They account for this factor, and several others, in the study. There's an world wide decimation of insect populations, and it has received minor coverage relative to its likely significance to ecosystems.
Think of a food chain, bugs are near the bottom meaning they are a food source for many other creatures like birds, reptiles, small mammals, fish. Fewer bugs means less food for mice, that means fewer mice, leads to less food for snakes, leads to fewer snakes, leads to less food for birds of prey, leads to fewer birds of prey.
There are many chains like this where bugs are a vital source of food. If there were zero bugs then these chains would collapse. Also, bugs are needed to pollenate many fruit bearing plants.
I think this is real, I'm traveling and borrowed a relatives car which is much lower profile and more sleek than my old Jeep. I was driving through the countryside the other day and there were a lot of critters flying about, I was surprised that often, they'd sort of just get "pushed" over the top of the car. Not sure what happened to them after that but yeah!
I did some googling to find a comparison of old and new cars in wind tunnels without much luck but this articles cover is fairly good[0].
> Not sure what happened to them after that but yeah!
One thing I did find is that for aerodynamic purposes the one place cars want turbulence is right behind them in their wake to disrupt a vacuum.
So I expect those bugs get smashed into the ground or even sucked into the radiator of any close behind cars as that air seems quite stagnant right behind a car.
Having had a VW bus all my life I can confirm they do get a lot of bugs, but far fewer these days. In the 80s my father used to try all manner of cleaning products to try and remove them but it's not such an issue any more.
