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

THE ELEGANT DUCK

When we think of ducks, we may think of familiar white waddling barnyard Pekins, but in fact these waterfowl are among the most strikingly colored birds. Some of them are downright gorgeous. Look at a Wood Duck if you like brilliant iridescence. How about a Long-tailed Duck for a pleasing pattern of black, brown, and white? Or if swatches of pure color attract you, peruse a Cinnamon Teal. Of course it is the males you will be looking at, as females are generally brown; not that they aren’t beautiful in their own ways.

The Northern Pintail (Anas acuta), not the most brightly colored of ducks, is surely the most elegant. The long, swanlike neck of the male of this species contributes to the look of elegance, as do the long, sweeping central tail feathers. The subdued gray and white body and rich dark brown head add patrician colors to the attractive shape. Even the females, somewhat smaller than the males, have longer necks than those of other ducks.

Why the long neck? Well, dabbling ducks often feed by upending in shallow water, their tail up in the air and their head and neck submerged to sample underwater fare such as leaves, buds, and seeds of aquatic plants and a great variety of invertebrates. You can only reach so far with an average-length neck, and over time pintails just outreached the competition by evolving that long neck. By feeding in water too deep for their near relatives, they presumably were able to take advantage of resources unavailable to the others.

But it must be added that most of the feeding done by pintails is in very shallow water or on land, where they take seeds from sedges and grasses. On their wintering grounds, they are very common among the dabbling ducks that feed on marine invertebrates on mudflats as the tide goes out. The long neck also serves them well in those situations, allowing a foraging bird to reach all around it. This adaptable species is one of the most abundant ducks in western wetlands.

As in other temperate-zone ducks, pair bonds are formed in fall and early winter, and you can expect to see pintail pairs from then on until the female has laid her 5-10 eggs. Male courtship consists of ritualized displays and vocalizations, with head up, bill down, and tail up prominent components. That long, slinky tail is surely impressive at this point. Females are impressed by both the intensity of courtship displays and the constant attentiveness of the courting male. Some of the choice may also involve appearance, males with more colorful scapulars and whiter breasts preferred.

Because mortality is heavier on females than males in most ducks, there is a surplus of males in late winter and spring after all the females are paired up. In this and other dabbling ducks, it is common to see groups of males in pursuit of a single female. These pursuit flights can involve up to a dozen males – although usually just a few – and last for many minutes. They may end with a forced copulation when the female is forced down on land, or the female may “escape” only to be harassed by other males that spot her. The female may have to be mated to avoid this.

Prime pintail breeding habitat is a shallow marsh. Because such marshes are subject to disappearance during any extended drought, they come and go in the landscape, and so do pintails. During wet years, they do well, and their numbers increase. During widespread droughts, the opposite is the case. Breeding populations wax and wane and have varied from about 2 million to about 10 million birds in recent decades.

Dennis Paulson

WASHINGTON CHIPMUNKS

Mammal watching has never achieved the popularity of bird watching for at least one reason: most mammals are nocturnal. Not only are most of them small and brown, but you can’t even see them! Mammalogists survey mammals by trapping them, netting them, looking for their tracks and scat, etc. Their survey methods don’t usually include walking around with a pair of binoculars on a nice, sunny day in spring.

But there are exceptions. Some mammals are much more visible than others, primarily because they are diurnal. These include many of the large grazing and browsing hoofed mammals (ungulates), the cute pikas of western mountains, and the squirrels. The Pacific Northwest is abundantly provided with squirrels, encompassing the taxonomic range of the squirrel family: flying squirrels, tree squirrels, ground squirrels, marmots, and chipmunks.

Chipmunks come close to being birdwatchers’ mammals. They are active during the day, with an emphasis on the “active,” they are brightly marked, they are territorial, they vocalize frequently, and they come readily to bird feeders. They vary from very shy to very inquisitive, even tame where they encounter people regularly. They are still basically brown, but their conspicuous stripes make them easily recognizable as chipmunks.

These small squirrels are usually associated with rock piles and fallen logs, where they nest. They forage on the ground and in shrubs, sometimes ascending well up into the trees. Hyperactivity describes them best, as they move jerkily along with tail cocked up into the air. When disturbed, they dart into cover, appearing some distance away for another look at the disturbance.

Basically seed eaters, chipmunks will take anything that comes along, including fruits, fungi, and arthropods. They are accomplished nest robbers. taking bird eggs whenever they can find them. During the fall, they busily gather seeds in cheek pouches and cache them in their protected nests. They can then hole up for the winter and feast on these caches without leaving their protected shelter. Caches can contain tens of thousands of seeds.

Most western states have several species of chipmunks; Washington has four. The most common and widespread species in Washington is the Yellow-pine Chipmunk (Tamias amoenus), so named because it is common in the ponderosa (or yellow) pine zone east of the Cascade Mountains crest. Absent from the dense forest of the western lowlands and mid elevations in the mountains, it is again common in the subalpine-alpine zone of the Cascades and Olympics. It is easily seen by hikers in the high country and drivers through almost any of the interior national forests. It is at home in trees, ascending high into pines to forage for the seeds.

The Red-tailed Chipmunk (Tamias ruficaudus) looks about like the Yellow-pine but is slightly larger and longer tailed, and the tail is more intense reddish below. It occurs in the mountains of far northeastern Washington, in Stevens, Pend Oreille, and northern Spokane counties. Its habitat zone is the montane conifer forest and open subalpine zone above that, mostly above the elevation range of the Yellow-pine.

