Nesting and Non-Nesting Occurrence of the Short-Eared Owl

Slovak Raptor Journal 2013, 7: 73–80. DOI: 10.2478/srj-2013-0006. © Raptor Protection ofSlovakia (RPS) Nesting and non-nesting occurrence of the short-eared owl Asio flammeus in the Záhorie region (SW Slovakia) Hniezdny a mimohniezdny výskyt myšiarky močiarnej Asio flammeus na Záhorí (JZ Slovensko) Michal NOGA & Martin DOBRÝ Abstract: The short-eared owl is a regular migrant and hibernant in the Záhorie region (SW Slovakia), though this species mostly escapes attention. In 1998 the species was found nesting in this region, and in 2012 individuals showing territorial behaviour were regularly observed, with high probability of nesting. Nesting habitats were localities with a high representation of meadows, corresponding to the preferred nesting sites in Slovakia. The foraging range of wintering birds was comparable with those from neighbouring regions (W Slovakia, Hungary), but with a higher number of harvest mice Micromys minutus and long-tailed field mice Apodemus sylvaticus. In both years when the nesting of birds was recorded, snowfall was significantly lower. Food sources were not monitored at these localities. Abstrakt: Myšiarka močiarna je v regióne Záhoria (JZ Slovensko) pravidelným migrantom a hibernantom, hoci tento druh zväčša uniká pozornosti. V roku 1998 bolo v tomto regióne zistené hniezdnenie druhu a v roku 2012 boli opakovane pozorované teritoriálne správajúce sa jedince, s vysokou pravdepodobnosťou hniezdiace. Hniezdnym prostredím boli lokality s vysokým zastúpením lúk, čo zodpovedalo preferovanému hniezdnemu prostrediu na Slovensku. Potravné spektrum zimujúcich jedincov je porovnateľné s údajmi zo susedných regiónov (Z Slovensko, Maďarsko), má ale vyššie zastúpenie myšiek drobných Micromys minutus a ryšaviek krovinných Apodemus sylvaticus. V oboch rokoch, kedy došlo k hniezdnym prejavom sov boli výrazne nižšie snehové zrážky. Potravná ponuka na týchto lokalitách sledovaná nebola. Key words: snow cover, wintering, nesting, diet, Natura 2000 Michal Noga, Raptor Protection of Slovakia, Kuklovská 5, 841 04 Bratislava 4, Slovakia. E-mail: [email protected]. Martin Dobrý, Raptor Protection of Slovakia, Kuklovská 5, 841 04 Bratislava 4, Slovakia. E-mail: [email protected]. Acknowledgements: We would like to thank everyone involved for providing their data, insights and consultation to this paper. In particular, we wish to thank David Horal, Rudolf Jureček, Ján Svetlík, Gašpar Čamlík, Alexander Sharikov, Miroslav Čapek, Radovan Václav, Vlasta Škorpíková, Reiner Raab, Erik Martinec and Jozef Madzin, as well as Jana Bacigalová from the Slovak Hydrometeorological Institute in Bratislava and Viera Stanová-Šefferová and Rastislav Lasák from the Institute of Applied Eco- logy Daphne. Data on the occurrence of the short-eared owl were collected during monitoring supported by the project CORO- SKAT Conservation of Raptors and Owls – Slovakia-Austria in the Slovak-Austrian cross-border cooperation programme 2007–2013, financed by the European Regional Development Fund. We are grateful to Marcel Uhrin for his valuable comments and we thank reviewers, David Horal and Vlasta Škorpíková, for their comments, which contributed to the improvement of the present research. Introduction estimated nesting population abundance for the whole In Slovakia the short-eared owl Asio flammeus (Pontop- territory of Slovakia (0–50 pairs) and in the estimated pidan, 1763) regularly occurs during migration and in wintering population (100–1,000 individuals) for the winter. This species nests irregularly and infrequently. It period 1980–2000 (Danko et al. 2002). is a typical fluctuant species with significant variations Only a few specific reports of the occurrence and in abundance. Appropriate local and trophic conditions nesting of short-eared owls have been published from are considered to be prerequisites of its nesting. These the Záhorie region (W Slovakia). Nesting was men- conditions are the gradation of abundance of the com- tioned in 1965 (Balát 1965), and later data on the nest- mon vole Microtus arvalis and the presence of taller ing at the Devínske jazero location in the years 1989, herbaceous vegetation (reed, ruderal communities, etc.). 1990 and 1998 (Tomovčík et al. in Šeffer & Stanová Species fluctuation also means a large range in the 1999) were published without more details. 