The range of cattle egrets has expanded between 1937 and today. how would an ecologist likely explain the expansion of the cattle egret?
a) the first egrets to colonize south america evolved into a new species capable of competing with the native species of herons and egrets
b) a habitat left unoccupied by native herons and egrets met the biotic and abiotic requirements of the cattle egret transplants and their descendants
c) there are no predators for cattle egrets in the new world, so they continue to expand their range

A habitat left unoccupied by native herons and egrets met the biotic and abiotic requirements of the cattle egret transplants and their descendants  

Option B

Explanation:

The cattle egret was a species of Heron to be first seen in Greater Caribbean Basin. They acquired their name “Cattle egret” as they were found to be co-existing with the grazing cattle and feeding on the insects that come out during grazing and also feed on the ticks present on the cattle’s body.

The cattle egret within a span of few years showed a dramatic increase in its population. This was attributed by their high reproduction rate leading to their extensive population growth. They also do not have any predators devouring them. They also feed on anything and everything to survive be it insects, rodents or small reptiles. They were good flyers and they were also able to get accustomed to their surroundings and reproduce.