CRANES AND HERONS

Many people call the large, gray, long-necked and long-legged birds we see wading near shore “cranes.” But they are not. They are herons. The Great Blue Heron (Ardea herodias) is in the heron family (Ardeidae). It feeds by standing or slowly walking on its long legs, sighting prey, and then capturing it with a lightning-fast strike of the bill. The head is brought back and the prey swallowed, usually headfirst.

Prey that is not killed by the strike is manipulated in the bill for a time to dispatch it. Fish that have spines they can erect are thoroughly handled, so they are dead before they make the long journey down the esophagus. In some especially spiny prey species, the herons actually manage to break off the spines before they swallow the fish.

Although usually feeding in the water or at the waterside, the herons’ diet is not confined to fish. They feed on just about anything they can catch in the water, including frogs, salamanders, garter snakes, crayfish, and even large insects. They also spend much time foraging on land, especially in winter when surface fishes tend to go deeper. In the Pacific Northwest, voles are an important part of the diet, and it is commonplace to see the herons hunting in meadows and farmlands.

Foraging by herons is usually solitary, and they are quite territorial at that time, with long, sometimes noisy, chases when one gets too close to another. They also fly by themselves, but at high tides, sometimes several birds roost in the same tree or on the same sand bank, near one another. This heron is an adult, with characteristic black head plumes. Herons fly with their neck folded back. Their wings are very large, about the size of eagles that are many times their weight, and they allow the heron to fly very slowly and land in shallow water with scarcely a splash.

The other bird shown here is a true crane of the family Gruidae, quite unrelated to the herons. This Sandhill Crane (Grus canadensis) is only very rarely encountered near Puget Sound, although large numbers migrate through eastern Washington and many birds winter in the southwest corner of the state, especially in the Vancouver to Woodland area, where they can easily be seen in open fields and marshes.

Sandhill Cranes are gray, often tinged with brown, and have red naked skin on top of their head. Their long tertials (innermost flight feathers) hang over their rump and tail, giving them a quite different shape from that of a heron.

Cranes forage by walking slowly through their habitat, often a partially flooded meadow, with head forward. They watch for prey in front of them, which they grab suddenly and then swallow it. Although they eat some of the same things that herons do, for example small mammals, reptiles, and amphibians, they take very few fish and many more insects, as they forage mostly on land. Herons eat no plants, but plants feature prominently in the diet of cranes, especially grains, berries, and the tubers of aquatic plants. As they do for geese and ducks, federal and state wildlife agencies manage refuges for cranes by planting grains.

Unlike the herons, cranes are often seen in flocks, sometimes large ones. They spread out somewhat to feed but return to their flocks to roost and to fly about the countryside. In flight, their wing beats are rapid and their neck is held out straight. A distant flock might be mistaken for a flock of geese, flying in a line or vee formation.

Dennis Paulson

RUDDY DUCKS ARE ODD DUCKS

Most ducks of the North Temperate Zone mate in the winter, then the pair flies to their breeding grounds, where the female builds a nest and lays eggs. When she begins to incubate the eggs, the male deserts her, and there is no pair bond until the next fall, when the cycle begins again.

Ruddy Ducks (Oxyura jamaicensis) are quite different, and this might have been predicted, as they are the only northern ducks in which males molt in the spring into a bright breeding plumage, much as many shorebirds and passerines do. This is the rich red color that gives the species its name. The male bill, gray during winter, turns intense sky blue from structural changes.

There is no courtship or mating on the wintering grounds, but as soon as the birds arrive on their breeding grounds in spring, intense mating activity takes place. The males display actively at each other and at nearby females. The display consists of the male bumping its bill on its chest rapidly, creating bubbles in the water around it. This Bubbling Display is usually followed by a rush across the water in Display Flight, looking and sounding like a little motor boat. The loud noise accompanying the latter is made by the feet.

Male Ruddy Ducks are fiercely aggressive to one another and to other waterfowl when in mating mode. Females also can be very aggressive. Grebes and coots are not happy sharing ponds with Ruddy Ducks, and vice versa. They are not territorial, but the male stays very close to the female with which he is mated, even if only temporarily. Many males form a monogamous pair bond with a single female, some form pair bonds with a second and rarely a third female, and some appear to form no pair bonds at all, merely attempting to mate with any receptive female.

Now, about duck breeding. Most birds copulate by the male and female pressing the opening of their cloacas together, during which time sperm is transferred. But some male birds, including ducks, have a copulatory organ, the penis. This organ is not homologous to the mammalian or reptilian penis but is an erectile extension of the cloacal opening, as if a glove were turned inside out.

