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Ospreys are amazing birds of prey whose return each spring is eagerly awaited.
If you’ve ever wondered what these iconic birds look like, where they spend the winter, or how long they have been nesting at Loch of the Lowes Wildlife Reserve this fact file should help answer your questions.
How to tell them apart from other raptors, and the difference between males and females.
Did you know? Female ospreys are around 20% bigger than males.
The osprey is a large fish-eating bird of prey. It has a white head with a distinctive brown eyestripe. Both males and females are generally white below and darker (brown) from above, although females usually have a brownish patch on their chest. Adult birds have a yellow eye, whilst the eyes of juveniles are orange.
They can be mistaken in flight for a very large gull or a buzzard but have a distinctively different silhouette shape.
The full wingspan of an adult osprey is around five feet. Females are around 20% bigger than males. They have a similar wingspan to a buzzard but smaller than a golden eagle – which can reach around seven feet across.
Ospreys are surprisingly vocal and the call is varied. Ospreys often “cheep” or chirp repeatedly, especially when begging for food.
The “cheep, cheep, cheep” of an osprey can become a highly agitated alarm call if the bird, its nest or young are threatened. They also make a sound like a whistle.
Unlike many birds, both sexes of osprey are similar in appearance. However, the female is larger, up to 20% bigger and a heftier bird. The females also often have more brown colouring on their chest than the males, a so-called ‘necklace’.
There is also a lot of individual variation, and unique markings, especially on their heads, which can help identify birds.
Ospreys have a number of features that make them perfectly adapted to hunting fish.
Did you know? They have a special transparent eyelid like a contact lens that protects their eyes underwater.
Although the osprey is a skilled flyer and hunter, like other raptors, it is truly unique among hawks physiologically. Its bone structure is different from other birds of prey, and its feet are more like an owl’s than a hawk’s.
Like most birds of prey, the osprey has a large hooked beak for tearing its prey. The bill or beak, although less than an inch long, is the perfect tool for tearing apart fish.
The upper bill forms a distinctive hook over the lower jaw, which is V-shaped or funnel-like. The upper bill comes to a sharp point below the lower jaw. The mouth is thin in the front, like the spout of a funnel, but stretches dramatically at the back, and its walls allow for opening the mouth wide. The tongue is thin and flat, like a long spoon, and mirrors the shape of the lower jaw.
The bill is entirely black, although the cere – the fleshy or waxy structure at the base of the upper bill – is light blue to grey. The nostrils, which take on an arched shaped when open, are located in this area. They can be closed completely when the osprey dives into water!
As well as supremely good eyesight ospreys, like many other birds, have a third eyelid. This is a semi-transparent membrane which is used to protect the eye during the dive for fish – built in water-goggles or “contact lens” for when they are underwater.
The legs and feet of an osprey are unlike that of any other hawk. The legs are heavily muscled, with short heavy thighs which are covered in short, dense feathers, and the toes, feet and lower legs are covered with heavy white, light grey, greenish or yellow scales. With four equal toes, one capable of pointing forward or backward, ospreys’ feet look more like an owl’s foot than that of its closer relatives, hawks and eagles.
Each toe is armed with long, sharply curved talons that resemble fish hooks, for grasping and holding fish in flight. The bottom of the toes are very rough to the touch because of the small spiky wart-like projections called spicules that cover them.
This sandpaper-like texture gives the bird a surer grasp, and resembles Velcro to provide a firm grip on wet, slippery fish. The black talons, like the toes, are different from those of most other birds of prey. Each talon is nearly cylindrical, rounded on the top and bottom, while most other birds of prey have flat or indented spaces on the underside of the talons.
Together, these characteristics, combined with its powerful wings, allow the osprey to catch and carry fish that weigh nearly as much as it does. It can also grasp and carry large sticks for its nesting material and it can grab and fly off with fish from up to 1m below the surface of the water, an incredible feat.
