You can spot a Great Blue Heron in almost any water body—streams, lakes, ponds, marshes, rivers or oceans—in the US and around the world. You might also see them stalking frogs, reptiles and insects in wet grasslands and agricultural fields; or hunting for fish at the edge of shallow marshes, where they slowly wade or stand still and wait patiently for prey to come within range of their long, blade-like bills.
They typically roost in trees or near water and often nest in colonies called heronries. Aside from human disturbance at the nest, which can lead to abandonment of eggs or chicks, herons are vulnerable to predators that target their young and adults: vultures, black birds, hawks and crows prey on eggs and chicks, while Bald Eagles and other raptors take adult herons. Natural hazards like flooding and harsh weather at breeding time can also cause early death.
Herons are an indicator species for ecological health, so they can be good indicators of toxins and habitat quality or loss. They require places to hunt, roost and breed, so habitat connectivity is important. This can be accomplished through reintroductions of beavers that create wetlands; the creation of "green belts" in urban areas; or through intentional restoration programs that may not directly benefit herons, but still improve the habitat for other species that do.
Herons are endothermic (cold-blooded) and cannot sweat or shiver to regulate their temperature, so they use other mechanisms to control their body heat. When it's very hot, you might see a heron with its wings drooped and fluttering its throat muscles, much like a dog panting; this is a way to increase evaporation from the ducts in its neck glands and cool down. On cold days, they fluff up their feathers to help trap in body heat.