It's an excellent question, and there were a number of factors: (1) I use a 500 mm lens, so it lets in a bit less light; (2) the picture was taken indoors in the Aviary, where the lighting conditions continually change, especially when the sky is cloudy, so I sometimes use a higher ISO to offset that; (4) I tend to use a higher shutter speed when photographing birds, which also needs to be offset somewhat by a higher ISO especially in darker conditions. That said, it was probably too high. It was observant of you to see that, though.
Thanks Well, I treat my responsibilities here pretty seriously, so I make time for the things I want to do here. But also, I have some pretty great people helping me, especially at #Birds-Club =mydigitalmind, *FForns, and ~DeeOtter are wonderful!