What I was told was: an ordinary bird going into a jet engine: no problem; it gets mashed up and incinerated; a bird with a tiny metal ring round its foot goes into a jet engine: a chain reaction as bits of rotor come off and destroy other rotors and the engine is totally destroyed. This information may be out of date or plain wrong, but perhaps this part of it is true: something hard enough can do a lot of damage to a jet engine when ingested even if it is very small. (Bird rings tend to be plastic or made of very thin aluminium, I think.)
Biting the hand that feeds IT
