Saturday, December 19, 2009

5,000+ bullfrogs dying in desert potholes

At Potholes Reservoir, Grant Co, Washington I discovered a rather dramatic scene of thousands of bullfrog tadpoles that were trapped in drying mud holes on 29 Aug 2009 (Photo 1). The small mud hole at the top right was about 3 ft and the larger in the middle of the picture about 12 ft in diameter. The larger contained approx 5,000 bullfrog tadpoles based on counts of a few subsamples; most were dead. The two mud holes in the photo had water about 4” deep a week prior to the photo and the surface quivered with wriggling tadpoles when approached. 

Typically bullfrog tadpoles in the Northwest remain in ponds for at least one winter and grow to a total length of about 130 mm+ before morphing into froglets. Most of the tadpoles had small to medium size hind legs and were less than 110 mm in total length, which is the lower extreme of the size when bullfrog tadpoles could morph (Photo 2). Under normal conditions with plenty of food and no crowding, the tadpoles in the picture would be about one year old, but if food limited or crowded, they could be two years old. Although most were not ready to morph, a few had started the process and were hopping away from the drying mud holes. The closest pond was 100 ft away, but with the heat and predators, their chances were not good (Photo 3 and 4). The mud recorded tracks of great blue herons, great egrets, killdeer or yellowlegs, coyotes and black-billed magpies (Photo 5). Yellowlegs have small mouths, but eat the tadpoles by vigorous shaking the tadpoles to pieces.

The dead and dying tadpoles illustrate one limit to this invasive species’ success – they can’t survive in ephemeral ponds. Although the area is flooded as the level of the reservoir rises during winter and spring, as the water level drops through the summer, they move to deeper water. The mud holes were at a low spot so presumably the tadpoles moved to the deeper water as the water level dropped through the summer, but they moved to the wrong pond and were cut off.

Bullfrogs have recently expanded into the main reservoir and are now extremely common in Crab Creek beaver ponds and in ponds near Job Corp Dike, which is at the NW corner of the reservoir. There were none in 2002, but tadpoles starting showing up in traps in 2006, and 2009 was the first year I observed adult and juveniles widespread throughout the region. One 12 m dia pond at the Job Corps Dike had over 100 frog heads visible as they floated on the surface waiting for a prey object to venture near (Photo 6). There were none at Dodson Road/Winchester Wasteway (10 mi to the west) or at I-road/Frenchman Hills Wasteway (16 mi WSW). They were recorded in lower Crab Creek, south of O’Sullivan Dam, prior to 2005 (WA Gap analysis). The species was introduced into Washington from east North American in the 1920-30’s for food, sport and for pond features and have since spread throughout lower Puget Sound and the Columbia basin and are slowly spreading into new regions such as Potholes Reservoir.

It is generally assumed that the bullfrogs are harmful to native species. But at Potholes Reservoir, they are simply joining other introduced species in the reservoir such as large and smallmouth bass, yellow perch, pumpkinseed, and bluegill that I caught on the same trip (Photo 7). Additional introduction include are catfish, carp, crappie, and rainbow trout. In prior years, I found Pacific Chorus Frogs common around the beaver ponds and leopard frogs rare, but always present. I found neither of these species in 2009 searches, and it is possible they were supplanted or eaten by more common bullfrogs.

I happen to like bullfrogs and felt for the little guys as they struggled to survive, but that’s life in the desert. They were all turned into tadpole jerky by the sun and are now in December probably providing coyotes and magpies with snacks.

Gary Shugart

Friday, November 20, 2009


Next time you’re at the water, whether salt or fresh, watch for a ducklike bird with a gray body, darker head and neck, and white, chickenlike bill. You’re seeing an American Coot (Fulica americana). Coots are often thought to be waterfowl (i.e., a duck), but they are not. They are in the rail family, in the same avian order as cranes. These birds are only distantly related to waterfowl.

