Tuesday, March 3, 2015

A WHITE BLACK BIRD


I look at a lot of birds every year, and I don’t see many that are as cool as this one, a leucistic Black Turnstone (Arenaria melanocephala). This striking bird is wintering at the end of Sandy Point, north of Bellingham, Washington, in a flock of its relatives, and I finally got around to checking it out in February. I found the flock feeding on rocks at the mouth of the marina there.

What a bird! From a distance it looked entirely white, but at close range elements of the pattern became visible, most of them very subdued. The more or less straight line across the breast identified it as a Black rather than a Ruddy Turnstone (Arenaria interpres), which has a bilobed pattern of black there. There was also a Ruddy with the flock.


By comparing the bird with a normal Black Turnstone, I could see how much the melanin pigment was reduced on this bird, yet it wasn’t entirely absent. The darkest areas of normal pigment were on the rump and tail, but tan areas all over the bird, most readily seen in flight, gave me a good hint of typical Black Turnstone pattern.

The bird is definitely leucistic, not albinistic, because it has normally pigmented eyes. Albinism is the complete absence of melanin pigment. Because that pigment is what gives brown eyes their color, when it is lacking in an albino, the blood vessels in the eyes give them a bright red color. Leucism is a reduction of all pigments, but not necessarily their absence.

The bird presumably grew most of its feathers in July and August, the time of fall molt in Black Turnstones, so they were about six months old in February and showing their age. In comparison with nearby normal birds, the primary feathers were distinctly more worn. The tertials, the long feathers that overlie the primaries, were very worn, much more than on the other birds.

The bright orange legs of this bird contrasted with those of normal Black Turnstones, in which they are brown to dull orange. Presumably in normal birds, melanin masks what would be bright orange otherwise. The legs of Ruddy Turnstones are bright orange, and one wonders whether they would remain exactly the same in a leucistic bird.


Its behavior appeared to be the same as that of the other birds, and they must have accepted it as a flock member. However, when the entire flock flew away, startled by a jogger coming down the beach, the white bird flew in the opposite direction with two of the black ones rather than with the flock.

Such birds are extremely rare, and I feel fortunate to have seen this one. One thing special about it is that it could never be mistaken for another turnstone, thus always recognizable. If we could recognize all birds individually, we would know a lot more about them!

The white turnstone’s presence is being monitored closely, so we may know when it has departed for the north, assuming some local falcon doesn’t pick it out of the flock. It is well known that birds of prey will home in on odd-looking birds, as they are easiest to follow in a twisting, turning flock.

If it does persist into spring, local birders will be watching closely for it late next summer, when Black Turnstones return here from their breeding grounds in the Yukon/Kuskokwim River delta. Let’s hope it makes it back.

Dennis Paulson

Tuesday, January 27, 2015

AN INTIMATE AVIAN EXPERIENCE




For a unique and intimate experience with waterfowl and other birds, visit George C. Reifel Migratory Bird Sanctuary west of Ladner, British Columbia.

Reifel Refuge, as it’s called by many, is a 300-hectare (740-acre) plot of land on Westham Island on the Fraser River, about an hour’s drive from the metropolis of Vancouver. George Reifel bought the land in 1927 and established a family recreational retreat on it, creating waterfowl habitats as well as road access by a series of dikes and causeways.

In the 1960s, the Reifel family granted a lease to the British Columbia Waterfowl Society to create a bird sanctuary on the land. Helped by the management of Ducks Unlimited Canada, wildlife habitat was preserved and expanded with the provincial government establishing a game reserve on adjacent land. In 1972, the family further donated and sold the land to the federal government on the condition that it would be maintained as a sanctuary.

The government designated part of the sanctuary and the area adjacent to it, some 328 hectares, as the Alaksen National Wildlife Area. Some activities are permitted on this land but not the free access to the public that characterizes the sanctuary.

The sanctuary charges a nominal entrance fee and is open from 9 am to 4 pm every day. Sometimes it has quite large crowds, not a place to go if you want to get away from people for your nature experience. However, the high density of humans day after day is what has conditioned the birds to be as unafraid of us as they are.

