Analele Științifice ale Universității „Alexandru Ioan Cuza” din Iași, s. Biologie animală, Tom LVIII, 2012

ECOLOGICAL ASPECTS CONCERNING THE ROOK (CORVUS FRUGILEGUS L.) NESTING

Emanuel TÂRNOVEANU Faculty of Biology, Alexandru Ioan Cuza University of Iași, B-dul Carol I, no. 20A, 700505 Iași, Romania; [email protected]

Abstract. The paper presents a series of ecological aspects related to the species (Corvus frugilegus L.), collected on the territory of Iași county. In the spring of 2011, we surveyed the distribution of the species in various localities in the county. We first covered the route Iași-Bivolari, locating more important colonies in the villages Popricani, Țigănași, Cârniceni and Probota. On the route Iași-Cristești, near the pharmaceutical company Antibiotice SA, there can be found one of the largest colonies (494 nests). Small and medium-sized colonies can be found at the exit from Lețcani and Podu Iloaiei. În Pașcani we spotted an isolated nest in the central park. The other routes – Iași-Grozești and Iași-Domnița – do not provide nesting habitats to the species. The widest nest distribution can be found in Iași, particularly in the Iași Railway Station area, Copou, Podu de Piatră, Dacia and Tătărași. The colonies in the rural area are situated in the proximity of agricultural units, which constitute potential food resources. For the determination of the flight direction we have examined the feeding places near the rivers Bahlui and Jijia. The rook is a synanthropic species, to be found in lower areas (plains and low hills). It nests especially in the tree-tops, more rarely at the basis of the crown, the nests being close to one another, superposed, or isolated. Some of the nests are occupied by the long-eared owl (Asio otus), the Eurasian hobby (Falco subbuteo) and the kestrel (Falco tinnunculus).

Keywords: routes, colonies, nest distribution, breeding grounds.

Rezumat. Aspecte ecologice privind cuibăritul la cioara de semănătură, (Corvus frugilegus L.). În lucrare prezentăm unele aspecte ecologice ale speciei Corvus frugilegus L., colectate pe teritoriul județului Iași. În primăvara anului 2011 am urmărit răspândirea speciei în localități din județ. Am parcurs inițial ruta Iași-Bivolari, reperând colonii mai importante în satele Popricani, Țigănași, Cârniceni și Probota. Pe ruta Iași-Cristești se găsește una dintre cele mai mari colonii, lângă compania farmaceutică Antibiotice SA (494 de cuiburi). Colonii mici și mijlocii apar la ieșirea din localitățile Lețcani, respectiv Podu Iloaiei. La Pașcani am reperat un cuib izolat în Parcul Municipal. Restul rutelor parcurse – Iași-Grozești și Iași-Domnița – nu oferă habitate de cuibărit speciei. Cea mai amplă repartiție a cuiburilor se află chiar în municipiul Iași, coloniile cele mai reprezentative situându-se în zonele Gara Iași, Copou, Podu de Piatră, Dacia și Tătărași. Coloniile din mediul rural se găsesc aproape de unități agricole, potențiale surse de hrană. Pentru aprecierea direcției de zbor a stolurilor de ciori am studiat locurile de hrănire aferente Bahluiului și Jijiei. Cioara de semănătură este o specie sinantropă, localizată în ținuturi joase (șesuri și dealuri mici). Cuibărește îndeosebi în vârful arborilor, mai rar la baza coroanei, cuiburile fiind alăturate, suprapusese ori izolate. Parte din cuiburi sunt ocupate de ciuful de pădure (Asio otus), de șoimul rândunelelor (Falco subbuteo) și de vinderel (Falco tinnunculus).

Cuvinte cheie: trasee, colonii, distribuția cuiburilor, teritorii de cuibărit.

Introduction As a component of the open habitat aviary fauna, the rook (Corvus frugilegus L.) is a good flyer which loves plains and lower hills and which is often met particularly in urban areas. It lives all through the year in flocks, with established roosting, feeding and breeding grounds. Its lifestyle is closely related to crop fields and its behaviour is noticeable for its special complexity connected to the well-developed nervous system.

