I've made particle birds!

I made a flipbook material which can be controller by the particle system:

The particle system spawns a burst of 2-6 birds in a single direction:

This is then managed by a blueprint, which spawn the emitter with a rotation towards the player, plus (90/-90) degrees in the make them go left or right at random, each 10-15 seconds. Parameters are passed from the blueprint to the emitter, and then to the material. (e.g. If the birds fly towards left, we set the scaleX of the UV in the bird material to -1, to mirror the image.)