Archives • Hirundo

Hirundo 1/1999

Edula, E.
Breeding biology of the birds in artificial nests in the surroundings of Viljandi, 1968-1987
Summary: Nest-boxes have been put in the gardens and woods near Viljandi. Since 1970 there have been permanently about 200 boxes: three large for owls, 20 for starlings and the remaining for small passerines. The area and bird population dynamics have been described in Edula (1998), and the earlier (1956-1967) results about breeding biology in Edula (1969).
In different years 45-87% of the boxes were occupied, altogether by 14 bird species. Regular breeders were the Starling, Pied Flycatcher and Great Tit; also the Wryneck (no breeding records in the latest years), Marsh Tit and Tree Sparrow often nested in boxes. Occasional breeders were the Tawny Owl, Robin, Willow Tit, Crested Tit and Blue Tit, Nuthatch, Treecreeper and House Sparrow. The recorded clutch sizes are summarized in Table 1.
Tawny Owl. Out of nine breeding attempts (breeding was considered to begin with laying) seven were successful, producing on the average 2.3 young per breeding attempt.
Wryneck. The eggs were usually layed between 21 May and 6 June (earliest 18 May 1975, latest 20 June 1971). In addition to 25 successful attempts which produced on the average 6.6 young, the breeding failed in ten cases.
Starling. Laying starts mainly in the late April or early May (Figure 1). Long-term dynamics in the clutch size and breeding success are presented on Figure 2. The largest clutches (8 eggs) were observed in 1968 and 1969. In 1970-1987 208 breeding attempts (189 successful) produced on the average 3.7 young per attempt.
Pied Flycatcher. This species is the most numerous in the nest boxes. It arrives between 23 April and 9 May, and starts to breed in the second half of May (Figure 3). Long-term dynamics in the clutch size and breeding success are presented on Figure 4. The average clutch size was similar to that in 1956-67. The largest clutch (13 eggs) was probably layed by more than one female. Average measurements of 201 eggs were 17.71×13.35 mm, weight of 102 eggs 1.53 g. The incubation period lasted usually 13-14 (12-18) days (n=31), the whole period between the laying of the first egg and the
leaving of young was 32 days. Altogether 3.8 young fledged per breeding attempt (n=1352; out of these 953 were successful).
Robin. The breeding in nest boxes was confirmed in 16 cases. Ten successful attempts produced on the average 5.4 young per successful attempt.
Marsh Tit. Laying started usually between 23 April and 7 May; the incubation lasted 14 days (one observation), and the nestling period 20 days (two observations). 28 nests out of 42 were successful, producing on the average 6.2 young per successful nest.
Willow Tit. Most nests were situated in snags, nest-boxes were inhabited in 15 cases. Laying started between 1 and 24 May, incubation lasted 12-14 days (n=4). Ten nests were successful, the average number of young per successful nest was 5.3.
Crested Tit. Usually nests in snags, but 25 nests were found also in nest boxes. Usually laying started in the third decade of April; incubation lasted 14-15 days (n=3). Only nine nests were successful and on the average 4.8 young fledged per successful attempt. The average measurements of 13 eggs were 16.02×12.39 mm.
Blue Tit. Only 15 nest-box breedings have been recorded. Laying started between late April and mid-May. Nine attempts were successful, on the average 8.3 young fledged per successful nest. Great Spotted Woodpecker predated three clutches completely and one partly.
Great Tit. Many birds lay two clutches (Figure 5). Incubation starts differently in first and second clutch; it lasted 9-16 days (n=37), usually (n=21) 12-13 days. The long-term dynamics in the clutch size and breeding success are presented on figures 6-8. The average measurements of 152 eggs were 17.92×13.44 mm, weight of 86 eggs 1.64 g. On the average, 5.9 young fledged per first (n=552) and 5.5 young per second clutch (n=301); per successful attempt 7.3 (n=427) and 6.3 (n=258), respectively. The eggs of the first clutch tended to fail more often, possibly because of more intensive predation by Great Spotted Woodpecker.
Treecreeper. Has nested in nest boxes only twice.
Nuthatch. Six out of nine clutches were successful, producing on the average 4.29 young per successful attempt.
Tree Sparrow. Breeds up to three times in a season, clutches have been found from April to late July. In the first half of the study period the nests were persecuted systematically. 30 successful clutches yielded 4.6 young per successful attempt. The average measurements of 176 eggs were 19.66×14.75 mm.
House Sparrow. One breeding case (in 1968).

