Vernon's Great Blue Herons - nests full of large chicks

Vernon's Great Blue Herons at the colony along 24th Street laid their eggs in March and April, incubated them through the latter half of April and the first half of May and are now (4 June) busy feeding the resulting chicks. Some nests are crowded with as many as four young herons per nest.

In some of the few nests that are still visible against the green canopy of cottonwood leaves the young are still kneeling in the nest. These scraggly ragamuffins are covered in a messy mix of punk spiky feathers and remnant down. Their body feathers are growing nicely and they are quite dark compared to their parents. However, the careful observer can discern a dark crown, and a whitish throat.

In other nests the chicks are older, larger and are standing. A heron's nest is not very large and three or four large youngsters pretty much fill all the available space. When one of the parents arrives with food, it must stand on the edge or on a supporting branch while the kids go wild with appetite. The nest becomes a cauldron of hunger, the chicks grabbing at the parent's bill. It's amazing nobody loses an eye. The parent regurgitates and the chicks fall to grabbing at whatever comes up.

Juvenile Great Blue Heron not long out of the nest - Crescent Beach, B.C. - 22 April 2010 Copyright Chris Siddle.  

The photo above captures the overall dinginess of a fledgling Great Blue fairly well. The chicks in the Vernon colony, however, have darker crowns that the one shown here.

The parents are kept busy foraging for food for their growing chicks. An adult doesn't tarry very long at the nest. Once the feeding has been completed, the adult may move away a few metres from the nest for a rest or may launch itself away for another hunting trip.

The parents may fly north towards Swan or Otter lakes, west toward Goose Lake or over the Bella Vista Range to Head of the Lake, southwest to Okanagan Lake or south to Kalamalka Lake. Some fly due east up the BX Creek valley. They are not all headed to bodies of water. Some forage in fields and pastures for rodents.

With the adults departing from the colony in a variety of directions, it's easy for the observer to image the heron colony as the hub of a wheel or the centre of a simple web, the strands marked with arrowheads to show the direction of the flow of energy in the form or food for the chicks from ponds, lakes, and fields back to the colony.

However, besides continuing to grow, there is at least one major developmental step the young herons must take before they leave the colony. Once they have a full set of primaries and secondaries they must learn to fly. The first drill is learning to flap while staying in place on the nest.

BLACK SWIFT UPDATE

Before I close, I would like to note that this spring, in spite of being absent for several days, I saw Black Swifts over Swan Lake as I have almost annually for the past 20 years (see blog entry for 31 March 2013). On 1 June I noted about 10 Black Swifts at medium height over the south-east shore of the lake.

GRASSHOPPER SPARROW UPDATE

My search of the grasslands on the east side of Goose Lake early on 6 June turned up no Grasshopper Sparrows. Clay-coloured Sparrows were frequent in the hawthorn thickets, but there was no sign of GRSPs among the grass tussocks.

COMMENTS

If you wish to make a comment about any entry, please do so via my email: chris.siddle@gmail.com

The Third Red-tailed Hawk Entry

The purpose of today's entry is to catch up with some of the readers' images of Red-tailed Hawks.

Gary Davidson of Nakusp, B.C. is an old friend and is familiar with my passion for Red-tails. This winter he captured an image of a Krider's Red-tailed Hawk that was hanging around the Davidson's RV in McAllen, Texas. You think our Red-tails can be pale in the Okanagan/Thompson? Take at look at this bird:

1. Photo by Gary Davidson - Krider's Red-tailed Hawk - McAllen, Texas- late Feb. 2013

This is an immature Krider's Red-tailed Hawk. Aging marks include the poorly developed dark border to the trailing edge of the wings, the multiple barred tail, the pale eye, and the pale panel near the end of each wing.

Why is this bird a Red-tailed Hawk at all? The dark markings just behind the leading edge of the inner wings are called patagial marks. Patagial marks are a diagnostic feature of Red-tails. Compare this bird with the light juvenile Ferruginous Hawks pictured on page 385 of Brian Wheeler's indispensible Raptors of Western North America (Princeton 2003). Also take a look at Dunne, Sibley, and Sutton's excellent second edition of Hawks in Flight (Houghton Mifflin Harcourt 2012) pages 76-77 to note that a light juv. Ferruginous may show something like a patagial mark though the marks are slightly farther towards the inner wing and more distant from the leading edge. You'll also want to look at the new Crossley ID Guide - Raptors by Crossley, Liguori and Sullivan (Princeton 2013).

Here's an image taken by well-known Kamloops naturalist Rick Howie of an immature Red-tail in the Kamloops area. It shows a large dark patagial mark, the pale window panel typical of an immature, the light eye (not quite so reliable as an indicator of age, I've read), and the many barred tail, plus a couple of other features worth looking at.

