Quick fact: The amount of urban wildlife you see each year is often dependent on how well your trees are doing. Specifically, the more acorns that oaks can produce, the more your squirrels can reproduce, too.
Random anecdote: One year I noticed a disturbing amount of dead squirrels lining the roadways in Westchester County, NY. Every few feet there was a dead squirrel, its fluffy little tail still waving in the wind.
I was a newspaper reporter, and so I used that as an excuse to do a little investigating and call people who would know what was up. Turns out that the previous year was a very good year for acorn production, which meant there was roughly double the amount of young squirrels. Frenzied to collect food for the coming winter, these juveniles were running about, rashly crossing roadways, ending up as roadkill.
As the state biologist told me, it had a way of bringing the squirrel numbers back down to normal, albeit in a particularly gruesome way. I haven’t quite seen the same phenomena since, because I got a job in Manhattan, where squirrels are far more savvy to human dangers, like cars.
For more on the connection between acorns and wildlife, read Acorns vital to natural balance.