If your BH is new how do you identify if there are any new visitors inside your BH?
And also how to differentiate between new spots and old spots?
Assuming you bought a canister of the "Super Pheromone" and you plan to apply to those new markings on the nesting planks.
How do you trace that there are some new visitors that came in after your last visit?
My recommendation is to use the marker pen technique.
Before you apply the marking you need to firstly clean the floor and remove all those old or dead bird shit spots found on your BH floor.
Sweep them and if they are stuck to the floor use your foot to squash them until they become powdery.
Sweep and remove all these so called dead shit markings.
You might want to clean even those found below those nests.
Once the BH floors are cleaned you know that from now on any bird shit spots found on the floor will indicate that they were from your old or new tenants.
Now you can start marking them one by one.
Use the marker pen and circle every path of bird shit spot on the floor.
Once that is done you know for sure that any new tenant will show new bird shit spots that are not being circled.
Once they are found you can now climb the ladder and try to pin point where do you think those birds were sleeping.
Identify the spot and spray the Pheromone liquid.
The new marking now can be circled with a different color pen marker.
So during your next visit you can start searching for any more new bird shit spots.
Do the same as per your previous visit.
If you continue doing this routine you will soon more and more nests inside your BH.
Usually the liquid pheromone will help to anchor the couple and once they smell the luquid they will have the urge to mate and start making their nests.
Try this idea and see if what I am saying is true.