Young ospreys start breeding by their 3rd year of life, but the mortality in young birds is incredibly high, with an estimated 57% of osprey chicks failing to reach breeding age. This rate decreases to 18% annually after the first year.
The average life expectancy for an Osprey is 10-15 years in the wild. An Osprey in captivity can live as long as 20 years or longer.
Nestlings and fledglings are most vulnerable to nest collapses, cold rains and high winds. In North America, the great horned owl is known to take over nest sites and has been documented to prey on young and adults.
Bald eagles compete directly with osprey for food resources and will often harass ospreys, forcing them to drop fish. Ospreys will typically avoid nesting in close proximity to eagle territories.
Osprey nests are often robbed by raccoons, American crows and the common raven.
Of course you know the DDT story. If you don’t, you should. Osprey numbers crashed in the early 1950s to 1970s, when pesticides poisoned the birds and thinned their eggshells. Along the east coast of North America about 90 percent of breeding pairs disappeared. After the 1972 U.S. DDT ban, populations rebounded, and the Osprey became a conservation success symbol.
As natural nest sites have succumbed to tree removal and shoreline development, specially constructed nest platforms and other structures such as channel markers and utility poles have become vital to the osprey’s recovery.
Contact with high power electrical grid lines near nesting areas continue to be a problem, but more important is the baling twine and fishing line issue.
Ospreys typically line their stick nests with soft materials such as moss, grass and lichen, but they have a propensity to pick up discarded baling twine and fishing line to bind and adorn their nests. This creates a problem as the osprey’s talons easily become entangled in these man-made materials. Each year baling twine and fishing line are the cause of death for many adult osprey and their chicks. It has been estimated that baling twine alone kills about 10 percent of osprey chicks in some areas.