An important part of wildlife photography is understanding the conditions you'll encounter when visiting a particular location. I'm often visiting wildlife locations with tidal bodies of water, such as harbors, rivers, or tidal marshes, such as you can find in the John Heinz National Wildlife Refuge.
Knowing the tides is important along harbors and tidal marshes, so you'll know what kind of birds you might expect to see at various locations you're visiting. If you want to maximize your chances of seeing smaller shore birds such as sandpipers yellowlegs, and dowitchers, you try to visit during low tides.