Coots are nonetheless interesting, even though they’re not ducks. They are rails that look like ducks because, over evolutionary time, they have come out of the marshes where rails are common and have become adapted morphologically and behaviorally for living a duck’s life. They swim like a duck and dive like a duck, but admittedly they don’t quack like a duck! The chickenlike bill is quite different from that of a duck. Ducks have sieve-like lamellae on the edges of their bill to allow a sort of filter-feeding, while coots just grab their prey items and swallow them.

To be able to swim well, coots have evolved lobed toes, much like those of grebes. Gallinules and moorhens, which are also rails and look much like coots, haven’t evolved the lobes, and they are rather intermediate between rails and coots, able to swim with their long toes even though they aren’t webbed or even lobed. Coots forage at the surface, dip below it somewhat as ducks do, and dive underwater in deeper water. They don't stay down very long, popping up like a cork after a brief visit to the nearest vegetation.

Coots breed locally in the Puget Sound area but more commonly in the dry interior, where they are on most freshwater wetlands. They prefer ponds and lakes with both dense marsh vegetation, from which they get material to construct their nests, and plenty of open water, where they feed. They migrate to larger lakes in the winter, where they form flocks, sometimes large ones. Poor fliers, they migrate at night, probably to avoid predation by bird-eating hawks.

Coots are much more tied to a herbivorous diet than are rails. Their principal foods in fresh water are pondweeds, algae, sedges, and grasses, although a wide variety of other plants are taken. Filamentous submergent plants seem to be favored overall. They also eat small numbers of freshwater invertebrates, especially in the breeding season. The young are fed almost entirely on animal matter. When seen in small numbers on salt water, they may be utilizing green algae such as sea lettuce.

Coots also leave the water to graze on land, and they are commonly seen doing so adjacent to city park lakes. They retain some of their rail heritage in being better walkers than ducks, and when disturbed, they can run over land. They are much less well adapted to flight than ducks are, and they have to make long take-off runs to get off the water, and then fly awkwardly. When Bald Eagles harass them, they cannot escape by flying, and a pair of eagles can tire out a diving coot fairly quickly and then share the meal.

Coots are feisty birds, very territorial in breeding season and inclined to chase just about any other birds of their own or other species away from their nesting areas. They display with both their white bill and white undertail coverts, then they may fight fiercely, locking feet and pecking each other. They do manage to get along with their mates, and they make big, sloppy floating nests out of marsh vegetation. They lay a lot of eggs, a typical clutch size being around 7 but often up to 10 or more. The young are semiprecocial, able to get around on their own but still having to be fed by the adults. They are strikingly colored in comparison with the drab adults.

Dennis Paulson

Tuesday, October 20, 2009

it's waterfowl time

Fall is the time when thousands of waterfowl (ducks, geese, and swans) move into the Pacific Northwest from farther north and east. Vast numbers of these birds breed in Alaskan and Canadian wetlands, far enough north that these wetlands freeze each winter, and the birds move ever southward as their habitats freeze from north to south.

The first to come in are the dabbling ducks of interior marshes. Flocks of Northern Pintails, American Wigeons, Green-winged Teals, and others begin to arrive in late August. When they come, they all look like females, the males still in the eclipse plumage that camouflages them while they molt all their flight feathers on the breeding grounds. But by October many of these males are in their distinctive and showy breeding plumage, which they wear through the winter and into the next summer.

Meanwhile, large numbers of scoters have been appearing at Northwest coastal locations, where they undergo the same flight-feather molt that the dabbling ducks undertook on their breeding grounds. Many of them remain for the winter in the same areas, even north to Alaska, as marine environments are more resistant to freezing. In October, many of the diving ducks that have completed their molt in northern waters arrive. These birds feed in deeper water, and deeper water bodies freeze more slowly than shallow ones, so they can remain longer at high latitudes. This group includes scaups and Canvasbacks and their relatives, as well as many more scoters.

