The link is very important and it is also important to link it back to the Black Death in the 1300s because there were the kind of weather conditions then -- warmer and wetter -- that we predict for the future,

After 1855, when it (plague) reappeared again, there were once again similar weather conditions.

That birds spread the bacteria is not in question but how important that is in the big picture is not yet clear.

Many, many bird species are spreading bacteria from one place to another, from one rodent to another, by carrying fleas,