Warble
Any fairly musical sound made by a bird, the term not being precisely defined. The song of the Skylark Alauda arvensis, or the Blackbird Turdus merula, has a truly warbling quality, but some of the so-called 'warblers' (family Sylviidae) do not make warbling sounds.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver