MERGANSERS, THE TOOTHY DUCKS

Mergansers are fish-eating ducks. They are closely related to Buffleheads and goldeneyes, but because they diverged sharply from their invertebrate-eating relatives, their anatomy has diverged sharply as well. The main point of divergence is in the bill. Buffleheads have a normal duck-shaped bill, only 2-3x as long as wide.

 A merganser bill, on the other hand, may be 4x as long as wide. But more than that, the structure of the bill has changed dramatically. Duck bills have plates or lamellae, fine transverse ridges on the cutting edges that let water escape from the bill when prey is brought to the surface. In mergansers, these plates have been modified to produce a saw-toothed effect. These aren’t true teeth, lacking in birds, but they are very toothlike, analogous to the teeth of barracudas, needlefish and dolphins, other fish-catching vertebrates.

We have three kinds of mergansers in the Pacific Northwest. Two of them are in the genus Mergus, the Common Merganser (M. merganser) and Red-breasted Merganser (M. serrator). Both of them are large ducks, the Common one of our largest. Both have relatively long, slender bills the edges of which look like saw blades. These toothy bills are perfectly adapted for capturing slippery fish, and mergansers feed only on fish.

The Common breeds in rivers all over the Northwest and extends its range in winter to lakes and marine environments, especially deep channels with swift currents. The Red-breasted breeds in the Arctic and Subarctic and descends on the PNW in the winter, primarily on salt water. It is one of the common and widespread wintering ducks on Puget Sound.

Both of these mergansers move around the landscape looking for fish, especially fish in large schools that are easier to capture than the individual fish that the ducks encounter most of the time. Thus herrings and sand lance, two of our common schooling fishes, are often prey. Like other ducks, these mergansers may be in flocks.

The Red-breasted is perhaps even better adapted as a fishing duck than the Common, as its bill is a bit more slender and cylindrical. The bills of these two duck species have converged on those of other fish-eaters such as loons, grebes and cormorants, but none of the latter have the “teeth.”

The least modified and smallest of the mergansers is the Hooded (Lophodytes cucullatus). It is close enough to the goldeneyes (Bucephala) to have hybridized with both Common Goldeneye (B. clangula) and Bufflehead (B. albeola) and is considered intermediate between the goldeneyes and the other mergansers.

The bill of the Hooded is also intermediate, with the “teeth” rounded or square and nowhere nearly as impressive as in the other mergansers. The species may eat as many invertebrates as fishes, especially crustaceans such as crayfish and aquatic insects. It is much more confined to fresh water than the other two, but small numbers winter in protected bays.

All three mergansers have nesting habits like the goldeneye group. Hooded Mergansers nest in tree holes like Buffleheads and goldeneyes, Common Mergansers, much larger, need much larger crevices in trees, but like Hooded, sometimes uses old Pileated Woodpecker holes. On the other hand, Red-breasted Mergansers nest on the ground, often in the shelter of rocks or fallen trees adjacent to their preferred breeding wetlands. With their northerly breeding range, there aren’t many trees big enough for a nest hole!

Dennis Paulson

URBAN YARDS CAN BE WILDLIFE FRIENDLY

During their first lab, I used to take the students in my vertebrate zoology class at the University of Puget Sound on a walk in the urban wilds. After we had walked a few blocks, I asked them to tell me why we weren't seeing any wildlife. When someone pointed out that we just saw a squirrel, I tell them that, sadly enough, this most obvious “wild” mammal isn’t native, nor are some of the “wild” birds we had seen.

But the answer is so obvious that eventually I always got the response I wanted:  “The habitat is so different from what it was.” They didn’t know the half of it! Not only do we cut down the trees, leaving a few token conifers, but we also wipe out the shrubs and herbs that make up the diverse understory of our forests. Each of those plant species has insects living on it, and all those insects disappear with their host plants. Guess the most important prey for our small wildlife species (amphibians, lizards, many birds and small mammals). That’s right, insects.

Don’t the cultivated plants we plant in the place of those we eliminate attract their own insects? Some of them do, but most aren’t native, and the insects that eat their leaves or pollinate their flowers may not occur here. And if they do appear, the typical response to them is a liberal application of pesticides. But it’s worse—most people favor evergreen plants such as rhododendrons and junipers that produce insect-deterring chemicals in their leaves and are thus relatively pest-free. Most evergreens fall in this category. And yes, I know honey bees aren't native, but they seem important in the pollination of many flowers, as our native bees have declined.

