Red-rumped Swallow ( Hirundo daurica) gathering mud for nest building, Bulgaria

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