Red-rumped Swallow (Hirundo daurica) on ground with beakful of mud for nest building, Bulgaria

vertebrates horizontals bulgaria birds bird mud animals daurica eastern european eastern east nest beakful horizontal behaviour wildlife eastern europe pond nature collecting hirundo swallows building swallow aves bulgarian hirundinidae east europe beak zoology passeriformes breeding bird east european vertebrate developed countries red rumped ponds developed country european ground hirundinidae europe animal europe