It is surprising how few birds actually contact the blades of a propeller as they pass through its arc.
It's Saturday, raining, let's see the numbers...
Say 250 KPH airspeed, 3-blade prop, 2000 RPM. Just for fun, not necessarily typical of anything.
250,000m per hour comes out at 69.4m per second, if Windows calculator is right. So the spinning prop moves forward that far through the air in one second, at that speed.
2000 RPM is 33.33 RPM per second.
So the propeller rotates 33.33 times in every 70m forward movement.
That would be 2.1 m forward movement for every propeller rotation.
So, between each blade's passage of a point on the disc, the forward movement is 0.7m. Or 1.4 m at 1000 RPM, interpolate or extrapolate as you will with speed/RPM variations; it's a straight line.
Hmmm, got to be a fairly agile bird to get through that, but possible, I would think; is my arithmetic flawed? I was never very good at it.