One bird that could be considered a transition birds would be the Osprey. While is lives on the dry land side of things, it lives completely on fish, so much of time we see them, they are hovering above the water fishing, as it were. They then return to the desert, and their favorite cactus, in order to dine on fresh fish.
Crested Cara cara's are a beautiful bird of prey, that while they have been known to eat a lizard, or mouse, tend to eat carrion more often then not. I guess they trade quality of the meal for ease of catching it.
When you move up into the brushy arroyos, that many of the birds gather in, both for protection, as well as increased food supply, then tend to get smaller as well. This one particular arroyo has been a real boom for me, with a larger number of species there.
I counted 26 California Quail one evening.
One of the most beautiful desert birds of all time, in my opinion, is the Green-tailed Towhee! They tend to stay down in the thick brush, so to get a shot like this, I was absolutely thrilled!
There are always a lot of the tiny little California Gnatcatchers...
One of the biggest surprises for me was when this lovely little White-crowned Sparrow showed up!
There are several different desert sparrows, but this Savannah Sparrow could be called a transitional bird as well, as it was found up in the scrub, and then an hour later, down grabbing bugs along the rocky ocean shore!