2. Photo by Rick Howie

Note that the hawk in Photo 2 has no dark bar on the trailing edges of its wings. The absence of such a broad rear border clearly and easily identifies this bird as an immature.  In the image (3) of an adult I photographed near Westwold in 2010 the rear wing border is obvious.

3. Photo by Chris Siddle - Westwold, B.C.- July 2010

Let's go back to Photo 2. When classifying Red-tails I always look at the breast first to note what the background colour is, in this case obviously white, and whether it is streaked or not, and how heavily. In this case the breast is unstreaked. Then I note the heaviness of the belly band and its width. The bird in 2. has a dark belly band on white underparts but the band doesn't appear particularly wide. Next comes the colour of the underside of the tail and the width and number of tail bands. That leaves us with undertail coverts, the tarsus and the head and throat which all appear quite "normal" in this case of Photo 2.

Here is another image from Rick Howie.

4. Photo by Rick Howie, 21 April 2013, Kamloops

What differences do you spot between the immature in 4. and the immature in 2? The most obvious difference is that 4. has a broader, more solid dark belly band. Noting individual differences such as this will help the birder keep track of the Red-tails around him.

I am ending this post with a summary of Red-tailed Hawk reproduction because I would like to encourage my readers to become familiar with the species beyond identification. I relied upon Charles R. Preston's book, Red-tailed Hawk (2000, Stackpole Books, 5067 Ritter Road, Mechanicsburg, PA. 17055.) for most of the information.

Nest Selection: The pair selects a nest site up to 3- 5 weeks before the female lays eggs. Nest sites in the North Okanagan include groves of cottonwoods and coniferous trees in or on the edge of forest. Nests are large piles of sticks often from the tree that the birds have chosen to nest in. Nests can be difficult to locate or very obvious.

Eggs and Incubation: The female usually lays an egg every other day. A complete clutch ranges from 1 to 5 eggs, with an average over North America of 2-3 eggs per clutch. Incubation is by both male and female, but mostly female, and commences with the laying of the first egg. The male provides food for his mate, but she may also hunt for herself. Incubation to the hatching of the first egg may be as short as 28 days though the period may extend as long as 35 days since hatching of first to last laid eggs may occur over several days. The first chick to hatch has the developmental advantage and siblicide is known.

Nesting period: lasts from 39 to 46 days.

Fledglings: have to learn to fly well, and at first beg incessantly, a well known sound of June and July around Vernon. This period when the fledglings are variously dependent upon the parents can last weeks, if not months.

To leave comments about this or any of my other posts, contact me at chris.siddle@gmail.com

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.

Spring Black Swift Flocks

Another feature of North Okanagan birding is the regular occurrence of flocks of Black Swifts over Swan Lake, north of Vernon, from about the middle of May through early June. Elsewhere in the Okanagan Valley, things are pretty hit and miss when it comes to seeing Black Swifts at anytime, but late spring is a good time to look for this species over the middle and northern sections of Swan Lake.

The Black Swift is quite simply an amazing bird. Dip into its Birds of North America account by P.E. Lowther and C.T. Collins and you'll find it is a species about which very little is known.

Adult Black Swift on nest at Banff, June 2010. Photo by Chris Charlesworth.

Historical changes in Distribution: No information. Migratory behavior: Little information. Physiology: No information. Winter Range: until very recently unknown. Food selection: No info. Daily patterns of vocalizations: No information. You get the picture.

And yet the Black Swift is, for many birders, a fascinating bird, a species of way more interest than just a checkmark on a life list.

For one thing there's the mysteries of its distribution. Look at the bird's range map and you'll see that Cypseloides niger's supposed ranges across the south two thirds of British Columbia (and yet fewer, probably far fewer, than a half a dozen nests have ever been found in B.C.) south through Washington and Oregon (no nests as of my info of 2007) and into California, and east in "colonies" to Colorado, with outposts in New Mexico and Arizona. Then the range appears again in central Mexico and Central America and on some of the Caribbean island. Are the three subspecies of Black Swift really subspecies, or species in their own right. No information.

Secondly, the Black Swift is notoriously FUSSY about its nest sites. An energetic, pioneering researcher in Colorado in mid century, Al Knorr, summarized the species' nest site requirements: a) the presence of water, and not just a pond or an alpine tarn, but usually a waterfall with a spray zone that keeps the nest site damp. In coastal California seepage around crevices in a sea cliff were acceptable as well b) high relief - in other words a site on a cliff or high on the vertical wall of a damp cave c) inaccessibility by predators. A nest on a rock shelf behind the outer spray zone of a waterfall is far less likely to be predated or even detected by some protein hungry predator d) unobstructed flyways and e) darkness.

These characteristics make to Black Swift's nest hard to find, but paradoxically, help reseachers develop   inventories of sites to search. Colorado reseachers have lead ther way for the past several decades in finding Black Swift colonies, although "colony" is a term used very loosely and may mean a site with only one nest. However, Black Swifts have a strong tendency to reuse old nests and many sites have been occupied for many years in a row.