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The paper will present several aspects concerning:  mapping rook colonies in Iași county in the spring of 2011;  ecology of the species. In 2009 Maria-Magdalena Croitoru presented in an ornithological study carried out in Iași city, the population dynamics of this species. For the city of Iași it was possible to make a quantity evaluation of the rook population carried out in the colonies.

Material and Methods The estimation of the nesting population was done by multiplying the number of nests recorded on the territory of the city by two (as represents the pair of reproductive individuals). In Iași city, in 2011 we carried out an inventory of the colonies in a series of green spaces, populated with rooks during the breeding season. We have also researched breeding areas on road routes such Iași-Bivolari and Iași-Cristești. In every colony registered in the study area we have identified the species of trees. For every tree with nests we have followed the location of the nests in the tree, their distance to the tree trunk and the report to the cardinal points. In order to measure the height of the tree and the height of the nest location on the tree we used a telemeter Laser Nikon 1200S 7×.

Results and Discussion According to our estimations carried out in 2011, the rook population in Iași city consisted of approximately 1842 individuals. The biggest rook colony in the city – around 988 individuals – occupies the surroundings of the pharmaceutical company Antibiotice SA. The next biggest is situated near Iași Railway Station, reuniting around 316 individuals. By means of trips into Iași county we made the first mapping of rook colonies in this part of central Moldavia. In Iași county, we recorded colonies in 7 settlements: Iași, Popricani, Țigănași, Cârniceni, Probota, Lețcani and Podu Iloaiei. The distribution of nests in the tree crown was analysed based on the scheme proposed by Z. Kasprzykowski (2007). He recommends dividing the tree crown into three horizontal areas – A, B and C – and in three concentric sectors – I, II and III – (Fig. 1). We applied the scheme elaborated by the named researcher in the study of the colonies in the settlements of Iași, Popricani and Probota. The vast majority of the colonies were distributed in area A I. In March and April the number of the nests observed in different areas of Iași county was an estimated 1620. In March 2011 we counted 534 nests in the rookery of Antibiotice SA. The maximum number of nests found on a tree was 17. Adjacent nests were found predominantly in areas A I and B I, which indicates a clear preference of the bird for building the nest towards the upper part of the tree and the middle of crown. The nest distribution is presented in Table 1, Fig. 2 (a and b). The working model presented in Table 1, Fig. 2 was applied to all colonies where the nest distribution study was carried out.

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Figure 1. Positioning of nests in the tree (after Z. Kasprzykowski, 2007).

In March 2011 we counted 534 nests in the rookery of Antibiotice SA. The maximum number of nests found on a tree was 17. Adjacent nests were found predominantly in areas A I and B I, which indicates a clear preference of the bird for building the nest towards the upper part of the tree and the middle of crown. The nest distribution is presented in Table 1, Fig. 2 (a and b). The working model presented in Table 1, Fig. 2 was applied to all colonies where the nest distribution study was carried out.

Table 1. Distribution of rook nests in tree canopy (areas and sectors) in the Antibiotice SA colony in the year 2011.

No. The area and Nests crt. the location of No. % of the total % of the total the nest / tree nests / colony nests / area 1. A I 117 21.9 32.6 2. A II 138 25.8 38.4 3. A III 104 19.5 29 Total A 359 67.2 4. B I 40 7.5 42.1 5. B II 30 5.6 31.6 6. B III 25 4.7 26.3 Total B 95 17.8 7. C I 20 3.7 25 8. C II 20 3.7 25 9. C III 40 7.5 50 Total C 80 15 Total of nests / colony 534

In the rookery from Iași Railway Station we recorded 158 active nests. From these, the most were built in area A, followed by B and C. There was clear preference for placing the nest in sector I for every area. In “Titu Maiorescu” campus (Copou) we observed two species of trees – the lime tree and the black walnut tree – on which we recorded a total of 38 nests. In both species, the preferential areas for placing nests was A and area C had no nests at all.