Lõhmus, A.
Monitoring of raptors and owls in Estonia, 1994-1998
Summary: Although in a few plots raptors and owls were studied already in the 1960s in Estonia, the monitoring has developed markedly only since 1989. In 1994 monitoring of raptors and owls at permanent study plots became a part of National Monitoring Scheme. This paper analyses the development and results of the project in five years (1994-98), and compares it with earlier data.
The project includes mapping the breeding territories (BT), checking potential nest sites and recording productivity of raptors and owls. At least 24 plots were studied in 1994-98 (Fig. 1). Although the locations are not randomly selected but determined by distribution of observers, the plots’ habitat composition is similar to Estonian average. Usually a plot follows UTM-grid square and covers 100 sq. km-s. If not studied for the first year, at least 150-200 work hours per 100 sq. km-s was needed to map the BT-s, and at least 250 hours to find 50% of nests (Fig-s 2-3).
The average breeding densities were calculated from average densities in every plot. Trends for most common species were reconstructed by comparing total numbers in plots studied in two subsequent years which were then standardized to the 1993 level. In general, potential nest sites were checked according to Haapala & Saurola (1986), the breeding results were recorded according to Lõhmus (1997a). Productivity is defined as number of fledglings per occupied nest.
The average breeding densities are presented in Table 1, occupancy of potential nest sites in Table 2, and average productivity in Table 3.
Coefficient of variation of densities in different plots gave the following order of distribution uniformity: Common Buzzard (35%), Honey Buzzard (43%), Sparrowhawk (48%), Hobby (52%), Goshawk (58%), Tawny Owl (80%), Long-eared Owl (82%), Ural Owl (100%), Montagu’s Harrier (104%), Kestrel (117%), Marsh Harrier (125%), Lesser Spotted Eagle (130%), Pygmy Owl (149%), Tengmalm’s Owl (173%), eagles (without Lesser Spotted) and the Osprey (186%), Hen Harrier (225%), Eagle Owl (231%), Short-eared Owl (387%), Merlin (400%).
The average densities in 1989-93 and 1994-98 were similar in most cases. The sharp decrease in Merlin, however, seems to have continued, and its present population in Estonia is estimated at 10-20 pairs (Lõhmus et al. 1998). Probably the numbers of Short-eared owl have decreased, too.
Evaluating trends by the samples of two subsequent years (Fig.-s 4-5) includes high risk of mistakes. When I eliminated the pair of largest change in every species, only decrease in the Goshawk and increase in Tawny Owl remained significant. In the first species also productivity has dropped, and I propose that it is mainly due to intensified forestry in the 1990s. The Tawny Owl population could have been restoring from impact of hard winter 1986/87.
The fluctuations in Long-eared Owl population are evident (Fig. 5). This overlaps with the three-year cycle of microtine voles which influenced productivity in several species, and occupancy of nest sites at least in two owl species. The top years in most of Estonia were 1990, 1993 and 1996, and minimum years 1989, 1992, 1995 and 1998 (or 1997). However, locally (e. g. near North-Estonian coast and in extreme south-eastern Estonia) the timing of cycles has been different.
In several aspects the productivity data overlaps with earlier results of a thorough local survey (Lõhmus et al. 1997). In this study, however, the productivity of Goshawk and Hobby was lower, and that of owls is overestimated as non-laying pairs were not taken into account.
The main conservation implications of the project were that 1) it allows monitoring of numbers of at least 16 and productivity of 11 species, and the further prospects for larger samples are good; 2) Merlin could have fallen into category of endangered species, there is a need for special survey and conservation plan for the species; 3) the Goshawk population will probably decrease significantly in the following years as possibly also the Lesser Spotted Eagle and Eagle Owl populations.

