single eurasian tree sparrow bird - latin passer montanus - known also as german sparrow at a tree hollow during the spring mating

eurasian tree sparrow passer montanus mazurek wrobel biebrza narew biebrzanski national park narwianski bird hollow trunk wood wooded forest reserve avian wetland wetlands moor moors lakeland brown gray wildlife nature natural life ecology fauna poland europe wing wings beak tail neck color colorful wild zoology travel exterior outside outdoor one single alone