-Will use a nest box - Benefits: eat mosquitoes, flying carpenter ants and wasps.
Mount nest box as high as possible. Paint (black) around the hole and in the hole so the birds can see "a hole" from a distance. Violet Greens take many days to figure out if a nest box is safe to go into, so drill holes in the bottom 4 corners of the floor, or cut the corners off before installing the floor. This will allow light in so they can see there is no danger in the box. After the nest is made, the holes will allow water to run out. V/Gs will be looking for nest sites very early in the morning. If the roof is over the sides(overhang) then you could also have a small hole in the side facing the morning sun, this will help in getting light in when they first come for a look.
The nest box can be any shape. The minimum floor space is 4 in by 4 inches, but an ideal inside floor space for swallows is 5x5. The roof needs to have an over hang on the front to keep crows from pulling the young out of the entrance hole. This happens just before they fledge. Make a ladder on the inside so young birds can climb up to the entrance hole. You could make a ladder with saw cuts or other tools. To create a ladder I make a moon shape with my forstner wood bits. The nest box must be able to open to clean it out. I like to have the front entrance panel removable, as that is the part that might need redoing later on, ie a new hardwood entrance hole. If you like you can paint the out side of the nest box to have it match your own home, but have the entrance hole darker than the front color of the box.
There should be no perch on the outside of the nest box, as other birds may harass the occupants. Mount the nest box where squirrels can not get at it. Make the hole size so the house sparrows can not get in. This is an oval shaped hole. Please see instruction sheet on how to make this hole. House sparrows kill other birds like swallows. If you allow house sparrows in your nest boxes then you are contributing to the city spraying for mosquitoes(that could carry West Nile virus) as violet green swallows feed on mosquitoes – sparrows do not. Spraying could lead to the decline in general health of people (eg. asthma). VG swallows also feed on flying carpenter ants(so could protect your home from these insects).
If an existing box has a hole that is too big, then make the
proper hole size in a 3/4" thick piece of hardwood. Then mount
this block of wood with the oval hole in it to the outside of your
nest box. The best nest boxes are the ones which have this block on
the front of an existing bird house, as this prevents English House
sparrows from sticking their heads in the box.
Do-it-yourself Hole Making
Swallows will return to the same location every spring to build a new nest. To have some fun with the swallows, you can hold up small downy feathers. When you get their attention, blow the feather up into the air. They will come grab it before it hits the ground and use it for nest building. Try to wear the same hat and jacket every time you want to give them a feather. Then they will know it is "feather time". This is very entertaining. In the fall, when the birds are gone, clean out the nest box. You could spray the nest box with a mild solution of bleach.