Ducks mate in the water, and cloacal appression might not be adequate for effective sperm transfer in the aquatic medium, so the evolution of a copulatory organ would have been an appropriate adaptation. The unequal sex ratio in ducks, with intense male competition for females, might also play a part in this adaptation. The penis is corkscrew-shaped, and the female vagina is similarly shaped in the opposite direction, so most mating attempts, especially between unmated birds in which the female does not cooperate, may be unsuccessful.

The Lake Duck (Oxyura vittata) of South America apparently has the longest penis in relation to its size of any vertebrate. It may be up to 40 cm, as long as the body. This species is closely related to the Ruddy Duck, which – as far as the present record books show – can develop a penis only about 25 cm long. A very interesting recent finding is that in a given wetland, only certain males develop the longest organs, and these are dominant to the others and the most successful breeders.

There is plenty more of interest about this odd duck. Ruddy Ducks lay the largest eggs with respect to body size of any duck, the average clutch of 7 eggs weighing about as much as the female herself. Thus the young hatch in a very precocial stage, grow quickly, and are abandoned by the female when about three weeks old, before they can fly. Speaking of flying, Ruddies are the poorest fliers among the ducks, rarely seen performing this activity. They apparently move around between wetlands and migrate entirely at night.

They are very highly adapted divers, with big feet that propel them under water, a compact body, and a long tail that may provide steering. They seem to be specialists on midge larvae, which make up the majority of their diet wherever studied. Because their prey is abundant and often evenly distributed, Ruddies can aggregate in large flocks that can find enough to eat even though there are many of them. They feed by diving to the bottom and slurping through the mud to strain out the larvae. They can feed actively for a while, fill up with midges, and then sleep, so our encouters are often with sleeping flocks.

Dennis Paulson

DUCK MATING GOES ON AND ON AND ON

It’s nowhere near spring, but believe it or not, there are many Pacific Northwest birds in the throes of intense mating behavior. Those birds are ducks. Ducks have a peculiar mating system, unique among birds. They form a strong pair bond, but it is mostly during the nonbreeding season!

Males of most temperate-zone ducks have bright, species-specific plumages, quite different from the drab plumages of females, many of which look very similar to one another. But these bright feathers are displayed from fall to early summer, and they are replaced during midsummer by a dull, female-like basic plumage (often called “eclipse” plumage). Displaying “breeding” plumage in fall, winter and spring and “nonbreeding” plumage in summer seems quite reversed from the situation in other birds, and in fact it is.

Most temperate-zone ducks are migratory, moving from breeding grounds in marshy freshwater wetlands to larger ponds and lakes and the ocean itself after breeding. Some duck species arrive on their wintering grounds while still in basic plumage, and the males molt fairly quickly into their beautiful alternate plumage. Other species, later migrants, molt farther north and arrive already in full color.

Almost as soon as the flocks arrive on their wintering grounds, the urge to mate kicks in, and the males begin to court the females. Those that arrive early wait until they have molted, but those that arrive late can begin the process immediately. Male ducks all have distinctive displays, which, coupled with their bright, species-specific colors, produce a dazzling show. Behavior involved in mating, both aggression and courtship display, is at its best in groups, with multiple individuals of both sexes.

Most male dabbling ducks have bright, contrasting markings around the head and breast and additional bright markings around their rear end. As soon as you see them display, you realize these color patterns are incorporated into the display. The displays are quite stereotyped, male Mallards, for example incorporating distinct display behaviors called Grunt-Whistle, Head-Up-Tail-Up, and Down-Up. Distinct behaviors are usually capitalized when written about in scientific literature.

Female Mallards perform head movements, bill-jabbing behavior, and characteristic vocalizations to indicate interest in copulating with a particular male. Females of most species will show aggression to males other than their mates. Copulation between pairs starts in the fall and continues through the winter into spring, when the birds return to their breeding grounds. Maintaining the pair bond seems to be the important function of this activity, which of course does not result in eggs being formed.

Displays in goldeneyes and mergansers are among the fanciest. In male goldeneyes, the head is thrown back almost onto the back, with a big splash when the feet kick back and an accompanying throaty note. In Red-breasted Mergansers, the male ends its display with tail down, back up, breast sinking into the water and neck extended upward with open beak, the whole thing reminiscent of some reptilian ancestor.