This species would not have been separated from the Yellow-pine but for its copulatory organ. Rodents have a bony structure in the penis called the baculum, and this structure differs among different species of chipmunks. That of the Red-tailed is distinctly longer than that of the Yellow-pine. I have not read of any structural characteristics that differentiated the females!

The largest Washington chipmunk is the Townsend’s (Tamias townsendii), restricted to the forested western lowlands and similar dense habitats up to treeline in the Olympics and Cascades. It occurs in both forested and open (e.g., clear cuts) microhabitats. It is not found in the more open ponderosa pine woodlands below the wet conifer forests on the east side. In addition to being larger and darker, not as brightly marked, it differs from all the other species in not having a clearly defined dark stripe extending from nose to eye. This and the Yellow-pine often occur together in ecotones between open alpine or ponderosa pine habitat on one side and dense conifer forest on the other. Washington Pass is one such location.

Finally, the Least Chipmunk (Tamias minimus) is restricted to sagebrush habitats in the southern part of the Columbia Basin. It is a smaller species, generally paler and grayer than the others, with the back stripes brown instead of blackish and very little reddish or brown color anywhere. It overlaps with Yellow-pine where sagebrush, grassland, and ponderosa pine come together. Least Chipmunks occur at higher densities than the other species, and one place to see this is at the Ryegrass rest stop east of Ellensburg on eastbound I-90. It is full of Least Chipmunks most of the year, gathering by the dozens at the feast of sunflower seeds put out by DOT employees.

There is also a pair of chipmunk lookalikes in Washington. The Cascade Golden-mantled Ground Squirrel (Spermophilus saturatus) is found throughout the Cascades, in both semiopen conifer forest and alpine meadows. The Golden-mantled Ground Squirrel (Spermophilus lateralis) occurs in similar habitats in the Blue Mountains and, less commonly, the mountain ranges east of the Okanogan River. Both are larger than chipmunks, with an unstriped golden-orange head. Most ground squirrels eat leaves rather than seeds, but these species are more chipmunk-like in their diet.

Dennis Paulson

DIVING BIRDS

Many kinds of birds dive for a living. Not from a diving board, but from the air or the water surface. Some of these birds fly over the water, see potential prey, and dive from the air to attempt capture. These birds are called plunge divers. Gulls plunge into the water to about their own body length and retrieve prey from near the surface. Terns, some pelicans, tropicbirds, and boobies dive from above the surface, the first three penetrating farther into the water column than the gulls do. Boobies (and their close relatives the gannets) penetrate well below the surface and actively chase fish underwater.

Many other birds dive from the water surface, including loons, grebes, cormorants, alcids (puffins and their relatives), diving-petrels, some shearwaters, coots, and many ducks. In this discussion let’s look at this group, so-called surface divers.

All diving birds have feet that are modified for swimming at the surface, and these same feet serve them well for underwater propulsion. The typical swimming foot is that of a duck, with the three forward toes joined by webs. The hind toe is much reduced. Among the diving birds, these webbed feet also characterize loons, gulls, terns, shearwaters, diving-petrels, and alcids (this last group lacks a hind toe).

A variation on this is to have the hind toe lengthened and all four toes connected by webs. This characterizes cormorants, pelicans, boobies, and tropicbirds. Finally, instead of webs, some birds have each of the toes, including the hind one, provided with large, flat lobes that are equally efficient in propelling the bird forward. Divers with lobed toes include grebes and coots.

Surface divers vary quite a bit in how they dive and how they locomote under water. Most of them just put their head down, slide under the surface, and propel themselves downward. Although the feet stroke alternately while swimming on the surface, when underwater they stroke in unison, like a pair of oars, and they are held out to either side. This must use different sets of muscles than those used for swimming on the surface. Smaller birds such as grebes, coots, and small cormorants may jump up into the air to enter the water with more momentum.

One group of birds exhibits a real variation in this theme. The alcids are wing-propelled surface divers, using their wings to swim just as if they were flying underwater. As they go below the surface, you can see their wings already open as their means of propulsion. In the guillemots, which feed on bottom fish, the feet are used along with the wings, but in murres and puffins and others that feed on midwater fish and krill, they are held behind and not used at all. The southern-hemisphere diving-petrels, related to true petrels, also use this method of propulsion, as do penguins. Not able to fly, penguins are the most highly modified birds for underwater living.

Scoters and some other sea ducks such as Long-tailed Ducks open their wings as they dive, easily seen. They may use them as diving planes underwater or may actually flap them just as alcids do. For the most part, diving birds surface just by stopping their underwater propulsion and, like a cork, popping back up to the surface. They go headfirst, the most streamlined way to go. Alcids sometimes swim actively upward and penguins always do.

Although you would think that fish are the fastest swimmers in the sea, the most amazing thing about diving birds to me is that they can swim faster than the fish, presumably a necessity if they are to catch them! Both animals streak through the water, and just like a smaller bird trying to escape from a hawk, the fish may or may not escape.

Still photos of birds swimming underwater are very hard to come by, although YouTube and other such online video sites show a variety of birds swimming underwater, very often misidentified (grebes and alcids called “ducks”). Notwithstanding these few videos, we have much to learn about how diving birds forage underwater.

Dennis Paulson