With a wingspan of 1.3m-1.8m, the osprey is a powerful and dramatic sight in the air. The wing of an osprey contains more feathers than other large predatory birds, and the wings are longer and thinner than the wings of other raptors. The four longest feathers, the primaries at the end of the wing, are notched.
The length, high arch and heavy feathering contribute to the enormous strength of the osprey’s wings. These factors give the osprey much more power than most other large raptors, and allow it to catch and carry much larger prey.
The wings are generally dark above, a mix of light and dark underneath with a pronounced stripe on the underside feathers.
An osprey’s plumage often prompts confusion for viewers, who regularly mistake the osprey for a buzzard. The head is primarily white, with a broad band of feathers stretching from in front of the eyes to the back of the head, whereas a buzzard has a dark head.
The osprey’s underside and head are primarily white, while the tops of the wings and back are dark brown. The tail is dark on top, striped underneath, and gives the appearance of a rounded fan when spread. The wings themselves are also white underneath, but the longer primaries, secondaries and under-secondary coverts are striped like the tail feathers.
Underneath, there is a black patch at the bend in the wing. The plumage is generally compact, but the crest feathers become erect when the bird is highly alert or annoyed. The thighs have extremely compact plumage, and the compact nature of the body plumage is believed to help blunt the impact of hitting the water when catching fish.
Juvenile ospreys have distinctive mottled appearance caused by a pale edge to each feather- they keep this colouration for the first year or two.
Find out what how ospreys catch their prey and what they eat.
Did you know? While its normal flight tops out at around 50km an hour, the osprey is capable of speeds of up to 125km/h in steep dives to capture unsuspecting fish.
Ospreys fish over large water bodies (lochs, rivers and estuaries) both fresh and salt water, and whilst hovering at around 90m they use their sharp eyesight to spot fish.
Once a fish is spotted, they capture it in one of two ways: diving down at a sharp angle at high speed, or by gracefully swooping down and plucking its quarry from the water with barely a missed beat of the wings.
The steep dive is the more spectacular and common, method. Once the osprey spies its target, it locks on to the fish with its eyes, and goes into a dive, of in some cases, more than 30m, pulling its feet forward at the last second, plunging into the water with a feet first dive.
The bird will enter or hit the water with a splash, in some cases going completely under, submersing itself in the water to catch the fish, going down up to 1m deep, before gracefully lifting off with the wriggling fish in its talons.
Remarkably, the bird will invariably use its four-toed feet with reversible outer toe, to shift the fish to a head-first position in flight – all the better to carry with minimal drag. Their large feet are covered on the underside with little spines, so the fish is held securely by both feet during the flight back to the nest or feeding post.
Once back at the nest or suitable feeding spot, the osprey will use its powerful feet to hold the fish and its hooked bill to tear chunks of flesh free. If the fish is too big to eat in one sitting, ospreys will often dump the remains, although they will sometimes return to the meal later on.
Ospreys are highly specialised fish hunters. Ospreys will eat most fish they can catch in the top layer of the water and virtually any fish species small enough to carry back to the nest or land.
At Loch of the Lowes they mostly eat trout, pike and perch, as well as smaller fish, from the nearby freshwater lochs. They very occasionally eat salmon presumably caught from the nearby River Tay. Ospreys also eat sea fish (they are fond of mullet and flounder) and commonly hunt in estuaries. An osprey is capable of carrying a fish equal to its own size, but most are smaller at a couple of pounds.
Although mainly fish-eating, ospreys have very rarely been observed feeding on small mammals, reptiles, water birds and invertebrates – mostly in Africa. They have never been recorded eating anything other than fish in the UK. This enables them to coexist with other predators including different birds of prey.
The ospreys at Loch of the Lowes hunt in local lochs and rivers within a 30km radius of their nest. They commonly use the Craiglush and Butterstone Lochs, other local lochs and the River Tay.
Find out about the osprey nest at Loch of the Lowes and why the reserve is a perfect place for successful breeding.
