THE BIRDS THINK IT’S SPRING

This is the time of year when our resident birds begin to sing. Already I have heard Anna’s Hummingbird, Bewick’s Wren, American Robin, Varied Thrush, European Starling, House Finch, Song Sparrow, and Dark-eyed Junco singing around my house. On the other hand, the vast majority of migrant species have not arrived yet, and those residents that are singing won’t be breeding until some time in April.

Why don’t all birds breed at the same time? Well, an easy explanation for raptors is that their incubation periods are long, so it behooves them to breed before many other species, so they have eggs hatching at a time when food resources are high. As it turns out, the eggs of the early breeders hatch at a time when many local mammals are weaning young.

Some species, for example raptors such as Barn and Great Horned Owls and Red-tailed Hawks, have already begun their breeding cycles. A Northwest pair of Red-tailed Hawks could have a complete clutch of three eggs laid by March 20. The first egg would hatch in mid April, and young would be ready to leave the nest by the end of May.

The bird-eating accipiter hawks (Cooper’s, Sharp-shinned) begin to breed later than the mammal eaters, because the supply of naïve young birds doesn’t really kick in until May or June. A Cooper’s Hawk pair that lays the first egg of a clutch of four on April 15 would expect the first young to hatch on May 20 and the first young to fledge about a month after that. By the end of May there are great numbers of young, naïve birds in the surrounding woodland that can provide prey for a family of Cooper’s Hawks.

A Barn Owl that laid her first of six to eight eggs on March 10 would see the first young hatch on April 10 and fledge in about two months. By hatching time, great numbers of young voles would have emerged from their grass nests to forage in their myriad runways, and the parents can find plenty of protein for their growing young. Furthermore, a just-fledged owlet should have no trouble detecting and catching those furry snacks.

Mammal-eating owls such as Barn and Great Horned breed early, but insect-eaters such as Western Screech and Burrowing Owls breed later for two reasons. First, incubation and fledging periods are shorter for smaller birds, so there is no reason to start so early. More importantly, their prey does not become active until ambient temperatures allow activity. So these owls are laying their eggs in April and even May.

A Burrowing Owl clutch of eight eggs might be completed on April 15, when incubation would ensue. The eggs would hatch around May 15, and the young would be ready to leave the burrow by the end of June, when insects and lizards abounded in its nesting territory.

So the eggs of the mammal eaters hatch about a month before the eggs of the bird and insect eaters, just as predicted. Not only the wonderful adaptations of living organisms, but also their exquisitely fine tuning, never fail to impress me.

Dennis Paulson

BIG BLACK BIRDS WITH BULGY BEAKS

These are the scoters, three species of ducks we are fortunate to see in the Pacific Northwest every winter. The males are black with bright head markings, the females mostly dark brown. They breed in Canada and Alaska and winter along most of the temperate coasts of the United States. They are mostly confined to salt water in the nonbreeding season, although wintering numbers on the Great Lakes have increased because of the proliferation of zebra mussels there.

The Surf Scoter (Melanitta perspicillata) is the most common of the three scoters wintering in the Pacific Northwest. While all three scoters include a variety of marine invertebrates in their diets, they seem to be bivalve specialists. The heavy bill of a Surf Scoter provides it with strength to pull mussels loose from their attachments to rocks and pilings. Accordingly, Surf Scoters are common where there are large beds of mussels, and that includes a lot of territory in this region.

Surf Scoter courtship displays are fun to watch. The male flies a short distance with loudly whistling wings, then slides to a stop on the water with both wings raised high. How could a female not be impressed? Like other ducks, they pair during the winter and fly back to the breeding grounds together. Most males probably don’t breed until they are two years old, and younger males can be distinguished in winter by less brightly colored bill and often smaller white head patches.

White-winged Scoters (Melanitta fusca) appear to be more locally distributed than their Surf cousins. They are most common in bays with sand substrates, where clams are much more common than mussels, surely indicating a food preference. The White-winged is a bit bigger than the Surf and is our largest duck. The big white wing patches are prominent in flight but may be hidden on a resting bird. Note the difference in feathering on the bill of the two species, useful when identifying juveniles, which look very similar.

The Black Scoter (Melanitta americana) is the least common and most locally distributed of the PNW scoters. Its head shape is more like that of other ducks, presumably indicating it is less extremely adapted for bivalve pulling. As in the Surf Scoter, the male wings whistle in flight.

