Ten years of monitoring of the tawny owl in Kharkiv Region

April 10th, 2012 Posted in Monitoring, Photos

We already published information on attracting the Tawny Owl to artificial nest boxes in Kharkiv region at our web-pages. The present material is dedicated to experience of attracting this owl species to artificial nests and some results of studying its ecology.

MONITORING RESULTS OF USING NEST BOXES
IN NATIONAL NATURAL PARK “HOMILSHANSKI FORESTS”

If you remember, in 2001-2002 a group of Kharkiv ornithologists and bird lovers installed 55 nests boxes for the Tawny Owl in the oak grove in the territory of the present NPP “Homilshanski Forests”. Regular checking of nest boxes and bird observations in the area allowed to receive a lot of information how the Tawny Owl lives in the oakery.
In particular, our initial assumptions about decreasing bird numbers due to felling of old hollow trees were not confirmed. The bird density was rather high (4-6 pairs/km2), similar to the highest known figures among European populations, and bird numbers in the studied area kept stable for 10 years. With such a high density, a number of territorial pairs in the area exceeded the number of installed nest boxes. However, most pairs preferred natural hollows for nesting. Special studies to clarify to what extent the birds are supplied with hollows showed that the density of hollows in the area (1.9 hollows/10 ha) much exceeds the number of owl boxes (0.1 box/10 ha). Though this parameter much depends on the forest age, obtained results can be extrapolated to other forest-steppe oak groves of Eastern Ukraine.

Percent of the boxes where bird nested was small (1-10 or 2-18%), much more boxes birds annually used for day roosting. A role of such closed shelters especially grew in the snow period, when birds could not find protection in foliage or fallen twigs on the ground, and was maximal in cold winters with a lot of snow.
Owing to a big portion of owl boxes, using for day roosts, it was collected a rich material on feeding of birds. It is known that in terms of food preferences the Tawny Owl is a generalist: food composition changes depending on availability of potential prey species and fluctuation of their numbers. Annual collections of pellets of the Tawny Owl allowed to detect changes in food composition of these birds during different years and specify a list of species of small mammals in this area. Thus, for the first time in NPP “Homilshanski Forests” there was found the tundra vole, which range in recent years is gradually expanding to the south. In different years in pellets there were dominated remains of the bank voles, wood mice, shrew mice, which is possibly connected with fluctuation of these species numbers. The prospective of monitoring of small mammals basing on composition of pellets of birds of prey and owls is getting especially interesting in terms of the recent regulation of Ministry of Ecology and Natural Resources of Ukraine which prohibits the usage of brake-back traps including territories of protected areas.

Artificial nests turned out to be very important to collect data on the population state of the Tawny Owl in the studied area. Well-built nest boxes are more durable than hollow trees, their location is precisely known, and they are always accessible for checking compared to the hollows, majority of which located high or on shaky trees, and many have more than one meter depth with rather a narrow entrance.

PLACING OF ARTIFICICIAL NEST BOXES IN THE TERRITORY
OF KHARKIV DURING 2010-2011

Basing on experience gained in Homishanski Forests in 2010 we decided to install nests boxes in the territory of Kharkiv woodland park. It is an upland oakery with the area approximately 1,800 ha wedging in Kharkiv from the north. A central part of this forest stand is represented by a relatively little transformed oak grove; a southern part has park plantations. The main current problem of Kharkiv woodland park is allocation of its lands for building and therefore destruction of forest: such a problem is typical for large cities of Ukraine.
In autumn 2010, thirty nest boxes were made in NPP “Homilshanski Forest” and transported to Kharkiv. It was placed in November –December with participation of students of biological faculty of Karazin Kharkiv National University and young naturalists of Kharkiv Zoo. We chose these terms of installation because a peak of using nests by the Tawny Owl is the second half of winter, and they choose their nesting places, according to our observations, also not later than mid-winter. In late winter and spring the birds are more conservative in selecting nests and not so eager to occupy new shelters. Placing of nest boxes in autumn gives birds an opportunity to get accustomed to new shelters before winter comes and also maybe important for young owls in searching territories for wintering.

According to the first check in spring 2011 the type of using nest boxes by birds in the woodland park was similar to Homilshanski Forests. In both cases birds used about 30% of nest boxes for day roosting during winter. There wasn’t recorded any nesting in these artificial nests though many records of broods testify that the Tawny Owl successfully breeds in this area. We still have few data on the density of population and breeding success of owls in Kharkiv woodland park, but preliminary we can say that population density is some lower compared to the forest, and territorial pairs are distributed less equally. The food of Tawny Owls contained more birds than in Homishanski Forests but in both cases rodents were dominated.
Repeated communications about records of Tawny Owls in Shevchenko Park in the centre of Kharkiv brought us an idea to place one nest box in Kharkiv Zoo, adjoining to this park. This nest box we made from remains of the boards collected in an attic of one of the buildings, together with young naturalists in April 2011. We doubt that the Tawny Owl will nest in in, but birds may live or winter there.
Other 4 owl boxes were placed in autumn 2001 in Zadonetsky pine forest (NPP “Homilshanski Forests”). There are much fewer data on the Tawny Owl in pine forests of Eastern Ukraine, and placing of boxes will give an opportunity to fill this gap.

Generally, in addition to 53 nest boxes, installed earlier, for the last two years in Kharkiv region in three sites were placed other 35 artificial nests. Annual observations for all owl boxes are planned.

Egor Yatsyuk, NPP “Homilshanski Forests”

References:

Yatsyuk E.O. Fauna of small mammals of the upland oak grove “Homilshanski Forests” according to the data of pellet analysis of the Tawny Owl // Bulletin of Karazin Kharkiv National University. Series: Biology. Issue 7, № 814., – 2008. – P. 132-139. [in Ukrainian]

Yatsyuk E.A. Using of closed shelters by the Tawny Owl (Strix aluco) in the forest steppe oak grove of NPP “Gomolshansky Forests” (Kharkov region, Ukraine) // Branta: Transactions of the Azov-Black Sea Ornithological Station. – Issue 13, 2010. – P. 177-183. [in Russian]

Yatsyuk E.A. Results of monitoring of population of the Tawny Owl (Strix aluco L.) in the forest steppe oak grove of NPP “Gomolshansky Forests” // Ornithology of North Eurasia. Proceedings of 13th International Ornithological Conference of North Eurasia. Abstracts.. – Orenburg: Orenburg State Pedagogical University Press, 2010. – P. 338-339. [in Russian]

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