tropical storm event in 2012).
Fact 45
Not all ospreys migrate. In warmer areas like Mexico, the Caribbean and UAE there are sedentary osprey populations. Migration is a reproductive strategy with advantages – good fishing grounds, fewer predators and cooler temperatures, and disadvantages – the energy expended, getting lost or blown off course. For these sedentary populations the benefits of staying put outweigh the downside of being in a warmer environment.
Fact 46
British ospreys tend to migrate to West Africa – to countries like Mali, Senegal, Gambia, Mauritania. In breeding populations, the females tend to go first, followed by the fledglings and finally the father, although this is not always the case. Males tend to arrive slightly earlier than females the following March/April but again, this is not always the case.
Fact 47
Not all British ospreys go to Africa. Some only go to Spain, Portugal and even France. In January 2012, Spain's Ministry of Agriculture, Fisheries and Environment reported a population of 77 ospreys in Andalusia and that this population was stable.
Fact 48
Scandinavian ospreys and eastern European birds tend to migrate to South Africa and East Africa. Russian birds tend to migrate to Asian countries. Canadian and North American ospreys tend to migrate to south American countries. Basically, northern ospreys tend to migrate directly south of where they breed.
Fact 49
2012 Dyfi chick, Ceulan, holds the record for one of the fastest migrations of a UK osprey that we know of. He left the Dyfi on Monday (Sept 3rd) - he was in Senegal on the Saturday the following week - over 3,000 miles in just 12 days, and five of those over desert. He was 97 days old starting his migration!
Fact 50
Pairs do not remain together outside the breeding season, but the same pair will often breed together at the same nest in subsequent years.