And the final habitat constraint most of us apply is instead of letting a great variety of (admittedly weedy) herbaceous plants become established in our yards, we literally mow ‘em down. If you watch your yard, you’ll see that the rare dandelions that go to seed are immediately attractive to any seed-eating birds in the neighborhood. But how many of us sanction this sacrilegious seed set? However we view them, seeds are the primary diet for many small birds and mammals.

So my answer is “Don’t do as your neighbors do.” If you’re like most of us and don’t live on a ten-acre lot with real habitat, do your best to simulate it. Remember two important food groups, seeds and insects. Plant native trees and shrubs, especially deciduous ones, which are more attractive to insects. Plant native flowers attractive to pollinating butterflies, bees and hummingbirds. Fruits are also important foods for many birds and mammals; plant plenty of fruiting trees and shrubs.

Don’t put any kind of biocides in your yard; save the aphids!

Leave a swatch of lawn unmown. Don’t rake up all the leaves and throw them away each fall; let them stay on at least part of your yard. Several of our wintering birds forage by turning over dead leaves, which shelter seeds from the summer before as well as a multitude of small arthropods and worms. Make a brush pile in one corner of the yard; songbirds love to shelter in it. Add a pond or fountain. You’ll be amazed at the wildlife habitat you’ve made.

Dennis Paulson

PELAGIC BIRDS ARE OUT THERE

Most people have heard of albatrosses; few people have seen them. But every summer they are common offshore visitors to the Pacific Northwest. Boat trips out of Westport, Washington, and Newport, Oregon, go out 20-30 miles and can dependably find albatrosses and a host of other pelagic birds. Pelagic means “out of sight of land,” and there are a lot of pelagic birds. Because birds can fly, they roam all over the ocean’s surface in search of food.

Of course, all birds lay their eggs in nests on land or floating in freshwater wetlands, so you wouldn’t think they would wander far out in the ocean, but in fact they do. Many species fly thousands of miles when they are away from their breeding grounds for half the year or more. Black-footed Albatrosses breed in the Leeward Hawaiian Islands, but they roam to our coast, 3000 miles away, when not at home. Even more astonishing, when feeding young a Laysan Albatross may fly from the same islands up to Alaska’s Aleutian Islands, 1500 miles away, on a single multi-day foraging trip!

Sooty Shearwaters fly several tens of thousands of miles on their migrations from their breeding grounds in New Zealand to their wintering grounds in the North Pacific, taking an extended figure-8 path that has them flying counter-clockwise around the North Pacific. Meanwhile, Pink-footed Shearwaters make almost as long a flight from islands off the coast of Chile.

The Northern Fulmars that visit us, on the other hand, breed in islands in and around the Bering Sea, so they have to fly south to approach our coast. The Fork-tailed Storm-Petrels we see offshore come from much closer at hand, the string of islands that stretch along the outer coast from off Cape Flattery to off Point Grenville.

All of these birds are in the order Procellariiformes, called “tube-noses,” because of their tubular nostrils. Members of this group all take their food from on or near the ocean’s surface. Some of them skim the surface, others dive down to several meters or more. They all feed on fishes, squids, and planktonic crustaceans—the larger the bird, the larger the prey. And they all have an excellent sense of smell, which helps them find smelly prey at sea and their nest site back on their home island.

These birds are supremely adapted for flying very long distances. Their long, narrow wings are perfect gliding surfaces. With any air movement at all, the larger species surf the wind, rising into it with the lift it provides, then falling off to the side to gain speed to turn and rise up again. Watch them on a windy day to see their roller-coaster flight over the ocean. And if you’re seasick-prone, you don’t have to go out on a boat. At times in summer you can see Sooty Shearwaters from shore in astronomical numbers.

Dennis Paulson

WATCH OUT, IT STINGS—OR DOES IT?

We all know when yellowjacket season rolls around, with pesky wasps that bother us on every picnic. You can usually chase them away easily, but they come back again and again. They are relatively innocuous when you’re trying to give them the brush-off, but don’t ever disturb one of their nests in the ground!

Western yellowjackets (Vespula pensylvanica) are members of the insect order Hymenoptera, the bees and wasps. Other wasps that are common in our area are bald-faced hornets (Dolichovespula maculata), bigger and fiercer than the yellowjackets and with a big turnip-shaped paper nest up in the trees; and introduced European paper wasps (Polistes dominula), with a much smaller paper nest with chambers open below.

