This study was conducted in Krapina river valley in north-western Croatia during 2004 – 2005. The mean nest density of the hooded crow on the research was 3.73 nest/km². The mean clutch size was 4.34 and egg size (volume) was 17.63 cm³. Mean egg length (2004 – 2005) was 41.11 mm, breadth 28.97 mm and egg shape index 1.42. The positive correlation between length and breadth was (p0.05).Istraživanje je obavljeno u nizini rijeke Krapine na području sjeverozapadne Hrvatske u razdoblju od 2004. do 2005. godine. Gustoća gnijezdećih parova iznosila je 3,73/km² (prosjek za obje godine istraživanja). U gnijezdima je bilo prosječno 4,34 jaja, a prosječni volumen jaja iznosio je 17,63 cm³. Prosječna dužina jaja iznosi 41,11 mm, širina 28,97 i indeks oblika jaja 1,42. Značajna je pozitivna korelacija između dužine i širine jaja (p0.05) ne podržava »hipotezu ustupka« (BROCKELMAN, 1975) prema kojoj bi
se u gnijezdima s većim brojem jaja morala nalaziti jaja manjeg volumena

Z. Dolenec

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short communication / kratko priop}enjeNEST DENSITY, CLUTCH SIZEAND EGG DIMENSIONS OF THE HOODEDCROW (CORVUS CORONE CORNIX)ZDRAVKO DOLENECDepartment of Zoology, Faculty of Science, University of Zagreb,Rooseveltov trg 6, Zagreb, Croatia (E-mail: dolenec@zg.biol.pmf.hr)Dolenec, Z.: Nest density, clutch size and egg dimensions of the hooded crow (Corvus coronecornix). Nat. Croat., Vol. 15, No. 4., 231–235, 2006, Zagreb.This study was conducted in Krapina river valley in north-western Croatia during 2004 – 2005.The mean nest density of the hooded crow on the research was 3.73 nest/km². The mean clutchsize was 4.34 and egg size (volume) was 17.63 cm³. Mean egg length (2004 – 2005) was 41.11 mm,breadth 28.97 mm and egg shape index 1.42. The positive correlation between length and breadthwas (p<0.05). There was no significant correlation between clutch size and the volume of eggs(p>0.05).Key words: hooded crow, Corvus corone cornix, nest density, clutch size, egg dimensionsDolenec, Z.: Gusto}a gnijezda, veli~ina pologa i dimenzije jaja sive vrane (Corvus coronecornix). Nat. Croat., Vol. 15, No. 4., 231–235, 2006, Zagreb.Istra`ivanje je obavljeno u nizini rijeke Krapine na podru~ju sjeverozapadne Hrvatske u raz-doblju od 2004. do 2005. godine. Gusto}a gnijezde}ih parova iznosila je 3,73/km² (prosjek za objegodine istra`ivanja). U gnijezdima je bilo prosje~no 4,34 jaja, a prosje~ni volumen jaja iznosio je17,63 cm³. Prosje~na du`ina jaja iznosi 41,11 mm, {irina 28,97 i indeks oblika jaja 1,42. Zna~ajna jepozitivna korelacija izme|u du`ine i {irine jaja (p<0.05). Korelacija izme|u veli~ine pologa i veli~i-ne jaja (volumena) (p>0.05) ne podr`ava »hipotezu ustupka« (BROCKELMAN, 1975) prema kojoj bise u gnijezdima s ve}im brojem jaja morala nalaziti jaja manjeg volumena.Klju~ne rije~i: siva vrana, Corvus corone cornix, gusto}a gnijezda, veli~ina pologa, dimenzije jajaINTRODUCTIONMany studies on the breeding ecology and density of hooded crow (Corvuscorone cornix) populations have been published during the last 40 years (e.g. TENO-VUO, 1963; PICOZZI, 1975; SONDELL, 1976; LOMAN, 1977, 1980; FASOLA, 1983; MELDE,1984; PARKER, 1985; CRAMP, 1998). However, there are no data for Croatia. Thehooded