Purple Martin questions

We purchased a martin house, carefully put it up and immediately had some kind of Swallows interested. Now here is my question. The birds look like they have white breasts. Are they all female or is it a different type of swallow? There is a bank swallow nest within 500 feet. The instructions that came with the house tell about flycatchers, starlings and house sparrows but not other kinds of swallows taking over the nests. It also says Martins fly high and don't eat mosquittos because they don't fly near the ground. These spend some time almost skimming the water of the pond. I wish I could tell the color of the birds but I know from experience that it is difficult for me to tell when they are flying around and all I can tell is that they are dark and most, if not all, have a light breast. I guess I just can't believe we filled up the house so quickly with the right kind of bird after all the information I read about how hard it is to get tenents. Sure would appreciate knowing for sure. Thanks.

White breasts on a Martin house sound like tree swallows to me. They're a great bird to have nesting, so if they are using your Martin house, I would not disturb them. Getting Purple Martins to colonize a new house is pretty difficult from my understanding. Enjoy the swallows this year and hope for the best next.

Hi kays, The male Purple Martin is entirely blue black and the females chest is a dingy gray brown as said on this Cornell page.

http://www.allaboutbirds.org/guide/Purple_Martin/id

When you described them it sounded like Tree Swallows.

http://www.allaboutbirds.org/guide/Tree_Swallow/id

Can you tell from the pics on these pages?