- What does an osprey look like?
- How big is an osprey?
- What do they sound like?
- Is there any difference between males and females?
- What adaptations do they have?
Diet and fishing
- Where is the osprey nest?
- Why have they nested here?
- How big is the nest?
- Do they have different mates over their lifetime?
Breeding and courtship
- When is the breeding season?
- How many eggs do they lay?
- How big are the eggs? What do they look like?
- How long do they incubate for?
- What happens to the chicks?
- How are the chicks fed?
- Do ospreys migrate?
- Do the youngsters migrate to the same area as their parents?
- How do they navigate?
- What happens once the adult pair reaches Africa? Do they winter together?
- What is ringing?
- What is satellite tracking?
- Are they found anywhere else?
- What predators do they have?
- How long do they live?
- Are they rare?
- Are they protected?
- Do ospreys fight?
- What do they do at night?
Ospreys in Scotland & osprey history
- Were ospreys extinct?
- Why did the osprey decline and become extinct?
- When did ospreys return?
- Why did ospreys return to Britain?
- How many are there in the UK?
- Where are ospreys found in the UK?
Ospreys at Loch of the Lowes
- How long have ospreys been at Loch of the Lowes?
- How long has the current female been coming to the Loch?
- What’s the story with the previous female?
- How did you know that this female was the same individual returning every year?
- What about the current male osprey? Do you know where he is from and how old he is?
- How do you tell the current male and female apart?
- Why are there often intruders at the nest?
- Is there a chance that our female could be driven off the nest by an intruder?
- What’s normal when with ospreys?
- Why are the eggs left for long periods of time occasionally?
- How long can the eggs be left alone?
- Do you have the ability to reposition the camera?
- Why does the female osprey, upon receiving a fish from her mate, promptly fly off to eat elsewhere?
- Where does the male go overnight?
- Could any of the ospreys flying in the vicinity of the nest be last year’s chicks?
- What would happen to the pair if our female fails to produce a healthy clutch and the chicks do not then hatch?
- Do you track your ospreys while they are wintering?
- How do ospreys migrate?
Satellite tagging ospreys
- What is satellite tracking?
- Why satellite track ospreys?
- Has it been done with ospreys before?
- How are the tags attached?
- Are the tags heavy for the birds to carry?
- How long will the tags last for?
- What happens if the tag stops showing movement during migration?
- How much will the project cost?
- How can I help?
What does an osprey look like?
The osprey is a large fish-eating bird of prey. It has a white head with a distinctive brown eye stripe. 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.
How big is an osprey?
The wingspan of an adult osprey is around 5 feet across. Females are around 20% bigger than males. A buzzard’s wingspan is similar but by contrast a golden eagle’s is 6- 7 1/2 feet.
What do they sound like?
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 its young are threatened. They also make a sound like a whistle.
Is there any difference between males and females?
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.
What adaptations do they have?
Although the osprey is a skilled flyer and hunter, like other raptors, it is truly unique among hawks physiologically. It’s 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.
Legs and feet
The leg and foot of an osprey is 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 gray, greenish or yellow scales. With four equal toes, one of them 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 of an osprey’s toes is armed with long, sharply curved talons that resemble fish hooks, for grasping and holding fish in flight. The bottom of an osprey’s 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 3 feet below the surface of the water, an incredible feat.
The wings of the osprey
With a wingspan of at least 50 inches and a maximum of about 6 feet, 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. Immature ospreys also have a distinct white tip on most of the feathers
An osprey’s plumage often prompts confusion for viewers, who with regularity 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.
How do they fish?
Ospreys fish over large water bodies (lochs, rivers and estuary areas) both fresh and salt water, and whilst hovering at around 300 feet 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 100 feet, 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 1 metre 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.
What do they eat?
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. In our area 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 (and are fond of mullet and flounder) and commonly hunt in estuarine areas. An osprey is capable of carrying fish that equals 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 raptors etc.
Where do they fish?
Our ospreys hunt in local lochs and rivers in a 20 mile radius of their nests. They commonly use the Craiglush and Butterstone Lochs, other local lochs and the River Tay.
Where is the osprey nest?
The nest is on Scottish Wildlife Trust land on the opposite 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 protected legally 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.
Why have they nested here?
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. In fact, 30% of Scottish ospreys nest on artificial nest platforms! Ospreys also nest on other artificial sites such as electricity pylons, phone towers etc.
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.
There is evidence that ospreys used to use ancestral nest sites, going back over hundreds of years, but this tradition was disrupted by their extinction in the UK.
