But once in the building i think they got into air ducts and from there followed light sources trying to get out and we ended up with dozens of flies on an inside window like you said.
Flies getting through vinyl replacement window.
Getting the dirt and dead flies out of your window tracks.
You can see the gap in the 2nd picture on the bottom right.
Then once they re in they just want to get out again.
The fly you see in your window may not be a housefly at all but a cluster fly.
Let s say you have wood windows in your home today.
They have the whole world to choose from when deciding to where to fly next.
They fly around outside.
Most are dead but i will see a few flying around.
They can get through any number of openings.
I think they are getting through from a small gap on the window.
Sometimes the glue that sticks to your window glass may have to be taken off with rubbing alcohol but it sure beats flies in every window on a sunny day.
So they spend the next ten hours bashing into the window trying to get out until they die of exhaustion or until they re swatted.
I have 7 windows in my house all of which have several dead flies.
For starters the concept of a replacement window can be a bit of a misnomer and contribute to the issue.
Unlike brick or wood homes the sugar particles which may not be detectable to the human eye stick to the vinyl siding causing flies to gather.
But they manage to find a tiny crack in your window.
Cluster flies look similar to houseflies but are slightly larger with overlapping wing tips when at rest.
They make a buzzing sound and fly in a sluggish manner.
You ve noticed a lot of draftiness and maybe even some operational challenges.
I would check your exterior walls patio yard etc for any remains.
Cluster flies can enter your homes through the smallest cracks around door and window frames or through any other tiny unsealed opening.
Fill all the cracks or crevices in walls window or door frames with caulking.
They don t really land anywhere.
As long as there s something inside the house to attract them and there usually is they will get inside in search for food.
I cut my strips in half put 2 strips on the top window glass 2 strips on the bottom window glass.
When the strips get full you just slowly pull them off replace with new strips.
By james clark insects such as flies are naturally drawn to vinyl siding because vinyl siding attracts build up of airborne sugar particles from nearby trees plants and brush.
It s one of the ickier household chores.
I still am not sure how or why the flies got from the bird to inside the house.
To prevent cluster fly infestation you could use following tips.
Your doors and windows aren t always closed.
These flies enter homes through cracks and gaps such as those found around windows.