Some ducks rush along the water or fly short distances in their courtship. Buffleheads bob their heads violently up and down, fly just over the female and land by skiing on their bright pink feet, and cock both wings forward, exposing their big white patches. As part of their display, male Black Scoters also rush along the surface but with head down. A male Surf Scoter flies for 20-30 feet, wings whistling loudly, then drops feet-first into the water with wings raised. These display components are stereotyped in form and the order in which they are presented.

Because there is heavier predation on females when they are nesting, there are more male than female ducks in winter. Thus by spring there are still many unmated males. Courtship becomes even more intense, as gangs of male ducks roam around trying to find unmated females and spending much time harassing pairs to try to separate them (usually unsuccessfully). A lone female may be harassed by numerous males, and forced copulations are common at that time.

Finally, it’s time to make something of all that time spent mating. The pair heads off to wherever it is they breed, still maintaining that bond. They arrive, and the male has a fresh bunch of rivals to deter. The female quickly constructs a nest and lays her clutch of eggs, all the while shadowed by her mate. As soon as she begins to incubate, he leaves the scene and begins to hang out with other males in the same state. They typically move out into deeper water, begin their molt into basic plumage, and drop their flight feathers in preparation for growing a new set. It’s a new year in the odd annual cycle of a male duck.

Dennis Paulson

THE SNOW GEESE HAVE RETURNED

Here it is late October, and the Snow Geese (Chen caerulescens) have made their annual transhemispheric trip from Wrangel Island, off the north coast of Siberia, across the Bering Straits and down into North America. Up to 100,000 or more birds are thought to make this journey, without a doubt the largest crowd of emissaries from Russia to the United States. Forty thousand pairs are thought to breed on Wrangel Island, and they bring with them the young produced each year.

Half of these birds remain for the winter in the Fraser River and Skagit River valleys of southwestern British Columbia and northwestern Washington, the other half continuing down to major wintering grounds in southern Oregon and California’s Central Valley. Many of the birds have been banded on Wrangel Island, and they bear conspicuous numbered plastic neck collars.

This migration, of very large numbers of birds moving from restricted nesting grounds to restricted wintering grounds, is typical of geese, which seem to function best in a highly social setting. They are herbivores, grazing on grasses and forbs in open areas, and there is usually more than enough food for all. If you’re a herbivore, the world is your breakfast (lunch, dinner) table! Especially if you can eat just about any kind of herbaceous green plant.

These large groups of geese probably facilitate mating (the young birds are surrounded by potential mates) and predator awareness (how could a potential predator sneak up on such a large number of eyes and ears?). The major predator of the Skagit Valley geese is the Bald Eagle, but predation is infrequent. Eagles probably get mostly sick and infirm birds, the ones that don’t make it into the air when an eagle flies over and flushes an entire flock (which may include thousands of birds).

On the nesting grounds on Wrangel Island, Arctic Foxes take their toll. But the greatest mortality source of our Snow Geese may be from hunting on their winter grounds. Birds wounded but not killed by shot probably fall victim to eagles and possibly other predators such as Coyotes. Nevertheless, hunting is strictly regulated and has negligible effect on the goose populations.

The average clutch of Snow Geese is about four eggs. Of them, 80% reach hatchling stage, and 75% of those reach fledging. Thus each pair of adults should produce on average about two young each year. Without heavy mortality, this would lead to a population increase, and that in fact is what is happening with Snow Geese throughout most of their range, leading to conservation and management problems. The widespread availability of agricultural land in winter and the opportunity to expand to new nesting areas in the Arctic combine to enhance population growth. The Wrangel Island population is an exception, having been stable in recent years.

Many immatures are evident in the Skagit flocks, in their distinctive gray plumage. The immatures attain adultlike plumage by the time they are one year old but do not breed until they are three years of age. The birds are censused annually, and the percentage of immatures in the wintering population is an easy way to measure breeding success in the previous summer. Young birds of this population pair during their third winter, and the pair stays together until one of them dies; life span may be two decades or more.

The Snow Geese of the Skagit Valley provide one of the most spectacular of wildlife spectacles in the state. Throughout each winter, carloads of people stop in designated parking areas and watch flocks, sometimes immense flocks, of the geese feeding and flying at pointblank range. They are surely the envy of groups of hunters waiting in vain in nearby fields with their “flocks” of decoys. The birds move between feeding areas, so there are often birds in the sky coming and going.