How big is the nest?
The nest is about 6 feet (1.8metres) wide and 2/3 feet ( 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 bits to the nest throughout the summer. (See how the female on the nest fiddles with the nest, adjusting bits here and there.) 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 are by this time buried quite deep in the ever-changing structure of the nest.
Do they have different mates over their lifetime?
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.
When is the breeding season?
The breeding season varies depending on location, but in Scotland 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.
How many eggs do they lay?
Two or three is the usual number of eggs for an established breeding pair. Ospreys tend to start breeding at 3 to 7 years of age. In the first year of breeding, however, they often fail to breed successfully, and younger birds often start off with one egg, producing two the following year, and hopefully 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.
How big are the eggs? What do they look like?
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.
How long do they incubate for?
The general rule is 5 to 6 weeks (35-42 days), the average being 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.
What happens to the chicks?
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 5 weeks and ready to fly by 7-8 weeks. It is a very fast track growth spurt fuelled by their very high protein diet of fish brought in by dad.
The chicks are often ringed at around 5 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. 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 is only 12 to 14 weeks from when they hatch to when they begin their migration back to Africa. By this time they will weigh around 3.5lbs.
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.
How are the chicks fed?
Whilst 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 is the case with a previous male at Loch of the Lowes 7Y who famously fed the chicks whilst his mate was very ill, hence 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 always not always so and this ‘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!
Do ospreys migrate?
Yes – they migrate to West Africa for the winter, covering up to 5,000 miles during their journey. The fastest migration recorded took just 31 days, but it can take months for the birds to arrive at their destination. The female 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.
Do the youngsters migrate to the same area as their parents?
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, between 40-60% 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, once their hormones kick in and they are old enough to breed, they begin their return journey.
How do they navigate?
Nobody really knows but we suspect a combination of inherited genetic instinct, visual clues, stars and geomagnetic perception. It is still a mystery!
What happens once the adult pair reaches Africa? Do they winter together?
Osprey pairs leave for migration separately. The female usually leaves first and the male remains for another few weeks to provide fish for the chicks. We believe that an osprey pair will spend the 6 months of winter apart in West Africa, though large numbers of ospreys roost in loose colonies in some areas. The pairs only meet up again when they return to their breeding nest next year.
What is ringing?
Many bird are ringed by experts to enable scientific study of their movements, survival etc and to help us identify individuals. Ornithologists across the world report sightings of ringed birds, enabling us to record their movements.
The large easy to see leg rings used on raptors etc are called Darvic rings. These are individually colour and letter coded for each bird. Birds also have a smaller metal ring with a unique BTO serial number.
These rings are usually put on when the osprey chicks are 5-6 weeks old: old enough to have an unshakeable bond with their parents, and adult size legs, but not old enough to fly yet! They are usually removed from the nest by a specially licensed climber for a few minutes, weighed, measured and ringed on the ground, before being returned to their parents on the nest- the only time in their lives they will be handled. They tend to ‘play dead’ on the ground and do not seem stressed by the experience generally.
Are they found anywhere else?
Yes. Ospreys are found in a wide world distribution from northern Europe, Scandinavia, Russia and Siberia, the Middle East and Africa, to North, Central and South America.
- UK ospreys are related to those in northern Europe, Scandinavia, Russia and Siberia.
- There is a distinct subspecies in North, Central and South America.
- All these northern hemisphere birds migrate to equatorial areas for the winter, and return north to breed in the summer
- There are even Ospreys in Asia, mostly Japan.
- In Australia the Ospreys migrate in the opposite direction to our birds- North for the summer!
- Are ospreys African or Scottish? 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!
What predators do they have?
Ospreys as adults have very few predators, though we know a few each year in Africa are eaten by crocodiles. Many more are lost to bad weather, power line collisions and shooters. However, eggs are sometimes stolen by corvids and the young are vulnerable on the nest to predation by things like pine martens, and goshawks, which is why ospreys are very vigilant parents.
How long do they live?
Mortality in young birds is very high with an estimated 50% of osprey chicks failing to reach breeding age. Young ospreys are capable of breeding by their third year of life.
We think they live on average about 10-15 years in the wild, longer in captivity. Our famous breeding female at Loch of the Lowes is over 20 years old and there was a male which returned to Loch Garten every year to breed, who was last recorded in 2002, aged 17 years. There are some records of birds surviving into their twenties, but these are considered rare.
Are they rare?