crow is found in most open habitats (CRAMP, 1998) and is adaptable in itsNAT. CROAT. VOL. 15 No 4 231–235 ZAGREB December 31, 2006Croatian Natural History Museum, Demetrova 1, Zagreb, Croatiafeeding behaviour (e.g. COOMBS, 1978). The dimensions of eggs are important life-history variables in birds as hatching mass is highly correlated with egg size for alarge number of bird species (e.g. HEGYI, 1996). Being hatched from a large eggcould be beneficial for a chick; from the viewpoint of the laying female, however,high investment into egg quality (size) might conflict with her own energetic de-mands and willingness to produce more offspring (HÕRAK et al., 1995).In this paper I present nest density and some breeding characteristics (clutchsize, egg length, egg breadth, egg volume and egg shape index) of the hooded crowin a mixed agricultural and wooded area in north-western Croatia. The question ofwhether females laying larger clutches produce smaller eggs was also analysed.The relationships among different egg dimensions were also investigated.MATERIALS AND METHODSThe study was conducted in the Krapina river valley (11 km²) in NW Croatia(45°00' N, 15°55' E). My studies cover the period from 2004 to 2005 (middle March –early May). Eighty-two clutches were investigated (356 eggs). The hooded crow is acommon bird in the study area. The altitude of the study area is about 140 m abovesea level. The tree vegetation is dominated by pedunculate oak (Quercus robur) andhornbeam (Carpinus betulus). Nest density was estimated only on the basis of foundnests. Egg length (maximum) and breadth (maximum) were measured to the nea-rest 0.01 mm using sliding callipers. Egg volume (V) was computed from the length(L) and breadth (B) of each egg, using the formula developed by Hoyt (1979):V = 0.51 x L x B². Egg shape index (ES) was calculated using the formula: ES = L / B.This study was based only on complete clutches. According to some authors (e.g.KNOX et al., 2002), the hooded crow and carrion crow can be considered differentspecies; Corvus cornix and Corvus corone. The aim of this study is to present dataabout density and breeding characteristics of the hooded crow in Croatia. These arethe first published data of the kind for Croatia.Statistical analyses were performed using the SPSS 12.0 statistical package.RESULTS AND DISCUSSIONThe mean nest density of the hooded crow in the research area was 3.73 nest/km²(2004 = 3.55 and 2005 = 3.91 nests/km²). This is high density for crow populations in arural area. Similar results were found by ZDUNIAK & KUCZYNSKI (2003) – 3.2 nests/km²,while most authors mention a lower density (e.g. VOGRIN, 1998; 1.5 pairs/km²) forsuch a habitat. Table 1 shows data on nest sites in trees. Out of 82 nests, themajority were situated in pedunculate oak and hornbeam (61.0%). Nests were si-tuated at a height of 4.5 – 18.5 (mean = 9.5 m, SD = 2.13).We recorded 2–6 eggs in the clutch. The mean clutch size was 4.34, SD = 0.835(2004 – 2005). There are no differences from other parts of Europe (e.g. WITTENBERG,232 Dolenec, Z.: Nest density, clutch size and egg dimensions of the hooded crow1968 = 4.53; LOMAN, 1984 = 4.3; MELDE, 1984 = 4.7; ZDUNIAK & KUCZYNSKI, 2003 =4.43).Mean egg length (2004 – 2005) was 44.11 mm (SD = 1.311, range 35.81 – 43.91 mm),egg breadth 28.97 mm (SD = 0.974, range 27.19 – 30.52 mm), egg volume 17. 63 cm³(SD = 1.526, range 12.21 – 20.32 cm³) and egg shape index 1.42 (SD = 0.071, range1.29 – 1.59) (Tab. 2). There is no difference in egg dimensions between years (length,Nat. Croat. Vol. 15(4), 2006 233Tab. 1. Height of nests above ground and nest sites of the hooded crow in NW Croatiaduring 2004 – 2005nest size height of nest n %mean rangepedunculate oak (Quercus robur) 12.3 6.5 – 22.0 31 37.8hornbeam (Carpinus betulus) 11.1 5.5 – 18.0 19 23.2ash (Fraxinus angustifolia) 10.8 6.0 – 18.5 3 3.7common elm (Ulmus minor) 8.5 8.5 1 1.2willow (Salix sp.) 7.7 4.5 – 11.0 14 17.1sticky alder (Alnus glutinosa) 7.1 4.5 – 15.5 8 9.8common maple (Acer campestre) 9.0 5.5 – 12.5 6 7.2total 9.5 4.0 – 18.5 82 100.0Tab. 2. Egg dimensions of hooded crow in NW Croatia during 2004 – 2005, number ofclutches = 82parameters mean SD rangelength (mm) 41.11 1.311 35.81 – 43.91breadth (mm) 28.97 0.974 27.19 – 30.52volume (cm³) 17.63 1.526 12.21 – 20.32egg shape index 1.42 0.071 1.29 – 1.59Tab. 3. Annual variation in egg dimensions of the hooded crow in NW Croatia (n = numberof clutches, t = Student's test)year n length (mm) breadth (mm) volume (cm³) egg shape indexmean SD mean SD mean SD mean SD2004 39 41.13 1.248 28.86 0.905 17.49 1.129 1.43 0.0442005 43 41.09 1.482 29.07 1.005 17.76 1.818 1.42 0.089t 0.141 0.835 0.801 0.543p 0.889 0.409 0.425 0.589Student's test (t) = 0.141, p = 0.889; breadth, t = 0.835, p = 0.409; volume, t = 0.801,p = 0.425; egg shape index, t = 0.543, p = 0.589) (Tab. 3). A statistically significantpositive correlation was found between egg length and egg breadth (Pearson's cor-relation (r) = 0.31, p < 0.01, n = 82). Very slight differences in egg dimensions can beobserved if we compare nests according to different clutch sizes (Tab. 4). The averageegg dimensions in my study area were similar to those found by other authors inEurope (e.g. NIETHAMMER, 1937; DURANGO, 1973; ROFSTAD & SANDVIK, 1985; CRAMP,1998).According to LACK (1967), species producing relatively large eggs must compen-sate by laying fewer eggs. There was no significant correlation between clutch sizeand the volume of eggs (p > 0.05). So we can conclude that the results of ourresearch do not support predictions based on the hypothesis of optimal clutch/eggdimensions (BROCKELMAN, 1975).ACKNOWLEDGEMENTSI would like to thank two referees and the editor for comments and for im-proving the manuscript.Received January 23, 2006REFERENCESBROCKELMAN, W. Y., 1975: Competition, the fitness of offspring and optimal clutch size. Ame-rican Naturalist 109, 677–699.COOMBS, F., 1978: The Crows. A study of the Corvids of Europe. Batsford, London.CRAMP, S. 1998: Complete Birds of the Western Palearctics on CD-ROM. Oxford Univ. Press.DURANGO, S., 1973: Les Oiseaux. F. Nathan, Paris.FASOLA, M., 1983: Mosaic distribution and breeding habitat of the Hooded Crow Corvuscorone cornix and the Magpie Pica pica in Padana plain (Northern Italy). Avocetta 7, 67–84.234 Dolenec, Z.: Nest density, clutch size and egg dimensions of the hooded crowTab. 4. Egg dimensions of the hooded crow in NW Croatia according to clutch sizesduring 2004 – 2005clutchsizen % length (mm) breadth (mm) volume (cm³) egg shape indexmean SD mean SD mean SD mean SD2 2 2.4 40.11 1.211 29.11 0.534 17.31 0.362 1.38 0.0573 8 9.8 41.46 1.277 29.23 1.009 18.09 1.535 1.42 0.0564 37 45.1 41.21 1.208 29.05 0.934 17.76 1.007 1.42 0.0845 30 36.6 40.95 1.438 28.82 1.114 17.41 2.048 1.43 0.0716 5 6.1 41.11 1.376 28.81 0.788 17.63 0.740 1.43 0.049HEGYI, Z., 1996: Laying date, egg volumes and chick survival in Lapwing (Vanellus vanellusL.), Redshank (Tringa totanus L.), and Black-tailed Godwit (Limosa limosa L.). Ornis hunga-rica 6, 1–7.HÕRAK, P., MÄND, R., OTS, I. & LEIVITS, A., 1995: Egg size in the Great Tit Parus major:individual, habitat and geographic differences. Ornis Fennica 72, 97–114.HOYT, D. F., 1979. Practical methods of estimating volume and fresh weight of eggs. Auk 96,73–77.KNOX, A. G., COLLINSON, M., HELBIG, A. J., PARKIN, D. T. & SAGSTER, G., 2002: Taxonomicrecommendations for British birds. Ibis 144, 707-710.LACK, D., 1967: The significant of clutch-size in waterfowl. Wildfowl 18, 125–128.LOMAN, J., 1977: Factors affecting clutch and brood size in the crow Corvus cornix. Oikos 29,294-301.LOMAN, J., 1980: Reproduction in population of the hooded crow Corvus cornix. HolarcticEcology 3, 26-35.LOMAN, J., 1984: Breeding success in relation to parent size and experience in a population ofthe Hooded Crow. Ornis Scan. 15, 183–187.MELDE, M., 1984: Raben– und Nebelkröhe (Corvus corone). Die Neue Brehm – Bücherei, Wit-tenberg Lutherstadt.NIETHAMMER, G., 1937: Handbuch der deutschen Vogelkunde. Passers, I. Academic Verlags-gesellschaft, Leipzig.PARKER, H., 1985: Breeding performance and aspect of habitat selection in sub-arctic HoodedCrows Corvus corone cornix. Fauna. Norv. Ser. C, Cinclus 8, 100–105.PICOZZI, N., 1975: A study of the carrion/hooded crow in northeast Scotland. Brit. Birds 68,409–419.ROFSTAD, G., SANDVIK, J., 1985. Variation in egg size of the Hooded Crow Corvus corone cornix.Ornis scand. 16, 38–44.SONDELL, J., 1976: Population development in the Hooded Crow Corvus corone cornix at Kvis-maren, Narke, in 1964-1973. Var Fäegelvarld 35, 113–121.TENOVUO, R., 1963: Zur brutzeitlichen Biologie der Nebelkrähe (Corvus corone cornix L.) inäusseren Schärenhof Finnlands. Ann. Zool. Soc. Vanamo 25, 1–247.VOGRIN, M., 1998: Abundance and habitat selection of breeding Corvus corone cornix on agri-curtural land in Central Slovenija. Acta Zool. Lit. Ornith. 8 (2), 127–130.ZDUNIAK, P. & KUCZYNSKI, L., 2003: Breeding biology of the Hooded Crow Corvus corone cornixin Warta river valley (W Poland). Acta Ornith. 38, 143–150.SA@ E TAKGusto}a gnijezda, veli~ina pologa i dimenzije jaja sive vrane(Corvus corone cornix)Z. DolenecOvo su prvi podaci o obilje`jima gnije`|enja sive vrane na podru~ju Hrvatske. Uosnovnim parametrima nema zna~ajnih razlika u odnosu na neke druge europskezemlje. To se odnosi i na gusto}u gnijezde}ih parova. Sve prisutniji antropogeni~imbenik ostavlja sve ve}i trag u istra`ivanom krajoliku, pa je stoga nu`no daljnjepra}enje i istra`ivanje populacije sive vrane.Nat. Croat. Vol. 15(4), 2006 235

Gustoća gnijezda, veličina pologa i dimenzije jaja sive vrane (Corvus corone cornix)

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