I've been watching the falcons for two years and have only ever seen them deliver/eat various birds. This morning, however, at roughly 9:00AST it seemed Trey delivered a rodent to the nest. Do peregrines occasionally substitute rodents when a bird might not be readily available?
It was a shorebird actually, a sora rail I think. The head was taken off (not unusual, that's the best part so the hunter usually gets it) and the floppy part were its long legs. As for substituting rodents, not here. To catch them you have to get to the ground and that's really just too dangerous for the birds in an urban environment. These guys need lots of open space to hunt in. Some bats have been taken by peregrines. Some bat caves in the US have peregrines that specialize in bat hunting. They wait for the bats to emerge en mass and they can be pretty confident of getting a couple before all the bats have dispersed. Not much eating on them, so probably a case of lots of bats, so lots of opportunity to be successful - the best equation for a predator sometimes. I think there is also a northern European or Asian subspecies that will hunt more rodents, but that is a result of their environment, open, flat terrain and an abundance of rodents that aren't too big to catch. Keep in mind that peregrines weigh between 1.5 and 2.5 lbs on average (the females are bigger & heavier) and they can only carry so much weight when they fly. Rodents, being mammals, are quite heavy for their size, whereas peregrines are much lighter in relation to their size.
As an aside, there seemed to be a funny exchange between Princess and Trey. She seemed to look at him with some puzzlement when he arrived, he fretted about for a moment, and then Princess appeared to shoo him away before tearing into the little critter.
May not have had anything to do with the hand-off, could have been another bird nearby, an strange sound, a sound from the chicks, lots of things. Keep in mind when you are watching them that they use one eye to look at things closely, so when you see them brooding the chicks and they turn their head sideways, the upside eye is looking at something overhead, not straight ahead. Its also why yous see them with one eye open and one eye closed lots of the time.
