Wednesday, 17 April 2013

Vernon's Great Blue Heron Colony

Just one block north of 48th Avenue, lodged high in the branches of a remnant grove of Black Cottonwoods along Vernon's 24th St. are somewhere between 40 and 60 huge stick nests built by Great Blue Herons, colonially nesting waterbirds that uninformed people often call 'cranes'. Standing about 1.2 m tall, the Great Blue Heron is one of Canada's tallest birds, a lanky, grayish long-necked fowl armed with a spearhead bill, staring yellow eyes, a compact gray body, long stilt-like legs and a wingspan of about 1.8 m, about two thirds that of a Bald Eagle. It is not a bird one expects to see flying around an urban area of shops, light industry, and a housing development. A flying Great Blue is a hard bird to ignore, whether it's rocking to-and-fro in descent into the colony trees, spilling air from beneath its great, broad wings before making a surprisingly graceful landing on a branch or nest, or it's in sustained flight with its long neck tucked back into a compact S curve over its back, making shallow, but powerful wing beats toward some distant shore. Cranes always fly with necks outstretched; large herons, in everything except short flights, curl their necks into a double curve and that's the main visual difference between the two groups.



In most of southern Canada Great Blue Herons locate their breeding colonies well away from human activity, but Vernon's herons are different, and therein is my story. Even in the mid-1980s when the herons first moved to town, the grove they chose to nest in was close enough to the local MacDonalds restaurant just off a main route through town that fast food diners began to notice 'the MacDonalds herons' as they were then referred to. The herons quickly expanded their colony into the tallest cottonwoods along 24th St. even as the area underwent a change from remnants of old farm fields and patches of young woods to retail and light industrial outlets, a vets' office, a duplex complex, a sports club, a building supply store, a flooring store, a rental place of lifts and aerial platforms, and eventually a housing development of single dwellings called, ironically enough, Heron Glen. The usual polarization occurred among Vernon's human population.  On the one side developers and chamber of commerce boosters in thin but powerful ranks rallied against the herons as impediments to development, while on the other side a greener mob of naturalists, educators, one or two politicos, and some of the public who thought the herons were interesting demanded a place for the herons in an otherwise rather featureless part of town.



The unsung heron hero was Mr. Jan Bos who owned a junkyard and the land adjacent to it, the land on which the cottonwoods grew that supported the herons' nests. Working around his junkyard, Jan started pausing to watch the herons build their nests, lay their eggs, and raise their young. He grew fond of the gangly birds that defied the odds to live at least part of the year alongside restless, often heedless humanity. Eventually in the middle of the unspoken debate about the herons' future in Vernon, Jan Bos visited a lawyer and had a restrictive covenant placed on the grove. The covenant stated that Jan couldn't sell his undeveloped land until a year after the last of the herons had stopped nesting on it. With real estate growing daily in value, Mr. Bos put his property on the line. For his trouble he has received almost no thanks from the people of Vernon, and when a tree fell from his property toward the houses of Heron Glen, a developer made motions to sue him.

With Mr. Bos as their protector, the herons have carried on with their reproductive cycle, with only a few minor interruptions. They don't like Bald Eagles,  one or two of which often hang around the colony some springs. According to some literature, a Bald Eagle killing an adult heron can cause the colony to desert, but like so much in the heron literature, this does not appear to be an absolute rule.

Hot air balloons certainly make the adult birds nervous and flighty, as I saw in the early 1990s when balloonists took to launching, landing near and overflying the Vernon colony. Fortunately the balloonists were co-operative in re-locating their activities.

Okanagan Great Blue Herons are both migratory and resident. Some remain year-round, while most leave us for the winter. Birds start returning to the colony in March. This year (2013) I saw the first herons (6) at the colony on 4 March. By 8 March, the count jumped to 16 birds and by 10 March 27 birds. On 15 March 44 birds were present at 9:05 AM, and thereafter for the remainder of March my counts were in the high 30s or mid 40s.

It is my belief though I have no proof to back it up, that some of the colony's herons are old spouses, familiar with each other and quick to form pairs and settle down to reproducing without much courtship. Certainly by 4 April this year it was obvious that several adults (females and males are difficult for humans to distinguish) were setting low in their nests, incubating eggs.



The female lays 2-6 dull blue eggs, and incubation starts with the first egg. The incubation period runs from 26-30 days with the parents sharing the duty of incubation. Incubation sessions can be quite long, sometimes up to 10 hours each. Occasionally, the incubating bird will rise and turn the eggs to ensure even heating. With most of the birds away foraging or low on the nests incubating, the colony can become a fairly quiet place. During this time look for the occasional adult bringing a stick his mate on the nest. According to the literature, males gather the sticks and females place the sticks into the structure of the nest. Sticks are gathered from trees and the ground around the colony, and old, unused nests quickly get picked to non-existence by stick-happy herons.

