Tree swallows

[Tengai]

Forth year landlord here. I’ve had tree swallows and bluebirds nesting within 30 ft of my martins.
Usually the TS and blues are already nesting when the martins arrive. This year the blues started but the martins showed up only a few days after the TS. I opened the Martin housing we are up to about 20 but the TS seem interested in the Martin housing. No nest building yet. My question is will they affect the martins? I know TS can drive away martins looking for a colony but will they drive away those returning to an existing one?
The TS are showing interest in both the Martin housing and the box designated for them but no building yet.

[jasalva]

My experience is that if TS are sharing the PM poles that the have already set their sights on the nesting box. I have had all three birds for sometime and know the difficulties of TS and BB possession of PM gourds and this is how it works for me. My TS have not built their nest yet, also, but they are defending their box. My BB have been sitting on eggs since Apr 1st and are guarding our PM gourds wonderfully.

[flyin-lowe]

As long as you have returning ASY martins, which it sounds like you do, the martins will not be run off by the TS.