73 Noga M & Dobrý M: Nesting and non-nesting occurrence of the short-eared owl Asio flammeus in the Záhorie region (SW Slovakia) acoustic monitoring. Olympus DM 550 and Olympus DM 650 digital voice recorders were used in this type of monitoring, with the recorders placed in suitable wet- land and meadow areas (Sekule, Borský Svätý Jur, Zá- vod – Abrod, Závod – Húšky, Gajary and Rohožník – Krížnica). They also recorded during the times of day with the highest supposed acoustic activity of short- eared owls (two hours after sunset, two hours before sunrise and one hour after midnight). A total of 220 hours of recordings were obtained. Our own data were supplemented with the observations of other authors, or by data extracted from online databases (Birding Slovakia, http://www.birding.sk/ and the database AVES Symfony; http://aves.vtaky.sk/); from records of the State Nature Conservancy of the Slovak Republic and the office of Administration of the Záhorie Protected Landscape Area (PLA Záhorie) and from Archive Auring-Verein (Austria). The nesting period (individuals showing territorial behaviour) and the occurrence during migration and in winter (from August to April, or individuals without nesting and territorial behaviour) were evaluated separ- ately. Data on the food composition of short-eared owls were obtained from the analysis of pellets. They were collected in daily roost places at two localities – the Moravský Svätý Ján locality (December 15, 2011; March 3, 2012) and a disproportionately smaller sample at the Petrova Ves locality (November 26, 2006). Pellets Fig. 1 . The map of the study area. Yellow square – nesting were processed in a 5% NaOH solution. Skulls of mam- areas (supposed breeding), green circle – Asio flammeus ob- mals and avian bones (skull, beak, humerus and tar- servations, blue pentagram – meteorological stations, green li- sometatarsus) were separated from the obtained ne – study area. osteological material and were determined using the Fig. 1 . Mapa sledovaného územia. Žltý štvorec – hniezdne lokality (predpokladané hniezdenie), zelený kruh – pozorovania available determination key (Anděra & Horáček 2005) Asio flammeus, modrý pentagram – meteorologické stanice, and by our own comparative collection. zelená linia – sledované územie. Data on vegetation land cover and landscape structure were obtained from the field work and by using available Methods satellite images (Google Earth). Specific additional data This study summarizes unpublished data and details were provided by the Institute of Applied Ecology from published information on the nesting, migration Daphne, and the Slovak Hydrometeorological Institute in and wintering of short-eared owls in the Záhorie region Bratislava provided meteorological data. There were pro- (Šeffer & Stanová 1999, Zuna-Kratky et al. 2000 cessed data from the period between 1997 and 2013. and Danko et al. 2002). This area, shown in Fig. 1, in- cludes the following geomorphological units: the Bor- Results and discussion ská nížina Lowland, the Chvojnická pahorkatina M i g r a t i o n a n d w i n t e r i n g Upland and the Slovak part of the Dolnomoravský úval The first observations of short-eared owls were recorded Ravine. Data were collected in direct observation, often in the middle of October (October 19, 2008, October 14, during the winter counting of the hen harriers Circus 2011). In wintering areas, short-eared owls were seen cyaneus. The species was determined during the monit- throughout the winter period. The increased number of oring of other species from 2011 to 2013 during con- species occurrences in March may signal the ongoing trols of suitable nesting habitats and also during spring migration. In most cases short-eared owls were 74 Slovak Raptor Journal 2013, 7: 73–80. DOI: 10.2478/srj-2013-0006. © Raptor Protection ofSlovakia (RPS) identified in meadow habitats or ruderal sites. However, they did not avoid settlements (two cases, Devínska Nová Ves, Senica). The species was even observed on a xerothermic hillside (Devínska Nová Ves) and on a heath (Rohožník). More than two-thirds of the observations came from areas included in the Natura 2000 network (Special Protection Area Záhorské Pomoravie, Special Area of Conservation Bežnisko). A summary of all observations of short-eared owls is provided in Ap- pendix 1. It is not possible to precisely express seasonal dy- namics because of the hidden way of the life, different intensity of visits at localities and targeted control of the Fig. 2. Non-nesting occurrences of short-eared owls, the meadow vegetation. Thus, these are only informative number of observations (n = 28) and the number of recorded data. The highest number of records was from Novem- individuals (n = 78). Blue columns – no. of observations, red ber and December and the highest peak was in the columns – no. of recorded inds. second half of November, with 21% of all observations Obr. 2. Mimohniezdne výskyty myšiarok močiarnych, počet pozorovaní (n = 28) a počet zaznamenaných jedincov (n = 78). and 29.50% of all recorded individuals (Fig. 2). There Modré stĺpce – počet pozorovaní, červené stĺpce – počet jedin- are also most occurrence data from November from cov. eastern Slovakia (from the period between 1872 and 2007, Danko 2008). with only a minimal range of free water surface, or quite N e s t i n g a n d n e s t i n g often without water. The surrounding land is made up of o c c u r r e n c e s mown meadow vegetation and agricultural land (in The Devínske jazero locality, 1998. The Devínske 2012, sunflower, rape, cereals). jazero locality is a large complex (1,264 ha) of flood- There are numbers of records on the wintering of plain meadows (Cnidion venosi communities) situated short-eared owls at this locality, but nesting has never in an area between a river dyke and the Morava River in been confirmed.

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