Adding bats to anything improves the late-in-the-year atmosphere.
There are many ways of drawing spooky bats, but this is a good one to start with — very quick and effective.
The shallow curves of an ‘m’ are frequently used to suggest flying birds and we recognise it because it’s like an agreed short cut that our brain has approved.
Start with some of them flying at different angles.
Practice on scrap paper another fatter ‘m’ with a long tail — on the diagonal.
And the mirror image on the other diagonal. As above.
Add the fatter ‘m’ with a long tail to the bird on one side, and on the other side with the tails meeting at a point. As above.