Eggs begin to hatch in May. The chicks initially are so small that they are not visible to the ground-based observer, but watch for both parents at the nest at the same time orient their activities towards the nest bowl. Adults bringing food to the nest is a tip-off that the young have hatched. You'll have to look carefully though, because herons usually swallow their prey and deliver it to their chicks by swift regurgitation. Also listen for the soft but persistent chattering that the chicks make when food is delivered. This chattering soon becomes a chorus when several nests contain hungry chicks. and is a characteristic sound of May and June.

The heron chick is hatched covered in pale gray down, bushy on its crown. Chicks attempt to preen at 6 days of age, stagger to their feet at 14 days and walk steadily at 21 days. By two weeks of age the little chick is covered in dark feathers but has a contrasting whitish throat. Wing-flapping occurs at the fourth week and hopping onto branches near the nest at the seven week. By 60 days of age chicks can make sustained flight. By the ninth week chicks recognize parents flying toward the nest. Nest departure happens at about 81 days (64-91 days range).

Both parents feed the chicks. It's highly entertaining to watch a nestful of older heron chicks become highly animated when they spy one of their parents flying toward the nest, presumably with food on board. Wings flap, necks weave back and forth like angry snake, and the chicks chatter loudly and look wild with their crests raised and yellow eyes blazing with anticipation. Perhaps hesitant to land amid these feathered maniacs, each armed with a long spear of a beak, the adult may land on a branch nearby and walk a few steps into the nest where the chicks swiftly grab repeatedly at the parent's bill. Up comes the catch, and down go the necks toward the floor of the nest, with chicks snatching and stabbing at everything within the dump zone. In such a sharp-tipped melee it looks like it would be easy to lose an eye.

At the Vernon colony chicks fledge from the nests beginning in July and continuing into early August. Fledglings have been seen by some heron observers to return to the nest to be fed by parents for three weeks after fledging.

Penticton and Kelowna both have heron colonies but they are situated in more conventional settings along waterways. For urban Great Blue Herons Vernon is the place.

Interesting things about Vernon's Great Blue Herons:

1. Great Blues don't restrict themselves to aquatic food like frogs and fishes. They will also hunt in fields for voles.

2. The location of the Vernon colony is conveniently central to Swan, Kalamalka, and Okanagan lakes. An observer standing next to the colony can note that herons will leave the colony on an obvious bearing to one of these three destinations. Herons will also drop in on any small pond, especially Vernon's backyard goldfish ponds, for easy fishing, and will fly upslope parallel to BX Creek, perhaps in search of fields and voles.

3. The adult Great Blue Heron's bill changes from dull multi-shading to a beautiful shade of orange at the onset of breeding season.

4. The land on which the colony trees stand is considered protected and trespassing is forbidden. A fence around the colony makes this clear.

5. A heron's droppings are ejected with force, often while the bird is in flight. The droppings are a sticky, fishy white liquid that lengthens as it falls. You thought sea gull whitewash was bad? Pray that you will never be hit by heron poop.

For more information about Great Blue Herons try:

Butler, Robert W. Butler. 1997. The Great Blue Heron: A Natural History and Ecology of a Seashore Sentinel. University of British Columbia Press, Vancouver, B.C.

Siddle, Chris. 2008. Status, Size, and Breeding Chronology of an Urban Great Blue Heron Nesting Colony at Vernon, British Columbia, 1986-2008. Wildlife Afield, 5: 1, June, 2008. The Biodiversity Centre for Wildlife Studies, Victoria, B.C.

Vennesland, Ross G. and Robert W. Butler. 2011. Great Blue Heron (Ardea herodias), The Birds of North AmericaOnline (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; http;//bna.birds.cornell.edu/bna/species/025doi:10.2173/bna25

All photographs in this article are copyright Chris Siddle.




6 comments:

  1. Excellent article Chris. I particularly like the cultural history behind the colony as it reminds us that conservation successes are often a result of a series of individual efforts by people to preserve something special.

    Rick Howie

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  2. I so enjoyed your article Chris...Is so nice to learn about these wonderful creatures....thanks for the insight...

    Carolyn Thacker

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  3. Excellent Chris,
    I visited that location and though it was the oddest place for a rookery.
    Well done!

    David Chapman

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  4. Just a test reply to this article Chris, trying to use another profile called "name/url."

    Rick

    ReplyDelete
  5. Fantastic!!! I just moved back to Vernon, these Great Blue's are flying over my house every day so I went searching online for more info and voila. Great article. Thanks for doing what you do.

    Baruch

    ReplyDelete