Migratory goose flocks, which begin to appear in late September, peak in October. They include Snow Geese from Siberia and Canada, Cackling and Greater White-fronted Geese from arctic and subarctic latitudes in Alaska and western Canada. These birds, in their V-formations and lines, are the most impressive migrants, but duck flocks, especially on the outer coast, can be impressive as well.

Finally, in November the last of the diving ducks begin to appear, including Buffleheads, goldeneyes, and mergansers. These birds stay as far north as they can as long as they can, but eventually they are driven out by the freezing of the larger lakes. By this time Trumpeter Swans from southern Alaska and Tundra Swans from farther north have appeared on our wetlands.

Many waterfowl continue their migrations beyond the Northwest, but so many of them stay here through the winter that this is close to the best, if not the best, region on the continent for ducks, geese, and swans. It’s time to go out and see for yourself.

Dennis Paulson

Tuesday, October 6, 2009

mammal watching can be fun

Many of us are birdwatchers (or birders, is there a difference?), but not so many are mammal watchers (mammalers?). But mammal watching can be fun too. There are only about half as many species of mammals as there are of birds, so there aren't as many to watch, but—of great significance—the vast majority are brown, so they don't attract the attention of those who love to see the varied colors presented by birds. Many birds are conspicuously, even rainbowly, colored. So the mammals have one strike against them (of course, we're one of them, surely a strike for them).

Perhaps of even greater significance is the fact that most mammals are nocturnal, and most of us do our nature study during the day, when we can see what's going on. Mammalogists know that if they want to have a lot of encounters with mammals, they go out at night. And they have to resort to a whole array of technology, from flashlights to mist nets (for bats) to sunken cans (shrews and mice fall in them) to live traps (especially for rodents).

Nevertheless, there are mammals that can be seen during the day. This includes all marine mammals, most ungulates (hoofed mammals), and some rabbits and rodents (especially squirrels). A trip to a big national park, where they are protected, may tally a surprising number of mammal species.

We found a few of these mammals, totaling seven species, on an early October trip to the Washington coast. Among them was a small herd of Elk consisting of a finely antlered male and two cows and their half-grown calves. Elk seem to be increasing in the Pacific Northwest, both the Roosevelt Elk subspecies on the coast and the Rocky Mountain Elk of the Cascades and East. There are small herds of Elk all over the southwest corner of the state, often visible in late afternoon as they come out of the forest to graze on herbaceous vegetation in prairies and second growth.
Of marine mammals, we saw quite a few Harbor Seals and California Sea Lions at the mouth of the Columbia River and the mouth of Grays Harbor. One big male sea lion was sleeping on a floating dock in the harbor at Westport, quite unconcerned with fishermen, crabbers, and tourists walking past about 20 feet away. As we watched, it had a good scratch, much like you'll see your pet dog or cat doing. From a population low some years ago, California Sea Lions have become more and more common, and the people who work in the harbor at Westport have become concerned as more and more of the big (and dangerous) mammals pre-empt parts of the docks.
Of rodents we saw numerous Douglas Squirrels, the common native squirrel in western Washington forests. Of lagomorphs (the rabbit order), we were enthralled by a baby Snowshoe Hare that grazed on weeds at the edge of the road in Leadbetter Point State Park. Unlike many of its species, this little gem sat there and fed calmly as we approached closer and closer with our cameras. It's a great feeling to get to photograph any wild mammal at leisure!

It's always special to see carnivores, and we saw two of the more common species of Washington. We watched a Coyote come out of the bushes at Leadbetter Point, trot over to the shore of the salt marsh, and lie down right at the water's edge. It was engaged in grooming rather than hunting, although it seemed to us that it was looking intently at a nearby foraging Great Blue Heron.

