Winter Roost Tree Selection and Phenology of the Long-Eared Owl (Asio Otus) in Crimea
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diversity Article Winter Roost Tree Selection and Phenology of the Long-Eared Owl (Asio otus) in Crimea Volodymyr Kucherenko 1,* and Pavel Kalinovsky 2 1 V.I. Vernadsky Crimean Federal University, Department of Ecology and Zoology, 95007 Simferopol, Crimea, Ukraine 2 V.I. Vernadsky Crimean Federal University, Department of Botany and Plant Physiology and Biotechnology, 95007 Simferopol, Crimea, Ukraine; [email protected] * Correspondence: [email protected]; Tel.: +7-978-066-41-96 Received: 23 August 2018; Accepted: 22 September 2018; Published: 27 September 2018 Abstract: The winter roost of the long-eared owl Asio otus in Crimea (South of Ukraine), located in Simferopol, is described. In 2015–2017, the number of long-eared owls varied on a convex curve, with the maximum reached at the end of November and in December. The birds exhibited a strong preference for roosting in conifers, where we recorded 89% of the owls. There was an inverse relationship between the mean of the maximum daily temperature (◦C) and the number of owls in both seasons. The owls were not sensitive to abrupt but short-term temperature changes, but the temperature decrease curve caused practically synchronous changes in the dynamics of bird numbers. It was found that the number of owls significantly differed based on weather conditions in 16 trees. The proportion of owls sitting on coniferous trees increased with unfavourable weather, and the converse pattern was observed for deciduous trees. Keywords: Long-eared Owl; Asio otus; communal roost; phenology 1. Introduction The long-eared owl (Asio otus) is widespread species, migratory in the northern part of its range, and sedentary in the south and west. In winter, it forms communal roosts [1]. Most studies of the long-eared owl relate to its feeding ecology and diet selection in different parts of its range [1–3]. Little information is available on the description and analysis of its numbers and diurnal roost sites [4–7]. The literature on roosting sites and attendant behaviour is limited, and few of the existing observations have been systematic [5,8]. Furthermore, relatively little work has been carried out on other aspects of the biology of this species, such as the phenology of winter roost occupancy and behaviour at the roost [9]. This ecology aspect has not been studied in Ukraine. A greater knowledge of the ecological correlates of communal roosting could help unravel issue about migration; the estimation of the population differences in behaviour of the long-eared owl in winter, and also to establish the anthropogenetic factors that threaten them in this period. 2. Materials and Methods Our research was conducted in the Agrarne, in the northern part of Simferopol, in the Crimea Republic (Ukraine) (45◦00060” N, 34◦03017” E). The roost was localized in the university yard of Academy Bioresourses and Environmental Management. It is almost completely surrounded by five-story buildings. The size of the yard is 49 × 78 m. It contains 34 trees: 10 London planes (Platanus sp.)—LP1–10, nine Austrian pine (Pinus nigra)—AP1–9, two maples (Acer sp.)—M1–2, two Platycladus (Platycladus orientalis)—T1–2, two junipers (Juniperus sp.)—J1–2, two oaks (Quercus sp.)—O1–2, one Turkish pine (Pinus brutia)—TP, one European yew (Taxus baccata)—Y, Diversity 2018, 10, 105; doi:10.3390/d10040105 www.mdpi.com/journal/diversity Diversity 2018, 10, 105 2 of 6 Diversity 2018, 10, x FOR PEER REVIEW 2 of 6 onelocust honey (Gleditsia locust sp.)—G, (Gleditsia onesp.)—G, birch (Betula one birchsp.)—B, (Betula one elmsp.)—B, (Ulmus one sp.)—E, elm (Ulmus one pearsp.)—E, (Pyrus one sp.)—P, pear (andPyrus onesp.)—P, spruce and(Picea one sp.)—S spruce (Figure (Picea 1).sp.)—S At the (Figure roost,1 the). At tree thes are roost, low, the about trees 5–7 are m. low, This about allowed 5–7 m.us Thisto consider allowed all us the to owls consider on the all trees. the owls on the trees. Figure 1.1. MapMap ofofthe the long-eared long-eared owls owls roost. roost. Red Red dots: dots: trees trees that that were were used used by the byowls, the owls, green green dots: trees,dots: wheretrees, owlswhere were owls absent, were TP—Turkish absent, TP—Turkish Pine, AP—Austrian Pine, AP—Austrian Pine, LP—London Pine, Plane,LP—London T—Platycladus, Plane, J—juniper,T—Platycladus, Y—European J—juniper, yew, Y—European G—honey locust, yew, B—birch,G—honey P—pear, locust, S—spruce,B—birch, M—maples,P—pear, S—spruce, O—oak, E—elm.M—maples, Numerals O—oak, near E—elm. the dots Numerals indicate near the serialthe do numberts indicate of the the tree. serial number of the tree. The owls were counted weekly from October to April 2015–2016 and 2016–2017 ((nn = 50 