Ospreys are listed by the IUCN on the species of Conservation Concern. Whilst not endangered on a worldwide level, in Europe where persecution has historically been worst, they are extinct or threatened in most of their old range, and are only now recovering. The UK is a good example. 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 areas of Scotland, one site in Cumbria, one in Wales, and at one artificially re-colonised site in Anglia: Rutland Water.
There are now approximately 240 breeding pairs in the UK, producing approximately 250 chicks a year.
Did you know that ospreys are still rarer in the UK than golden eagles?
Are they protected?
Yes – ospreys have the highest full legal protection under UK law (Schedule 1) and it is an offence to injure or disturb any bird, nest or egg.
Do ospreys fight?
Ospreys, like most raptors, rarely fight physically, but 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, the talons are used to emphasis the point! In defence of their chicks ospreys can be very violent towards predators, using their talons and beaks.
What do they do at night?
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.
Were ospreys extinct?
Ospreys were driven to extinction in most of the UK in the late 19th century, hanging on in Scotland until 1916. Whilst ospreys were considered extinct in Britain as a breeding bird from 1916, during the subsequent years, ospreys were still occasionally seen in Britain while on migration but there was no breeding success.
Why did ospreys decline and become extinct?
Historically, ospreys were killed because they were seen as a threat to fish stocks that were used as a source of human food. Ospreys were considered as vermin as they ate trout and salmon, and were routinely shot by gamekeepers and sportsmen.
Improvement of 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 osprey’s essential food.
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 pesticide in agriculture. This caused a build up of DDT in the food chain which led to many birds laying very thin shelled eggs which broke very easily and so reduced breeding success.
Many wild birds are still killed for sport in countries such as the Mediterranean region, as they pass on their annual migration and unfortunately this is still happening – even to ospreys!
When did ospreys return?
Ospreys returned for the first time to breed in 1954 to RSPB 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 here successfully.
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.
Why did ospreys return to Britain?
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 exchange between these populations historically.
As DDT pesticide 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 etc. .
The improvement in water quality, recovery of fish stocks and more availability of nesting sites helped returning birds.
The provision of artificial nesting platforms has proved a key to this success, dramatically improving breeding success rate in 1980s and 1990s.
How many are there in the UK?
There has been a steady increase in breeding success in Scotland from 2 pairs in 1967 to 150 pairs in 2000, and approximately 240 in 2012. There are also many juvenile birds around each year but the total population is probably less than 1,500 birds- still rarer than golden eagles in the UK.
Where are ospreys found in the UK?
The heartland of Scottish ospreys is in Speyside, the Cairngorms and Perthshire.
Ospreys have been at Loch of the Lowes since 1969. At that time this was only the fifth known nest 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 daylight in summer longest.
Newest growth areas for osprey populations are in southern Scotland (The Borders and Dumfries and Galloway), the Lake District, and Northumberland.
There are also now at least two pairs in Wales and a distinctive artificially reintroduced population at Rutland Water in East Anglia.
How long have ospreys been at Loch of the Lowes?
Since 1969 when they first appeared, and at that time this was only the fifth known nest in the UK. They have been breeding here successfully for most years since 1971, aside from a period in the mid-late 1980’s. There have in fact been four sites on the loch used by the various birds over the years, but the current nest has been the site used since 1991.
How long has the current female been coming to the Loch?
A new female arrived at Loch of the Lowes in 2015, replacing the previous female who had been breeding here for an incredible 24 years. Unfortunately because the new female has no leg rings we cannot identify her, therefore we don’t know her age, her origin or her breeding history. But what we do know is she arrived at Lowes in great condition and quickly paired and bonded with our male osprey. Regardless of her past she has been an incredible mother in her first season here, and the pair did a fantastic job culminating in the fledging of 3 healthy chicks – the first time this has happened in 12 years.
What’s the story with the previous female?
We believe she had been returning to breed for more than 20 years at Loch of the Lowes (from 1991). Since she must have been at least 3 or 4 to breed initially, she may have been as old as 27 years or more, 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 this year, and this is all part and parcel of nature. However the arrival of this new breeding female has successfully started a new chapter in osprey conservation at Loch of the Lowes.
How do you know that this female was the same individual returning every year?
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 on our HD camera a distinctive “lightning bolt” mark could be seen in the yellow iris of her right eye.
What about the current male osprey? Do you know where he is from and how old he is?
The current male 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 2010/2011 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 in Perthshire in 2000. Unfortunately he didn’t make it back in 2012 and has been replaced at his nest by our current male.