Finally, there is a nice viewing platform on the rocks in Westport where you can look out over the harbor with a scope and take in the bustling avian activity. Local people put out food and water for a crowd of feral cats there, and I wonder if they know they are feeding native carnivores as well. A Raccoon came out of the rocks as we watched and meticulously cleaned up a pile of cat chow, then finished with a drink from the water bowl and ambled back into the rocks. Not a bad day for furry encounters.

Dennis Paulson

Wednesday, September 30, 2009

Mother Nature's art gallery

Among the many signs of seasonality, one of the most spectacular is the display of beautifully colored leaves that tells us that the season must be autumn. This painting spree by Mother Nature lasts for one or two months and then is gone. When a child asks why the leaves change color in the fall, the question ranks right up there with "why is the sky blue?" It's one of those things of the world around us that we accept without questioning, unless we're a child or a scientist set on finding the answer.
Botanists have figured out how this works. As the days become shorter, plants with deciduous leaves stop producing the green pigment chlorophyll, and the chlorophyll already present in the leaves begins to break down. Carotenoids that have been present as insoluble pigments in the plant's chloroplasts are then exposed as the bright yellows that we see in cottonwoods and aspens and bigleaf maples.

The brilliant reds are produced quite differently. The autumn drop in temperature reduces the transport of sugars out of the leaves, and in some trees the excess sugar is used to synthesize anthocyanins, the same pigments found in red flowers. This happens in our vine maples, our blueberries, and our mountain ashes, among others. A combination of anthocyanins and carotenoids produces the range of colors that we see in many species.

Even knowing the "how," have we answered the "why?" Is there any advantage to a plant in having these colors in its leaves in the fall? That question remains to be answered. Perhaps this particular phenomenon has no adaptive significance. But perhaps it does!

Autumn is a time during which nature can be enjoyed at a distance; just look at forests or tree groves or individual trees in a park. In New England, the whole world changes color. In the Pacific Northwest, the brilliant reds and yellows of the deciduous trees are scattered through landscapes of evergreen conifers.

The color change is very different in different groups of plants. Red alders are prominent in our Northwest forests, but they contribute nothing to the fall extravaganza, the leaves merely turning brown and then dropping from the tree. This leaves many of our westside forests rather dull except for bright spots of red vine maples and yellow cottonwoods. For total immersion in autumn colors, a resident of the Puget Sound area should head into and east of the Cascades.

Dennis Paulson

Thursday, September 24, 2009

Winter hummers

It's late September. Got a hummingbird in your yard?

Most people think of hummingbirds as tropical, and indeed most of them are. But a fair number of species have moved quite far north into the United States (including Alaska!) and Canada since the last glaciers receded. The Southwest has a great diversity of species, as many as 15 species breeding north of the Mexican border. But many of the border species migrate south for the winter, and all that occur north of the border region are migrants to Mexico and beyond, except one—Anna’s Hummingbird (Calypte anna).

This species was historically resident in southern and central California and northern Baja California, areas that remained warm enough in winter that the birds could remain through the cold season and find enough insects and winter-blooming flowers to sustain them. But that was then, and this is now. Over a half century ago, people discovered they could attract hummers to their yard by hanging out special feeders filled with sugar water, typically one part sugar dissolved in four parts water. It worked like a charm. People feed hummers all over North America now, and birders gather to watch these birds at southern localities with dozens of feeders and, sometimes, hundreds of hummers. These sites are especially rich during fall migration, as hummingbirds are streaming south through the western states on their way to Mexico.

All species may have benefited from the existence of these feeders, but none more than Anna’s. This species has extended its breeding range all the way north to southern British Columbia and east to the Arizona-New Mexico border, with occasional breeding attempts even outside this range. Nonbreeders have wandered east as far as Minnesota and Florida and north to southern Alaska.

