Several years ago after having shut down at a base for lunch & a break (that didn't happen often!) I went out to my AS350D & noticed a couple of grackles perched on the engine intake screen. These birds will eat anything, & aren't my favorite species. The LTS101 Lycoming engine installed in the Death Star has the air intake on top of the engine, & a screen covers most of it, but a couple of inches at the rear is open. On a hunch, I climbed up & looked down in there. The grackles had found someone's discarded Kentucky Fried Chicken, & dropped the bones down inside the engine intake. It took some doing to get them all out, & if I hadn't checked, those bones would have soon been through the engine & out the exhaust, along with some compressor blades, I expect. During the summer, 206's sometimes have tree frogs go through the engine - usually they're small enough that there's just a hiccup, but sometimes it causes a forced landing. We install intake covers during the summer to try to keep them out.
I've also had a mockingbird build a nest in my intakes, & it wouldn't give up. Twigs, bits of wire, whatever it could find, it kept putting in there until I installed the intake plugs. It then built a nest in a BO105 on the next pad, inside the engine cowling.