Did you know? There is evidence that ospreys used to have ancestral nests which were used for hundreds of years.
The nest is on Scottish Wildlife Trust land on the left hand side of the loch to the Visitor Centre. The site is a large Scots pine tree, with an artificial nest added to the top. The location of other osprey nests are not revealed as the two main threats to successful breeding are persecution (egg collectors raiding the nest) and disturbance – such as people going to look for the nest. Disturbance may also come from other birds of prey, or machinery (such as helicopters).
Remember: all osprey nests are legally protected and give them all a respectful wide berth so as not to disturb the birds whilst breeding (an offence) and cause the nest to fail.
Osprey nests can range from a small collection of sticks in a treetop to massive, thick-walled homes like those of the eagles. Most often, ospreys return to the same nests year after year, adding to the structure over time and building substantial walls.
Their predilection for returning to the same nest is a factor in what is often lifelong bonding of osprey pairs. In some instances, especially in North America, ospreys nest in colonies surprisingly close to one another, as long as there is enough food to go around.
The main factors affecting where any bird nests are predator risk, habitat and food supply. Here in Scotland we are relatively predator free, compared to the African alternative. Crucially we also have very long daylight hours during the peak breeding season, which enables osprey parents to maximise the time available to feed a hungry family.
Suitable habitat for nest sites for ospreys needs to have mature trees that will support the very large eyrie. As these are not always naturally present, over the past few years various organisations have set up a number of artificial nest platforms across Scotland, to encourage ospreys to breed in that area.
As well as habitat for nest sites, a good food supply is vital. There are a number of clean and healthy rivers and lochs locally that the birds can fish in.
Ospreys are site faithful and will return to the same nest site for many years.
The nest at Loch of the Lowes is about 1.8m wide and 60-90cm deep. Nests often get damaged over winter, but each year the birds return to the same nest site and as soon as they arrive, the nest is added to and built up, so it can end up being huge.
Ospreys are quite house proud and constantly add to and adjust the nest throughout the summer. Over the course of the summer the nest shape changes too. It starts off with quite a cup-shaped hollow, to protect the eggs and reduce the risk of them rolling out.
As the eggs hatch and the chicks start to grow, the adults add more material to the sides of the nest, so that as the chicks get older and bigger, it is more of a flat platform, giving them more space to move around. Any eggs that don’t hatch become buried deep in the ever-changing structure of the nest.
Find out about the mating rituals of ospreys, what their eggs look like and how long it takes them to hatch.
Did you know? Male ospreys will sometimes bring so many sticks to the nest that their mate ends up buried!
Ospreys are generally monogamous and pair for life, very rarely leaving a living partner, both having a strong attachment to the nesting site. However, if their mate fails to return from migration, ospreys will choose another partner, and may therefore have more than one in their lifetime.
In Scotland the breeding season for ospreys is generally late March / April to July/ August.
Courtship may not be very elaborate in established pairs but usually involves the male bringing fish to the female at the nest, and both birds indulging in extensive nest renovation.
The male brings in amazing numbers of fresh sticks to the nest, sometimes almost burying the female with material which she usually then arranges to her satisfaction. Mating is repeated and quick, and may take place even after the first egg is laid, generally ten days or so after first mating attempt.
The usual number of eggs for an established breeding pair is two to three. Ospreys tend to start breeding at three to seven years of age.
In the first year of breeding, however, they often fail to breed successfully. Younger birds often start off with one egg, producing two the following year, and building up to a standard clutch of three. Rarely four eggs are laid, although these may not all hatch, nor all survive to fledging.
The eggs are laid individually one to three days apart.
Surprisingly, osprey eggs are only the size of a large hen or duck egg. The eggs are off-white to pinkish or buff, and are highlighted with mottled dark brown or reddish splotches, that vary in their size and distribution. Some eggs have a uniform mottled appearance while some can have more of this reddish brown colouration at one end.
Osprey eggs are incubated for around five to six weeks until they hatch, an average of 37 days. Both ospreys will tend to the eggs safety, although the female always does the majority of the incubation.