Thirdly, and I personally find this the most fascinating of all the strange facts about this bird, Black Swifts lay a single egg. Of North American land birds, the only other species to lay a single egg is the Band-tailed Pigeon.

The swift's cousins, the Vaux's Swift and the White-throated Swift, both lay multi-egg clutches, but the Black Swift lays one. Its incubation period is very long, 23-26 days, a period common to species that hatch precocial young, like grouse, covered in feathers and almost ready to fly. However, in the case of the Black Swift, after 23-26 days, the chick is born naked and helpless. The young grow slowly and may slip into periods of tropor, an adaptation to long periods between feedings.

While the chick remains in the nest, it may be brooded by both parents at night. When it's older than 20 days, only one parent may stay with it during the dark hours. During the day the parents are generally away soaring around for their principal food, flying ants, which the parent bird binds with saliva into a bolus in its throat pouch. Californian young were fed twice a day.  Once over 30 days of age the chick was brought food only once, in the evening, but perhaps fed several times from the same bolus during the night.

The chick leaves the nest when it is about 44 days old, usually in early September. Once it leaves the nest, that's it. Nests are not revisited until it's time to nest again. The fledgling is presumed to join migratory flocks of adults.

I am deliberately omitting some information about the Black Swift which is quite as interesting as any of the facts herein. If I have whetted your appetite to learn more about the Black Swift, visit the American Birding Association's website to download Rick Levad's book, The Coolest Bird, A Natural History of the Black Swift and Those Who Have Pursued It. Try http//www.aba.org/thecollestbird.pdf

More Red-tailed Hawks

Figure 1 RTHA - white-chested adult with fairly heavy belly band.  Okanagan Landing 3 March 2013. 

This light morph adult has a white chest, fairly strong side of the chest streaking and a fairly heavy belly band. These areas - chest colour and pattern, and extent and heaviness of belly band - are key features I look at when classifying a Red-tailed Hawk. As well, I try to note the darkness of the head, the colour and pattern of the leggings, the colour and pattern of the tail, the darkness and extent of the patagial mark, the colour and patterns of the underwings, the shade of the upperwings and the extent of lightness on the scapulars.

This white-chested, dark belly banded type appears to be common around Vernon.

 Figure 2 shows a close variation on this plumage but with a slightly darker chest and a less heavily marked belly band. Birds of Fig 1 and 2 dominated the Vernon area in the first  half of March this year, probably a normal situation.

Figure 2. Tawny or light brown chested adult with medium belly band. Bella Vista Drive, Vernon 4 March 2013

Figure 3 is an unusual RTHA with a orangey-tinted tan chest and underparts as well as a minimal belly band. Vernon Commonage 4 March 2013.

The Invisible Sparrow

The Invisible Sparrow

Eastern race of Grasshopper Sparrow by Louis Agassiz Fuertes . Plate 81 from Birds of America (Garden City, New York, 1917, 1936). 

Another bird that the North Okanagan used to be well known for is the Grasshopper Sparrow. In 1983 Jim Grant, well known Vernon naturalist, showed me my first Grasshopper Sparrow in the grasslands along Goose Lake Road which connected Old Kamloops Road and the south end of Goose Lake. This site had contained as many as six pairs in 1963 and was well known the THE spot in the province to find this species. Early one late June morning we watched as a tiny sparrow energetically sang its thinly musical song from a tussock of grass east of the summit of Goose Lake Road. This became my go-to spot for the Grasshopper Sparrow from 1989 when my family and I moved to Vernon.

In the 1990s a few large houses were built on the west side of Goose Lake Road eliminating the sparse grass habitat favoured by the sparrows and the road was paved. Thereafter I was unable to find any Grasshopper Sparrows on the west side and the population on the east side dwindled to one singing male, and eventually from 2007 onwards to none.

Meanwhile during the 1990s and the first decade of the 2000s a few more Grasshopper Sparrows turned up – all of them singing males in June or July, never more than two a year. One was on the grassy slopes of Middleton Mountain in a spot now covered by big houses, and another sang in a weedy former horse pasture opposite Desert Cove Estates along Head-of-the-Lake Road.

Both of these locations were good for only a year. At this time I do not know of any spot for this species in the North Okanagan where the public can go. However, if you don’t mind going to the South Okanagan you might find a Grasshopper Sparrow in the grasslands near the parking lot of  Ecological Reserve 100 at the end of Meadowlark Lane off Black Sage Road east of Road 22, or one in the grasslands along the paved road that leads from Highway 3 to the Chopaka border crossing from mid to late May into August. Good luck. Unless the male is singing, the Grasshopper Sparrow is as hard to find as a grassland mouse. As Peter Dunne points out, the birds don't respond to pishing either. 