Several other species of hummingbirds (Black-chinned, Rufous, Calliope) nest widely in the Pacific Northwest, but all except Anna’s leave in late summer and head for Mexico, not to return until the following spring. Anna’s is supremely adapted to live with people, taking advantage of nonnative plantings and feeders in a way the other species have not been able to do, and this has allowed it to overwinter in regions apparently too cold and/or food-free for the other species. All hummingbirds go into torpor during low temperatures at night, so why can’t the other species take advantage of feeders that are provided throughout the winter? Perhaps the fact that Anna’s was resident in the first place, with no genes for migratory behavior, allowed it to be perfectly adapted to take advantage of the changes we make in the natural world.

Dennis Paulson

Tuesday, September 22, 2009

it's sparrow time!

It’s September, and the days are getting shorter at great speed. Today is the first day of fall, notwithstanding that the temperatures will be in the 80s in the Puget Sound area. Bird migration has been in full swing for almost three months, and most of the insect-eating birds have moved on southward. But the sparrows are still passing through at this time, some heading as far south as Mexico, others intending to hang around our area.

Why are there so many sparrows? Simple answer is that they eat the small seeds of small plants, and there are an awful lot of small plants out there. The seeds of many herbaceous plants are formed during the summer or fall, then hang around at or near ground level before sprouting into young plants the following spring. Before that happens, however, there is a whole winter of predation ahead of them and a whole array of predators lurking to pounce on an unsuspecting seed.

Insects eat the seeds, chipmunks and mice eat the seeds, and birds eat the seeds. Predominant among the birds are our native sparrows. Song Sparrows are probably the most common, but there are lots of wintering White-crowned, Golden-crowned, and Fox Sparrows as well, with smaller numbers of American Tree, Savannah, and Lincoln’s Sparrows.

Although not sharing the name, Dark-eyed Juncos and Spotted Towhees are common wintering birds also closely related to the native sparrows. In fact, all of them are closely related to the Old World buntings, and we should have called them buntings when common names were coined for them several hundred years ago. But we didn’t. Instead, we co-opted the name of an unrelated European seed-eating bird, the House Sparrow.

As all of these small birds eat small seeds, how do they avoid intense competition with one another? Turns out that each sparrow species has its own habitat preference, which means they’re not all feeding in the same place. Savannah Sparrows like open country and live and feed happily among grasses. American Tree, Golden-crowned, and White-crowned Sparrows like to feed in the open but need dense shrubbery to retreat into when threatened or spending the night. Song, Fox, and Lincoln’s Sparrows prefer dense shrubbery all the time, although they will often come out to the edge where they can be seen by birdwatchers.

Many of us—in fact, hundreds or thousands of us—feed these birds, putting out millet and mixed bird seed on the ground or in feeders, and they respond readily. If you’re lucky, you might have most or all of these species at your feeder if you live in the suburbs with good plant cover around your house. Watch them with binoculars to see how quickly and efficiently they crack and eat those seeds.

Dennis Paulson

Monday, September 21, 2009

Scoter wrecks and risky molt strategies

The scoter wreck or strandings on the outer Washington coast at Kalaloch and La Push has received attention in the media and birding email. I spent 16 Sept 2009 surveying beaches and collecting specimens for the museum. I visited six beaches and encountered 166 beached birds including 83 Surf and 65 White-winged Scoters (see TABLE) (Photos 1-3). Unreported in media and related information was that all the scoters were in wing molt. This realization first hit me while standing in the dawn drizzle with crashing surf and a line of dead scoters visible along the beach in the dim light. Since then I’ve been mulling over the question, why were the scoters attempting to molt on the open coast?

Molt in scoters and many seabirds is a simultaneous molt. All flight feathers are lost and grown in a 3-4 week period. Unlike sequential molt, which allows birds to retain the ability to fly, birds are flightless during simultaneous molt. Body molt is also ongoing, resulting in lessening of the protective cover afforded by the body feathers, which can lead to loss of buoyancy and hypothermia. Molt timing and strategies evolve so that birds minimize risks during the period when flightless. Presumably molt staging areas are located in protected areas with plentiful food. However, on the outer coast it would seem that flightless birds would be continually hammered by the crashing surf and rocks in the shallow water they need for feeding. The protected waters of Puget Sound or Straits of Georgia would seem to be safer molting areas. From what I gather, there are few baseline data regarding the distribution of migrating scoters for the outer Washington coast, so it is unclear if the beached birds were indicators of an unknown staging area used for molt during migration, or if their presence was an anomaly, perhaps related to ENSO (El Nino/Southern Oscillation) that is developing in the Pacific.

