The golden eagle is a large bird of prey, powerful and clever, with a wing span of up to 227 cm and a body mass of 3-3.5 kg in case of male birds and 4.5-5.5 kg in case of female birds. The brow of an adult bird is dark brown, the rest of the crown and the nape are golden brown, while the beak is black and the cere yellow. The upper half of the bird’s body is dark brown with light (worn) feather edges and the entire lower half looks rather dark outdoors. A young bird is dark chocolate brown, has a golden crown, white spots on its wings and a wide white area on its tail stock.
Feeding habits
In Estonia, the golden eagle feeds mainly on white hare, black grouse and great grouse. The diet is diversified by mammals like grey hare, roe, squirrel, marten and racoon dog, and birds like raven, hazelhen, mallard and crane. In winter, the golden eagle often feeds on carrion.
Nesting
The golden eagle is sedentary and spends the winter near its nesting place. Young birds who are not yet sexually mature, travel about more.
The golden eagle inhabits suitable nesting places for decades – at least a quarter of the current nesting places can be traced back through literary references to information passed on by word of mouth to the 19th century.
Golden eagles have usually chosen the pine as their nest tree. Only on rare occasions have nests been built in firs or aspens. At times, one pair of eagles has two nests that are inhabited in turn. A clutch consisting of one or two eggs is laid in the nest during the first half of March. The chicks hatch during the second half of April, and on most occasions, only one of the offspring learns to fly by the beginning of July.
Distribution and numbers
The golden eagle is common throughout Estonia. It inhabits larger natural massifs and prefers to live in bogs. At the beginning of the 20th century, 20-30 pairs of golden eagles nested in Estonia. In the years 1964-1973, the eagles were only observed in up to 12 nesting locations and nesting was successful in just 4-6 nests every years. During the last couple of decades the situation has improved and the number of golden eagles nesting in Estonia has remained rather stable at 40-50 pairs. A few nests have also been found in untraditional locations, such as on the edge of peat deposits or on lakeshores.
Reproductive parameters
The results of the Golden Eagle broods in 2004, 2005 and 2006 are as follows:
|
2004 |
2005 |
2006 |
| Number of occupied nests with known breeding results |
34 |
28 |
25 |
| Number of successful nests |
6 |
13 |
13 |
| Total number of fledglings |
6 |
13 |
14 |
| Mean number of fledglings per occupied nest |
0,20 |
0,50 |
0,56 |
The white-tailed eagle is our largest bird of prey, with a wing span of 200-245 cm and a body mass of up to 6 kg. The upper and lower parts of an adult bird are (dark) brown, the head and the neck are pale brown with dark stripes, the entire tail is white, the beak is sallow and the
feet are yellow. The plumage of young birds is dark brown, making them easily confused with spotted eagles, especially in case of a brief encounter. However, the white-tailed eagle is significantly sturdier than the spotted eagle and its wing movement is slower. Visually, thewhite-tailed eagle is reminiscent of aflying carpet.
Feeding habits
The white-tailed eagle feeds in coastal sea areas with shallow water and in larger bodies of inland water. Some pairs have adapted to hunting in fish ponds, thus “robbing” the ospreys of their prey.
The staple diet of the white-tailed eagle includes waterfowl (ducks, grebes, gulls) and fish, in wintertime also carrion.
Nesting
In Estonia, adult white-tailed eagles are usually sedentary, while younger birds move around quite a bit. The nesting places are usually located in fully grown coastal pine forests, mixed forests, or on bog islands. A pair of nest at the top of an old pine or aspen, and a nest that has been used for decades can weigh nearly a ton.
White-tailed eagles begin repairing their nest already in the middle of the winter, adding green pine branches to the construction. A full clutch, 1-3 eggs, has usually been laid by the second half of March. The white-tailed eagle must brood for approximately 38 days without break.
Most often two fledglings have learned to fly by the beginning of July, but almost every year, clutches of three have been seen near better hunting grounds.
