After reading Paul's account of taking some nice photos of the Costa's Hummingbird, I decided to take a look for it - and I've never even been to Arizona (other than Bullhead City).
Of course at 33rd and Camosun there are two alleys. Upon arriving I just walked around a little not carrying a camera. I did notice a conspicuous feeder in one backyard and guessed that this was the location to catch a "fleeting glimpse" of this bird. However, I didn't see any Hummingbirds in the area and walked around a little more. Finally upon returning to my car, I caught sight of a Hummer sitting atop of a fir tree at about 20 meters elevation. I couldn't ID it.
So I got my camera gear and headed back. I watched for a few minutes and saw a juvenile Anna's come by for a sip. Then the Costa's. It seemed civilized. The Costa's came from the left and the Anna's from the right.
Then I encountered a local resident who was just walking home and he asked me if I had seen "the Hummingbird". I told him that I had and showed him a couple of images on the LCD. He then added that it had also come to his feeder (in the other alley adjoining 33rd Avenue. That is, it has been seen in both alleys.) Moreover, it also visited a woman's feeder down a couple of blocks - 34th or 35th. He said that it had been chased from this latter woman's feeder by a male Anna's.
That made some sense to me as when I had watched the Costa's fly off, on one occasion it had gone south heading to greater numbered avenues and on another occasion, it had flown north. I didn't try to find a resting place for it as I had seen it fly high, low, north and south.
As it was a cloudy day I decided to try again today (8th), hoping for some sun to highlight the bird. Again, it was easy to find, but distant. Moreover, it was now being assailed by Anna's at this other feeder.
I then checked the feeder in the other alley and spotted two Anna's using it, one juvenile and one an adult male. So if the Costa's comes to this one, he may be attacked again. In other words, like the Anna's that disappear from Richmond Nature Gardens upon the arrival of the aggressive Rufous Hummers, the Costa's may be pushed out of this area and be very difficult to find in the near future.
Photo showing the Costa's in a defensive posture being forced from feeding by an approaching Anna's. i don't know if the open bill is for uttering threats, but the Costa's flew off, leaving the Anna's.