A few known facts about scoter migration come from Birds of North America accounts. Molting areas are known for the coasts from Alaska south to BC. After females lay eggs, male scoters start moving to molting areas followed by females after scoterlings fledge. Juveniles are last to migrate and appear to skip molting areas and do not undergo wing molt. Notably, the beached birds were mostly adult males and there was only one juvenile. Using molts scores, I will be able to estimate the onset and completion of molt for this group which will provide significant data regarding timing of molt. In addition all the dead birds appeared to be emaciated, which can be confirmed from examination of salvaged specimens.

Based on existing distributional data, it appears the birds were too far south, but perhaps they have just been missed because of insufficient surveys. Reportedly there was a combination of high surf, tides and wind over Labor Day weekend and beached birds started showing up two days later with peak numbers 3-4 days after Labor Day. The scoters might be doing a normal molt migration, but were trapped by the storm and forced ashore. It is also possible that ENSO has altered the ocean conditions or currents. Birds might have started molt at the normal time and place, but because of altered currents, they did not follow normal routes. The general consensus is that feeding is necessary during molt because molt is energetically costly. Perhaps they arrived in poor condition with insufficient reserves to make it through the molt, and their condition was exacerbated by the Labor Day Storm.

Another factor that could have caused mortality and is being tested is that an algae bloom resulted in a red tide and paralytic shellfish poisoning (PSP) which could kill birds outright. Indirect mortality can also result. The dinoflagellates associated with red tide can also produce a compound that is whipped into a foamy surfactant (soap) by the surf. This foam washes protective oil from feathers leading to loss of buoyancy and hypothermia, and birds come ashore as they attempt to cope. That latter mechanism, discovered in 2007, was the cause of stranding and mortality in Monterey Bay, California. However, I found none of the signs of surfactant-mediated mortality that were detailed in the original paper. There are many factors that could have contributed to the wreck, and my speculation highlights how little we know about some of the common bird species in the Northwest.

Gary Shugart

Thursday, September 17, 2009

where have all the birds gone?

I have perceived a lack of songbirds lately, and you probably have also. Not only did birds stop singing at the end of their breeding season, but most of them departed for parts unknown.

Where do these multitudes of birds go? You have to answer this question for each species, as each species has its own unique distribution. But we don't know where each individual goes, and when a Barn Swallow flies by me, I fantasize about it carrying a little flag that says "on the way to Bolivia." The great mobility of birds has long been recognized as one of the most characteristic things about them, and they use this mobility to good avail in their annual migrations.

By migrating north in spring, birds that have wintered in the tropics can take advantage of a seasonal flush of food resources, avoid competition with the great diversity of resident species, and get away from the nest predators—among others ants, snakes, kinkajous, and toucans—that are so common in the tropics. When winter comes at our high latitude, and insects and other primary sources of food are no longer available, they return whence they came.

Some of our breeders, for example Varied Thrushes that dig insects from the forest litter and Dark-eyed Juncos that subsist on weed seeds, may winter in the Washington lowlands, just downslope from where they bred. Seed-eating birds such as finches and sparrows often winter quite far north, as there is an abundance of seeds—the plant's dormant stage—at that season. So our backyard winter avifauna features seed-eaters, and many of our breeding sparrows winter not far away, in California and the Southwest.