Distribution and numbers
The white-tailed eagle is apparently native to Estonia. The first written records of white-tailed eagles encountered in the Baltic States date back to the final quarter of the 18th century. In 1815, the white-tailed eagle has been mentioned as a bird that is not particularly rare in Estonia, especially near Lake Peipsi. Based on the observations of ornithologists from the 19th century, the number of white-tailed eagle pairs can be estimated at no less than 30. A decrease in the numbers of white-tailed eagles evidently began during the last quarter of the 19th century and culminated during the 1960s, when no successful nestings were reported for several years. The situation did not improve until the second half of the 1970s, and currently, the number of white-tailed eagle pairs nesting in Estonia is nearing 150.
Reproductive parameters
The results of the White-tailed Eagle broods in 2004, 2005 and 2006 are as follows:
|
2005 |
2006 |
2007 |
| Number of occupied nests with known breeding results |
107 |
107 |
134 |
| Number of successful nests |
40 |
49 |
55 |
| Nest success (%) |
63 |
68 |
74 |
| Total number of fledglings |
54 |
73 |
74 |
| Mean number of fledglings per occupied nest |
0,9 |
1,06 |
1,12 |
| Mean number of fledglings per successful nest |
1,42 |
1,55 |
1,51 |
The osprey is the smallest of Estonia’s eagles, but also has the most distinctive appearance. Its light lower body, the dark bends of its wings, the multicoloured head and its gull-like appearance when flying help differentiate the osprey from other eagles even without the help of optical instruments. One still has to be observant when identifying the osprey – at the first glance they look remarkably similar to large gulls. Its wing span is 145-160 cm, its body weight is 2 kg for female birds, and about 1.5 kg for male birds. When tracking its prey, the osprey flies in place (hovers in the air) similarly to the common buzzard, the short-toed eagle and the common kestrel. The osprey makes high-pitched squeaking sounds—it is especially vocal when its nest is being disturbed.
Feeding habits
As its Estonian name (literally “the fish eagle”) suggests, our smallest eagle feeds almost entirely on fish. It is probable that the sleeker body of this species has developed during evolution in order to improve its chances of catching fish and makes the osprey better suited for executing moves requiring dexterity. Its more dextrous and faster flight is the osprey’s advantage compared to its larger relatives. However, the osprey can never be sure that the fish it has caught will remain its prey, since in many good hunting grounds, white-tailed eagles have specialised on taking over the ospreys’ catch. Fish are caught from as deep as a meter below the surface, and sometimes, the entire osprey can disappear under water during this process. The osprey’s favoured prey is fish weighing 200-300 grams: it is difficult to fly far with a larger fish and catching smaller ones would be inefficient. The osprey can transport prey to its nest from a distance of over 25 km! Ospreys are everyday visitors at some fish farms and perform the necessary task of removing injured or diseased fish, although healthy fish also fall victim to their attacks. However, when the fish in the ponds grow too large for the birds (over 400 g), the ospreys relocate to other hunting grounds. One osprey needs about 300 g of food per day. If the ospreys reach the final destination of their migration before the ice has melted, or if their nesting period is dominated by especially bad weather, the birds have to either fast or feed on other prey—thus, osprey have also been seen hunting mice and frogs.
Nesting
The ospreys reach their nesting areas in spring, even before the first bodies of water have been freed of ice. They immediately begin repairing their old nests, or building new ones if the previous nests have not survived the winter. Natural nests are often destroyed by storms—the nests are always located at the tops of trees, and therefore, have no protection against the forces of nature. The nests also collapse due to the fact that the osprey cannot find nesting trees that are strong enough to withstand the winds. To alleviate this problem, eagle enthusiasts have built artificial nests in place of destroyed ones or on nearby trees that are suitable for nesting. Nests built in treetops also have their advantages—the birds can recognise potential danger earlier, flying onto the nest is easier and it is easier for the fledglings to learn to fly. The hen stays with the nest after laying the eggs and it is the task of the male bird to bring enough prey to the nest to feed the hen and the chicks. If you happen to find an eagle’s nest located on top of a tree, like that of a white stork, it probably belongs to an osprey. By the way, in America the osprey usually nests in places preferred by the white stork in Estonia. The osprey lays 2-3 eggs and the hatched chicks usually learn to fly by the end of July. After achieving flight, they still have much to learn about catching their prey, however. Thanks to the environment (primarily bodies of water) being freed of pollution by chlorine organic compound (e.g. DDT), and partly due to the construction of artificial nests, the productivity of Estonia’s ospreys (i.e. the average number of chicks hatched by nesting pairs) is one of the highest in the world.
