Winter Roost Tree Selection and Phenology of the Long-Eared Owl (Asio Otus) in Crimea

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.

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120

100

Number of birds 40

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). Only Only three three deciduous deciduous trees weretrees wereused byused the by owls: the owls: London London plane, plane, honey honey locust, locust, and birch. and birch. The preference The preference of long-eared of long-eared owls toowls select to selectroost treesroost from trees among from among clumps clumps of conifers of conifers was also was noted also [noted5,7]. [5,7]. ◦ There waswas anan inverseinverse relationship relationship between between the the mean mean of theof the maximum maximum daily da temperatureily temperature ( C) (°C) and andthe numbersthe numbers of owls of owls in both in seasonsboth seasons (Figure (Figure3a–d). 3a–d). In 2015–2016, In 2015–2016, the inverse the inverse correlation correlation was r = was−0.57, r = −p0.57,< 0.05. p

Diversity 2018, 10, 105 4 of 6 Diversity 2018, 10, x FOR PEER REVIEW 4 of 6

160 160

140 2015-2016 140 2016-2017

120 120

100 100

80 80

60 60 Number of birds Number of birds 40 40

20 20

0 0 5.10 5.10 28.12 01.03 15.03 29.03 28.12 01.03 15.03 29.03 19-21.10 02-04.11 16-18.11 14-16.12 18-19.01 01-02.02 15-16.02 19-21.10 02-04.11 16-18.11 14-16.12 18-19.01 01-02.02 15-16.02 30.11-02.12 30.11-02.12 (a) (b)

30 30

25 2016-2017 25 2015-2016 e e 20 20 15 15 10 10 Daily temperatur Daily Daily temperatur Daily 5

5 0

0 -5 5.10 5.10 28.12 01.03 15.03 29.03 28.12 01.03 15.03 29.03 19-21.10 02-04.11 16-18.11 14-16.12 18-19.01 01-02.02 15-16.02 19-21.10 02-04.11 16-18.11 14-16.12 18-19.01 01-02.02 15-16.02 30.11-02.12 30.11-02.12 (c) (d)

Figure 3.3.(a ,(ba),b The) The number number of birds of birds counted counted weekly weekly from October from October to April to in 2015–2016April in 2015–2016 and 2016–2017; and ◦ (2016–2017;c,d) Temperature, (c,d) Temperature,C, on days °C, of observations.on days of observations.

We divideddivided thethe weather weather conditions conditions that that accompanied accompanied the countthe count sessions sessions into ﬁveinto classes: five classes: sunny, sunny,cloudy, cloudy, overcast, overcast, rain/fog rain/fog and snow. and A one-waysnow. A ANOVAone-way foundANOVA that found the number that the of owlsnumber signiﬁcantly of owls significantlydiffers depending differs on depending weather conditions on weather for conditions 14 trees (Table for 141). trees (Table 1).

Table 1.1. TheThe listlist of of trees trees for for which which a signiﬁcanta significant difference difference was was found found in the in numberthe number of long-eared of long-eared owls owlsin different in different weather weather conditions. conditions. % Owls Sitting on a Tree under Different Weather LabelLabel on on the % Owls Sitting on a Tree under Different Weather A Tree Species Conditions from the Total Number of Owls in This WeatherA One-Way p-Value Tree Species theFigure 1 Conditions from the Total Number of Owls in This Weather One-Way p-Value ANOVA Figure 1 SunnySunny Cloudy Cloudy Overcast Overcast Rain, Fog Rain, Fog Snow Snow ANOVA PlatanusPlatanus sp.sp. LP1 LP1 7.4 7.4 8.1 8.1 3.7 3.7 4.5 4.5 0.1 0.1 F = F 4.69 = 4.69 pp< < 0.0010.001 TaxusTaxus baccata baccata Y Y 1.2 1.2 2.5 2.5 3.2 3.2 2.3 2.3 2.7 2.7 F = F 10.69 = 10.69 pp< < 0.0010.001 JuniperusJuniperus sp.sp. J1 J1 5.6 5.6 5.1 5.1 8.4 8.4 6.3 6.3 6.5 6.5 F = F 13.57 = 13.57 pp< < 0.0010.001 JuniperusJuniperus sp.sp. J2 J2 0.6 0.6 2.8 2.8 0.4 0.4 2.0 2.0 2.2 2.2 F = F 3,04 = 3,04 pp< < 0.050.05 PinusPinus brutia brutia TPTP 20.3 20.323.1 23.113.4 13.4 13.1 13.1 11.4 11.4 F = F 11.48 = 11.48 pp< < 0.0010.001 PinusPinus nigra nigra AP1AP1 29.7 29.7 24.8 24.8 37.0 37.0 32.2 32.2 35.0 35.0 F = F 39.69 = 39.69 pp< < 0.0010.001 PinusPinus nigra nigra AP3AP3 7.5 7.5 5.6 5.6 10.1 10.1 11.4 11.4 12.9 12.9 F = F 23.03 = 23.03 pp< < 0.0010.001 PinusPinus nigra nigra AP4AP4 5.5 5.5 7.6 7.6 7.3 7.3 9.6 9.6 10.2 10.2 F = F 30.18 = 30.18 pp< < 0.0010.001 Pinus nigra AP5 1.1 1.4 2.2 1.7 3.3 F = 11.52 p < 0.001 Pinus nigra AP5 1.1 1.4 2.2 1.7 3.3 F = 11.52 p < 0.001 Pinus nigra AP6 0.1 0.1 0 0.3 0.5 F = 4.87 p < 0.001 Pinus nigra AP6 0.1 0.1 0 0.3 0.5 F = 4.87 p < 0.001 Pinus nigra AP7 5.0 3.6 7.3 7.9 6.4 F = 15.48 p < 0.001 PinusPinus nigra nigra AP7AP8 5.0 2.7 3.6 1.6 7.3 2.9 7.9 4.4 6.4 3.9 F = F 15.48 = 16.57 pp< < 0.0010.001 PinusPinus nigra nigra AP8AP9 2.7 0.4 1.6 0.4 2.9 0 4.4 0.2 3.9 2.7 F = F16.57 = 4.00 pp< < 0.0010.001 PinusPicea nigrasp. AP9 S 0.4 0.1 0.4 1.1 0 0.4 0.2 0.3 2.7 0 F = F 4.00 = 3.12 p < 0.001 0.05 Picea sp. S 0.1 1.1 0.4 0.3 0 F = 3.12 p < 0.05

