Classified as extinct in the United Kingdom in 1916, and threatened with a steep decline in numbers during the 1950s to 1970s in the United States, ospreys (Pandion haliaetus) were once considered one of the world’s most endangered bird species.
However, since the late 20th century, the species has undergone a dramatic revival in numbers, with established breeding populations thriving across the northern hemisphere. But how long do these fearsome fish-hunting birds of prey live for and what factors influence their survival in the wild?
Ospreys live for an average of 8 to 10 years in the wild. Many juvenile ospreys fail to survive to breeding age, although some individuals have been recorded at more than 20 years of age. Captive ospreys are notoriously hard to care for and may fail to match the life expectancy of wild birds.
Conservation projects that aim to protect, support, and monitor nesting ospreys exist across the United States and Europe, and their observations have provided a fascinating insight into individual ospreys' lives and breeding patterns, as well as the general mortality rate of younger birds before they reach maturity, or in some cases even leave the nest.
Read on to find out why so many juvenile ospreys die before they reach maturity, and what other factors influence the life expectancy of these fascinating fish-eating predators.
The average lifespan of an Osprey is usually between 8 and 10 years
The average lifespan of an osprey is between 8 and 10 years. Ospreys in the wild will naturally have a shorter life expectancy than those in captivity. The oldest wild osprey recorded lived to 32 years of age, and there are several known examples of individual birds that have been observed for more than 20 years.
In the wild, it is thought that up to 60 percent of ospreys die during their first year. Competition among nestlings for food and treacherously high nest sites are two major factors that may affect whether a young hatchling survives.
If a juvenile osprey survives for the first three years of life and successfully navigates its first migration to a breeding site, it stands a good chance of reaching at least 8 years.
Osprey in flight
Ospreys are notoriously tricky to care for in captivity and fare far better in a natural environment than in a captive setting wherever possible. This is due to the need for regular feeding on large volumes of fish, and a resistance to eating when in captivity.
Several documented cases of injured ospreys that have been cared for in wildlife rehabilitation facilities do not have successful outcomes, and the life expectancy of captive birds is significantly reduced.
Juvenile ospreys have a high mortality rate, with just under two thirds not surviving until breeding age. Natural selection plays its part, with young nestlings competing for food; earlier born chicks tend to have better survival rates than later hatchlings.
Accidental fatalities are also common among newly hatched osprey chicks, with some young birds falling from high nesting platforms before having mastered the art of flight. Nestlings may become caught up in bailing twine or plastic fishing line that is often used as a nest construction material.
Other life-endangering hazards that may lead to death of older ospreys include power cables (entanglement and electrocution), aircraft strikes, and in the past, ingestion of harmful chemicals from polluted water or food sources.
Ospreys are relatively high up in the food chain, but can still fall victim to predators, including larger birds of prey, such as great-horned owls and various species of eagle.
Juvenile Ospreys have a high mortality rate
Female ospreys lay between two and four eggs over a period of several days. The eggs are then incubated for a period of 36 to 42 days by both the male and female. Osprey pairs nesting for the first time will usually lay two eggs, while more experienced pairs will lay up to four.
The chicks that hatch first generally stand a greater chance of survival than those that hatch later, due to rather aggressive competition for food among nestlings. After about two months, osprey chicks begin to prepare to fly. They remain with their parents at the nest for another two months, learning vital hunting skills and developing stamina for longer sustained flight.
Once they are ready to leave the nest, young ospreys then migrate south to wintering grounds, where they stay for up to three years until they are ready to start breeding. Ospreys reach sexual maturity by the age of three to four, although breeding may be delayed if there are no suitable nesting sites. They pair up ahead of the breeding season, but are generally solitary birds that live alone for most of the year, roosting in loose flocks rather than staying exclusively with a mate.
When an osprey has successfully survived until breeding age, it can have a life expectancy of at least 8 to 10 years.
A pair of Osprey chicks being fed in the nest
Major predators of ospreys, depending on geographical location, include great-horned owls, bald eagles, golden eagles, and white-tailed eagles. These large birds of prey target both nestlings and adult birds.
Perhaps more common than preying on the birds themselves is kleptoparasitism of ospreys, a phenomenon where predatory birds harass another bird in order to feed on the prey that bird has caught, or to steal food that they have stored for a future meal.
Again, depending on geographical location, predators such as foxes, racoons, and skunks may raid osprey nests and take eggs and chicks. However, an osprey’s choice of nest site that is as inaccessible as possible will usually mean that this is a relatively rare occurrence. At African overwintering grounds, opportunistic crocodiles may prey on ospreys as they fish.
The oldest wild osprey recorded in Europe reached 32 years of age. Lady of the Lowes, a veteran female osprey returned to a Scottish breeding site for 24 consecutive years, making her an estimated 28 years of age when she was observed for the final time in 2014.
The Montana Osprey Project has observed a breeding female known as Iris, since 1998, when she was first spotted nesting at a site near the Clark Fork River. She is thought to be the world’s oldest known breeding female osprey, aged an estimated 28 or 29 years in 2022.
A perched osprey
Ospreys need to feed every day, and several times a day when they are raising chicks. Males will hunt and swoop for fish in the early mornings when they have nestlings to provide for.
Adult ospreys need around 400 g (0.88 lb) of fish each day to sustain their energy requirements. An osprey’s feeding schedule depends on wind direction and tides, as these affect fishing conditions, and dawn and dusk are the most common hunting times.
Ospreys are typically migratory birds, breeding in northern regions and then flying south in winter in search of a steady and readily available food source. Ospreys resident in Florida, the Gulf Coast, and the Caribbean and those native to Australasia, however, do not migrate, as food is plentiful in their native habitats all year round.
An osprey fishing in Scotland
Osprey numbers continue to show a steady increase, recovering from a sharp decline during the 1950s to 1970s caused by a rise in pesticide usage. In the UK, ospreys are listed on the Amber List as a rare breeding bird.
Between the 1950s and 1970s, the osprey population in the United States underwent a sharp decline, and the species was listed as endangered. This significant drop in numbers was caused by a rise in the use of agricultural chemicals and pesticides, including DDT. The widespread use of these pollutants, ingested through polluted food sources and water supplies, led to breeding failures in ospreys, as the chemicals made it difficult for birds to produce enough calcium to be able to lay eggs that were durable enough to successfully hatch.
Since 1972, when the use of DDT was banned, the species has witnessed a reassuring revival in numbers, although it is still classed as endangered in a number of US states.
A number of UK conservation projects aim to increase the range of ospreys, by providing protected nest platforms, which are secure from predators and well monitored throughout the breeding season. From one breeding pair in Scotland in the 1950s, numbers have swelled to at least 250 pairs in the UK by 2022, with established sites in the Lake District and Wales as well as throughout Scotland.
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