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67.2 % 70 % 30 25.8 A I A II 25 21.9 60 A area 19.5 A III 50 B area 20 B I C area B II 40 15 B III 30 7.5 7.5 C I 17.8 10 5.6 15 4.7 3.7 3.7 C II 20 5 C III 10 0 0 A A A B I B B C I C C A area B area C area I II III II III II III

Figure 2a. Nest distribution by areas. Figure 2b. Nest distribution by areas and sectors, against the total number of nests.

The rookery in Popricani consists of 83 nests, situated on different species of trees, distributed predominantly in area A. The sector distribution is approximately uniform. The rook colony in Probota consists of 233 nests, mostly built along the axis of the trees and conglomerated. It was noticed, as in the other colonies, that there was preference for the upper part of the tree. From the colonies observed in the field, only a small part were located in plantations of a single species of trees, such as the elm tree in Târgu Cucului, and the plane tree in Parcul Teatrului Național in Iași. In most cases we found colonies in clumps of trees from different species, distributed haphazardly, such as on the plantations in the parks in the cities of Iași and in the village of Popricani. The species of trees mostly used to build nests in the colony of Antibiotice SA are as follows: the Euro-American poplar (Populus euroamericana), the Chinese poplar (Populus simonii), the locust tree (Robinia pseudacacia), the sycamore (Acer pseudoplatanus), the maple (Acer platanoides), the ash (Fraxinus excelsior), the cherry tree (Cerasus avium), the lime tree (Tilia tomentosa). We have not found nests on a species of maple (Acer tataricum) which does not grow high (Fig. 3). The poplar is one of the trees favoured by the rook, both in terms of breeding and of roosting, since it is a tall tree and not accessible to predators. We also found nests on shorter trees, located at 4 metres from the ground. According to our observations, the rook does not prefer a certain species of trees to build the nest. It usually chooses the richly branched trees, probably because they ensure stability for the nest. In order to research the placement of the nests in relation to cardinal points, we studied the following breeding grounds: the industrial area and Tătărași district (Iași), the green space at Antibiotice SA (Iași), Iași Railway Station and the area of “Haralamb Vasiliu” Agricultural School (Podu Iloaiei). The percentage of nests for every position in the tree is depicted in Figure 4. The rook does not display any preference for a certain cardinal point, but rather for the individual ramification particularities of every tree.

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100 91 90 85.5 81 80

70 62.5 64 58 60 55 Number inspected trees 47 50 Trees with nests No. 40 40 36 Trees with nests % 29 28.6 30 25 20 20 15

7 10 3 2 0 Ash Acer sp. Locust Cherry Populus Lime tree tree tree sp.

Figure 3. Species of trees with rook nests in front of Antibiotice SA.

45% Industrial area and Tătărași district (Iași) 40% Antibiotice S.A.

35% Iași Railway Station 30% „Haralamb Vasiliu” Agricultural 25% School (Podu Iloaiei)

20%

15%

10%

5%

0% N N-W N-E S S-W S-E W E

Figure 4. Placement of nests with regard to cardinal points in Iași county.

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Conclusions As an element of the open habitat aviary fauna, the rook uses plantations in the anthropic environment for breeding. The aspects under study in this paper refer to reproductive activity in the wild. The analysis of the nest distribution in the tree crown has revealed a tendency to occupy the upper part of the tree, less accessible to predators. The preference for a certain species of trees for breeding has not been established. Tall, branchy trees who offer the nest stability are usually occupied. The placement of the nest is done according to the individual branching characteristics of every tree, without any preference for any cardinal point. The new aspects of our study refer to the mapping of the rook colonies in Iași county.

Acknowledgements To research activities that are the subject of this article were carried out with financial support POSDRU/88/1.5/S/47646 project, financed by European Social Fund, the Human Resources Development Operational Programme 2007-2013.

References Croitoru, M.-M., 2009. Păsările din zonele verzi ale orașului Iași, Ed.Universității „Alexandru Ioan Cuza”, Iași. Kasprzykowski, Z., 2008. Nest location within the tree and breeding parameters of Rooks Corvus frugilegus. Bird Study, 55 (1): 59–65.

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