The Grasshopper Sparrow still occurs in the North Okanagan, but not anywhere that’s open to the public. I have found a tiny handful of individuals on the Indian Reserve and on the Department of Defense lands while running surveys for the land owners, but it would be the unwise birder indeed who dares to trespass on either of those large chunks of land.

Nine things you may not know about the Grasshopper Sparrow:

1.Currently the species Ammodramus savannarum is divided into twelve subspecies. The widespread ones are A.s. perpallidus in western North America and A.s. pratensis east of the Great Plains. One non-migratory population, A.S. floridanus, the Florida Grasshopper Sparrow, is in deep trouble. Despite habitat management in its very limited range north and west of Lake Kissimmee, the Florida Grasshopper Sparrow has been called the most endangered bird in the continental United States. Birds are known from only five breeding sites, and in 2012 steep population declines continued.

2. “Our” Grasshopper Sparrow, A.s. perpallidus, is considered endangered in British Columbia. The only areas where breeding evidence has been found are the Okanagan and Similkameen valleys.

3. The Grasshopper Sparrow belongs to a group of equally reclusive and secretive relatives, Henslow’s Sparrow, Le Conte’s Sparrow, Nelson’s Sparrow, Saltmarsh Sparrow, Seaside Sparrow, Baird’s Sparrow, and two South Americans, the Grassland Sparrow and the Yellow-browed Sparrow.

4. Ammodramus savannarum means sandrunner of the meadows. According to The Handbook of Birds of the World (Vol. 16) the German name for the species is a throat-clearing “Heuschreckenammer”.

5. The female Grasshopper Sparrow builds a grass nest on the ground, often hidden beneath a dome of grasses.

6. According to The Birds of Oregon, in that state east of the Cascades the Grasshopper Sparrow inhabits native bunchgrass remnants on north-facing slopes.

7. The males require elevated perches in their breeding habitats from which they sing their two types of song. Like most Ammodramus species, the Grasshopper Sparrow appears to put a huge effort into delivering its song.

8. It tolerates some shrubs in its habitats but favours the grasses and bare patches between the shrubs. The more the shrubs, the less chance that the sparrow will find the habitat suitable.

9. A fossil bird very similar to the Grasshopper Sparrow was found and dated to be from 10 million years ago. Two major differences were that the dinobird was eleven metres tall and sported a beak almost a metre in length, capable of crushing coconuts. Sorry, I made that up. The fossil was of a very small sparrow, A. hatcheri,  from the late Miocene.

I find magic and wonder in the Grasshopper Sparrow. Imagine this atom of a bird speeding unheaded through the darkness over the Great Basin, oriented we know not how towards Mexico where it will find just the right patch of grasses in which to winter, surviving predation, disease, exposure, and hunger, and towards mid spring with the stars shining in its eyes, it grows restless and in an instant takes flight once again toward the north and a very unsure future. 

Varieties of Red-tailed Hawk Plumage in the North Okanagan

Red-tailed Hawk - brown-chested adult. About 20% of North Okanagan Red-tails are brown-chested.

The North Okanagan is home to more varieties of Red-tailed Hawks than I have seen anywhere else in North America. By varieties I mean plumage varieties,variable plumages being a feature for which the Red-tail is well known.

Red-tails are both resident and migrant in the North Okanagan. For the past several years I have been keeping a rough track of the plumage types I have seen. I haven't formerly analysed my data yet but I have formed some impressions.

The majority of residents are light morph birds, by which I mean they have dark upperparts and lighter underparts. Many, perhaps as many as 25%,  resemble the adult calurus (a widespread western subspecies) illustrated on page 145 of the new (6th edition- 2011) of National Geographic's Field Guide to the Birds of North America.

The image above shows a fairly typical calarus type, though the large white feathers showing in the folded wing are unusual.


About 30% of North Okanagan Red-tailed Hawks are intermediate or dark morph birds, two thirds of these being brown-chested birds like the one shown at the top of this article. Here's another variation of the brown-chested Red-tail

 photographed

Perhaps the most uncommon plumage locally is that of pale birds like this immature shown below ( Swan Lake - 1 March 2013). Some birders are too quick to slap a label like Krider's Red-tail on such a bird. Since we don't know whether the bird is local (which is out-of-range for Krider's) and simply the product of a local genetic mutation, it's perhaps best to call it just a white breasted type.

Complicating matters are Harlan-type Red-tailed Hawks that appear in the North Okanagan as both
birds of passage and as winter residents. Harlan's Red-tail can be dark morph or light morph. It appears that dark morph Harlan's-types are much more commonly encountered in the North Okanagan than light morph Harlan's which I have yet to identify with certainty.

Below is a dark morph immature which could possibly be a dark morph Harlan's type photographed at Okanagan Landing in winter.