我很困惑，什么情况下可以在help后省略to？什么情况下不能省略？

OG-SC中有两个句子，一个是省略了to的，一个是没有省略的。有什么区别吗？

236. The Coast Guard is conducting tests to see whether pigeons can be trained to help find survivors of wrecks at sea.

216. Many policy experts say that shifting a portion of health-benefit costs back to the workers not only helps to control the employer's costs, but also helps to limit medical spending by making patients more careful consumers.

help (to) do sth.

to 可以省略。