The saleslady showed me nest boxes with slits on the top quoting statistics claiming that bluebirds will nest in slitted boxes and house sparrows won't.
Since we have a serious house sparrow problem here (the house sparrows kill bluebirds for their nest box)
The boxes were mounted in pairs on opposite sides of the back field. Bluebirds won't nest close to each other. The second box of each pair is for the tree swallows. Ideally, at full occupancy, there would be one bluebird nest and one tree swallow nest in each pair of nest boxes.
The outcome didn't agree with the saleslady's statistics. The bluebirds completely shunned the slitted houses except to perch on them for their early morning poop. The tree swallows were also unimpressed and selected the second box with the standard hole, making it unavailable for bluebirds.
The final straw for the slitted boxes was when the house sparrows moved into them. That was better than the house sparrows stealing the bluebird's nest box, but I was still unimpressed.
This year I bought two new boxes with standard round holes to replace the slitted boxes. Granddaughter Kimmy and I put them up last week and threw the slitted boxes in the garbage.
The bluebirds have been here for several weeks. They claimed their nest box from last year while there was still three inches of snow on top of it.
Since the weather warmed, they've been busy building their nest. It is ready for eggs.
Some morning soon when I take the dogs out for a walk, I'll see the female peeking out the round hole at me and we will detour so she can finish laying her morning egg.
Last April we repeated that routine for five days, five eggs. All eggs hatched and lived to fledgling size. Then the parents repeated the process to produce four more fledglings.
I'm hoping for another productive bluebird year and for some tree swallows to move in next door.