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Nest-site Attendance of the Resident White-tailed Sea Eagle (Haliaeetus albicilla) Outside the Breeding Season
Abstract
The territorial pairs of White-tailed Sea Eagle are mainly sedentary and highly faithful to breeding territories and nest-sites. Due to a dramatic population decrease, many recent studies deal with the population status and habitat requirements of the species, but contemporary data on the nest-site attendance activity of the recovered population outside the breeding season are scarce. In the present study, we analysed the bonds of resident adult Sea Eagles with their nest-sites outside the breeding season (20 September – 20 February). We found that Sea Eagles actively attend their nest-sites during the non-breeding season, however, nest-site attendance varied between months, but not between years. Besides, almost half of the checked pairs repaired old or built new nests long before incubation, during September–December. We discuss the obtained results in the light of nest-site protection from forestry-related disturbance and propose to extend the protection of Sea Eagle nest-sites from above mentioned disturbance both during the breeding and non-breeding season.
... Moreover, more activity was observed at distance 0-500 m than further away from the nearest active nest. There was more activity at 0-500 m than further away from the nest, which probably could be due to defending territories and delivering food to the nest (Dementavicius & Treinys 2009). Neither distance to nearest turbine, nor the locations seem to have any effect on the general activity. ...
... Regarding flight activity, the results from the multinomial regression analyses showed a statistically significant difference between moving flight and soaring in number of individuals observed together, with more individuals observed together in moving flight than in soaring ( Figure 30). This could possibly be caused by pairs of individuals performing moving flight when moving back and forth between territories and feeding areas (Dementavicius & Treinys 2009). ...
... A decrease in breeding performance with advanced breeding date, including the body condition of nestlings (Griebel & Savidge 2003), has commonly been observed in migratory birds (Sergio et al. 2007, Morrison et al. 2019). Pairs of White-tailed Eagles occupy their nesting territories for many years (Struwe-Juhl & Grünkorn 2007), and pairs are resident in the region we studied (Dementavičius & Treinys 2009). Therefore, it is likely that earlier clutches were laid by females that were in good body condition just after the winter months, which may have been influenced by the local food supply and/or individual traits, such as age (Pietiäinen & Kolunen 1993, Solonen 2011. ...
Capsule
We found no evidence of decreased reproductive performance of the White-tailed Eagle Haliaeetus albicilla, despite ongoing population increases in an environment characterized by different types of utilized habitats.
Aim
To characterize temporal and spatial variations in several components of breeding performance in an increasing White-tailed Eagle population.
Methods
The breeding performance and number of pairs located in the region east of the Baltic Sea was monitored between 2005 and 2020. We analysed the trends in the numbers of pairs and several reproduction parameters for 16 years, and compared variation in breeding performance in four different habitats through application of generalized linear (mixed) models.
Results
The number of White-tailed Eagle pairs increased three-fold locally between 2005 and 2020, but we found no evidence for a deterioration in breeding performance parameters (nesting success, brood size, proportion of females among nestlings, body condition of nestlings). The probability of successful nesting, nestling sex and number of nestlings in a brood were found to be similar between pairs associated with different habitats, ranging from coastal lagoons to natural waterbodies within an inland landscape. The body condition of the nestlings, however, was habitat-dependent, with the best body condition evident in nestlings reared near the Curonian Lagoon.
Conclusion
Results indicate that the abundance of this predator population will continue to grow in the region east of the Baltic Sea.
... The White-tailed Eagle (body mass, ∼3.1-6.9 kg) is largely a resident raptor species occupying territories most of the year (Dementavičius and Treinys 2009). Populations in the countries around the Baltic Sea decreased rapidly in the 1960s and 1970s, but wide-range protective measures yielded positive results, and the population of the species increased substantially between 1970 and 1990 (Helander and Stjernberg 2003;Stjernberg et al. 2005). ...
The processes of competition and predation determine the degree to which species can coexist; the importance of competition
in particular has been emphasized at high trophic levels. Competition exclusion will occur when habitat overlap between sympatric
species is high. In this study, we investigated nesting habitat overlap between internationally protected diurnal tree-nesting
avian predators of central Europe, namely, White-tailed Eagle (Haliaeetus albicilla), Lesser Spotted Eagle (Aquila pomarina), Black Stork (Ciconia nigra), and Osprey (Pandion haliaetus). We found significantly different nesting habitats among the study species and suggest that this could be a consequence
of the resource-based segregation, but not a consequence of asymmetrical interspecific competition. The results also show
that habitat of the recovering populations of White-tailed Eagle overlapped with the habitat used by the Lesser Spotted Eagle,
Black Stork, and Osprey to varying extents with a niche overlap values being below the competition exclusion threshold. Nevertheless,
we suggest that competition by White-tailed Eagle at a population level may limit Osprey, though not Lesser Spotted Eagle
or Black Stork.
