Cattle Egret (Bubulcus ibis, more closely related to herons): A non-native species that arrived in Florida from South America after arriving there from Africa. Naturally, on their own industrious volition, with no human help.
I have been fascinated with Cattle Egrets since shortly after their arrival in Florida. Yes, I’m that old and they’re that new of an arrival. 1941 in Florida.
When I first saw them on the south Florida prairies riding on the back of Brahma bulls I knew I was growing up in a wild and wonderous place. A place much like many of the photos of Africa in our National Geographic magazines. I’ve since learned the reason for this similarity. Their story of 20th century migration making them even more fascinating to me.
They had not been reported in South America before 1877. Then they arrived in North East South America from their native Africa. On their own. There is no evidence of human transportation. They apparently took advantage of favorable weather patterns and a wanderlust personality. They reached Tierra del Fuego the southern most point of South America by 1977.
They were first sighted in Florida in 1941. By 1956 they were being reported in South Carolina and Louisiana. They were most likely in all the other Southeastern states too, including Georgia, but the birders in these states were not quite as dedicated to recording and reporting. SW GA is still considered under reported on eBird.
They were on the West Coast by 1962.
Because of this rapid expansion, they are listed as invasive by wildlife agencies. Which begs the question, I think, of what does it take to be declared a native. If one point-of-view is invasive is when a species is intentionally or unintentionally introduced by humans, then cattle egrets are being short-changed for their industriousness and evolutionary fast tracking.
The good news is they are not invasive in the commonly held bad connotation. This is because they are usually not seriously deleterious to ‘native’ species in their new homes. For the most part, they do not overlap or compete in diet or breeding timing with native herons and egrets, or most other natives for that matter. Rather than wetlands like their native cousins, their preferred foraging habitat is dry, dusty, insect filled, open expanses, with large mammals to stir up the insects. Making the insects readily available for easy consumption while hitchhiking on the back of their willing and appreciative hosts. This is their evolutionary native African homeland niche. To their good fortunate, it is also the niche being rapidly expanded with the growth of large scale cattle ranching – a real ecological nightmare of species introduction for the, ahem, benefit of humans.
Cattle Egrets do not live by insects alone however. They enjoy a range of foods and do not concentrate on an individual source that another species may be dependent upon. For example, they will consume crustaceans and fish in the wetlands in which they establish rookeries (sometimes with natives). But, because they do have a broader range of foods to consume they do not over indulge in one habitat. They get along with the natives.
There were Snowy Egrets foraging in the same wetland. Seemingly all getting along just fine.
All-in-all I think a story that migrants are not all bad.