Elts, J. & Aua, J.
Roding of the Woodcock in Kuhjavere
Summary: On 3-12 April 1998 roding woodcocks were studied in a permanent station in Kuhjavere (Viljandi county). Every evening, between 20.30 and 21.30, the number of birds seen or heard (hereafter: contacts) was determined.
The timing of the roding flights is shown on Figure 1. The first five days were cold and no flights were detected at all. The first flight was observed on 8 April, followed by one day of no activity. The flights became regular since 10 April. A significant rise in roding intensity took place on 14 April, but on 17 April the number of contacts was again similar to that of 13 April. The following intensification turned to a continuous decline up to the end of the period.
In different evenings 0-20 contacts were counted. It is not known whether the woodcocks had arrived for the first count days, hence it is perhaps not correct to consider these days as unsuitable for roding. However, this conclusion could apply for 9 April, which was both preceded and followed by an active evening.
According to the number of contacts only one male could have been roding up to 12 April. It is supposed that on 13 April two, and on 14 April already 4-5 males could have been participated.
The frequency distribution of count results (Figure 2) indicates four clusters. The clusters suggest that a male, when it was alone, performed an average of 2.5 flight rings per hour; when one additonal male participated the number of rings was 3.7, and in the case of three males 4.2 rings per male per hour. The number of rings depends on many factors, of course, but the number of males seems to be among major impacts. The two evenings with maximum number of counts suggest on average 4.5 rings per male; this high intensity could have occurred because of participation of females.

Mikk, R.
When do birds stop singing?
Summary: Based on systematic observations during more than ten years near Tõrva (Valga county) the author presents data on annual last dates when singing or territorial calls were heard.

