Hirundo 1/2000

Kuresoo, A. & Ader, A.
The point counts of breeding land birds in Estonia, 1983-1998
Summary: The Estonian point counts are aimed at monitoring long-term trends in breeding bird populations, which also reveals changes in bird habitats and the environment in general. Between 1983 and 1998, 72 birdwatchers of the EOS participated in the project, covering a total of more than a hundred routes. The average “life-span” of the routes exceeds seven years and 26 routes have been checked in at least ten years. Changes in the observers’ activity are shown on Fig. 1. The number of records (according to the summer count, 25 May-20 June) was at its highest in 1986-1990, decreased in the next five years and has stabilised recently.
The analyses were made with program “TRIM/Trends and Indices for Monitoring Data” (vers. 2.0 for Windows). On the basis of the summer count population indices (PI), which compare the numbers with those in 1983, were calculated for most numerous species. In appendices 1-2 the indices are presented for 55 species, including 33 species of “early breeders” (mostly resident and short-distance migrants) and 22 species of “late breeders” (mostly long-distance migrants). For many species, the trends are presented on Figs. 2-3. Data on some more scarce and aggregated species (>40% of pairs counted in a few routes and on the average less than 50 pairs counted; Table 1) should be treated with caution.
According to the long-term trends, the species were divided into six groups (Table 2). If the numbers (by linear trend) did not change more than 25% in 1983-1998, the population was considered to have been stable. In 1983-1998, large increases (>50%) were observed in breeding Columba palumbus, Dendrocopos major, Troglodytes troglodytes, Erithacus rubecula, Turdus merula, Garrulus glandarius, Corvus corax, Sylvia communis and Carpodacus erythrinus populations in Estonia. In the same period, alarming (>50%) decreases were observed in Oriolus oriolus and Gallinago gallinago, significant decreases also in Anthus trivialis, Hippolais icterina, Phylloscopus sibilatrix and P. collybita.
Table 2 also presents comparisons with the trends in Finland, Sweden and Denmark. 75% of resident and short-distance migrant species had similar trends in Estonia and the Nordic countries and only 8% had completely different trends. In general, most of these species have occurred in stable numbers both in Estonia and the Nordic countries, although many species have fluctuated significantly. Trends of long-distance migrants coincided much less frequently in different countries.

Sellis, U.
Will the Black Stork remain to breed in Estonia?
Summary: The Black Stork (Ciconia nigra) is at the north-western border of its distribution range in Estonia. The paper summarises data on its numbers and distribution in Estonia in 1999, reproductive success in 1991-1999, and results of the special Bird of the Year project in 1998. The latter, which was aimed at rising public awareness and gathering additional data, resulted in three new nest sites and a total of 62 territories counted. The main result, however, was propagation success – in public opinion the Black Stork was among the most well known protected species in 1999.
The numbers were estimated at 100-120 pairs in 1999, which is 2-2.5 times less than two decades ago (see Renno 1993, Lõhmus et al. 1998). Distribution concentrated into the largest forest areas rich in rivers and streams (Fig. 1). The population decline coincided with low productivity in the last decade, on the average 1.09 young per occupied (at least some nest-building activity registered) nest and 44% of nest sites successful (Table 1). Trends in all reproductive criteria were negative (although not statistically significant), except the number of dead young in nests, which was highest in the years of summer droughts (1994-1997; Fig. 2). Most probably the reasons of decline and poor reproduction are in our breeding grounds, because some other populations that use the same migration route and wintering areas are increasing. Productivity in the neighbouring countries is as poor as here (Fig. 3), thus, there is no potential for immigration.
Characteristically to declining population, the reproductive rates in Estonia fluctuated widely between years. Therefore, it is important to monitor the population every year. However, in the 1990s state monitoring program covered the Black Stork only in 1994 and 1999, which are not representative, as these happened to be the best years for breeding (Table 1).
In general, the status of the Black Stork in Europe is alarming. Decreases in the previous source-populations of Poland and the Baltic States are not compensated by increases in other, much smaller populations (Strazds et al. 1995). For conservation, it is important to find out the reasons of declines, which probably will be successful only by international co-operation. The study and (especially) conservation of the Black Stork in Estonia is carried out by two closely co-operating NGOs, the Eagle Club (urmas.sellis@mail.ee) and the Nature Conservation Society “Kotkas”. Legally, the Black Stork is included in the strictest conservation category (I) and the state, represented by the Ministry of the Environment, is responsible for organising the conservation. Probably, the national management plan for the Black Stork will be compiled in 2000.