Although facultative scavenging is very common, little is known about the factors governing carrion acquisition by vertebrates. We examined the influence of carcass characteristics, carcass state, and weather conditions on carrion use by main scavengers. Carcasses (N = 214, mainly ungulates) of various origins (predation, natural deaths, harvest) were monitored by systematic inspections (N = 1784) in Białowieża Forest (Poland). Common raven (Corvus corax L., 1758), red fox (Vulpes vulpes (L., 1758)), and European pine marten (Martes martes (L., 1758)) mainly used the prey remains of gray wolves (Canis lupus L., 1758). The kills of predators were the preferred carrion, rather than dead ungulates. Common ravens, common buzzards (Buteo buteo (L., 1758)), white-tailed eagles (Haliaeetus albicilla (L., 1758)), and domestic dogs scavenged more frequently on carcasses in open habitats. Carcasses located in the forest were the most available to European pine martens, jays (Garrulus glandarius (L., 1758)), and wild boar (Sus scrofa L., 1758). The common tendency was to increase scavenging when temperature decreased, except for raccoon dogs (Nyctereutes procyonoides (Gray 1834)). As snow depth increased, jays and great tits (Parus major L., 1758) increased scavenging. We suggest that carrion use by scavengers is not random, but a complex process mediated by extrinsic factors and by behavioural adaptations of scavengers.
A young White-tailed Sea Eagle Haliaeetus albicilla from the Uckermark (Brandenburg, NE Germany), which had been found on the ground by foresters and taken to a local veterinary center, was fitted with a satellite transmitter (PTT) and placed back into its nest. lt was thus possible to track its reintegration into the family, fledging, transition to independence, dispersion and movements in its wintering grounds. At the same time the suitability of a novel, solar-powered version of a PTT could be tested. We here report results up to the end of 1993, the year of the eagle‘s birth. The young eagle was accepted and fed by its parents without any problems. Its behaviour differed in no way from that of its sibling. Up to early October the bird roosted near the nest, while continuously expanding its range of daily activity. Up to the end of August it kept to a home range of only ca. 9km² but this was extended to 120 km² up to the end of September and thereafter to 170 km². On the l9th October it flew ca. 60 km in a south-westerly direction from tbe nest as far as Rheinsberg/Alt-Ruppin, where it also spent the night, returning thereafter to the forest of its birth. From l3th November it finally abandoned the nest site and took up permanent residence in the Mecklenburg lake district ca. 100 km WNW of its birth place.
Since this was the first time anywhere that a wild bird has been fitted with a small solarpowered version of a PTT weighing less than 100 g and with a theoretical life of 5-6 years, some technical aspects are also discussed. During the period of l5th July to 31st December 1993, 147 satellite locations were obtained, each location corresponding to a customarily obtained recovery of a ringed bird with tbe important difference that all locations are linked in a cham, following the route of one individual.
Keywords: Haliaeetus albicilla, satellite tracking, ground tracking, VHF telemetry, solar-powered PTT, break-up of family, dispersion.
As a follow-up of national distribution maps for Germany and Poland, a common map for both countries was produced, for the first time also including density data. In total, 1150 to 1200 breeding pairs were recorded in 2004, with the highest density in the Odra-Lagoon-area in Poland (9 pairs per German 1:25,000 ordnance map grid cell = roughly 100 km 2). The further continuing increase of the population size will likely be followed by an increase in density as well.
The White-tailed Eagle nests in the Åland Islands (and SW archipelago) and the islands of the Quark region in Finland, and also close to the large reservoirs in Lapland. Prey remains collected from nest sites in these areas in 1978-90 indicate that birds constitute on average 51% of the prey, fish 42% and mammals only 7%. Pike constituted some 33% of the prey. Some large regional differences were observed in the frequencies of given types of prey, the proportion of fish being as much as 67% in Lapland but only 32% in the Quark region and 27% in the Åland Islands, while the opposite trend was observed in the case of birds (29%, 59% and 65%, respectively). The birds were primarily composed of Anatidae, which constituted 51% of all prey in the Åland Islands and 17% in Lapland. Temporal differences also occurred in the diet, Eiders and gulls, for example, increased in the diet in the archipelago regions, in parallel with prey population changes.
