Bird songs are acoustic communication signals primarily used in male-male aggression and in male-female attraction. These are often monotonous patterns composed of a few phrases. yet some birds have extremely complex songs with a large phrase repertoire. organized in non-random fashion with discernible patterns. https://www.markbroyard.com/deal-time-gtech-airram-mk2-k9-roller-roll-brush-bar-filter-vacuum-cleaner-hot-on-sale-best-find/