To see a V-formation of Snow Geese approach from high in the sky, then drop toward the ground by dumping air from under the wings, some of them even briefly upside-down, furnishes a thrill for all who are watching. At the last moment of their descent, the birds extend their webbed feet and spread their tail, as if putting on the brakes, flap vigorously, and settle to the ground. Heads down, they move slowly forward, biting off grass blades as they go. Grass is planted in wildlife management areas set aside for the geese.

These flocks should be checked for the so-called blue morph, previously thought to be a different species, the “Blue Goose.” This morph is common in the central Canadian breeding populations that winter in central United States but has always been rare in the Pacific Northwest. Apparently a few such birds have found their way into the Wrangel Island population, and we see them every winter. They are easily recognized by their dark body and white head; the immatures are much darker than typical Snow Geese.

Dennis Paulson

BIRD FEEDING – SHOULD WE DO IT?

In North America, more people feed birds than ever before. The number of bird feeders is surely in the millions all across the continent. In some urban and suburban neighborhoods, it seems as if most yards have a feeder or two. However, any quick survey will show that some of them have not been recently replenished. Bird feeding has its aficionados, but not all of them are passionate about it.

So many people feed birds that a cottage industry of feeders and food types has sprung up. A trip to the nearest Wild Birds Unlimited store will make that clear. Seed feeders are among the most common, with a wide variety of seeds, especially millet and sunflower seeds. Look at the ingredients of a bag of some of the fancier seed mixes sometime to see the breadth.

Suet is another ingredient in the cuisine served in many a yard. This fat-based item has always been especially favored by birds during the low temperatures of winter, but there are now many “no-melt” types that provide food during the heat of summer as well. You can get suet now with just about anything in it, from raisins to insect parts. Suet diversity follows the evolutionary pathway common to all of our consumer items, although it’s not clear how much difference all these additives make to the birds.

Presumably most people who feed birds are sympathetic to animals and nature, and surely the majority are environmentalists. But as such, shouldn’t we be thinking about what effects we are having on the birds and the environment? What are the pros and cons of bird feeding?

It strikes me that there are really two positive aspects of bird feeding. First, we are supporting bird populations (or at least individual birds). This is probably not very important during the summer or at any time when there is plenty of natural food available. Most birds live in places that furnish sufficient food and adjust their migratory behavior to the availability of food.

But there is always the possibility of unusually hard times, when weather phenomena make food suddenly more difficult to obtain. The most obvious example of this would be a heavy snow storm, blanketing the ground and all the potential food on and in it. Think of a finch eating weed seeds or a jay digging up cached acorns. Suddenly, these resources would be unavailable, and the presence of a dependable bird feeder could make all the difference between life and death. This could be called “bird benefit.”

The other important positive aspect of bird feeding is human benefit, to bring the birds closer to us in greater numbers. Birds that come to a feeder daily are in far greater density and variety than we would see just by randomly looking out the windows of our homes. This must be a prime motivator for many people who feed birds. Of course, our gaining a better love of and understanding for birds in this way probably benefits the birds as well.

Are there negative aspects of bird feeding? The seeds that spill from feeders are avidly eaten by rats at night; some of them are out in broad daylight! For those who don’t like rats much, this is a consideration, although they are usually out of sight and mostly out of mind. Many people also consider Eastern Gray Squirrels unwelcome pests at feeders, as indicated by the great variety of “squirrel baffles” on the market.

More seriously, bird feeding does affect the birds. Feeders attract birds near houses, and occasionally a bird will be startled from a feeder and fly into a window with fatal consequences. Of course, many birds strike windows even without feeders.

Our feeders also may attract predators, from bird-eating hawks to cats, and by concentrating the prey at a feeding location, the predators may have an easier time capturing them. This is surely the case for cats. Some have even called these locations “cat feeders.” In addition, parasites and diseases are surely more easily spread when birds gather at abnormal concentrations of their food. Seed-eating siskins and grosbeaks may contract salmonella and even die at feeders during outbreaks of that disease.

Hummingbird feeders are particularly widespread; hummingbirds seem to find them readily no matter where they appear. These feeders have been responsible for dramatic changes in the winter range of some North American hummingbirds, and their presence has allowed Anna’s Hummingbirds to greatly expand their breeding range in all directions, including far to the north.

As a resident species, the Anna’s have to take the consequences of a hard freeze and a feeder-owner without the motivation or opportunity to keep the feeder thawed. Perhaps there are so many feeders that there is usually an alternate one not very far away. One consequence that has not been examined is the loss of pollination by flowers that were formerly visited by migratory hummingbirds!

Bird feeding has even become part of the tourist industry. Numerous sites in the New World tropics feature clusters of hummingbird feeders that attract hundreds of individuals of up to a dozen species of hummingbirds, providing education as well as recreation for nature-minded tourists.