Male scoters see their mates on a nest on the breeding lake and then head for the coast in what is called molt migration. Female Surf Scoters follow the males after they raise their young, but female White-wings undergo this molt on the breeding grounds. The molt migrants arrive at their destination and begin their body and wing molts. They are flightless during wing molt, so they need to be somewhere with abundant food resources for that period. After completing molt, many continue farther south along the coast.

Scoter migration is dramatic on the outer coast, where flock after flock of Surf Scoters pass by just offshore, heading south in September and October and north in April and May.  Smaller flocks of White-winged Scoters are interspersed, but you’ll have to look long and hard for the much smaller numbers of Black Scoters. Migrants of many other seabirds, in flocks and by themselves, add to the thrilling experience of a few hours spent on an outer-coast point.

Dennis Paulson

THE LARGEST SONGBIRD

This is not a bird that you think of when you think of songbirds, but in fact that’s exactly what a Common Raven (Corvus corax) is. Along with all the other members of its family, the Corvidae, it is a bona fide member of the suborder Oscines, the “songbirds” of the order Passeriformes.

Although no one would ever accuse a raven of singing, its vocalizations are varied. Most of the time we hear ravens giving their single or multiple somewhat musical croak, lasting for a second and with distinct harmonics. This is apparently a location call, making other ravens aware of the bird’s presence, and it is most commonly heard from birds moving over the landscape. That call is the epitome of raven sounds, but the species expresses a wide variety of other calls in varied circumstances. They are similar enough so that elaboration of their function has been difficult.

The Common Raven is also the widest-ranging corvid and a fine example of a successful species. It is distributed throughout the Far North, including Greenland and Iceland, and all across the northern hemisphere south to Nicaragua, northern Africa, northern India, and central China. Populations occur in all terrestrial habitats except rain forest.

Ravens are true omnivores, taking just about anything edible they can find in their environment. Because they are so large, they can be effective predators on a wide range of animals up to the size of pigeons. They spend much time hunting voles where those rodents are abundant, and a vole is just the size to be swallowed in a single gulp.

During breeding season, any bird with a visible nest is in danger from sharp-eyed ravens. Pairs fly over the tundra, and when a shorebird such as a Whimbrel spots a raven coming, it will leave its nest to begin mobbing actions. Unfortunately for the bird, the raven’s mate, off to the side, may have seen exactly where the nest was located.

Garbage dumps are favored hunting grounds for ravens, which may visit them in large numbers. A thorough analysis of their “prey” there is not for the faint of stomach. Similarly, well-traveled roads with their road kills furnish a linear cafeteria for ravens, especially in the morning when they can often be seen systematically searching their length. The guaranteed presence of carrion (everything dies eventually) may be one of the factors that allow ravens to live just about anywhere, from tundra to mountain forest to desert.

Ravens are well-known to accompany wolves and other predators on hunts for the chance that food scraps may await them. They have been suspected of purposefully attracting both wolves and human hunters to moose and caribou.

Ravens mate for life and are commonly seen in pairs. They are superb flyers, soaring like hawks or plummeting through the sky in spectacular dives. A typical raven antic is to do a half-roll or even a full barrel roll in flight, and they have been seen to fly upside-down for considerable distances.

As should be evident by now, ravens are near the top of the list of brainy birds. Corvid intelligence is well documented, and books on ravens by Bernd Heinrich (Mind of the Raven and Ravens in Winter) and John Marzluff (In the Company of Crows and Ravens and Dog Days, Raven Nights) present this documentation as fascinating reading.

Pet ravens are especially playful birds, especially young ones, and whether their varied antics (sliding downhill, hanging upside down, dropping and catching objects while in flight, pecking dogs on the tail) are all related to survival is debatable. (Don't try this yourself; ravens are a protected species). One certainty is that raven watching will never be boring.

Dennis Paulson

FLOCKING BIRDS

A question that is often asked is why birds flock. And why do some of them form mixed flocks?

It is certain that birds flock for evolutionarily sound reasons:  to avoid predation and to find and capture prey.

By flocking, birds have a better chance to avoid predators than when they are by themselves. First, with more birds together, there is a higher level of alertness, as individuals are likely to be looking in different directions, and not all of them will have their heads down at the same time. In fact, it has been found that birds spend more time feeding and less time looking around when in flocks. Some shorebirds that feed by constantly probing the substrate, for example godwits, may flock with other species that forage with heads up, for example curlews, for the added vigilance.

Second, when birds fly in flocks, they make it more difficult for aerial predators such as falcons to catch them, because the falcon has to concentrate on a single bird, while a group promotes confusion. Furthermore, a bird in a flock of 20 has only a one in 20 chance of being caught, whereas a bird by itself has a statistically more serious problem. When a Bald Eagle flies over a flock of coots, they scatter in all directions.

