Ospreys can start breeding at the age of 3 years (except for a few exceptional cases), with the average age of first breeding recorded at 3.8 years in France. The more territories that are available in the region where the birds were born, the earlier they start to breed. However, if the best nests are already occupied by other Ospreys, young adults prefer to delay breeding rather than go further afield to seek new territories elsewhere. Continue reading Breeding
Remarkable fishers
Ospreys are the only diurnal raptor to feed almost entirely on live fish, and their fishing skills are legion. Flying or hovering high in the sky, they make spectacular dives into the water once a potential prey is spotted. With luck they will then snatch their fish with their enormous talons, firmly gripping it with their reversible toe. They generally take fish that either live in shallow water or at the top 10-20 cm of the water column, for example chub or roach. Unlike species like cormorants or grebes, Ospreys do not dive and swim underwater.
At times it seems that the fish is too large for the bird to carry, and there are even reports of an Osprey being unable to release a fish that is too heavy, causing the bird to drown. There are no documented cases of this actually happening, but the story is repeated in many places. We will believe it when we see it!
A fantastic video of an Osprey fishing can be seen here, showing the North American subspecies, which is not the same as the subspecies found in Europe (see taxonomy).
Where are Ospreys found today?
The Osprey, a cosmopolitan species subdivided into four sub-species, occurs in the Palearctic, North America, the Caribbean and Australia (see taxonomy). It is a migratory species which can be found on every continent except Antarctica. Nowadays the Palearctic sub-species has an irregular distribution, mainly occurring from Scotland to the west to the Kamchatka Peninsula and Japan to the east. While its European population is fairly large (with an estimate of about 10,000 pairs), this population is quite fragmented and has undergone strong declines and extinctions in the relatively recent past. Continue reading Where are Ospreys found today?
When did the Osprey last breed in Switzerland?
Ospreys in Switzerland were recorded as breeding for the last time along the Rhine River in 1914, with the last observation of a territorial male observed in 1915 or possibly even in 1919. Since this time Ospreys are only seen in Switzerland during migration periods in the spring and fall, with occasional visits during the summer.
In his book Die Adler der Schweiz (1932), Carl Stemmler has provided invaluable information on the last breeding Ospreys in Switzerland. He recounts how, on April 15, 1911, a young man named Merk brought him a dead female Osprey that he had wounded with buckshot (and afterwards tried finishing her off with a Swiss Army knife, and ended up strangling her with a rope)! He had been planning on taking the bird to the taxidermist to get it stuffed. After some discussion, he agreed to sell the bird to Stemmler as well as show him the nest where he had killed the bird, which was located in Ellikon am Rhein (canton of Zurich). The lad explained how he and a friend had stolen the eggs at night, because they knew that if they had waited, three other lads were getting ready to steal the eggs the following morning. Stemmler bought the bird from him for 15 francs and the three eggs for 5 francs. The young man told him that he killed an Osprey each year to sell to the local taxidermist. After this encounter, Stemmler recounted that Merk then emigrated to Texas! Continue reading When did the Osprey last breed in Switzerland?
Migration
Most European Ospreys nest in the north and winter in Africa south of the Sahara (apart from a few Mediterranean populations which are more or less sedentary). A few birds stop before crossing the Mediterranean and winter in Spain or even in the south-west of France, but this is unusual. In Switzerland Osprey migration occurs over a fairly wide period, and small numbers of birds can be seen mainly from mid-March to the end of May in the spring and from mid-August to the end of October in the autumn. Continue reading Migration
Why did the Osprey disappear as a breeding species in Switzerland?
The Osprey once bred throughout Europe where there was suitable aquatic habitat, but they disappeared from a large part of western, central and southern Europe. For the most part only populations in northern Europe, specifically in Fennoscandia but also some small populations in Eastern Germany and Poland, remained. Continue reading Why did the Osprey disappear as a breeding species in Switzerland?
Why won’t the Ospreys return to breed in western Switzerland by themselves?
The reason that it is very unlikely (with nature you can never say impossible, but we can say very unlikely) that the Osprey will start breeding in western Switzerland again without help is due to “philopatry”. Philopatry is the tendency of an individual to stay or to return to the place where they were born in order to breed. Some species, like the Osprey, have a very strong philopatry, which results in a very limited ability to disperse to new areas. This means that when a population disappears, it is exceedingly unlikely that individuals who were not born in this area will recolonise it, even if suitable habitat exists. Continue reading Why won’t the Ospreys return to breed in western Switzerland by themselves?
