Key finding is:

"The findings don't prove whether structural brain differences are the cause or effect of birdwatching expertise."

Not a big surprise that this observation proves exactly nothing as there are thousands of other factors they could not control for (and apparently didn't want).

"Her team's findings have prompted German health insurance companies – who, among others, initially funded the research project – to invest in setting up bird feeders and viewing areas in more than 400 nursing homes across Bavaria. "

This is kind of hilarious and I would not believe that if it weren't Germany, a country that intentionally destroyed its nuclear plants capabilities in order to burn Russian gas and emit CO2. Obviously in the name of reducing CO2 emission.