Third, birds in flocks can actually intimidate predators. Starlings form a swirling superentity and dive on any hawk that approaches them; the tactic works quite well.

There are other advantages. Birds may discover food by associating in groups. Vultures and gulls roost in flocks, then spread out to feed while keeping a distant eye on one another. A vulture that drops to the ground is at the center of a contracting circle of birds heading in its direction. Gulls and terns have been attracted from boats by a handkerchief thrown in the air, simulating a bird dropping to the water.

Birds may also flock to capture prey more effectively. Pelicans in a line drive fish in front of them. Auklets surround a herring school and control its movements just as border collies herd a flock of sheep (why don’t falcons do this with shorebirds?).

Presumably birds form mixed-species flocks for the same reasons. If a flock of 100 is more effective than one half its size, then it makes sense for 50 blackbirds and 50 starlings to forage and fly together. For the most part, birds of similar size and habits flock together, so you’re unlikely to see a mixed flock of murres and juncos.

One of the most commonly seen mixed flocks is a winter feeding flock. In this area, it usually contains chickadees of one or more species, often Red-breasted Nuthatches, and sometimes Golden-crowned and/or Ruby-crowned Kinglets. The flock may be joined by a Downy Woodpecker or Brown Creeper or Townsend’s Warbler or Hutton’s Vireo. By moving through the woods together, these birds may help one another spot particularly good feeding areas, and they are surely more alert to predators as a group than if they were foraging individually.

I wonder if it’s possible to explain any of our own social behavior by this reasoning. Or can we explain bird behavior by what we know of our own? Perhaps some birds flock just to check out members of the opposite sex for the next breeding season.

Dennis Paulson

THE GULLS OF PUGET SOUND

Gulls can be best viewed where we concentrate them, anywhere from fast-food restaurants (French fries are a favorite) to waterfront parks (white bread a staple of the menu) to a meat- or fish-processing plant where they relish the offal, awful as it is. For the most part, the large gulls dominate these assemblages, although if there are few of them, smaller species may be in attendance. The smallest species, Mew and Bonaparte’s Gulls, have different feeding habits and are not part of these spectacles.

As pointed out in a previous blog, the Glaucous-winged is the most common and certainly most ubiquitous gull in Puget Sound. It and the much smaller Mew Gull are the ones you see everywhere throughout the winter. During spring and fall migration, large numbers of Bonaparte’s Gulls appear, and during fall migration there are even larger numbers of California and Heermann’s Gulls.

In addition to these five species, several others are seen in much smaller numbers. Thayer’s and Western Gulls are uncommon during winter, Herring and Ring-billed Gulls even less common. After these nine regularly occurring species, any other species is much rarer. This discussion will concern itself with adult plumages; the immature plumages are usually quite different.

Heermann’s Gulls (Larus heermanni) are medium-sized and stand out by their entirely gray body and black tail; the bill is red, the legs black. In breeding season, the head is white, but we don’t see it in that plumage, as it is a fall visitor from breeding colonies in Baja California. It is more common in the northern part of Puget Sound, mostly in September and October.

Bonaparte’s Gulls (Larus philadelphia), usually seen in migration but remaining for the winter in small numbers, are easily distinguished by their small size, black bill and red legs, and extensively white wingtips. In breeding plumage, they have a black head. They tend to be in flocks, sometimes large ones, and they often feed along convergence lines, or “tide rips.”

All the other gulls have gray mantles, yellow bills, and white heads, bodies, and tails in breeding plumage. Mew Gulls (Larus canus) are the smallest of these, not much larger than Bonaparte’s. Adults have thin, almost pigeonlike, yellow bills and yellow legs. The eyes are brown, the mantle (back and upper surfaces of wings) medium gray. In nonbreeding plumage, the head and neck are strongly marked with gray. The extreme wingtips are black, with large white spots that furnish a characteristic field mark. Like Bonaparte’s, this species is most commonly seen feeding along convergence lines but is common and widespread throughout the region in winter.

The next larger is Ring-billed (Larus delawarensis), with mantle paler gray and contrasty black wingtips. The white tip spots are smaller than in Mew. The bill is yellow with a black ring, the legs yellow, and the iris yellow. This freshwater species is only occasionally seen on Puget Sound but is noteworthy for its very contrasty markings.

