That's about all you can do. Look and see if there is a stainless steel mirror that size. I have a small one.

You also could look at resin mirrors. They should stand up outside, but might not be advertised as such.

Annztoo is right. That will be really nasty and a terrible fate for the wildlife. What is the purpose of the mirror?

The purpose of the mirror is to break up a big ugly wall when sitting and reflect some of the surrounding greenery.

I don't think birds will be an issue in this location. People do have windows that are reflective.

Could you use a window frame, with or without glass, and secure e mirror to the back with clips, screws, etc, so that you can replace the mirror if it deteriorates?

From: This article on garden mirrors

"So, I’ve found if you use a good quality interior mirror, they will look good and last longer than cheaper mirrors, outside. They won’t last forever, and yes when you go to purchase one there will be a lot of tutting and head scratching and “that won’t last outside dear” type of comments from the mirror supplier!

The main problem with using a mirror outside is that the water gets in and separates the reflective surface from the glass. In the past, I’ve used a flexible metal-like tape over the top of the mirror to help prevent the water getting in. If you ask in the mirror place, or builders merchant, they will hopefully know what I’m talking about and be able to supply you with some, once they’ve stopped telling you what a bad idea it is to use a internal mirror in the garden!"

I'm wondering if using the rubber sealant you see advertised in commercials...you know where they spray a screen in the bottom of a boat...seal the top, sides and back of the mirror, would work?

Yeah- I thought about that too. I think there are a couple issues. One is you don't want the back of the mirror flaking off. The other is the frame. That sealant might be good for the back.

Birds also break their necks on unscreened windows. Put a screen over the mirror or go with something else. Also if it reflects direct sunlight it could start a fire.

What practigal said. In my area a couple of years ago, sun reflecting off of a piece of sheet metal started a fire that burned 1600 acres. I can imagine a mirror would be even more dangerous.

What did you end up doing about the mirror? I would like to place one in my screened porch.

I am planning on putting one on my new screened porch. It will face inward so that sun does not reflect off of it directly.

Had one over a fireplace on an outdoor patio that was covered by a pergola. It lasted out there for about 4 years without any covering before the wood started to deteriorate. I took it down before something bad happened. We never had any problems with birds hitting it, but did have them hitting our front and back windows in the spring time. The mirror was not directly in full sun, but did get the late morning sun for a few hours.

BTW- I had some real wood blinds catch fire after leaving my make-up mirror on my vanity. The morning sun hit it at just the right angle to catch the blinds on fire. I was really careful after that!

I bought one that had a plastic frame (that looked like wood). I sprayed the entire back and front excluding the mirrored part with a polyurethane that was good for outside. I had the mirror for several years and then moved and it didn't show any signs of wearing. It was hanging on a trellis attached to the garage so it probably didn't get a ton of direct water.

Good tip!