In some pairs males never incubate the eggs, and in other pairs males will incubate for an hour or more whilst the female has a break to fly, toilet and eat. The male is the sole food supplier once the eggs are laid.
Just as their eggs are laid at intervals of one to three days, ospreys hatch a day or two apart. They are covered in down when hatched, but begin to grow new feathers within days. The chicks must rely entirely on their parents for food, and they grow very, very fast- they are three-quarters the size of an adult within a month.
Some sibling rivalry and bullying is normal but extreme violence and eating siblings is not – unlike in owls or eagles. Only if food is in short supply do some chicks fall behind or not survive as ospreys are very tender and attentive parents.
They are almost adult size by five weeks and ready to fly by seven to eight weeks. It is a very fast track growth spurt fuelled by their very high protein diet of fish brought in by the male.
The chicks are often ringed at around five weeks of age. By this time their leg bones are fully formed and the parents have had time to bond with them so that they won’t be abandoned as a result of the disturbance, but they are still too young to flap accidentally out of the nest.
This should be the only time they are ever handled or disturbed by humans at the nest site. Information on size, weight, sex, health etc is often collected during this brief process. At Loch of the Lowes, 2 rings are placed on the bird. A metal BTO ring and a darvic colour ring, this allows us to be able to identify them from a distance. This is also when satellite tracking devices can be attached to the birds.
By about six to seven weeks of age, osprey chicks are ready to test their wings for the first time. They often exercise on the edge of the nest and lift off in short hops before taking off properly for the first time. To encourage the chicks to fledge, the adults will bring less and less fish back to the nest– effectively starving them off the nest.
Once capable of flying, the chicks learn how to hunt for themselves, though they will generally stay near their parents for another 30 to 50 days.
The growth rate of osprey chicks is amazing – it only takes twelve to fourteen weeks from when they hatch to when they begin their migration back to Africa. By this time they will weigh around 1.6kgs.
Young ospreys typically separate from their parents permanently in the autumn. They migrate separately from their parents, and probably won’t meet them again.
If they survive until their second or third year of life (the odds against which are probably more than 50% due to the hazards of migration and man) the young will spend a good ‘gap year’ or two in Africa and when they are ready to breed they are usually driven to return to the country where they were hatched and attempt to set up their own nest.
While the chicks are on the nest, the male does all the fishing and providing for the family. The female generally receives the fish, often headless, from the male and serves it to the chicks by shredding it into tiny pieces for them. She will continue to do this until they are ready to fledge.
Occasionally in some but not all osprey pairs, the male will also feed the chicks himself if the female is absent- and this was the case with 7Y, a previous male at Loch of the Lowes who famously fed the chicks while his mate was very ill, saving their lives.
Most often, the female osprey will feed the strongest chick first, until it is full, then the next chick and so on, so as to ensure if there is a limited supply, at least one chick survives. This tends to be the eldest chick, but not always. The ‘pecking order’ is established in the first few days to prevent squabbles over every mouthful.
Ospreys have also been recorded actually favouring a ‘runt’ and ensuring it gets enough food to catch up to its siblings – fabulous parenting!
Ospreys can travel up to 5,000km on their migrations to and from Scotland. How they navigate, and how young birds manage to make the journey on their own at a young age is still a mystery.
Did you know? Young ospreys always start their return migrations in a south westerly direction.
Ospreys migrate to West Africa for the winter, covering up to 5,000 km during their journey. Autumn migrations can be as short as 13 days of continuous flight.
The female typically begins her migration first, leaving the nest and her young shortly after they are fledged. The male remains, and continues to fish for the young until they are able to fish for themselves.
Finally, the young are left to begin their migration on their own. Nobody knows how young ospreys know what route to take, but they always begin their journey by heading off in a south-westerly direction.
There is some recent evidence that some ospreys are now ‘short stopping’, that is, overwintering in southern Europe, for example Spain and Portugal, rather than travelling all the way to Africa.