Although facultative scavenging is very common, little is known about the factors governing carrion acquisition by vertebrates. We examined the influence of carcass characteristics, carcass state, and weather conditions on carrion use by main scavengers. Carcasses (N = 214, mainly ungulates) of various origins (predation, natural deaths, harvest) were monitored by systematic inspections (N = 1784) in Białowieża Forest (Poland). Common raven (Corvus corax L., 1758), red fox (Vulpes vulpes (L., 1758)), and European pine marten (Martes martes (L., 1758)) mainly used the prey remains of gray wolves (Canis lupus L., 1758). The kills of predators were the preferred carrion, rather than dead ungulates. Common ravens, common buzzards (Buteo buteo (L., 1758)), white-tailed eagles (Haliaeetus albicilla (L., 1758)), and domestic dogs scavenged more frequently on carcasses in open habitats. Carcasses located in the forest were the most available to European pine martens, jays (Garrulus glandarius (L., 1758)), and wild boar (Sus scrofa L., 1758). The common tendency was to increase scavenging when temperature decreased, except for raccoon dogs (Nyctereutes procyonoides (Gray 1834)). As snow depth increased, jays and great tits (Parus major L., 1758) increased scavenging. We suggest that carrion use by scavengers is not random, but a complex process mediated by extrinsic factors and by behavioural adaptations of scavengers.
There is very little confirmed information on the social organisation of breeding Lesser Spotted Eagle populations, the turnover
rate of adults, and their nest-site and partner fidelity. According to established knowledge, however, breeding individuals
are territorial and defend at least the immediate vicinity of the nest site against their own species. It has further been
thought that females rearing young, as with the females of other raptor species, remain within a radius of only a few kilometres
of their eyrie. Using GPS satellite telemetry and DNA microsatellite analysis (DNA STR typing), we were able to disprove this
prevailing hypothesis. A satellite-tracked female flew over 50km away from her eyrie (D) in at least two different directions
and visited at least one other occupied eyrie (T). It was also established that at least two strange females arrived at her
eyrie, which contained young, from as far away as 57km, and probably remained there for some considerable time. The pool
of alleles represented at the different loci analysed, as well as the distribution of these alleles among the individuals,
excludes the possibility that these females could be sisters or even half-sisters. Visits of strange eagles at this eyrie
were also confirmed by direct observation. It can therefore be assumed that males only exhibit territorial behaviour towards
their own sex and not towards strange females and that females do not exhibit territorial behaviour towards other females;
but all these assumptions must be confirmed by further studies. For the first time it could be proved by means of microsatellite
analysis that almost all females studied used the same breeding site for 2consecutive years. The longest established period
in which both partners of a pair remained at the same breeding site was 3 consecutive years.
Most of the white-tailed eagle (Haliaeetus albicilla) populations in Europe experienced dramatic declines during the twentieth century. However, owing to intense conservation actions and the ban of DDT and other persistent pollutants, populations are currently recovering. We show that despite passing through demographic bottlenecks, white-tailed eagle populations have retained significant levels of genetic diversity. Both genetic and ringing data indicate that migration between populations has not been a major factor for the maintenance of genetic variability. We argue that the long generation time of eagles has acted as an intrinsic buffer against loss of genetic diversity, leading to a shorter effective time of the experienced bottleneck. Notably, conservation actions taken in several small sub-populations have ensured the preservation of a larger proportion of the total genetic diversity than if conservation had focused on the population stronghold in Norway. For conservation programmes targeting other endangered, long-lived species, our results highlight the possibility for local retention of high genetic diversity in isolated remnant populations.
I studied the characteristics of 26 White-tailed Sea Eagle (Haliaeetus albicilla) nest trees and 24 nesting forests in Hokkaido, Japan. Nest trees were an average of 7.9 m taller and an average of 45.6 cm larger in dbh than the surrounding forest, and many of them were near the forest edge. Eagles preferred Glehn's Spruce (Picea glehnii) and Japanese Alder (Alnus japonica) as nest tree species, though not exclusively. Nests were an average of 2.8 m higher than the average height of surrounding trees, and all nests had canopy openings above them. Openings above nests in the forest interior were an average of about 110° wider than those above nests near forest edges, because the nests were built on emergent trees. Eagle nesting habitat in Hokkaido requires trees large enough to support the nest, and a surrounding structure which allows accessibility and good visibility.