Lõhmus, A.
When, and how, do Ural Owls call?
Summary: Vocal activity of the Ural owl (Strix uralensis) was studied near Laeva (ca 28°27’ N, 26°19’ E) in 1991-94 (occasional data from 1983-90 and 1995-98). Near the known nest-sites, territories were checked during at least ten minutes for any vocal activity, and the intensity of calling was measured as the probability of detecting a territory. Most observations were made after sunset in the evening. In addition, the repertoire was quantitatively described, using a “call cycle” (all calls of one adult during an hour) as a counting unit. The start of calls was determined in the cases when a territory was listened for several hours in the evening. Everywhere, time is expressed as East-European summer time.
Calling was significantly more intense in spring (recording probability 36%) than in summer (11%), autumn (8%) and winter (6%). The data did not reveal higher activity in autumn, which is documented in the Tawny owl (Strix aluco) and claimed to occur also in the Ural owl. Also, the frequency of territorial calls was much higher in spring (Table 1) than recorded by Lundberg (1980) in Sweden, suggesting that territorial activity in the study area mostly occurred in spring. Within breeding period, the vocal activity remained on high level from March to early May (Fig. 1). In March 1993 calling was more active than in 1991, 1992 and 1994. The reason could be that 1993 was a good vole year, although some later results (e. g. in 1999) do not support this. Instead, the difference can be a result of better weather conditions in 1993.
Wind and rain strongly influenced the vocal activity (Fig. 2). In addition, the air temperature and cloud cover seemed to be of importance, but their effects were not significant statistically. These results are in accordance with other studies.
The start of calling was associated with sunset (Figs. 3-4). Calling started on the average 19 ±10 minutes after sunset in spring, but relatively later in winter. Similar pattern has been described in the Tawny owl (Hansen 1952).
The repertoire was sexually diverse but did not change significantly during the year (Table 1). Especially in breeding season, males were much more vocal than females.
In Estonia, monitoring of owls has been mainly based on territory mapping via spontaneous calls. According to rough calculation, using also the data by Lundberg (1980), during ten minutes of listening about 20% and during twenty minutes up to 40% of Ural owl territories could be detected in spring. However, this means that the locations of (potential) territories are known in advance. Whenever possible, searching for nests and playback-method should be used as additional tools in owl counts.

Edula, E.
Breeding of the Linnet in the surroundings of Viljandi
Summary: In 1959-1998, the author has studied Linnets (Carduelis cannabina) near Viljandi, south-central Estonia. The numbers of Linnets peaked in the 1960s and have dramatically decreased since then (see Edula 1998).
The spring arrival has taken place between 14 March (1967) and late April, on the average on 4-5 April. The breeding season was very long and probably included several clutches (Fig. 1). More than 40% of clutches were laid before 15 May, and 31% of clutches between 16 May and 15 June. Only 12% of clutches have been laid after 15 July. Laying lasted seven, incubation 10-14 and nestling period 11-14 days.
Majority of nests were situated in spruce hedgerows along roadsides, but also in cemeteries, single trees etc. Only few nests were built on deciduous trees or bushes. Usual height was 0.7-1.3 metres (range 0.4-2 m) above ground. The average measurements of 32 nests were: diameter 11.7 × 10.1 cm, height 7 cm, depression diameter 6.1 × 5.7 cm and depression depth 4.1 cm.
The average size of 613 clutches was 5.12 (range 2-7). Largest clutches were laid between 16 May and 15 June, the latest clutches were the smallest ones. However, this difference was not observed in the proportion of successful nests (Table 1). Altogether, 68% of nests were successful (n=382). In long term, both the clutch size and breeding success followed the changes in numbers, being at their highest in the late 1960s and showing a decline since then (Fig. 2).

Nellis, R. & Nellis, R.
Winter birds in the surroundings of Maleva
Summary: Numbers, trends and habitat use of winter birds were studied near Maleva village (58°19’N, 22°31’E) in Saaremaa, 1992/93-1998/99. Three transect counts during winter were performed. 42 species occurred, nine of them in 70% of counts. The average density was 29 ind. per km but it varied a lot. Birds were most abundant in settlements although the numbers decreased significantly during winter there. Decrease during winter was not correlated with climate, and it was not smaller than in Saue, mainland Estonia, despite the milder climate of Saaremaa. Long-term changes in bird numbers coincided mostly with those reported about whole Estonia.

Notes
Aua, J.
Food parasitism in the Mistle Thrush
Elts, J.
Antagonistic behaviour between the Fieldfare and the Blackbird
Lõhmus, A.
A buzzard laid egg without shell
Aua, J.
On the breeding phenology of the Little Ringed Plover
Aua, J.
A clutch of eight eggs in the Barn Svallow

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