This could be in response to milder winters in continental Europe (as a result of climate change) or could be an old tradition disrupted by the ospreys recent extinction in these countries.
Yes, we believe so – It is thought that young osprey chicks follow inherited genetic programming which tells them where to head on their first migration.
Migration is a very dangerous undertaking for young ospreys – in the wild, on average 60% of all young birds die in their first year.
Once they have arrived in Africa, the young ospreys don’t return for the first three or so summers. However, it has been observed that some youngsters do a practice migration around the age of 2 years old. Returning before they are old enough to breed. Possibly to scope out future nesting opportunities and refine their migration routes.
Osprey pairs leave for migration separately. The female usually leaves first while the male remains for another few weeks to provide fish for the chicks.
We believe that an osprey pair will spend the six months of winter apart, although large numbers of ospreys roost in loose colonies in some areas. The pairs meet up again when they return to their breeding nest the following spring.
Many birds are ringed by experts to enable scientific study of their movements, survival and to help us identify individuals. Ornithologists across the world report sightings of ringed birds, enabling conservationists to record their movements.
The large coloured easy to see leg rings used on raptors are called Darvic rings. These are uniquely colour and letter coded for each bird. Birds also have a smaller metal ring with a unique BTO serial number. In Scotland the Darvic ring is placed on the left leg, whereas in England and Wales it is placed on the right.
These rings are usually put on when the osprey chicks are 5-6 weeks old. Old enough to have an unshakable bond with their parents, and adult size legs, but not old enough to fly.
They are ringed by a specially qualified and licensed BTO bird ringer. Weighed, measured and ringed on the nest – the only time in their lives they will be handled. They tend to ‘play dead’ and do not seem stressed by the experience generally.
Ospreys have a worldwide distribution. The ospreys that come to the UK are related to those in northern Europe, Scandinavia, Russia and Siberia. There is a distinct subspecies in North, Central and South America. There are even ospreys in Asia and Australia.
Traditionally a breeding bird is considered ‘local’ but since the osprey spends only five months a year here, you could think of it as an African bird that visits the UK, not a UK bird that visits Africa!
Discover which creatures prey on ospreys, what they do at night, and how long they live for.
Did you know? At night male ospreys sleep on a branch close to the nest.
Adult ospreys have very few predators although a few are eaten by crocodiles each year in Africa. Many more are lost to bad weather, power line collisions and shooters.
However, eggs are sometimes stolen by corvids and chicks on the nest are vulnerable to predators such as pine martens and goshawks, which is why ospreys need to be very vigilant parents.
Mortality in young birds is very high. An estimated 70% of osprey chicks fail to reach breeding age (their third year).
We think they live on average about 10 – 15 years in the wild, longer in captivity. One breeding female at Loch of the Lowes lived to be over 24 years old.
Did you know that ospreys are still rarer in the UK than golden eagles?
Ospreys are listed globally by the IUCN as a species of Least Concern. While not endangered on a worldwide level, in Europe where persecution has historically been worst, they are extinct or threatened in most of their former range, and are only now recovering.
In Africa where they migrate for the winter they are not generally protected and so are vulnerable to persecution. However, they are not considered rare or threatened in all of their ranges – for example they are comparatively common in the Americas.
Ospreys are now found in several parts of Scotland, one site in Cumbria, two in Wales, and at one artificially re-colonised site in Anglia: Rutland Water. There are now approximately 250 breeding pairs in the UK, producing around 260 chicks a year.
The most recent re-introduction project has been at Poole harbour in Dorset, to recolonise the South coast of England.
Ospreys have the highest full legal protection under UK law (Schedule 1). It is an offence to injure or disturb any bird, nest or egg.
Like most raptors ospreys rarely fight physically. They do engage in spectacular aerial dog fights and defensive displays such as mantling and alarm calling if a rival appears on or near the nest. In rare instances, talons are used to emphasise the point!
