Could declining insect populations be the reason windscreens don't seem to be as bug-splattered as they used to be? Two recent publications in Science—an article in 2014 and another in 2017—suggest that's the case. This may also relate to the decline in House sparrow populations overseas—see work by the Royal Society for the Protection of Birds and the British Trust for Ornithology.
(If you're interested in local bird numbers, you could take part in a survey like those run by the Friends of Merri Creek—see their website www.friendsofmerricreek.org.au).
Chris Lassig, Stuart Burns, Claire Farrugia and Manisha Bhardwaj.