Why is so much literature being written about enlarging the compartment sizes of houses?
A lot of study has gone into this subject and it’s now a proven fact that martins prefer the larger cavities, say 6″ x 6″ x 12″. A long time ago, some aluminum house manufacturers decided that the size of a martins’ nest should be 6″ x 6″ square. How they derived at this number isn’t exactly known because the parent birds are around 8″ long, but it probably had something to do with the cost of building their houses. The less material used, the more profit for them. That just isn’t enough room for two adults to raise a brood of babies. Modern testing has now proven that martins, if given the choice, will quickly take the larger, deeper cavities over the smaller ones. This allows them to get back out of the way of predators, something they can’t do with the smaller cavities. In fact, this is one of the major reasons people that have these type of houses can’t get martins to stay. However, if the compartments are enlarged, they often move right in.
