The osprey is unlike any of our other raptor species. Living almost exclusively on the fish it catches with its dramatic dives, it was extinct as a UK breeding bird between 1916 and 1954. Happily, its natural return to Scotland in the 1950s, followed by successful translocations to Rutland and Poole Harbour, makes it a welcome success story in an age of biodiversity loss. And while most of the UK’s approximately 300 pairs of ospreys breed in Scotland, many nests are now viewable via webcam, making it possible to watch these incredible birds during the breeding season wherever you live. However, if you’d rather see one in the flesh, September is a great month for bumping into birds as they migrate south.
The Fisher King
Ospreys are large, long-winged birds of prey. They can actually look quite gull-like in flight. Their upper wings and backs are brown. Their underparts are white save for a faint brown chest band and some brown barring and patches on the wings. A dark eye mask and relatively long, muscular legs complete the look. Males and females are identical although, like all raptors, the female is bigger. She also has longer wings. While they are undeniably raptor-looking, they are distinct enough from other eagles and hawks to be placed taxonomically in their own genus and family, Pandion and Pandionidae respectively. Fish makes up around 99% of their diet. Indeed, the adaptations that help it catch fish are mainly what sets them apart from other raptor species.
To hunt, they usually fly above larger bodies of water, including coastal stretches, using their excellent binocular vision to look for prey. Once located, they then sometimes briefly hover before diving straight down, extending their long legs at the last minute. Sometimes they enter the water fully. They will also skim the water with their talons if fish are close to the surface, though. Fishing adaptations include reversible toes that help them grasp fish tightly with two toes in front, two behind. They also have closeable nostrils to keep out water and a rump gland that produces a waterproof oil for their feathers. In addition, dark feathers in front of the eye help reduce the glare off the surface of water so they can see their prey better. According to some observations, they have a catch success rate of about 25%, but others suggest it is much higher.
Ospreys start breeding at around three years old and have a lifespan of, on average, nine or ten years. The oldest bird recorded, however, was an impressive 32 years old. UK ospreys are all migratory. Birds travel back from their West African wintering grounds in March and April each year. Although they often mate for life, males and females spend the winter apart. They return to the same nest each year, often repairing and adding to the large stick structure. This is usually in a large tree close to fresh or brackish water of some kind. They will also, though, readily use manmade nest platforms. After a short courtship period, the female lays two to three eggs. She alone will incubate them while the male catches fish for her. After hatching, he continues to provide food while she looks after the young.
Between August and September, the birds set off for Africa, with the female often leaving first. Because there isn’t the time pressure of needing to breed as in spring, the journey south is quite drawn out. Birds often stop of for days or even weeks at suitable fishing spots en route. At this time of year, they can turn up at any large water body, from lakes to estuaries. It is worth remembering to look out for them. Once they leave the UK fully, migration becomes a much more perilous undertaking. Birds often die, usually because of bad weather. Whether travelling to or from their breeding site, storms can blow them out into the Atlantic. In fact, one Scottish bird ended up in the Caribbean last autumn, the first record of a Eurasian osprey reaching the Americas. Crossing the Sahara is also dangerous.
One of a Kind?
For such a small genus, the osprey has an extremely large distribution, second only amongst raptors to the peregrine falcon. They breed on every continent except South America (where they do at least winter) and Antarctica. This has led to some differences of opinion when it comes to deciding whether separate populations are subspecies or full species. Until fairly recently, most authorities classed the bird as one species divided into four subspecies: Eurasian breeders, North American ones, Caribbean birds and Australasian ospreys.
Now many taxonomists regard Australasian birds as a full species called the eastern osprey, with all others becoming the western osprey. Western ospreys, apart from Caribbean birds, are migratory, while eastern birds aren’t. Most North American birds travel to South America for the winter, although a few may stay in southern states such as Florida. Birds breeding in western Europe migrate to West Africa. Eurasian ospreys from further east winter in India and Southeast Asia.
Approximately 300 pairs of ospreys now nest in the UK, with the vast majority in Scotland. This is a remarkable turnaround for a species that was extinct as a breeding bird in England by the 1840s and Scotland by 1916. Egg and skin collecting, as well as persecution due to its talent for catching fish were the main causes of its demise here. Incredibly, though, in 1954 a pair arrived at Loch Garten in Scotland from Scandinavia and successfully bred. The site was initially confidential to protect the birds from egg collectors. In 1959, though, the RSPB decided on a new, radical approach. By inviting the public to view the nesting pair, albeit at a safe distance, they not only encouraged people to invest emotionally with the return, but they put hundreds of extra protective eyes on the nest.
Recolonisation after this first pair was slow for some time. This was almost certainly in part because of the effects of chemicals like DDT on the eggs of birds higher up the food chain, as highlighted by Rachel Carson’s 1962 book Silent Spring. However, by 2018, approximately 250 pairs were breeding in Scotland. Meanwhile, in England, the Rutland Osprey Project, with help from the Roy Dennis Foundation, began translocating birds to Rutland Water from Scotland in 1996. The first birds bred in 2001 and there are now around 10 breeding pairs at the reserve. A similar project began in Poole Harbour in 2017, with a pair breeding in 2022 and 2023. Birds have also returned under their own steam to sites in Wales (2004), Cumbria (2001), Kielder Forest (2009) and more recently North Yorkshire and Leicestershire. A pair also bred in Northern Ireland this summer; the first on the island of Ireland for over 200 years.
Back for Good?
With the osprey’s return to Scotland in 1954, and to England and Wales in 2001, there is hope that we won’t lose this amazing bird in the UK again. We cannot be complacent, however. After decades of gains in terms of water quality in the UK, the last ten years has seen a huge backward slide, with pollution from water companies and agricultural runoff in particular threatening our aquatic ecosystems. If the situation isn’t reversed, the osprey’s spread across England could be halted before it has even really begun.