Mägi, E.
Birding towers in Matsalu

Note
Elts, J.
A clutch with five eggs in the Redshank

EOS chronicle

Hirundo 2/1998

Lõhmus, A., Kuresoo, A., Leibak, E., Leito, A., Lilleleht, V., Kose, M., Leivits, A., Luigujõe, L. & Sellis, U.
Status and numbers of Estonian birds
Summary: The paper gives an updated list of Estonian bird species, their status and numbers in breeding season and midwinter.
Methods
The estimates were evaluated as follows (hereafter the abbreviations as in Table 1).
Categories: A – species which has been recorded in an apparently wild state at least once since 1.1.1950; B – species which has been recorded in an apparently wild state only before 1950; C – released or escaped species which has established a self-supporting breeding population in the own country, also birds coming from category C population of another country; D – every other species unless it is almost certainly a genuine vagrant or almost certainly an escape from captivity; E – escapes from captivity.
Status: H – regular breeder; S – summer visitor; L – passage migrant; T – winterer; ( ) – irregular (breeder etc.); [ ] – occasional (breeder etc); E – vagrant; int – introduced. A species was considered occasional breeder/winterer etc. if its occurrence fitted in this pattern in 1950-1997. Irregular and regular breeders etc. were however determined by occurrence pattern in the last 20 years (1979-98) or (if status considerably changed during this period) according to the most recent years (e. g. Citrine Wagtail is a regular breeder although its first breeding dates back only to 1991).
No. of breeding pairs was taken as the common term of breeding population size, although in several species (e. g. gallinaceous birds, waders, raptors) pairs, in fact, were not counted. The minimum-maximum values consider both year-to-year variation (in some recent years) and inaccuracy of estimate. If numbers had changed unidirectionally in recent years, the estimate reflects the latest known situation (preferably in 1998).
Evaluation methods are shown for breeding estimates: 1 – complete count (a full or near-full census); 2 – expert estimate (the best estimate in the opinion of experts studying the population of the species); 3 – compilation (an estimate derived from a number of sources); 4 – extrapolation from sample surveys in different habitats and/or random plots; 5 – a rough method using the previous estimate (Lilleleht & Leibak 1993) and the known recent trend for correction (the previous method is indicated before / character, e. g. 2/5= previously expert estimate); 6 – a rough estimate from few quantitative data and densities in neighbouring countries (mainly Southern Finland).
Breeding estimate reliability is divided into three classes:
A – reliable quantitative data from recent years; B – generally well known, but quantitative data incomplete; C – very poor or missing (recent) quantitative data.
The changes in breeding populations (trends) are expressed as follows: e = extinct as a regular breeding bird during the study period; — = strong decrease (more than 50%); – = moderate decrease (10-50%); (-) = probable decrease (verification lacking); 0 = stable, no detectable change; (0) – probably stable; f = widely fluctuating, without steady trend; (+) = probable increase (verification lacking); + = moderate increase (10-50%); ++ = strong increase (more than 50%); (n) = newcomer with a few sporadic breeding records; n = newcomer as a regular breeding bird; ? = status largely unknown. In several cases also earlier (1971-90) trends were corrected if previously unknown data were available.
Winter numbers (individuals) are given according to January data, excluding years with extraordinary weather conditions. Most estimates are obviously very rough and (except for waterfowl) with unknown reliability.
Results
The estimates are shown in Table 1 (270kb). Some exotic and tamed species have been excluded from analyses.
As of 1.1.1998, 339 bird species have been recorded in Estonia (categories A-D), 222 of these are breeders (209 regular, 7 irregular and 6 occasional), 150 species have been observed in winter (94 regularly) and 212 species on migration (194 regularly).
329 species have occurred naturally, four of these (Gavia immer, Tetrax tetrax, Syrrhaptes paradoxus, Athene noctua) only before 1950. Three more species have occurred naturally in earlier times but recent records concern either escapes (Tadorna ferruginea) or birds with unknown origin (Gyps fulvus, Aegypius monachus). Seven species have probably always been escapes from captivity and two regular species (Columba livia, Branta canadensis) belong to category C. Four species (Pelecanus onocrotalus, Phoenicopterus ruber, Bucephala islandica, Bucanetes githagineus) are of unknown origin, as previously also Anser caerulescens (recent records concern escapes).
According to this study 7.9-15.7 million pairs of birds breed in Estonia, ten most common species making up 56-57% of this. Only 13 breeding species have been counted highly reliably, most of species with B-level reliability, and as many as 60 species with C-level reliability.
Recent addition rate of new breeding species seems lower than previously: in 1971-90 altogether 6 regular and 3 irregular new breeders settled in Estonia, compared to one species (Citrine Wagtail) in 1991-97. In 1971-90 69 species decreased and 77 species increased, in 1991-97 those numbers were 55 and 57, respectively. In this decade Falco columbarius, Charadrius dubius, Philomachus pugnax and Jynx torquilla have shown strong decrease, while Phalacrocorax carbo, Ciconia ciconia, Cygnus cygnus, Branta leucopsis, Haliaeetus albicilla, Tringa nebularia, Locustella luscinioides and Panurus biarmicus have shown strong increase.
Altogether, 2.4-8.6 million individuals were estimated to occur in midwinter, ten most numerous species making up 57-68% of this.
Table of status and numbers

Elts, J. & Tuule, E.
Changes in the numbers of winter birds in Saue

Lõhmus, A.
Does the Great Spotted Woodpecker build its nest economically?

Ader, A.
Birdwatchers and internet

Notes
Lõhmus, A.
A mallard bred in an occupied nest of Common Buzzard
Lõhmus, A.
An extraordinaly dark harrier
Elts, J. & Aua, J.
Yellow wagtails on migration

EOS chronicle and news

Hirundo 1/1998

Edula, E.
Population changes of passerines in the surroundings of Viljandi in 1956-1995

Lõhmus, A.
Numbers of the Greater Spotted Eagle and the Lesser Spotted Eagle in Estonia

Leito, A.
The Common Crane in Estonia in 1997

Luigujõe, L., Kuresoo, A., Ader, A. & Ots, M.
Birds of Ropka-Ihaste floodplain meadow in 1992

Aua, J.
Interesting bird observations in 1977-1982

Elts, J., Aua, J.
How to determine the number of occupied burrows in Sand Martin colonies

EOS chronicle and news

Hirundo 2/1997

Edula, E.
Breeding of the Redwing and the Song Trush in the surroundings of Viljandi, 1969-1993

Rootsmäe, L.
Autumn migration of geese in 1994

Rootsmäe, L.
Spring migration of geese in 1995

Lepisk, A. & Leito, A.
Spring migration of geese at Räpina polder in 1997

Edula, E.
Breeding birds at sample plots in the surroundings of Viljandi in 1994

Pärnamets, H. & Lepisk, A.
Number of breeding raptors and owls in Räpina parish and Laheda plot

Aua, J.
Birds of quarries in Jõgeva county

Aua, J.
Why is the Little Ringed Plover most bound to man among Estonian Charadriiformes?

