2 · Nature
25 · earth, world as celestial body
25F · animals
25F3 · birds
25F32 · song-birds
25F32(...) · song-birds (with NAME)
25F32(SWALLOW) · song-birds: swallow
25F32(SWALLOW)(+4) · song-birds: swallow (+ animal behaviour)
25F32(SWALLOW)(+42) · song-birds: swallow (+ feeding and care of young)
25F32(SWALLOW)(+421) ·
song-birds: swallow (+ nest, den, burrow)