The sanctuary was set up for waterfowl, and there is always a good representation of local waterfowl species, both dabbling and diving ducks. Large numbers of Snow Geese migrate through the adjacent wetlands, some of them remaining for the winter, and mostly those will be seen overhead moving between feeding areas. All the ducks present are somewhat used to people and will furnish close viewing and great photo opportunities.

There is a small population of resident Sandhill Cranes, most of them not pinioned, and some of them will feed from the hand. Some of them are good at gently taking seeds from an open palm, but be aware that you’re taking the chance of a poke with a sharp beak from those that aren’t. There are also Black-crowned Night-Herons roosting near the entrance to provide good looks at another unexpected species.
There are feeding stations everywhere, and during the winter they attract great numbers of seed-eating birds, for example Black-capped Chickadees, Red-winged Blackbirds, Spotted Towhees, Fox, Song, and Golden-crowned Sparrows, House Finches and House Sparrows. The chickadees are so tame that anywhere along the trails they will land on your hand if you open it with sunflower seeds on it. Occasionally a Red-breasted Nuthatch may do the same.

Brown Creepers and kinglets are also often seen, and like other birds there are quite tame. Quite a few other passerines inhabit the patches of woodland, and unusual visitors are seen with some regularity, for example Bohemian Waxwings and Pine Grosbeaks recently. And it’s always worth watching for less common sparrows such as Swamp, Harris’s, and White-throated along the path.

Because of all the feeders and seeds, rats and mice and Eastern Gray Squirrels (including the black morph, established in the Vancouver area) are also attracted to the area, and the local owls know it. A pair of Great Horned Owls is regularly seen, and there are always Northern Saw-whet Owls present, if very hard to see in the dense foliage where they roost. Other species of owls are seen from time to time, and there are usually hawks and falcons about, interested in the songbirds as well as the rodents.


You can buy sunflower seeds at the office and carry them around to feed to whichever birds you like. You may give them all to chickadees, as there is something wonderful about one of these tiny birds landing on your hand. You may be attacked by Mallards before you barely get going onto the trail, and Mallards are the most abundant and insistent ducks in the place. But look closely, and among the Mallards there will be at least a few American Wigeons and a few Northern Pintails.

More than these, there are Wood Ducks scattered around the area, and they too are interested in handouts if they can get to them before the omnipresent Mallards. They are shy enough that you’ll have to seek them out, but one way to feed them is to put seeds on top of fence posts, which the Wood ducks—tree dwellers that they are—can easily get to. Of course they have to beat the chickadees and Song Sparrows to them.

Dennis Paulson



Thursday, January 22, 2015

A COMMUNITY OF SAPSUCKERS


North America has the distinction of being the only continent on which a group of birds has evolved the ability to tap into the sap of living trees. These are the four species of sapsuckers (Sphyrapicus): Yellow-bellied (S. varius), Red-naped (S. nuchalis), Red-breasted (S. ruber) and Williamson’s (S. thyroideus). The first three replace one another from east to west across North America, while Williamson’s occurs with both Red-naped and Red-breasted in the West.

Sap flows through the xylem and phloem of a tree with a function rather similar to that of blood in animals. It’s not important in respiration, as it is in us, but nutrients and other chemicals circulate in it. It is full of sugars, presumably an important component of its nutritive value. Phloem sap of deciduous trees can contain concentrations of greater than 25% sugars in summer.


Sapsuckers dig holes in the bark of trees to get at this sap. They dig phloem holes, usually square and shallow, and continue to enlarge and add to these holes, excavating new ones above the old in a vertical arrangement. They also dig xylem holes, smaller and usually circular and penetrating the cambium layer to reach the xylem. These are arranged in horizontal rows. Some trees show both types of holes, easily distinguished.


As soon as these holes are dug, sap begins to flow into them, and they can then be considered sap wells. They continue to flow while temperatures are sufficiently high, but when air temperatures drop below freezing, the sap freezes in the wells and is then inaccessible to the sapsuckers. This is why sapsuckers are the most highly migratory of woodpeckers. As temperatures drop during the winter, many Red-breasted Sapsuckers, normally nonmigratory, descend from the mountains to appear in Pacific Northwest lowlands in numbers.