All these species have in common a black and yellow or black and white banded abdomen. That coloration is common in wasps and bees and is thought to be aposematic (Greek ‘away sign’), a word used to denote a warning coloration. “Don’t mess with me” is a loose translation.

Some birds, for example kingbirds, are able to take stinging insects in their stride, catching them in flight and beating them to death, even squeezing out their stinger, but a lot of animals doubtless leave them alone because they pack such a punch at the end of their abdomen. The warning coloration assures that they are safe either because the predator species has a genetic memory of them or has tried to capture one previously and was stung by it, a much more immediate memory!

As these wasps move through our environment, relatively impervious to predation, other insects have benefitted by evolving coloration, shape, and even wing sound that mimic the wasps. Most of them in our area are flies (Diptera), especially hover flies of the family Syrphidae. Here are a few of them. They look very much like the wasps as they fly around, and even seasoned entomologists often have to look closely. I for one have grabbed what I thought was a fly from an insect net and been stung for my mistake.

By mimicking stinging wasps and bees, these so-called Batesian mimics (from Henry Bates, early student of this phenomenon) gain protection from predators, mostly birds, that mistake them for their models and leave them alone. It must work very well, as there are so many kinds of flies that mimic wasps. There are also grasshoppers, beetlees, moths, and other insects that do the same, especially in the tropics, where there are so many more species of insects and so many more birds that eat them.

A study done in Illinois that involved extensive collecting of model Hymenoptera and mimic Diptera showed that the mimics are common in the spring, when adult birds are present as predators, but virtually absent during the period in midsummer when young birds are fledging. Some of them appear again in fall. The authors speculated that the mimic flight seasons were adjusted to miss the time when young, naïve birds were everywhere, birds that wouldn’t know enough not to catch them!

Dennis Paulson 

THE PACIFIC NORTHWEST IS SLUG COUNTRY

With our very wet climate (favorable for terrestrial mollusks) and our relatively acid soils (not so favorable for forming snail shells), we furnish great habitat for slugs.

The ones most of us see are garden slugs (Arion ater). This slug, native to northern Europe, comes in two forms, a black and a reddish one. Long thought to be subspecies of one another, Arion ater ater and Arion ater rufus, they have recently been split as two separate species Arion ater and Arion rufus. Unfortunately for the field worker, both of them come in a great variety of colors and can only be distinguished by dissection or molecular analysis.

So we’ll just call them all garden slugs. They have proven to be very successful imports to our region but aren’t well liked by gardeners because of their predilection for garden plants. In fact, it’s the easiest thing in the world to go online to find out how to get rid of slugs. I am choosing to extol their virtues, perhaps the most important one just to familiarize people with slugs.

Our big native slug is the banana slug, Ariolimax columbianus. After a European species that grows to a foot (30 centimeters) in length, ours is the second largest in the world, reaching lengths of 25 centimeters. Four of these in a cup would weigh a pound! Rarely are such monsters seen, though; most that we encounter are in the range of 10-15 centimeters, just a bit larger than the much more familiar garden slugs.

But walk into a mature wet forest, and if it’s a moist day, you are likely to find lots of banana slugs. They come in a variety of colors, from white to plain yellow to heavily spotted with black. There must be some genetic differences among these color types, as often all the ones you see in one spot look about the same.

The big hole on the right side of these slugs is the pneumostome (breathing hole). An active slug shows two eyestalks above that detect light or movement and two tentacles below that are chemosensitive. They have mucous glands all over the body that keep them protected from dehydration and that can lay down a trail for easier locomotion.

Most slugs are herbivorous, feeding directly on plant tissue (garden slugs) or on detritus and mushrooms (banana slug). The leopard slug (Limax maximus), a large pale brown, black-spotted species that is also introduced in our region, feeds on other slugs as well as detritus and garden plants. In turn, garter snakes and ducks eat a lot of slugs, apparently able to combat the mucous that protects them from many other predators.

Slugs are hermaphrodites, both sexes present in the same animal, and when they mate each one contributes sperm to the other. The lack of separate sexes may make sense in slow-moving animals that might have trouble finding a mate. In this case, every slug encountered would be a potential mate, not every other one!

Dennis Paulson