Lilleleht, V. & Lõhmus, A.
List of birds of Europe

EOS chonicle and news

Hirundo 1/1997

Special issue on raptors and owls

Lõhmus, A.
Population changes of raptors and owls in north-western Tartumaa
Summary: The paper analyses the occurrence of raptors and owls during the last 100 years by publications, archive materials and author’s own data. The study area (900 km²) is situated in east-central Estonia (ca 58°25’N, 26°20’E). Forests covered ca 20% of the area in the beginning of the century and 40% in 1990s.
In 100 years 14 Accipitriformes, 5 Falconiformes and 8 Strigiformes species have been recorded as breeders. Their present population sizes are presented in Table 1. Additionally, 4 raptor or owl species have occurred as transit migrants, winter visitors or vagrants. Both in 1894-1904 and 1987-1996, 26 species were recorded. The Peregrine disappeared and Montagu’s Harrier appeared as regular breeders in 100 years. Among breeders another 7 species have decreased and 8 species increased in number, while all winter visitors have become more rare.
The present frequency compared to the situation 100 years ago is probably:
a) similar in Pernis apivorus, Milvus migrans, M.milvus (very rare vagrant), Circus cyaneus, Accipiter gentilis, Bubo bubo, Asio flammeus, Aegolius funereus;
b) lower in Circaetus gallicus, Accipiter nisus (ca 5 times), Buteo lagopus, Pandion haliaetus, Falco tinnunculus (ca 3-4 times), F.columbarius (10-20 times), F.peregrinus (extinct), Nyctea scandiaca, Surnia ulula (ca. 10 times), Glaucidium passerinum (at least 3-5 times), Strix aluco (at least 3 times);
c) higher in Haliaeetus albicilla, Circus aeruginosus (doubled), C.pygargus (newcomer), Buteo buteo (3 times), Aquila pomarina, A.chrysaetos, Falco subbuteo, Strix uralensis (5-10 times), Asio otus (5-10 times).
However, because of persecution the numbers of P.apivorus (?), Circus aeruginosus, A.gentilis, A.nisus and B.buteo decreased significantly to the 1920-1950s and have recovered since then. Compared to the present situation the frequency of Milvus migrans was higher in the middle of the century, and of Bubo bubo and Asio flammeus in 1950s-1970s.
The trends are unknown for Circus macrourus, Aquila clanga and Falco vespertinus.

Evestus, T.
Raptors in the surroundings of Otepää
Summary: The author has studied numbers and breeding success of raptors near Otepää (Valga district). Up to 1991, 150 sq. km-s were investigated, instead of 190 sq. km-s since 1992. Forests cover 50% of the area, nemoral forests and boreal pine forests dominate.
Nine raptor species were detected in 1988-1996, two of them (Montagu’s Harrier and the Osprey) as non-breeders. The number of occupied breeding territories of other species is shown in Table 1. The dominating species is the Common Buzzard (on average 17.3 territories per 100 sq. km-s).
The brood size was almost stable in the Common Buzzard contrasting to the declining trend in the Goshawk (Fig. 1).

Ojaste, I.
Observations at Palivere raptor plot
Summary: The plot (100 km²) is situated at the territory of Taebla and Oru parishes (Lääne district), ca 59°02’N, 23°52’E. Regular observations are carried out since 1992, some occasional data has been gathered earlier. Main attention is paid to numbers of breeding raptors and owls.
A total of 14 species of Accipitriformes (including 9 breeders), 4 (3) of Falconiformes and 5 (5) of owls have been recorded. Number of occupied territories has fluctuated between 32 and 41 (Table 2). From vagrants the Pallid Harrier was observed.
In 1987-96 arrival or departure of raptors has been recorded in 33 cases (Table 1). In autumn 1993 raptors were regularly counted by a 25 km road. 329 observations of 13 species were made (Fig.1).