During the long-term research on White-tailed Eagles (Haliaeetus albicilla) conducted in the continental part of Lithuania since 1995, live Common Buzzard's (Buteo buteo) nestlings were found in nests of two pairs of eagles in 2002. On the one hand, this could have been atypical feeding behaviour of eagles: adult birds used to bring buzzard.s nestlings to their nests, keep them alive there and feed them up to their own nestlings later. On the other hand, this could have been breeding parasitism of Common Buzzard on White-tailed Eagle.
According to literature sources, the White-tailed Eagle was a common bird in Lithuania in the middle of the 19 century; however, the species became rare and ceased to breed in the first half of the 20 century. Today, the White-tailed Eagle is listed in the Red Data Book of Lithuania, category 3 (R). Estimation of species abundance is based on literature published sources (1900-2002) and field work data (2003-2007). The first breeding pairs of the White-tailed Eagle were noticed in different parts of Lithuania in 1987. During the field work period, I checked all White-tailed Eagle breeding territories recorded in Lithuania in 1987-2002 and identified 41 breeding pairs. White-tailed Eagle population abundance increased twofold in 1993-2002. In the period 2003-2007, 24 new breeding territories were recorded and adult eagles were noticed in 25 places during the breeding period, but their nests were not found. Throughout the recent 5-year period, the number of breeding territories registered increased by 50%. The reasons for such increase could be related with better investigation of the species and formation of new pairs. The present White-tailed Eagle population consists of about 90 territorial pairs. I assume that White-tailed Eagles were breeding in Lithuania in the beginning and middle of the 20 century, but their numbers significantly declined like all over Europe, and only in the 1990s the White-tailed Eagle population began to increase distinctly.
Since 1957, 200 m zones around known nests of the black stork (Ciconia nigra) and white-tailed eagle (Haliaeetus albicilla) have been strictly protected in Estonia. Yet, the black stork population has recently suffered a large decline, which coincides with the intensification of forestry. To check whether higher disturbance levels could have caused the decline, we related the extent of forestry operations and mature forest near black stork nests to their occupancy, treating the increasing eagle population as a comparison. For both species, we studied 1 km zone around 38 nest sites and, for each nest site, around two random points 2 km away. The total annually cut and reforested area was used to quantify forestry activity, since this single variable explained most of the variability in the extent of different forestry operations. Management was significantly more extensive in the landscapes inhabited by black storks than those inhabited by white-tailed eagles, but the periods of nest occupancy and unoccupancy did not differ significantly in either species. There were neither species-specific nor occupancy-related differences in the total area of mature forest. We conclude that, compared with the white-tailed eagle, the black stork is more vulnerable to disturbance and landscape change due to forestry operations, but these processes are probably not responsible for the recent decline of the stork population.
Sixty-eight white-tailed sea eagle territories were studied on the Swedish Baltic coast in 1964–1982 and 22 territories in Swedish Lapland in 1976–1982. Older data were assembled for comparison. The breeding frequency of adult pairs was high in both study areas (ca. 90%). Median egg-laying dates were 17 March (Baltic) and 7 April (Lapland). Average clutch size and egg volume did not differ between samples from the Baltic taken between 1856 and 1982. Average clutch size was significantly smaller in Lapland (1.6 eggs) than on the Baltic coast (2.1 eggs). Clutch size in Lapland was positively related to carrion availability during March. Nestling survival was significantly lower in Lapland, due to starvation in broods of more than one young. Brood loss was significantly more frequent in Lapland. At the Baltic, nest success decreased from 75 to 22%, and brood size from 1.8 to 1.2, from the early 1950's to the mid 1960's. Nest success in 1976-1982 was significantly lower at the Baltic (26%) than in Lapland (45%), with a much larger proportion of consistently failing pairs. The proportion of eggs laid that resulted in fledged young was estimated at 16% at the Baltic and 39% in Lapland. It is concluded that egg production and nestling survival were suppressed by limited food supply and nest success by human interference in Lapland, and that the reproductive impairment of the Baltic population was due primarily to contamination with toxic substances, mainly DDE.
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