TOP DAY MATE....

.... was the whistle from this Red-whiskered bulbul ! 
Check the link on Birds in Backyards and scroll down to hear the whistle on the right side of link. The comment made mention you here their whistle well before you see them!

Yes, that was the case today - heard that whistle however did not see it till it flew into the tree above me.

Enjoy, and have a look in LARGE

... thoughts to all in the massive rain storms /floods in USA.