THE DYNAMI CS OF WADERS NUMBERS DURI NG THE SPRI NG MI GRATI ON IN FLOOD PLAI NS OF THE NAREW RI VER VALLEY NEAR WI ZNA Andrzej Górski and Jacek J. Nowakowski ABsTRACT Górski A., Nowakowski J, J. 1999, Ęnamics of waders numbers during the spring migration in flood plains of the Narew ńver valley near Wkna. Ring 21, 2: 69-78. The study was conducted in years I990-t992 in the flood terrace of the Narew river near Wizna (525 ha). Censuses were carried out once in a pentade between 20 Feb, and 20 May. Sęventeen species of waders were noted during the spring passage. Twelve species regularly migrated across this area. Ruff (53.7%), Lapwing (27.8%) and Black-tailed Godwit (L0.8%) dominated in waders assemblies. In this paper the dynamics of spring passage of some spe- cies (Lapwing, Ruff, Black-tailed Godwit, Redshank, Wood Sandpiper and Common Snipe) are described in detail. A, Górski, J, J. Nowakowski, Dept. of Ecology and Environmental Protection, Warmia and Masuria University, 10-561 Olsztyn, Zolnierska 14, Poland, E-mail: andrzejg@mat- man.uwm.edu,pi Key words: waders, spring migration, numbers dynamic, the Narew river valley. I NTRODUCTI ON Problems connected with migration dynamics of waders in river vallęys were de- scribed in previous studies only as issues accompanying studies on waterbird assem- blies and thus fragmentarily presented data covered usually only some part of the migration period (Kozł owski 1,967,Dyrcz 1971, Luniak 1971, Bednorz1976,Boro- wiec and Thrnawski 1982, Winiecki 1983, Dyrcz et al. 1984, Chmielewski 199'7). More complęte studies on migration of some species in the area of Poland refer mainly to the Baltic coast (Sikora and Meissner 1992, Meissner and Sikora 1995, Remisiewicz 1996, Meissner 1997), to Silesian barrier-reservoirs (Stawarczyk et al. I996,Dyrczet al,1998), ponds (Cieś laket al,1991, Kuł akowski 1995, Witkowski and Ranoszek 1998) or the sewage treatment plant near Bialystok (Polakowski and Ju- niewicz 1998). In many papers the migration dynamics was usually drawn for the autumn period and fieldwork covered mainly the area of artificial water bodies. As- pects of waders migration in river valleys, especially in the area of one of the morę important in the northeastern Poland river valleys of the natural character - the