Why is the egret a "neck-shrinking" bird?

The physiological structure is like this.

Possible reasons,

It may be due to the predatory habits of egrets. Its neck muscles need an instant force to "bounce" its head into the water like a spring in order to quickly prey on fish and shrimp. We need to talk about this first. Put your neck away.

Its evolutionary principle may be that when the neck muscles relax, it is such a phenomenon of neck contraction. As soon as the muscles are tightened, the neck straightens.

The result is.

Not only can he fly, but he can walk normally, and his body is S-shaped.