Distribution and numbers
The osprey inhabits almost every continent. Here it nests mainly in Eastern and Southern Estonia and is slowly expanding towards the west. As of 2005, 50-55 pairs of osprey nest in Estonia. As recently as 1985, there were only five known pairs nesting in Estonia, so the number of ospreys has grown 10 times during the last quarter of a century.
Reproductive parameters
The results of the Osprey broods in 2004, 2005 and 2006 are as follows:
|
2004 |
2005 |
2006 |
| Number of occupied nests with known breeding results |
35 |
44 |
37 |
| Number of successful nests |
26 |
31 |
29 |
| Nest success (%) |
74 |
71 |
78 |
| Total number of fledglings |
56 |
60 |
61 |
| Mean number of fledglings per occupied nest |
1,6 |
1,36 |
1,65 |
| Mean number of fledglings per successful nest |
2,15 |
1,94 |
2,10 |
The greater and lesser spotted eagles look similar. Their wing span is 130-180 cm. The plumage of adult birds is entirely brown, while young birds are covered with light spots to a lesser or greater degree. Externally, spotted eagles resemble the common buzzard and from afar it is only possible to differentiate between the species by their silhouette when they fly: while the spotted eagle usually keeps the tips of its wings down when it glides, the common buzzard generally holds them up. When inspecting the birds from closer quarters, it can be noticed that the common buzzard usually has a lot of white in its plumage, while the spotted eagles are usually uniformly brown and have only a few white spots in their feathers. Upon even closer inspection, the observer will find that the feet of the spotted eagle are covered in feathers down to its toes, while the legs of the common buzzard are devoid of feathers. Telling the difference between the two species of spotted eagles is difficult. As a rule, the greater spotted eagle is darker, slightly larger and sturdier than the lesser spotted eagle. Differentiating between the two is also difficult because the lesser and the greater spotted eagle form mixed pairs and produce hybrids.
Feeding habits
Spotted eagles usually hunt their prey on grasslands that are not intensively managed, but also on wetlands, fields and other open landscapes and infrequently even in forests. Their hunting grounds are usually located near their nests, located up to 1-2 km from the nesting site. The spotted eagle usually hunts its prey in flight or by stalking from trees located near the edges of forests and other higher places (lone trees, balls of hay, electric posts), and occasionally, the eagle looks for its prey walking on the ground. The eagle actively hunts its prey by flying or walking in case of poor food resources, but in case of rich resources opts for stalking prey. The prey consists mostly of small mammals – voles, moles, with frogs and birds often included in the menu. Sometimes the spotted eagle also hunts for snakes and larger insects.
Nesting
Spotted eagles are migratory birds that winter in the Middle East, Southern Europe, Central and Southern Africa. The migration to Africa and back takes place mainly via the Bosporus Strait, the Middle East and the Nile Valley. The greater spotted eagle arrives in Estonia at the end of March and the first lesser spotted eagles can be spotted somewhat later—at the beginning of April. Both species leave in September, but individual birds can still be sighted in October. The spotted eagles live on a mosaic landscape, where forests alternate with meadows, pastures, fields, river valleys and swamps. Lesser spotted eagles are more adapted to life on agricultural terrains than are their larger relatives. Spotted eagles usually construct their nests themselves and inhabit them repeatedly on subsequent years, especially if not disturbed. Occasionally they use the old nests of other larger birds of prey (the common buzzard, the northern goshawk) or of the black stork. Sometimes a pair of spotted eagles has several nests which are used alternatively during different years. The eagles start building or repairing the nest immediately upon their arrival. By the end of April or beginning of May there are one or two (very rarely three) eggs in a full clutch. The hen begins brooding right after laying the first egg, due to which the chicks hatch at different times. The hatching process lasts for 37-41 days. The fledglings are able to fly at the age of 8-9 weeks, which in Estonia usually coincides with the first half of August. Of the fledglings one, or very rarely two, learn to fly. The procreational success of Estonia’s spotted eagles is characterised by a 3-year cycle which results from the change in the numbers of voles, the eagles’ prey of choice. During top years, the productivity can reach an average of over 0.8 young birds raised per pair, but during the lows of the cycles, the number can drop to below 0.3.