How do you tell the current male and female apart?
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, and has a prominent dark brown “Y” shape on the top of her head. Whilst 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.
Why are there often intruders at the nest?
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.
Could it be her old partner? It is definitely not her previous partner (pre 2010) as it doesn’t have his coloured leg ring.
Is there a chance that our female could be driven off the nest by an intruder?
The female does all she can to defend her nest, especially at the early stage of the season, in order to keep possession, 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.
What’s normal when with ospreys?
- Our birds usually arrive in the last week of March or early April.
- The female is usually first to arrive, followed by the male, between 1 and 10 days later.
- There are frequently other ospreys around at this time and some try to disturb the nest. These are mostly youngsters trying to ‘muscle in’, and sometimes mate with one of the resident birds.
- Eggs are normally laid by the end of April.
- Chicks on this nest generally hatch late May or early June
- Chicks are sometimes ringed at approximately 5 weeks- early to mid July
- Chicks fledge at about 7 weeks old- generally late July
- The family stays at the nest until mid to late August.
- The female leaves on migration first, often late July or early August
- The male and chicks hang around our area until late August or early September (sometimes later) but are seen at the nest less and less.
Why are the eggs left for long periods of time occasionally?
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, desperately hungry, or distracted by rivals etc- but they don’t usually leave the eggs for long.
How long can the eggs be left alone?
This depends on two things; predators and weather. Obviously any egg unguarded is vulnerable to opportunistic predators, such as crows, pine martens, herons etc. 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.
Do you have the ability to reposition the camera?
We do have the ability to move the HD camera view around and can zoom in and follow birds’ movements. 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 whilst the birds are nesting – this would be unethical and illegal, as it may cause the parents to abandon the eggs.
Why does the female osprey, upon receiving a fish from her mate, promptly fly off to eat elsewhere?
This behaviour is normal. It is very common in the period before the eggs are laid. Once incubation has started, the male will usually consume the head of the fish himself, and will then deliver the other half to the female, who will leave the nest, allowing the male to take over her duties. This gives the female a welcome break and a chance to get some exercise, and have a ‘toilet stop’ away from the nest to help keep it clean and hygienic.
Where does the male go overnight?
Although he is often absent from the nest he 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.
Could any of the ospreys flying in the vicinity of the nest be last year’s chicks?
Ospreys will not return to the UK until they are mature enough to breed at around 2-5 years old. So they spend the first few years of their lives in Africa and won’t return to Scotland until they are of breeding age. It is possible that some of the birds are past chicks from Lowes, and we have had at least one ringed chick in 2008 return right back to its natal nest area in the past for several days.
What would happen to the pair if our female fails to produce a healthy clutch and the chicks do not then hatch?
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.
Do you track your ospreys while they are wintering? And where do they go?
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 the Gambia in late September. A few birds also seem to overwinter en route, for example in southern Spain. This is one question we hope to gain more insight into from our satellite tracking studies, and we will be closely following our two tagged chicks, Blue FR3 and FR4 on their journey south later this season.
How do ospreys migrate?
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 crossing desert.
We know most ospreys take between 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 and wander more before settling down to habitual yearly pattern. 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, at up to 100km a day and can even fly up to 48hrs 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, 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!
What is satellite tracking?
Modern technology allows us to attach small satellite transmitters to a lightweight harness on birds. This is expensive to do, but enormously useful in collecting detailed information such as exact routes, timings and behaviours of migrating birds. .
Our birds were tagged for the first time in 2012 but previously ospreys had been radio satellite tracked from Speyside by Roy Dennis from the Highland Wildlife Foundation and birds from Rutland Water, as well as ospreys from Scandinavia. There are also some websites where the migration of radio tagged ospreys can be followed.
Satellite studies tell us:
- Most ospreys take a month or more to get to their destination
- All ospreys stop and feed on route and stick to areas with waterways
- Most go to the same over-wintering area each year
- Young birds make more stops and wander more before settling down to a habitual yearly pattern
- Ospreys take longer to migrate in autumn than in spring when they take short cuts in order to get back to their nests fast!
- The weather affects how far and fast they travel
- Birds that don’t make it often end up too far west or over the sea for too long
Why satellite track ospreys?
