My birdhouses are empty now, so today I emptied their contents. We watched several sparrow families use the 1st house this summer, but we didn’t see any birds using the 2nd one. However, there were nests in both houses. House 1 has a 1-1/2″ diameter hole, while house 2 has a 1-1/8″ hole. The nests I removed were very different from each other, the first being very deep, from the bottom up to the hole, and rudely constructed of sticks and straws. The 2nd nest was entirely different, made of small soft threadlike bits and the top surface lined with fluff, that looked like fine cotton wool.