What can I do to make birds stop perching on the gate because they mak

https://www.absolutebirdcontrol.com/blog/keep-birds-off-fence/

Spikes you could paint them to match your gate (diy-nails not pounded all the way in but it won't be attractive if your gate is visible by all)

Purchase one of those plastic owls they sell everywhere. Birds being bird brains think it's real.

I place rubber snakes on my tomato plants. Birds leave the tomatoes alone. Of course, they scare everyone, even me!

there is available commercially a product that is basically polyurethane mesh with little spikes all over it. you could staple it onto the top of the gate so they couldn't perch there (the spikes are small and non-lethal, just enough to make the birds uncomfortable) I think they come in clear, green and black, but its been a long time, and that may have changed. Just search Bird Spikes and you'll find it.

thank you

mount an owl or hawk on the post.

Put a bit feeder in another part of the garden, preferably near a tree where they can perch without causing a problem.