I know this is a really old thread but as no-one else had mentioned it, there are 4 fantastic bird scaring songs in a book called The Painful Plough: A Portrait of the Agricultural Labourer in the Nineteenth Century from Folksongs and Ballads and Contemporary Accounts edited by Roy Palmer. Highly recommended if you can get hold of a copy.
All 4 songs have really distinctive lines of vocables which look like they could be related to ancient british animal call words as documented by David Thomas in his book Animal Call Words (Carmarthen, 1939).