17 KB2790 KB15 KB198020211999Vogrin, Milanletnik:205 straništevilka:93str. 45-49ISSN:0351-2851COBISSID:12710617URN:URN:NBN:SI:doc-66Z67A2VslDruštvo za opazovanje in proučevanje ptic SlovenijeAcrocephalusbirdBirdsEcosystemgnezdenjeNesting behaviorornitologijaPopulation densitypticePrimerjava dveh metod za ugotavljanje števila gnezdečih malih ponirkov Tachybaptus ruficollis, črnih lisk Fulica atra in zelenonogih tukalic Gallinula chloropus| Comparison between two different methods for estimating numbers of pairs of the breeding little grebe Tachybaptus ruficollis, coomon coot Fulica atra, andcoomon moorhen Gallinula chloropus|In the article a comparison of two different methods for estimating numbers ofpairs of the Little Grebe Tachybaptus ruficollis, Common Coot Fulica atra and Common Moorhen Gallinula chloropus during the breeding season is presented. According to the first method, individuals/pairs were counted during the breeding period and the number of breeding pairs estimated on the basis of the average number of the counted individuals. Both methods were applied at Vrbje pond in the Savinja valley and at Rače ponds (Dravsko polje) in 1998. All ponds were heavily overgrown (40-75%) with water vegetation. Numbers of the counted pairs per dates and localities and numbers of the foundnests at separate localities are presented in Tables 1 and 2. A comparison between the two methods has shown that during normal counting the number of the Little Grebe is underestimated by twice, and the number of the Common Moorhen by approx. 2.5 times. Numbers of the counted Common Coot dependmainly on the locality and the bird's migration dynamics. When Common Coots begin to gather at a certain locality already in the middle of the summer, they can be grossly overestimated (the case of Vrbje pond: Table 1). On the basis of the results and data from literature (DOMBROWSHI et al. 1993),the author suggests that on waters where vegetation covers approx. 50% of the surface, the number of the counted Little Grebe is multiplied by 2, andthe number of the Common Moorhen by 2.5. For more accurate results, however, nests must be found or the number of pairs checked by playbacks of the territorial calling of the speciesAvtor v članku podaja primerjavo dveh metod za ugotavljanje števila parov malega ponirka Tachybaptus ruficollis, črne liske Fulica atra in zelenonoge tukalice Gallinula chloropus v gnezditvenem obdobju. Pri prvi metodi je štel osebke/pare med gnezditvenim obdobjem (6 oziroma 7x) in na podlagi povprečnegaštevila preštetih osebkov izračunal število gnezdečih parov. Pri drugi metodi je iskal gnezda omenjenih vrst. Obe metodi je opravljal na ribniku Vrbje v Savinjski dolini in na Račkih ribnikih (Dravsko polje) v letu 1998. Vsi ribniki so bili zaraščeni z vodno vegetacijo od 40 do 75 %. število preštetih parov po datumih in lokalitetah ter število najdenih gnezd na posamezni lokaliteti je podano v tabelah 1 in 2. Primerjava obeh metod je pokazala, da pri običajnem štetju število malega ponirka podcenimo za dvakrat,število zelenonoge tukalice pa za približno dvainpolkrat. število preštetih črnih lisk je odvisno predvsem od lokalitete in njhove selitvene dinamike. V primeru, da se liske pričnejo zbirati na določeni lokaciji že sredi poletja, jih lahko močno precenimo (primer ribnik Vrbje: tabela 1). Na osnov rezultatov ter podatkov iz literature (DOMBROWSKI et al: 1993) avtor predlaga, da se na vodnih površinah, ki so z vodno vegetacijo zaraščene približno 50 odstotno, število preštetih malih ponirkov množi z 2, število zelenonogih tukalic pa z 2,5. Sicer pa je za natančnejše rezultate treba bodisi iskati gnezda ali število parov preverjati s posnetki teritorialnega oglašanja vrstTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaDruštvo za opazovanje in proučevanje ptic Slovenije