Distribution and numbers
The lesser spotted eagle is the most numerous species of eagles in both Europe and Estonia. A hundred years ago, the species was not as common as today, and their numbers further decreased during the first half of the 20th century as a result of the “hawk war”. Afterwards, the population has gradually recovered. During the 1960s and 1970s, there also occurred a change in the ecological niche: the eagles began nesting near cultivated landscape. After that, during the 1980s, the number of lesser spotted eagles probably grew rapidly. In Estonia, the number of lesser spotted eagles is currently estimated at 480-600 pairs (up to 20,000 pairs in the world). The largest areas of habitation of the lesser spotted eagle are currently located in Belarus (3,150-3,350 pairs), Latvia (2.000-2,800 pairs), and Poland (1,660-1,850 pairs). There is no significant information regarding the numbers of greater spotted eagles in Estonia from earlier years—definite proof of their nesting dates from 1995. According to present estimates, 20-30 pairs of greater spotted eagles live in Estonia.
Reproductive parameters
The results of the Lesser Spotted Eagle broods in 2004, 2005 and 2006 are as follows:
|
2005 |
2006 |
2007 |
| Number of occupied nests with known breeding results |
132 |
145 |
158 |
| Number of successful nests |
92 |
99 |
33 |
| Nest success (%) |
91,1 |
87,6 |
76,7 |
| Total number of fledglings |
99 |
101 |
33 |
| Mean number of fledglings per occupied nest |
0,83 |
0,74 |
0,22 |
| Mean number of fledglings per successful nest |
1,08 |
1,02 |
1,00 |
The short-toed eagle is somewhat larger than an osprey, with a wing span of 170-185 cm and a body mass of 1.8-2.3 kg. The lower half of the bird is light, usually with dark spots (the pattern can vary to a great degree), the head and chest are darker and the upper half of the body is greyish brown. The head of the rather vocal short-toed eagle is large like that of an owl and its eyes are large and yellow-orange. When flying, the eagle is easily recognized by its light underside that does not have dark contrasting patches (the osprey and the common buzzard that also have a light underside have clearly noticeable dark patches on the bends of their wings). The short-toed eagle’s rather long tail has 3-4 dark stripes and the bird’s wings are wide and flexible.
Feeding habits
The staple food of the short-toed eagle are reptiles—in Estonia usually adders and common lizards. The short-toed eagle hunts its prey over open ground—flying above treeless bogs, meadows, sands, burnt woodlands, clearings, and flood plains or stalking its prey on the top of trees that provide a good field of sight.
Nesting
Unlike other Estonian eagles, the short-toed eagle does not usually nest in the same place in subsequent years. A new, relatively small nest is constructed on top of a pine every year, and only one whitish egg is laid there in the middle of May. The hatching period lasts for a month and a half and the chick stays in the nest for two and a half months—therefore, an average Estonian summer is too short for the short-toed eagle to nest successfully. The last sighting of a short-toed eagle nest in Estonia was at the beginning of the 1970s.
Distribution and numbers
The short-toed eagle has always been very rare in Estonia, since the main natural habitat of the species lies to the south, stretching from the Mediterranean region to India. The birds encountered each year mainly in Western and Northern Estonia are mostly single, although during more favourable years, an estimated five pairs of short-toed eagles may nest here. Short-toed eagles prefer natural landscapes and they can be spotted mainly around larger bogs and widing rivers, but they also favour thinner pine forests located in bogs, heaths and moorland.
The wing span of the black stork is 185-205 cm. It resembles the white stork, but is a little smaller than its relative and has a black neck and the underside of its wings is black. An adult bird is white from its chest down to the underside of its tail, the rest of its plumage is black with a strong purple-green metallic shine and its beak and legs are red. In case of a young bird, the black colour of the plumage is replaced with dark brown and the olive green of the legs and beak range with greyish pink. Ancient Estonians believed that this timid and rarely seen inhabitant of the woods pordents death. Probably this bird with a deathly black “cloak” was also the one “generally considered a holy bird” (Helme). It is likely that the bird called “piva-lind” (the holy bird) in the Livonian language also indicated the black stork. Sadly, no one remembers the ancient Estonian names for the black stork, however, Russian linguists have discovered that, in the old Novgorod region, the word “aist” (stork) had the same meaning as the word “estonets” (an Estonian) does today to the people of that area.
