The Great Egret and the Green Heron are both of the heron family, but the difference in size is great! I didn't realize how great until I saw them close together. I think this Green Heron is a youngster, thus perhaps a bit smaller than the adult. But still the picture shows just how big the Great Egret, as well as the Great Blue Heron, really are!

According to the National Geographic website, here are some Great Egret facts:

Average life span in the wild:15 years
Size: Body, 37 to 41 in (94 to 104 cm)
Wingspan, 4.3 to 4.8 ft (1.3 to 1.5 m)
Weight:2.2 lbs (1 kg)

The Great Blue Heron is slightly larger and heavier.

Average life span in the wild:15 years
Size:Body, 3.2 to 4.5 ft (1 to 1.4 m)
Wingspan, 5.5 to 6.6 ft (1.7 to 2 m)
Weight:4.6 to 7.3 lbs (2.1 to 2.5 kg)

The Green Heron is much smaller, the smallest North American heron:

"This bird is 17-22" in length with a wingspan of 25-26". Green herons are small and stocky, with legs that are relatively short, compared to other herons. Their body length ranges from 41 to 46 centimeters. Adults have a glossy greenish-black cap and back, wings that are black grading into green and/or blue on the edges, and a grey underbelly. The bill of a green heron is dark with a long, sharp point and the legs are orange. Female adults tend to be smaller, with duller and lighter plumage than that seen in males, particularly in the breeding season." http://thewebsiteofeverything.com/animals/birds/Ciconiiformes/Ardeidae/Butorides-virescens