Sapsuckers may spend over half of their foraging time constructing and maintaining their sap wells. They seem to prefer tree species with higher sucrose content in the sap rather than those in which flow rates are higher. However, their wells have been found in about 1,000 species of woody plants, native and introduced.

They also feed on insects attracted to or trapped in the sap as well as additional arthropods captured on the bark or in the air. They also take some fruit and leaf buds. Insects are captured to feed the young, but the adults often stop at sap wells and dip the insects in sap before taking them to the nest. This may be for added nutritional value or to acclimatize the young to feeding on sap.


Numerous other species find these sap wells nutritious, including both birds and mammals. In the Pacific Northwest, species that I have seen coming to the wells include Anna’s and Rufous Hummingbirds, Downy Woodpeckers, Black-capped Chickadees, Ruby-crowned Kinglets, and Eastern Gray Squirrels. The wells may be especially important to hummingbirds, some of which actually follow individual sapsuckers to note the distribution of their wells. Sapsuckers actively defend their wells against some of these species, but each sapsucker has so many wells that this isn’t a very productive tactic.


The fact that there aren’t any sapsucking woodpeckers in the temperate forests of Eurasia is an elegant example of the idea that not all niches are filled. But of course sapsucking insects of the order Hemiptera (true bugs, aphids and their relatives) are everywhere in the world.

Dennis Paulson

Friday, November 7, 2014

BAND-TAILED PIGEON


You’ve doubtless seen the pigeons feeding in the city square or along the freeways roosting on light standards and nesting under the overpasses. These are Rock Pigeons (Columba livia), formerly called Rock Doves, and they are native to Eurasia but have been introduced all over the world, first as captive birds and then established in cities, towns and the countryside outside of captivity. They are rock-dwelling birds that nest on cliffs, and they see our city buildings and barns as just another kind of cliff.

However, we also have a bona fide wild pigeon in the Pacific Northwest, the Band-tailed Pigeon (Patagioenas fasciata). These are birds of the forest, birds that roost in trees and not on buildings. They are common west of the Cascades, occasionally seen on the east side. Many migrate south in autumn, but good numbers persist through the winter in areas where they can find food, both wild and human-provided.

We are fortunate that Band-tailed Pigeons are easily attracted to bird feeders with mixed seeds, as they are really quite attractive birds. They look something like Rock Pigeons but are slightly longer-tailed and rounder-winged, evident when they fly overhead. They are gray above, with more reddish underparts and a dark band bordered by a pale tip on the tail (thus the name). The bill and feet are bright yellow, and there is a white half-collar on the neck with an iridescent patch of feathers behind it.

These pigeons are vegetarians with a varied diet. Their range coincides with the range of oak trees throughout much of the West, and they eat a lot of acorns. But they also take pine nuts, fruits of all kinds, seeds of herbaceous plants, especially grains, and a variety of buds and flowers.

Band-tails build flimsy nests of twigs well up in trees, averaging about 10 meters but up to 50 meters above the ground. The nest is usually on a firm limb not far from the trunk. They lay a single egg, quite unusual among pigeons and doves, which usually lay two. The egg is incubated alternately by both male and female for about 18 days to hatching.

Both parents produce “pigeon’s milk,” a curdlike substance that sloughs off from the inner walls of the crop (production mediated by prolactin, just as in mammalian milk!); this is unique to pigeons. The young bird (“squab”) remains in the nest for three or more weeks and may be fed by the adults after it fledges.

There has been an uptick of interest in Band-tailed Pigeons in recent years. A group of researchers are committed to de-extinction of the Passenger Pigeon (Ectopistes migratorius), and they are moving rapidly toward that goal. Their method involves working out the genomes of both species and the systematic replacement of Band-tailed Pigeon with Passenger Pigeon genes: “converting viable Band-tailed DNA to viable Passenger Pigeon DNA.” They have now fully sequenced both species, so stay tuned!

On October 30, a juvenile Band-tailed Pigeon landed on the feeder right in front of me, and it looked just enough like a Passenger Pigeon, not seen alive for over a century, that a chill ran over me.

Dennis Paulson