Ospreys can be very violent towards predators in defence of their chicks using their talons and beaks.
Osprey sleep at night of course. During the breeding season the female will sit on the nest with eggs or young chicks, sleeping on them to keep them warm with her head tucked under one wing, shifting occasionally to rotate the eggs.
The male is usually absent from the nest but he will remain in close proximity in order to protect it- usually perched on a nearby branch or tree close at hand.
Discover the threats that led ospreys to extinction in the early 20th Century and how legal and environmental changes helped to bring them back.
Did you know? Ospreys are still rarer than golden eagles in the UK.
Ospreys were driven to extinction in most of the UK in the late 19th century. They managed to hang on in Scotland until 1916, the year ospreys were considered extinct in Britain as a breeding bird. Recent research suggest that a handful of ospreys may have clung on as individuals or tried to breed in very isolated pockets after 1916, but they were so few and far between that they were deemed functionally extinct, due such low numbers and wide geographical spread. Ospreys were still occasionally seen in Britain while on migration but there was no successful breeding for nearly forty years.
Historically, ospreys were killed because they were seen as a threat to fish stocks that were used as a source of human food. They were considered vermin because they ate trout and salmon, and were routinely shot by gamekeepers and sportsmen.
Improving land for agriculture led to the destruction of their habitat and in particular destruction of nest sites, and industrial pollution meant water quality was low and fish stocks declined.
The fashion for specimen collecting, taxidermy, and in particular egg collecting, greatly reduced breeding success.
Worldwide threats to the osprey and many other birds of prey included the use of DDT, an agricultural pesticide. The build of DDT in the food chain led to many birds laying very thin shelled eggs which broke very easily, reducing the chances of breeding success.
Many wild birds are still killed for sport in countries such as Malta as they pass on their annual migration and unfortunately this is still happening – even to ospreys!
Ospreys returned for the first time to breed in 1954 to Loch Garten near Aviemore. This was a natural recolonisation from Scandinavian stock, but the birds needed a huge amount of help and protection to breed there successfully. It wasn’t until 1959 that osprey successfully bred at Loch Garten. It took until 1971 before the first osprey successfully bred at Lowes, the 5th known nest at the time.
After a very slow start when many birds lost eggs to human thieves and interference, several pairs of osprey began to breed successfully in more remote parts of Scotland. Many birds were helped with artificial nest platforms and nest protection watches, and a huge public enthusiasm for the birds helped ensure their survival.
A population of breeding ospreys still survived in Scandinavia, and some of their young birds may have been looking for new territory to breed in. There has probably been a lot of historical exchange between these populations.
As DDT was phased out, breeding populations in Europe slowly increased back to normal levels, this meant healthy numbers and even a surplus of birds able to expand into the UK.
The osprey was given the highest level of legal protection in the UK against shooting and egg collecting, which helped deter egg thieves and other human threats. The improvement in water quality, recovery of fish stocks and more availability of nesting sites helped returning birds.
The provision of artificial nesting platforms also proved key to their success, dramatically improving the breeding success rate in the 1980s and 1990s.
There has been a steady increase in breeding success in Scotland from two pairs in 1967 to 150 pairs in 2000, and approximately 250 in 2018.There are also many juvenile birds around each year but the total population is probably less than 1,500 birds.
In comparison there are around 510 breeding pairs of golden eagle in the UK.
The heartland for Britain’s ospreys is Speyside, the Cairngorms and Perthshire.
Ospreys have been at Loch of the Lowes since 1969. At that time it was only one of five known nests in the UK.
Most ospreys still nest in the more remote areas of Scotland, where privacy, clean water, fish and big trees are plentiful, and the summer daylight is longest.
Current growth areas for osprey populations are in South Scotland, the Lake District, and Northumberland.
There are also now at least two pairs in Wales, a reintroduced population at Rutland Water in East Anglia and more recently there has been a reintroduction on the South coast at Poole Harbour.
