Great Blue Heron    by Janis Ringuette

Patient observers can see herons mating on nests they have constructed. Following the action of courtship, nest building and mating is a quiet period of 14 to 35 days when clutches of three to five chicken-size eggs are incubated in shifts by both parents. The adults lie low in the nests and are sometimes difficult to see, but according to one study, they are present about 90% of the time.

Adults throw empty egg shells out of the nests when the chicks have worked themselves free. A fresh bluish shell on the ground is evidence a chick has hatched. Anyone finding a shell can assume the egg was laid 27 days before and that egg formation began ten days prior to laying.

Park visitors walking under nest trees to examine discarded egg shells might want to wear hats. Feces is directed out of the nest and down the tree, splattering leaves, branches, the ground and the unwary. In fact, one of the best ways to locate nest trees is to look down, not up: white feces is a reliable marker of heron residence.

The action, noise and pungent smell in the colony increase noticeably during the long period when parents are feeding their demanding, growing young. For sixty days, parents fly day and night in all four directions from the Park colony to ocean shores including the Esquimalt Lagoon, Oak Bay, Dallas Road and the Inner Harbour.

According to researcher Robert Butler, most small fish caught by herons during this period are gunnels, sculpins and shiner perch. Prey is most abundant in summer and the best tides for fishing occur in May and June, when 7/10 of low tides occur in daylight. If the adults nested early enough, this abundance coincides with the extra demand of feeding growing chicks.

When chicks are small, parents regurgitate partially digested fish into the nest; later they regurgitate directly down their throats. At four weeks, chicks are large enough to lift and swallow whole fish dropped into the bottom of the nest. The photo on the left shows a returning parent met by two large chicks lunging at its bill. The young pull the parent’s head into the nest where it drops food before flying back to the fishing grounds. After 60 days of non-stop feeding, the chicks weight has increased from 50 grams--the weight of l/3 of a medium apple--to a full adult weight of 2,400 grams (over five pounds). When they finally attempt flight, it is likely the young outweigh their hard-working parents

If five eggs hatch, it is likely three or more chicks will die. Some chicks die from exposure if the weather is poor; some are attacked by siblings. A sizeable number of chicks are eaten by Bald Eagles. Adult herons respond to Bald Eagle attacks with thunderous cries of alarm and mass flights. Though impressive to human observers, these displays are completely ignored by eagles; the predators swoop low over the nests, grab heron chicks with their talons and land on nearby Park trees to dismember and consume them. Heron feathers falling like snow indicate to observers where the eagle is perched.

A large number of young herons fall to their deaths. Flimsy nests in constantly moving tall treetops--already dangerous places to live--become increasingly crowded as chicks grow. Young birds perched on wobbly branches outside the nest can lose their balance. Siblings rush to meet returning parents, jostling each other in the process. Gusts of wind catch flapping chicks by surprise. Park gardener Margaret Marsden collected 30 dead heron chicks from under nest trees in 2002, when there were 90 active nests.

Dead chicks on the ground present Park visitors with rare opportunities to examine young birds. One can appreciate their phenomenal growth rate when viewing the incredibly large beaks and legs of three or four week old chicks up close.

A young heron exercises its wings before daring its first short flight in this June, 2004 photo taken by Brian Hepburn. Young birds are called "fledglings" for the first few weeks after they leave their nests and "juveniles" the rest of their first year. Though the same size as adults, fledglings can be distinguished by their clumsy behaviour and remnants of down protruding from slate-gray crowns. Juveniles are distinguished by their gray heads and the absence of white and black crowns and long body plumes. During June, July and early August, fledglings and juveniles can be seen flapping awkwardly around the Park, landing on low trees and odd locations such as the baseball diamond.

By the end of August and sometimes earlier, all herons have left the nest area, not to return until the following February.

Herons spend the winter scattered along the coast, searching for food. Catching enough calories every day to survive is a major challenge for young herons; it is possible 90% die during their first year. Successful hunting requires many skills, acquired only with time and practice. A heron fledging in June has a much better chance to learn how to catch fish than a heron leaving a nest in August when tides are poor and fish less abundant. Winter is the hardest time of all; by December, only 1/10 of low tides occur during daylight hours. Young herons strike at, miss and drop prey more often than adults, according to Butler, and they are unable to catch very small fish or large fish. In addition to being less skilled hunters, young herons more likely to run into electrical wires, fences and cars; they are also shot by people and killed by eagles and dogs.