Great Blue and Gray Herons will kill and eat damn near anything they encounter near the water where they hunt. 

We had a large ornamental pond in our backyard for years and I had to do battle with the Florida Fish and Game Commission many times over the years over the 'alleged' deaths of these birds on my pond.

LAKE APOPKA, Fla. – Check out this video of a Great Blue Heron killing and eating a juvenile alligator. Shellie Gilliam, the owner of Florida Wildlife & Exotic Animal Sanctuary and Rehabilitation Center, spotted the bird grab the gator December 5 in Lake Apopka, just northwest of Orlando. Gilliam said the heron spent about 25 minutes killing the alligator and swallowing it.

 

https://www.youtube.com/watch?v=BAHgvuKQUsU