Väli, Ü.
Raptors and owls in southern Hiiumaa
Summary: The raptors and owls of Hiiumaa Island have been only scarcely studied earlier. The author counted breeding birds of prey at a 35 sq. km study area in southern Hiiumaa in 1995-96, by mapping the breeding territories and searching for nests. The results are presented in Table 1.
The earlier published data showed Accipiter nisus and Strix aluco as verified breeders of the area, but during this study the breeding of Pernis apivorus, Accipiter gentilis, Buteo buteo and Falco subbuteo was also detected. Circus cyaneus and Haliaeetus albicilla used the area in the breeding season only for feeding. Buteo lagopus, Circus aeruginosus, C. cyaneus, Falco tinnunculus and Strix uralensis have been observed as transit migrants, Haliaeetus albicilla, Buteo lagopus and Aquila chrysaetos as winter visitors.

Klein, A.
Raptors observed by Finnish birders in Pärnu district, 1996

Randla, T.
Eagle Owls at Nõva

Lõhmus, A.
How to study reproductive success in birds of prey?

Lõhmus, A., Evestus, T., Lauk, K. & Väli, Ü.
‘Reproductive success of raptors and owls in eastern and south-eastern Estonia*
Summary: We present data on eleven species of birds prey in four Estonian districts (Tartu, Valga, Võru and Põlva). The data were mainly gathered in 1986-1996 with standard methods (according to Lõhmus 1997, see this volume). The parameters were defined as follows. Breeding frequency – percentage of nesting territories where breeding started (eggs were layed). Successful breeding produced at least one fledging. Breeding success – number of succesful breedings / total number of breeding attempts. Productivity – mean number of fledgings per territory per year. Young birds were regarded fledgings if their age exceeded 80% of normal fledging age.
The main results are presented in Table 1. Compared with other European data, at least two species (Pernis apivorus and Bubo bubo, presumably also Strix uralensis) showed lower reproductive rate.
In three species (Buteo buteo, Circus aeruginosus, Asio otus) the reproductive success was normal. Falco tinnunculus showed normal reproductive output (2,62) in the 1970s – a time of population crash, which suggests that population decline was related to other reasons.
The results about Accipiter nisus, Falco subbuteo and especially Accipiter gentilis exceeded the average rates reported in Europe. All three last-mentioned species depend largely on avian prey. In A.nisus and A.gentilis the average productivity was much higher in highly fragmented south-eastern districts compared to less mosaic Tartu district.
Some other species (Pernis apivorus, Buteo buteo) were less productive in areas of wilderness (Alam-Pedja) compared to mosaic mineral land. However, the differences could not be seen in the mean number of fledgings per succesful nest. In Buteo buteo the average brood size differed between years (Fig. 1).
In Strix aluco and Asio otus the clutches and broods were smaller in 1986-1996 compared to earlier data (Table 3).

Lelov, E.
Notes on raptors and owls
Summary: The author presents some interesting observations on birds of prey in south-western Estonia.
Circus cyaneus. Three observations have been made in winter (Jan. 1967, 09.12.1984, 10.12.1996).
Circus pygargus. The flight speed of a foraging adult male was 30-35 km per hour. Two nests of the species have been found within 200 m distance from human settlement, but both broods failed.
Accipiter gentilis. An adult male brought prey to nestlings from a distance of 4.5 km. In winter, corvids feeding on carcasses are afraid and desert their feeding place when goshawk appears.
Buteo buteo has started to winter more often: of 33 winter observations in 1976-1996 even 29 have been made in 1990s. The nest-building of a Buzzard lasted five days. Pseudo-attacks (without physical contact) to the ringers and feeding on carcass are described. The distance between two occupied nests has been 550 m.
Aquila chrysaetos. Two pairs nested 9 km from each other.
Falco subbuteo. A nest was situated 60 m from the nest of Haliaeetus albicilla and twice brood has contained 4 nestlings. Wintering was observed in 1976 and 1992.
Strix uralensis. One nest is situated in a farmyard, the other in village oak alley (1.2 km away from the nest of Strix aluco).
Asio otus. Six times since 1976, young that have just left the nest have been observed late in summer (between 10 July and 27 Aug).

Project “Raptors and owls at permanent study areas”

Chronicle