This morning the Violet-crowned Hummingbird wintering in my yard in North-Central Tucson began singing a new song. I presume this is the advertising song – meant to attract a mate. I had just stepped outside about 15 minutes before sunrise to see if he was at the feeders already and heard this vaguely familiar repeated "squee" sound. I've heard it in Mexico or in Patagonia (Arizona), but it's been a long time. I ran inside to get my Olympus LS-11 and got this recording.
The much quieter "gurgle" song can be heard in this recording from last winter, and he's been giving it all the time.