Odd that this list considers Cattle Egrets as invasive, I have never heard that before. They came here naturally just fairly recently. Their range expanded due to human activity but, rather interestingly, it was because they had more available food sources rather than physically being moved by people. They eat parasites off cattle so as cattle farming expanded so did their range.

Herons are already capable of traversing entire continents, as can be seen with Night Herons. Cattle Egrets just didn’t really have a reason to expand until recently.