A couple of threads here have discussed ways of trapping pest House Sparrows and Starlings that eat up your chicken feed, and I'm very happy with the success of the sparrow trap I bought after learning about it here on BYC. (House Sparrows and Starlings are flying vermin unprotected in the United States, as they are both introduced species who displace and kill native cavity-nesting birds.)
My method of dispatching the captured birds has been individual "swimming" periods in a narrow glass of water, but I came upon an easier, humane method of euthanizing on a site about purple martin management that may work out better:
What you need:
1. A plastic jug -- I use an old plastic 1-gal jug (cornmeal and mayonnaise are packaged in them). The jug has a large 4.25-inch lid, which simplifies dumping the dead birds out later, and I have drilled a 2.25-inch hole in the lid in which I have placed a cork.
2. Engine Starting Fluid -- Engine starting fluid consists mainly of diethyl ether, which was used years ago as a general anesthetic in human medicine, and is still used in research labs to put down laboratory rats, etc. You can purchase it at any auto parts store.CAUTION: Ether is highly flammable! -- DO NOT use near fire or any open flame (including cigarettes)!
What you do:
1. Remove the birds from your trap and put them into the jug through the small, uncorked opening. Be sure to immediately replace the cork each time or they will escape; especially starlings, which can jump up into the opening as you put the cork in.
2. When you have placed all of the birds into the jug that are going to be euthanized, spray a couple of squirts of starting fluid through the small opening, being careful not to allow any birds to escape.
3. The birds will be put to sleep in about 30 seconds, and will be dead in less than 30 minutes. I always go off and leave the jug for at least 30 minutes, then dump the dead birds into my compost tumbler.
http://www.purplemartin.org/forumarchives/archive/Humane.htm
Has anyone tried this method?
My method of dispatching the captured birds has been individual "swimming" periods in a narrow glass of water, but I came upon an easier, humane method of euthanizing on a site about purple martin management that may work out better:

What you need:
1. A plastic jug -- I use an old plastic 1-gal jug (cornmeal and mayonnaise are packaged in them). The jug has a large 4.25-inch lid, which simplifies dumping the dead birds out later, and I have drilled a 2.25-inch hole in the lid in which I have placed a cork.
2. Engine Starting Fluid -- Engine starting fluid consists mainly of diethyl ether, which was used years ago as a general anesthetic in human medicine, and is still used in research labs to put down laboratory rats, etc. You can purchase it at any auto parts store.CAUTION: Ether is highly flammable! -- DO NOT use near fire or any open flame (including cigarettes)!
What you do:
1. Remove the birds from your trap and put them into the jug through the small, uncorked opening. Be sure to immediately replace the cork each time or they will escape; especially starlings, which can jump up into the opening as you put the cork in.
2. When you have placed all of the birds into the jug that are going to be euthanized, spray a couple of squirts of starting fluid through the small opening, being careful not to allow any birds to escape.
3. The birds will be put to sleep in about 30 seconds, and will be dead in less than 30 minutes. I always go off and leave the jug for at least 30 minutes, then dump the dead birds into my compost tumbler.
http://www.purplemartin.org/forumarchives/archive/Humane.htm
Has anyone tried this method?