A bit larger, the California Gull (Larus californicus) is patterned about like the Ring-billed but has a darker gray mantle, like the Mew, and brown eyes. Note both mantle color and eye color alternate with progression from Mew to Ring-billed to California. The yellow bill features a black spot in front of the red spot characteristic of all the larger species.

The rest of the regularly occurring gulls, larger yet, have yellow bills with a red spot on the lower mandible and pink feet. Thayer’s (Larus thayeri) and Herring (Larus argentatus) are very similar, both with pale gray mantles and less black at the wingtips than either California or Ring-billed. Herring always has a yellow eye, Thayer’s usually a brown eye, but the eye is pale in some individuals. Thayer’s is slightly smaller, with a distinctly smaller bill and more rounded head shape. The wingtips of Herring are blackish above and below, while in Thayer’s, there is not only less black but it shows up scarcely at all from below. So wingtips black above and pale below are characteristic of Thayer’s.

Finally, the two largest species, Glaucous-winged (Larus glaucescens) and Western (Larus occidentalis), differ primarily in mantle and wingtip color. In Glaucous-winged, the mantle and wingtips are gray and darker gray, in Western dark gray and black, respectively. Very different-looking birds, they unfortunately (for the birdwatcher) hybridize freely in the Puget Sound area, and the hybrids come in all shades of gray. These have been called “Olympic gulls,” and they complicate field identification. The wings are always more uniform than they are in Herring and Thayer’s, in which the light gray mantle and black wingtips contrast strongly.

Western Gulls have slightly larger bills than Glaucous-winged and are more likely to have yellowish eyes. The skin around their eyes is yellow, the same in Glaucous-winged is pink. But again, the hybrids complicate the issue. Western is much less common in Puget Sound, but there are pure Westerns along with the hybrids. A pure Western usually retains a white head throughout the winter and doesn’t acquire a black smudge on the red bill spot as does Glaucous-winged.

See the Slater Museum’s gull web page (http://www.pugetsound.edu/academics/academic-resources/slater-museum/biodiversity-resources/birds/identification-of-pacific-nort/) for more images and further information on identification.

Dennis Paulson

THE COMMON SEAGULL

Seagull? Everyone knows what a seagull is, but why do we use that name for them? They are gulls, GULLS. We don’t have “seaducks” or “sealoons” or “seaterns,” so why “seagulls?” I don’t know, but I’ll never stop asking that question. Although all of them visit the sea for at least part of the year, more than half of the gull species breed on fresh water.

On Puget Sound, there is one very common gull, the Glaucous-winged (Larus glaucescens). In winter, most of the large gulls you see are Glaucous-winged, just as most of the small gulls are Mew Gulls. A moderate variety of species make up the other few percent.

Although in winter they wander inland to near-coastal freshwater lakes and well up the larger rivers, Glaucous-wings are basically marine birds. They breed throughout the protected marine waters of the Pacific Northwest in good-sized colonies on islands and scattered as single pairs at ferry docks or on rooftops. On the outer coast, the Glaucous-winged is replaced by the Western Gull as a breeding species.

Each pair nests in a scrape on the ground, lined with grass, twigs, and anything else that can be found in the limited nesting territory. The female usually lays three eggs totaling about 10% of her body weight, the last egg laid a bit smaller than the others. Both sexes alternate incubation for a period of about 27 days. Hatching takes a surprisingly long time, 2-3 days from pipping (first crack appears) to completely out.

The adults quickly begin to forage for the young, foraging trips lasting several hours. Prey items are brought about 10 times/day to a nest of three young. The young grow rapidly and are able to fly at about six weeks of age. They typically leave the colony at about eight weeks but are fed by the adults for some time afterwards, even well away from the breeding site. Young birds will beg from their own parents and other adults well into the winter, with diminishing returns.

Fully fledged juveniles are brown, coffee-with-cream colored with fine markings on most feathers. The wings and tail are very slightly darker than the body feathers and relatively unmarked. The bill is black, the legs dull pinkish. Limited molt begins during the fall, and the brown feathers of the back are replaced by gray.

Large gulls, including this species, seem to molt during a large part of the year, so plumage changes signaling a transition from immaturity to maturity occur not only between years but within years. The largest gull species take about four years to reach maturity, and their plumage changes throughout that time.

A typical first-year gull is brown, like the Glaucous-winged described here. By the time it is a year old, certain changes are evident in its plumage. Typically the mantle (= back) has become some shade of gray, and white feathering is increasing on the head and breast. The bill becomes pale (pinkish) at the base. The rest of the body and wings and tail look about the same.