counting sessions), except for in the first first ten days of January in each year. Each time, we recorded a quantity of birds on every tree and registered the mean of th thee maximum daily temperature, the weather, and the direction of the wind. The weather was categorizedcategorized as sunny, cloudy,cloudy, overcast,overcast, rain/fograin/fog and snow. To determinedetermine the seasonal dynamics of bird numbers,numbers, we divided all months into three 10-day periods and calculated the mean value of the number of owls for two years in this period. A one-way analysis of variance (ANOVA) was used to test whether there was a significantsignificant difference between the number of birds sitting on the trees of differentdifferent speciesspecies andand thethe weatherweather conditions.conditions. The Pearson correlation coefficientcoefficient was was measured measured to to determine determin whethere whether there there was was a relationship a relationship between between the value the ofvalue the of daily the temperaturedaily temperature and the and number the number of owls of on owls the on roost. the roost. 3. Results and Discussion During the study period, the number of long-earedlong-eared owls changed on a convex curve, with the maximum occurringoccurring fromfrom the the end end of of November November to to the the middle middle of of December December (Figure (Figure2). According2). According to the to literature,the literature, the maximum the maximum number number of long-eared of long-eared owls was owls in December was in December in Milan, inin SouthernMilan, in Europe Southern [9], orEurope with the[9], peakor with in December the peak orin JanuaryDecember in Moscow,or January in thein Moscow, north of thein the winter north range of the [10 ].winter In Romania, range the[10]. number In Romania, of owls the was number the highest of owls in was February the high andest inin NovemberFebruary and [11 ].in ComparingNovember [11]. our resultsComparing with thoseour results of other with sites those from of Europe, other sites it can from be seenEurope, that it the can observed be seen roostthat the phenology observed is roost the most phenology similar tois thatthe most of North similar Italy. to that of North Italy. Diversity 2018, 10, 105 3 of 6 Diversity 2018, 10, x FOR PEER REVIEW 3 of 6 120 100 80 60 Number of birds 40 20 0 October November December January February March April Figure 2. TheThe mean mean value value of ofthe the number number of long-eared of long-eared owls owls at the at roost the roost site per site 10-day per 10-day period period from 2015–2017.from 2015–2017. The owls owls arrive arrive for for wintering wintering to to the the south south of ofUkraine Ukraine from from Finland, Finland, the thenorthern northern regions regions of the of Russianthe Russian Federation, Federation, and and the thenorthern northern regions regions of ofUkraine Ukraine [12]. [12 ].When When we we started started the the count count in in the middle of October, in both seasons the owls had already begun roosting. A possible explanation for this fact may be the arrival of birds in Crimea (south(south of Ukraine) in September. As noted earlier by Yu. KostinKostin [[13]13] andand N.N. TovpinetsTovpinets andand I.I. Evstaf’evEvstaf’ev [[7],7], the wintering owls flyfly into Crimea in October or in the middle of November. However, A. Poluda’s [[12]12] study of the migration of long-eared owls in the south of Ukraine has demonstrated that it takes place from the end of SeptemberSeptember in Kherson Oblast (just north of Crimea). The results presen presentedted in our work correspond more closely with the data, collectedcollected byby A. A. Poluda. Poluda. It canIt can be seenbe seen from from the datathe data in Figure in Figure2 that the2 that number the number of birds changesof birds changessmoothly, smoothly, and there isand no sharpthere increaseis no sharp due toincrease migratory due birds. to migratory Most likely, birds. birds Most migrating likely, through birds migratingthe Crimean through peninsula the Crimean do not use penins this roostula do region. not use this roost region. From the data in Figure 1 1,, itit cancan bebe seenseen thatthat onlyonly 2020 treestrees ofof aa totaltotal ofof 3434 were occupiedoccupied byby owls, and 14 trees that were mostly deciduous were not used by them at all. Errors in the counting of the number of the owls were minimized because of low trees height in the study site. The birds exhibited a strong preferencepreference forfor roosting roosting in in conifers. conifers. A A total tota ofl of 89% 89% of theof the records records were were taken taken in these in these trees, trees, and andabout about 31% 31% of the of owls the owls were were observed observed on the on Austrian the Austrian pine (AP1).pine (AP1).