In any case, there is no concrete evidence that feeding birds is either totally good or totally bad for them, so we can use our own judgment to decide. We might not put food out because we are concerned that a bird might fly into one of our windows because of the feeders. Or we might put food out just to enjoy their presence, perhaps even helping them survive a cold snap.

Dennis Paulson

DIFFERENT MOLT STRATEGIES

Most birds molt their flight feathers in a fairly straightforward way, as explained in the last blog. The feathers on each wing molt sequentially, starting with the innermost primary and usually ending with the innermost secondary. This is called sequential wing molt.

But there are two other ways to do it.

Very large birds (above about 1 kilogram in weight) that need to be able to fly at all times, for example eagles, cormorants, and herons, can retain feathers for more than one year and molt only some of them each year. The largest among these take about three years to replace all the flight feathers. This molt strategy is called stepwise wing molt.

In many large birds, you can see the different feather generations in an outspread wing because the older feathers are more worn and thus a bit paler. These differences should be evident in this Turkey Vulture wing specimen from the Slater Museum collection.

The other strategy is simultaneous wing molt. If predation is the only reason they need to be able to fly, and birds can avoid predation, they can give up flight for a period of time and drop all their flight feathers simultaneously. This is the case in anhingas, ducks and geese, loons, grebes, and larger alcids, all of which can remain in the water during this period, out of range of their potential predators. Note this group includes the very large swans and geese, which perhaps could not fly very efficiently with gaps in their wings.

The female Mallard is typical of midsummer ducks with all flight feathers missing. The Common Murre also is in full wing molt, usually obvious because the wingtips can’t be seen above the tail.

This Anhinga has dropped all of its flight feathers and most of its tail feathers simultaneously and is in the process of growing them back.

Dennis Paulson

IT'S TIME TO MOLT

All birds have a complex coat of feathers, thousands of them, which they use for insulation, display, camouflage, and flight. Look at a feather closely and you’ll see that it looks flimsy, yet it does its job very well by meshing with others of its kind. Flight feathers can hold up birds such as Trumpeter Swans that weigh in excess of 30 pounds and provide thrust and lift for continuous flight in birds on migrations that extend thousands of miles.

But these feathers, while strong, are not indestructible. Inexorably, a feather wears over its lifetime, and if a bird grew only one coat of them, eventually wear would take its toll. If not naked, a bird would look rather frazzled. Over time the feathers would lose their strength and insulating ability as the microscopic structures that hold them together wore off. Look at the same feather when about a year old, and you can easily see that wear. This Little Gull wing in the Slater Museum collection, from a one-year-old bird just molting into its second set of wing feathers, shows you how worn feathers can become before they are replaced.

The solution to this problem is the annual molt that all birds undergo. All the feathers on the body are replaced each year, usually soon after breeding, which would be in fall in our north temperate zone. Not only are the contour feathers of the body replaced, but all wing and tail feathers are replaced as well, except in the very large birds in which this isn’t energetically possible (see next blog post).

It takes a lot of physiological energy to grow a feather, so molting is a fairly slow process. A complete body molt takes as long as a month for an average songbird. Individual flight feathers take about three weeks to replace completely, so a complete wing molt may take a month or more. These constraints are very important to migratory birds, as they may not be able to migrate until they have finished growing all their flight feathers, and they molt only after breeding, with its own energetic demands, has been completed.

Wing molt is typically sequential. The innermost primary is shed, and its replacement begins to grow. Before it completes its growth, the second primary is shed and its replacement begins to grow. Etc. The molt progresses out the primaries and, at some point, begins in the secondaries, where it moves from the outermost (adjacent to the primaries) inward. This gull is in the middle of primary molt, with the two outermost feathers from the previous generation and the feather just in from those growing in. You can also see that some of the outermost secondaries have been shed.



This adult Black Turnstone shows body molt (worn brownish feathers being replaced by crisp blackish ones) and wing molt (worn brown primaries and newly grown blackish ones, with a gap where the intervening feathers have been shed and are regrowing). Most birds would look something like this in fall.

Of course, in birds that change plumage color between breeding and nonbreeding times, molt of the body feathers must occur twice each year, spring and fall. This molt is one of the most obvious ones to those of us who look carefully at birds. This juvenile Short-billed Dowitcher is just beginning its molt into its dull first-winter (much like adult) plumage; the scapular feathers are often the first to molt.

Dennis Paulson