By the second spring (about 20 months old), much more of the head and underparts are white, the bill has more pale color at its base, and gray feathers are appearing in the wing coverts. The wings and tail are still the same shade of brown, although both have been molted once.

By their third spring, Glaucous-winged Gulls look much more like adults. The bill has dark markings restricted to the tip and may be starting to turn yellow. Most of the head and body feathers are white (except for dark streaks and smudges on the head and neck). The wings are largely gray, the primary feathers with slightly darker tips and restricted white spots at the very ends. The tail is white, with or without gray spots toward the ends of the feathers.

One of these birds could easily be mistaken for an adult, but the white primary tips are more restricted, there is often a dusky wash across the upper surface of the wings, and the bill usually has a dark tip or subapical ring. there is much variation in plumage at this age. Some individuals look more like two-year olds, others more like fully adults. A small percentage defy categorization.

When the gull is mature, it has an entirely white body and tail and gray mantle, with slightly darker wingtips with white spots in them. The iris is brown, the bill bright yellow with a red spot on the lower mandible, the feet pink. The circumorbital skin is also pink. In nonbreeding plumage, the head and neck are suffused with dusky markings, and a black smudge appears on the red bill spot.

Back in the 1950s, a small group of these gulls from the Protection Island colony were raised to maturity in captivity by Zella Schultz of Seattle Audubon Society, and the variation within any given year class was surprisingly great. This is presumably because different birds have different hormone levels and apparently molt at slightly different times and/or with different degrees of completeness.

That tremendous variety of gulls that we see out there is caused, at least in part, by the gradual plumage change from young to adult in each species. Learn it in the Glaucous-winged Gull, and you will feel a sense of satisfaction at having made complexity somewhat simpler.

Dennis Paulson

THE HAWK OF THE OWLS

When you first encounter a Northern Hawk Owl (Surnia ulula), you will understand why it has two different types of raptors in its name. Clearly an owl because of that big head and forward-facing eyes, nevertheless it has the rakish look of a hawk about it, with long tail, rapid flight, and – of course – diurnal habits.

One of these birds spent the winter of 2010-2011 on Westham Island in southwestern British Columbia, delighting birders and nature photographers by the hundreds. Because of their open perching habits and tameness, Hawk Owls are readily detected where they occur, so it is likely that at least some of the few individuals that make it to peripheral wintering areas are found as observers scrutinize the winter landscape. In my case, it was a wonderful way to start the year - and on a beautiful sunny day!

In the Pacific Northwest, we don’t get veritable invasions in winter, with dozens of Hawk Owls showing up like they do in the Great Lakes region. Nevertheless, at least a few birds make it down to Washington in most winters, and with increasing knowledge of where to look for them, more have been seen in recent years. Breeding has been confirmed at Manning Provincial Park, just north of the border in British Columbia, and suspected at Harts Pass in Washington.

Hawk Owls perch, usually at the very top of a tree or other conspicuous perch (often on utility wires in this day and age), and survey the surrounding semiopen landscape for their prey. Their primary prey is voles, but they are willing to take anything they can subdue from a long list of mammals up to the size of hares and birds up to the size of grouse.

Hawk Owls are not modified like many other owls for auditory hunting. Their two ears are symmetrical, and they don’t have a well-developed facial disk. They must have good hearing, however, as they are occasionally seen to plunge into snow to capture a vole. With long tail and short, rounded wings, they hunt somewhat like accipiter hawks, detecting prey visually and dropping from a perch to move at high speed with rapid wing beats. Most prey is captured at fairly close range, but their distant vision is excellent.

There are other diurnal owls. Most pygmy-owls hunt during the day, small birds their primary prey. Snowy Owls and Burrowing Owls are conspicuous features of open landscapes, although both hunt at night as well. Short-eared Owls can be seen during the day, but much of their hunting is at dusk. The same is true for Great Gray Owls. Hawk Owls, conspicuous on their perches all day long, also tend to hunt more in the afternoon, so hunting in dim light seems to be hardwired in owls.

Bear in mind that owls of the Far North must be able to hunt both day and night, as the days are so long in summer, the nights so long in winter. Fortunately for them, voles are active day and night.

Like many other owls, Hawk Owls nest in natural cavities, for example at the hollow tops of broken-off snags, and holes abandoned by woodpeckers. Their clutch size varies from 3-13 eggs, with a mean of about 7. It is a large and variable clutch size, as is the case with several owl species that seem to depend on voles and lemmings for their reproductive success.

Keep your eyes peeled for the owl that acts like a hawk!

Dennis Paulson