Feeding habits
The main food of the black stork includes all kinds of fish and amphibians that it prefers to catch from small forest rivers and ditches. On rarer occasions, the black stork can be seen feeding from lakes, fish ponds, shallow seawater, and meadows. Research in recent years indicates that male birds can fly distances of up to 25 km from the nest to reach good feeding grounds.
Nesting
The black stork is a migratory bird. The male birds reach Estonia by the beginning of April, even before the snow and ice have melted and the female birds follow a week or two later. During the period 1987 – 1996, the earliest date of sighting was March 16th, the average arrival time was March 30, and the last autumn sightings occurred during the middle of September. The black stork travels to its wintering area, extending from the Mediterranean countries to the Equator, either alone or in a small group. After returning, the male birds start to repair their nests right away to win the approval of the soon-to-arrive female birds. Since Estonia is situated on the northern border of the black stork habitat, not all male birds find mates here. Black storks attain sexual maturity at three years of age. The oldest known black stork living in the wild reached the age of 18 and its zoo-dwelling counterpart survived till 30. After mating, the female bird lays 2-5 (6) eggs and the parents take turns brooding the eggs for approximately five weeks. After the chicks have hatched, one adult bird always stays with the nest in order to guard its offspring against predators and unfavourable climate conditions. As the young birds grow and their needs increase, both adult birds have to leave in search of food. At the beginning of August, the offspring fly out of the nest, but still return to stay the night for a week or two.
Distribution and numbers
The black stork is common from Western Europe to the Far East and the population of the species is estimated at 15,000 pairs. The number of black storks nesting in Estonia has fluctuated greatly since the middle of the 20th century. At the beginning of the 1960s, an estimated 150 pairs nested in Estonia. This was followed by a significant increase in the population—according to the bird atlas, 250 pairs nested in Estonia at the beginning of the 1980s. During the last 20 years, the number has fallen to 100-115 pairs. Serious attention must therefore be paid to the protection of the black stork, and in addition to protected nesting sites, it is necessary to preserve former nesting sites, so that the population can increase. Meanwhile, the black stork has started expanding its habitat towards the west and has begun nesting in several Western European countries like Belgium, France, Luxembourg and Italy. A similar tendency has been noted in Estonia—until 1970, no proof existed of the black stork nesting on our western islands, but now the distribution map shows that Saaremaa has become one of Estonia’s most densely populated counties. The nesting sites of the black stork are located in larger forest masses, far from human habitation. Their preferred forests include marshland forests and mixed forests, but black stork nests can also be found in moorland pine forests.
The choice of a nesting site is affected by three main criteria:
- an old tree with strong branches, fit for nest construction
- nearby suitable feeding grounds: shallow, sheltered water(course)s
- lack of disturbances
Reproductive parameters
The results of the Black Stork broods in 2004, 2005 and 2006 are as follows:
|
2006 |
2007 |
2008 |
| Number of occupied nests with known breeding results |
|
|
43 |
| Number of successful nests |
|
|
14 |
| Nest success (%) |
|
|
32 |
| Total number of fledglings |
29 |
27 |
37 |
| Mean number of fledglings per occupied nest |
1,3 |
1,1 |
0,86 |
| Mean number of fledglings per successful nest |
2,7 |
2,6 |
2,64 |
The golden eagle is a large bird of prey, powerful and clever, with a wing span of up to 227 cm and a body mass of 3-3.5 kg in case of male birds and 4.5-5.5 kg in case of female birds. The brow of an adult bird is dark brown, the rest of the crown and the nape are golden brown, while the beak is black and the cere yellow. The upper half of the bird’s body is dark brown with light (worn) feather edges and the entire lower half looks rather dark outdoors. A young bird is dark chocolate brown, has a golden crown, white spots on its wings and a wide white area on its tail stock.