Loch of the Lowes Wildlife Reserve has played a part in the return of ospreys to Scotland for over half a century. Find out about the birds that have nested at the reserve and the common behaviour witnessed from our wildlife hides and live osprey webcam.
Did you know? A female osprey known as Lady bred at Loch of the Lowes for an incredible 24 years.
Since 1969 when they first appeared, and at that time this was only the fifth known nest in the UK.
They have bred successfully at Loch of the Lowes in most years since 1971 apart from a period in the mid-late 1980s.
Four sites on the loch have been used by various birds over the years, The current nest has been used since 1991.
A new female arrived at Loch of the Lowes in 2020, replacing the previous female who had been breeding here for 5 years. She has a blue darvic leg ring on her left leg, NCO. This allowed us to identify her by contacting the BTO to find out her age, her origin and her breeding history.
We do know she hatched in Loch Ness area in 2016. So 2020 was likely to be her first breeding season.
We believe she had been returning every year to breed at Loch of the Lowes from 1991-2014. Since she must have been at least three or four to breed initially, she may have been as old as 27 years, although it is impossible to be precise as she was not ringed as a chick.
In her 24 years at Lowes, this remarkable bird laid 71 eggs and managed to successfully raise 50 chicks to fledging – an incredible achievement. There are many reasons why she may have failed to return to the nest, and this is all part and parcel of nature.
However the arrival of LF15 a new breeding female successfully started a new chapter in osprey conservation at Loch of the Lowes.
Many of our staff and volunteers had been watching this bird for many years and were familiar with every detail of her plumage, markings and behaviour.
She also had a unique mark in her eye which helped to make her easy to identify – on close examination of our HD camera a distinctive “lightning bolt” mark could be seen in the yellow iris of her right eye.
The current male (named LM12) has been returning to Loch of the Lowes since 2012, but as he is not ringed we can’t be sure of his exact age (though he appears to be relatively young) or his place of origin.
The previous male that bred here in 2010 and 2011 had a coloured Darvic leg ring with the unique colour and letter combination Green 7Y on his left leg, which told us he was born 12 miles away from Loch of the Lowes in 2000. Unfortunately he didn’t make it back in 2012.
Our adult birds are relatively easy to tell apart by looking closely at their size, plumage and wing tips. Our female is slightly larger than the male. While she has a large patch of mottled brown colouration on her chest, the male has much less colouration on his front and has overall darker brown plumage.
If you look closely, you will also see that he has much longer wing tips which cross past the end of his tail, whilst hers are shorter. The brown feather plumage on the back of his head is often referred to as the ‘spanish dancer’. However, she has a very similar pattern on the back of her head.
She also has a blue Darvic ring on her left leg with NCO in white.
The intruders are usually other ospreys – probably juveniles – who have yet to find their own nest and partner, who think it is worth chancing their luck dropping in on the established pair. There is a chance they could even be one of their previous offspring, or those of a nearby pair returning to their natal area as instinct dictates.
There are always young ospreys hanging around established nests looking for their first chance to breed, and they commonly cause trouble, but can get lucky and take over the nest if one of the established birds doesn’t make it back from migration.
The female does all she can to defend her nest, especially at the early stage of the season, while she waits for the return of her mate. While there is a small chance that a younger, fitter intruder could drive her off the nest, we don’t think there’s much to worry about as her attachment to the nest is very strong.
Initially this can be because up until the remaining eggs are laid, incubation will be done intermittently to ensure that hatchings occur closer together, allowing all chicks a fair chance of survival.
Sometimes during incubation the adult birds get scared off the nest, are desperately hungry, or get distracted by rivals – but they don’t usually leave the eggs for long.
This depends on two things – predators and weather.
Any unguarded egg is vulnerable to opportunistic predators, such as corvids, pine martens or herons. Raptors such as buzzard and goshawk will predate on young osprey in the nest
If the weather is mild, the eggs can be fine for up to half an hour or so, but if it is cold and wet they can quickly get cold and the chicks inside may die.
