Sorry, just my two cents worth:
I must admit as much as I enjoy birds and birdhouses and the fact that the Purple Martin eat a ton of insects...I would not want to cause harm to a beneficial snake - the snakes keep down the rat/mouse population.

Wish it were possible to find a way to exclude the snake from the bird house without killing the snakes - maybe put up a sign "Private Propery, No Trespassing"...

I'm inclined to agree with greene; I'm fond of harmless snakes. Although, my feelings wouldn't be hurt if that system worked for rattlesnakes!

there has to be another way to keep them out. What is the point of killing one beneficial animal to save another just because one is prettier.

I encountered my very first snake several years ago, at the then-DH's house, sunbathing in a Sago Palm. I quickly snapped a pic, posted it on this thread to inquire, and learned it was an Eastern Hognose, known for "playing dead," but, most importantly, for keeping down the rodent population.

I left it alone, since it was a "bennie" (beneficial), and was so excited to show it to the DH when he came home. The DH promptly grabbed a shovel, and damn near took down the whole Sago Palm trying to kill the sleeping snake. He confirmed it was an Eastern Hognose when he told me he had killed another one just like it, and "that son of a gun tried to play dead..."

Shortly thereafter, the property was being overrun by rats and mice...He had killed every one that had been on patrol...

I have long since learned to live in harmony with the "bennies," and respect the right of the "baddies" to go their way, while I go mine... No harm, no foul...

I agree with not killing beneficial snakes, even though they may may invade purple martin houses, etc. Thinking there has to be a better way to prevent them from climbing the poles. Grease the poles, maybe a mild shock type barrier. Rodents repopulate much faster than the snakes that live much longer and are slow growing. In my opinion, rodents carry more disease and filth, or cause more damage than a few harmless snakes that can control the population. Even poisonous snakes are beneficial in that respect.

On our ranch in South Tx, as a kid and for a decade or so, we killed so many rattlesnakes every year, they were thick as fleas. Then there was a big resurgence in the roadrunner population. Seldom see any rattlesnakes these days. So there is a balance in nature, we need to learn how to protect it.