so we have one of those bird feeders that stick to the window, but it's pretty small so we need to refill it often.

When the birds peck on the window while trying to get the last few seeds wedged between the feeder and the glass, it makes the creepiest fucking noise, especially because we're not at ground level so like, nobody should be knocking on our window

That's usually the noise that alerts us we need to refill the feeder

The birds have learnt this

I keep forgetting the sound, because I have headphones on most of the time

anyway, creepy pecking and scratching half-heard through my headphones sure does not give me three heart attacks per day