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Dive Dry with Dr. Bill

#441: What's All The Squawk About?

I spent much of the Memorial Day weekend with six hot "chicks" to prepare myself for this week's column. I don't make a habit of writing about birds. After all, most of them are landlubbers and I'm like a fish out of water when it comes to our fine feathered friends. Yes, we do have "fish that fly and birds that swim," so I do feel somewhat compelled to talk about those winged wonders, at least the ones with good intentions. I'm referring to the denizens of dry land that take to the water to feed. Residents and visitors to the island have had several great opportunities to closely observe these semi-amphibious species thanks to the four great blue heron chicks in the nest at Abalone Point and the two black crowned night heron chicks hanging around the County building and Mr. Nings.

Today I'll focus on the night herons (Nycticorax nycticorax), since so many of my readers have seen them recently. Most of you have only observed the "chicks" on steroids that fell out of their nest a few weeks ago. However, I've been seeing a number of the adults feeding right in Avalon Bay and along our beaches. Normally they are nocturnal, and feed at night. Perhaps they are foraging close to home to make many return trips back to the nests to feed their hungry chicks.

Some assume this species is a new comer, yet they had been roosting and nesting in the eucalyptus trees in the miniature golf gardens for many years. You could hear the adults heading out to feed with their shrill croaking squawks as they headed out to sea. I often had them fly overhead as I was preparing to do my night dives. When those trees were cut down or pruned a few years ago, the night herons took to the palms and other trees along Sumner and by the County building. When the city trimmed them back, the stability of some of the nests was undoubtedly affected. That coupled with the high winds we've had all-too-often this month probably blew the nest, and the two chicks, to the ground.

Black crowned night herons are generally found in fresh and salt water wetlands throughout much of the world. They have the widest distribution of any heron species, and are therefore very cosmopolitan. Scientists have separated them into several subspecies: one found in North and South America down to northern Argentina and Chile; another in southernmost South America; a third in the Falkland Islands and the fourth in Europe, Asia and Africa. These birds are migratory in the northern part of their range, heading for the southern US, Mexico, Central America and the Caribbean in our hemisphere. In the Old World they winter in Africa and southern Asia. I like their philosophy and hope to adopt it next winter!

Night herons are rather stocky compared to other herons, reaching a length of about two feet and weighing less than two pounds. The adult bears a black crown (hence its name) with a gray back and white breast. Their eyes are red, but not from late night partying. The yellow legs of adults are short compared to larger herons like the great blue. Young birds are brown with highlights of white and gray. Their yellow bills turn black when they mature. There are two or three long white plumes on the back of the head which are displayed when greeting other birds or during courtship.

The adults are ambush predators. They stand very still at the water's edge and lunge forward to capture their munchables. One reputable source states they grasp food in their bill rather than stab it, while another says they spear their food. Munchies may include small fish, marine invertebrates like crustaceans or molluscs, insects, snakes, lizards, amphibians, small mammals and even small birds and their eggs. I was amused to watch the chicks snapping at, and capturing flies that buzzed around their head. Not my idea of a hardy meal or an appealing appetizer! The Cornell Lab of Ornithology states that young birds often disgorge their stomach contents when disturbed, but I have not seen evidence of that in our two chicks. If they did, you would probably find various seafood items fed to them by Leonard at Mr. Nings, as well as swordfish offered by the L. A,. County Sheriff. I think I'm going to stand in line at feeding time!

Black crowned night herons nest in colonies, as one can probably tell from the multitude of crow-like squawks (translated as quok or woc woc by the Smithsonian) in the vicinity of the courthouse... and the many white splats on the sidewalks and street. They prefer building nests of sticks in clusters of trees, but will nest on the ground in areas protected from predators such as small islands. Three to five and possibly as many as eight eggs are laid in the nest. The Cornell Lab states that adult herons will brood the young from other parents so I guess it is an example of "it takes a village." Several pairs may nest in the same tree. I guess that's a heron condo.

During courtship the males will bow, stretch, rock back and forth on their feet (hmmm.. I haven't tried that yet!), hiss and slap their beaks together to create a sound. Once a pair is established, the bond is strengthened by mutual preening. The nests are constructed below the crown of the tree to hide it from aerial predators such as ravens. The eggs are brooded for about 25 days. Initially the chicks are fed regurgitated food, but eventually they are switched to whole prey. Glad my son and daughter-in-law didn't have to use the first method with my granddaughter Allison! Within three weeks the chicks are climbing around the nest. After six to seven weeks they fledge and can fly, but don't develop full adult plumage until near their first birthday, and then may breed in their second or third year.

The IUCN (Intl. Union for the Conservation of Nature) considers the presence of black crowned night herons to be a very good indicator of ecosystem health. These birds are sensitive to changes in water quality, but in general their populations are stable with some even on the increase. Given that, it must be a good sign that our waters are ecologically productive and healthy here on the island!

© 2011 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Young night heron chick outside the County building and adult out by the Pleasure Pier.

This document maintained by Dr. Bill Bushing.
Material and images © 2011 Star Thrower Educational Multimedia