The trees are grouped into two classes, dependin dependingg on their use by owls under different weather conditions. The ﬁrstfirst classclass isis allall coniferousconiferous trees trees (Y, (Y, J1, J1, J2, J2, AP1, AP1, AP3-9, AP3-9, S). S). The The number number of owlsof owls sitting sitting on onthese these trees trees during during precipitation precipitation (rain (rain or snow) or snow) increased, increased, but in sunnybut in andsunny slightly and cloudy,slightly weathercloudy, weatherit decreased. it decreased. The reverse The reverse trend was trend observed was observed in the secondin the second group group of trees: of trees:Platanus Platanussp. (LP1) sp. (LP1) and Pinusand Pinus brutia brutia(TP). (TP). The The number number of owlsof owls on on these these was was higher higher in in good goodweather weather thanthan in bad bad weather. weather. This cancan bebe explainedexplained by by the the peculiarity peculiarity of of the the structure structure of theof the tree tree crown. crown. Conifers Conifers have have a crown a crown with witha sharp a sharp peak, peak, broadening broadening in a cascadein a cascade towards towards the underside. the underside. Obviously, Obviously, this protectsthis protects the owls the owls that thatare sitting are sitting inside inside against against the rain. the rain.Platanus Platanussp. is sp. a deciduousis a deciduous tree thattree shedsthat sheds foliage foliage in the in winter, the winter, thus thus protection from precipitation on this tree is minimal. Pinus brutia differs from other pines due to a spreading crown, which also offers less protection from rain, snow, and fog.

Diversity 2018, 10, 105 5 of 6 protection from precipitation on this tree is minimal. Pinus brutia differs from other pines due to a spreading crown, which also offers less protection from rain, snow, and fog. Additionally, we investigated the influence of the wind direction on the distribution of owls. However, no significant difference was found in the number of birds on trees under different wind direction conditions. The buildings surrounding the university yard sheltered the owls from the wind. This is confirmed by the fact that another park is localized outside the buildings. However, the owls were not registered in all period of the study there. Fallen owls were not found during the study period. Nevertheless, the protective properties of residential buildings also contain potentially dangerous factors for owls. During one of the counting sessions, we registered that scared owls tried to fly into buildings and beat against the windows. We observed four attacks, with the result of one being that the owl fell and was disoriented completely for some time. Small passerine birds, as well as crows, were indifferent to owls in roosting places. At the same, time in another park of Simferopol, we observed the aggressive attack of small passerines and hooded crows (Corvus cornix) on a long-eared owl. Possibly, the specific feeding behaviour of birds is important. We regularly investigated the pellets (more than 100 samples) at the roosting place in Agrarne, and they contained only parts of rodents. The pellets of owls collected from under the trees from another park included the bones of birds (goldfinch, Carduelus carduelus). Perhaps, the individual feeding preferences of owls are associated with external signs for other birds. On the other hand, roosting behaviour of many owls may be a strategy to limit mobbing [14]. However, more research on this question needs to be undertaken before this relationship can be more clearly understood.

4. Conclusions 1. In Crimea, the maximum number of roosting long-eared owls was recorded from the end of November to the middle of December, and the minimum in October and April. The number of owls is changed smoothly in the winter roost, and there was no sharp increase due to migratory birds. 2. The birds exhibited a strong preference for roosting in conifers. The distribution of owls on some trees differed signiﬁcantly under different weather conditions. 3. The temperature decrease curve caused a practically synchronous change in the dynamics of the increase of the number of birds, but abrupt short-term anomalies did not have an effect.

Author Contributions: Conceptualization, Methodology, Data Curation, Writing—Review & Editing V.K.; Software, Validation, Formal Analysis, P.K. Funding: This research received no external funding. Conﬂicts of Interest: The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

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