It is an enormously useful tool in collecting detailed information such as exact routes, timings and behaviours of migrating birds- it is amazing that for such a high profile species, there is still an awful lot we don’t know. This work is crucial to more detailed scientific study of the species and a better understanding of the ‘other half’ of the ospreys’ lives. If we know more about their migratory routes for example, we can work more closely with organisations and governments in those countries to ensure the areas that ospreys use are protected. It may also help answer such questions as: Are there countries where osprey, and indeed other migrating birds have a higher mortality rate? If so, can we find out why? Do birds from UK stock migrate to the same locations as their cousins in Scandinavia? Are the birds from the UK more prone to flying off course and ditching in the Atlantic?
Indeed, the data provided by tagging will contribute to the research theory that reintroduced and recolonised birds such as the UK population, produce chicks which tend to set off on migrations in a direction which relates to their ancestral origins (we think the information is part of their biological programming and therefore their course of travel might be predictable). Unfortunately, in the case of reintroductions, this is not necessarily the best route from the country of birth. Proving or disproving this theory has repercussions for future re-introductions.
Has it been done with ospreys before?
This technology has been around for many years but is getting smaller and cheaper all the time. It has been used very successfully on mammals and many birds such as raptors, geese, swans, and now even songbirds! Ospreys have been radio satellite tracked from Speyside and Rutland Water have been, as well as ospreys from Scandinavia and America.
A famous example is ‘Logie’ a female osprey tracked by Roy Dennis from the Highland Wildlife Foundation, and more recently chicks from the Lake District Osprey Project, RSPB Loch Garten, and CorsDyfi Osprey Project in Wales. There are several websites where the migration of radio tagged ospreys can be followed.
One of our Loch of the Lowes birds Blue 44 was satellite tracked for the first time in 2012, along with a chick from an SWT reserve in Angus Blue YD. In 2013 we tagged Blue YZ, a chick from Loch of the Lowes. Most recently in 2015, chicks Blue FR3 and FR4 were also fitted with a satellite transmitter.
How are the tags attached?
The tiny transmitter packs are sewn to a lightweight harness which goes around the birds back and wings, like a small rucksack, The chicks are sewn into the harness with a few threads at the front – leaving enough room for the chicks to put on weight and allowing the harness to drop off at the end of its useful life. This ensures the harness puts no strain on the bird. There is a small flexible aerial on the top of the pack which receives the satellite signal. Crucially the pack doesn’t interfere with flight or the ospreys’ hunting behaviour, leaving their legs free. See our video on youtube of the process in action in 2012 at Loch of the Lowes at: http://www.youtube.com/watch?v=C6THdM7FsS4
Are the tags heavy for the birds to carry?
The tags weigh approximately 5% of the bird’s body weight, approximately 30 grams. This is not thought to significantly impede the birds in their usual movements, or increase chick mortality.
How long will the tags last for?
Tags will run on their solar charging units for three to five years. The life of the tags can vary depending on battery life and the amount of data that is to be collected, as well as the conditions that it has to survive in. The bird may also lose its tag before the tag itself gives up, in which case the tag can be retrieved and reused. In most cases, osprey tags last 1-3 years.
What happens if the tag stops showing movement during migration?
If the tracking device suggests the osprey has stopped moving this could be for several reasons, including the following possibilities:
- The bird could be resting– this is common during migration / bad weather
- The battery could be flat due to lack of solar power
- The satellite might not be able to detect a signal, e.g. if the bird is in forest
- The bird might be dead
It is possible to tell from the data received whether the battery was failing or if, in fact, the bird has stopped moving. In cases where transmission indicates no further movement, we will check the recent data and wait to see if more data is collected.
If we finally believe the bird is dead our actions will depend on where it was last located. We may try to recover the body if possible to find out what happened. This can obviously only be done in certain locations.
How much will the project cost?
The total cost for the project is currently budgeted to be £23,444; this includes the purchase of the satellite tags, costs associated with downloading information collected by the tags, webpage development and data analysis.
This project is only possible following a fantastic fundraising drive led by our dedicated members and volunteers. We thank everyone who has donated to date in support of the satellite tagging.
How can I help?
Please consider donating today to support our work to protect the osprey, or support us by becoming a member of the Scottish Wildlife Trust.
This document was written by Emma Rawling, the previous Perthshire Ranger, and updated by Charlotte Fleming, the current Ranger. Information herein is from a range of sources, but with very special thanks to: Roy Dennis of Highland Foundation for Wildlife, Diane Bennet of Tweed Valley Osprey Project and Valerie James. Thanks to all the volunteers who gave feedback and to all the bloggers and webcam viewers who got in touch with osprey questions.
Still need to know something? Email us on firstname.lastname@example.org and we will try our best to help.