This behaviour is normal and very common in the period before the eggs are laid.
Once incubation has started, the male will usually consume the head of the fish first and then deliver the other half to the female who will leave the nest and allow the male to take over her duties.
This gives the female a chance to get some exercise and a toilet stop away from the nest, helping to keep it clean and hygienic.
Although he is often absent from the nest at night the male osprey will remain in close proximity in order to protect it. He usually perches on a nearby branch or tree in order to remain close at hand.
Once they have arrived in Africa, the young ospreys don’t return for the first three or so summers. However, it has been observed that some youngsters do a practice migration around the age of 2 years old. Returning before they are old enough to breed. Possibly to scope out future nesting opportunities and refine their migration routes.
It’s possible that some of the birds are past chicks from Lowes or from the surrounding area. In May 2019, ringed chick PH1 returned and landed on the nest. Only to be chased off by his father LM12.
Where eggs fail to hatch, the pair of ospreys are likely to eventually give up incubating, but remain in the area for a while and often then make for an early migration in late summer.
It has been known that the birds (particularly if a nest is disturbed) will build a ‘frustration’ nest, though this will not be used for breeding until possibly the next season.
At Loch of the Lowes in 2011 and 2014, the birds incubated unsuccessful eggs for more than 70 days before giving up, burying them in the nest, and later left on migration around their usual time.
We know most UK ospreys travel south via a route that takes them over England (though some go west over Ireland) and then usually over western France, then Spain or Portugal. They often cross near Gibraltar, then hug the African coast to their eventual destination, as too far inland means a lengthy dangerous crossing of the Sahara desert, where osprey can succumb to predation at night when roosting on the ground.
We know most ospreys take 4-6 weeks to make the journey in autumn, but are considerably faster on the way up in spring (the breeding instinct is strong and they must get to the nest first!).
Young birds make more stops on their first migration, as this will be the first time they learn effectively how to fish for themselves The youngsters will also wander around a little more before finding a wintering ground where they can become established. Most birds go to the same over-wintering area each year routinely – creatures of habit!
They stop many times on route and can spend up to a week or more on a particularly good estuary or river, especially if weather is unfavourable. They can fly at considerable heights and with the right tailwind cover up to 100km a day and can even fly up for 48 hours non-stop!
Most miraculously of all, we still do not know exactly how they navigate – probably some combination of visual clues (we know they fly more in good clear weather) and certainly genetic instinct to fly south west, and probably some form of geomagnetic perception we do not yet understand.
I often ask our younger visitors if they could walk to Africa at age 10, with no parents to follow, no map and catch all their dinner with their feet on the way! It does put our young ospreys achievements in perspective – migration is truly miraculous!
Unfortunately we do not know exactly where the male and female spend their time, but we know that most UK ospreys migrate to West Africa, commonly to Senegal, Mauritania and Gambia in late September. A few birds also seem to overwinter further north, for example in southern Spain.
Satellite data from chicks at Loch of the Lowes has helped researchers at St Andrews University to gain a better understanding of osprey migration.
A live webcam has helped us share the story of ospreys with people from all over the world since 1999.
We do have the ability to move the HD camera view around and can zoom in and follow birds’ movements however, we are mindful of not doing this too often, so as not to disturb the birds on the nest, particularly during sensitive periods such as incubation and hatching.
The camera is mounted on the nest tree so we cannot approach the nest to alter the camera, move its overall position or fix it while the ospreys are nesting – this would be unethical and illegal, as it would disturb the parent and may cause them to abandon their eggs.
In 2020 the ospreys failed to breed on their usual nest, although they did fledge a chick from a nest at a nearby location. While ospreys are wild birds we want to provide a suitable nest site where they are well protected. After speaking to osprey experts we cut back overhanging branches to ensure an osprey sitting in the nest has a good line of sight of any incoming intruders. We also ripped out couch grass that had gradually taken root and covered the nest with a generous layer of leaf mould.