Hi, friends.  Our bird this week is the great blue heron, which I really want to write with a comma after “great.”  Befitting its name, it is the largest heron in north America.  The great blue heron has a very large range, it can be found from Alaska down to northwestern south America.  It is also found in the Caribbean and the Azores, which is probably how it ends up as an occasional vagrant all the way in Europe.  Birds who live east of the Rockies migrate south in the winter, but birds west of the mountains stay put.  They can continue to hunt anywhere water doesn’t freeze over, which would be the case in some rivers or streams even in the depth of winter.  I thought it was interesting that great blue herons can hunt and feed in fresh and salt water.  For some reason I thought those things would be exclusive to each other, but I guess brackish water is a thing and tasty fish are tasty fish no matter where one spears them with one’s giant, pointy beak.  The birds are considered hardy, and can essentially live anywhere in their range where there is water with fish in it, even in an area densely populated with people.  The great white heron is exclusive to Florida, but scientists have not yet determined if it is merely a morph of the blue heron, or a distinct species. 

The great blue heron mostly eats fish, but seems willing and able to eat anything it can catch.  A study in Idaho showed that between 20-40% of what local great blue herons were eating were voles, and Wikipedia has a whole gallery of our enthusiastically murderous new friend eating all kinds of critters, including crabs, turtles, gophers and squirrels. Like the shoebill, the great blue heron hunts alone and mainly by sight.  It employs several varied approaches, including standing still, slowly stalking the water, and sallying from a perch or diving on the wing.  It can also float on the water and hunt that way.  It seems like nature went ahead and gave it about every trick in the bird tool box.

Herons naturally like to roost in trees near the water, ideally on an island in order to escape predators.  A breeding group of herons is called a heronry, which is a pretty fun word to have such limited utility.  Herons will have one mate each breeding season, but will pick a new mate every year.  Although nests tend to survive year to year, male herons will pick a new nest each breeding season.  Nests grow larger as they are added onto by new residents.  Both parents will sit on the eggs to incubate them, but the male will take around 11 hours of the day and the female the other 13.  The parents are so good at cooperating that the nests are left without any incubation for about six minutes every hour.  I don’t know if that’s an average over the course of a day or if the brooding parent will take regular breaks, but that’s pretty impressive coverage.  The chicks grow very quickly, and have 86% of the parents’ mass 45 days after hatching.  Newly fledged herons are only about half as good at hunting as adult birds.  They will strike at prey as frequently but come up empty twice as often.  Herons that live in the US and Canada have benefitted from the recovery of the beaver population, as beavers naturally make networks of little ponds, swamps and streams replete with conveniently placed dams on which to stand and wait for a fish to wander by.

Eggs and young face predation by a variety of birds, and a couple of species of eagle will hunt them at any stage of life.  Most of the pressure on great blue herons comes from humans interacting with them, particularly disturbing their nests, which could lead to abandonment of the area by the entire heronry.  

Look out for yourselves out there, my friends. Remember, rest is not a reward, you’re just entitled to it.

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