But the majority of our small birds are insect-eaters. These birds—the thrushes, sparrows, vireos, warblers, tanagers, flycatchers, and swallows—head for warmer climes.
Many birds glean caterpillars and other insects from leaves. Leaf-eating insects become inactive at low temperatures, and leaf-gleaning birds can't find enough food to keep their metabolic furnaces stoked, so off they go. Most of our vireos and warblers winter in western Mexico and northern Central America, as do Western Tanagers, Black-headed Grosbeaks, and Bullock's Orioles.

Flying insects are even less likely to be active during winter, as they need real warmth to be able to fly. So those birds that eat flying insects can't make a living anywhere near these parts, and many of them are long-distance migrants. Western Wood-Pewees and Olive-sided Flycatchers head for the mountains of Central America, Bank and Cliff swallows and Eastern Kingbirds to the Amazon Basin, and Barn Swallows rarely make it all the way to Tierra del Fuego. These are long flights, but ones quite possible to long-winged birds such as swallows.

They’re gone but not forgotten, and they will return. Of course they leave behind many resident birds such as chickadees, jays, woodpeckers, and others, but that's another story.

Dennis Paulson

Wednesday, September 16, 2009

why poisonous fruits?

This is the time of year in the Pacific Northwest when many wild fruits are evident, their conspicuous colors standing out against the green landscape. Most of them are eaten by birds, but some of them are toxic to humans, for example, red elderberry (Sambucus racemosa), red baneberry (Actaea rubra), and deadly nightshade (Solanum dulcamara). Why can birds eat these fruits and we (and often other mammals) can’t?

Here we have to deviate from known facts and move into the speculative realm. In other words, we know what but we don't know why. But this is a subject about which I have speculated for many years, since I was first told about a poisonous blueberry (Pernettya) in the mountains of Costa Rica.
We all know that bright fruits are intended to attract and be eaten by birds, their seeds defecated out at some other time and place. This is the way these plants get their seeds dispersed.
It would seem that it is in a plant's best interest to have its seeds dispersed at some distance from the parent plant to avoid competition with it for light, water, and nutrients. Thus birds, with their great mobility, should make excellent seed dispersers. Mammals are just as fond of fruits as birds are, but they are not so mobile and are probably less effective at dispersing seeds. Therefore, we might expect some plants to evolve mechanisms to discourage mammals while at the same time encouraging birds.

I consider this a likely explanation of the many kinds of fruits that are eaten by birds but poisonous to some or all mammals (including humans). Birds and mammals have a long independent evolution, and it would not be surprising to find compounds that were toxic to one group but not the other.

I am inclined to extend this reasoning to account for two other types of plant adaptations. Many plants produce skin-contact poisons, and all the ones I know about produce edible fruits and bird-dispersed seeds. Poison ivy is a good local example. This might also be an adaptation to keep mammals away from their fruits.

Finally, think of all the spiny shrubs that produce edible berries, for example blackberries and roses and gooseberries. Might this not be still another way to keep those hungry mammals away? The common wisdom is that spines protect the leaves from potential herbivores, but why not question the common wisdom? Remember, a mammal has to climb into a plant, while a bird can fly in and out without a scratch.

The only data I know of to support this hypothesis comes from a study of chili peppers (Capsicum) in the Southwest conducted by Don Norman, Seattle ornithologist and toxicologist. Mammals shunned the fruits while birds ate them avidly (perhaps birds always eat avidly). There is much more material here for PhD dissertations. The fact that the poisonous baneberry produces both bright red and white berries is surely a fascinating natural-history story of its own. And why does red elderberry have a black-fruited subspecies at high elevations in the Northwest?

Dennis Paulson

feeding birds

People often ask me whether feeding birds is good or bad. Perhaps it’s both. I feed birds because I love to have them in my yard, not because I think I’m doing them a great favor. In the lowlands of the western part of the Pacific Northwest, perhaps the only time we really aid birds by feeding them is when snow covers the ground, making it difficult for some species to find food. That’s when I see species at my feeders that I didn’t even know were in the neighborhood. Varied Thrushes and Fox Sparrows are two good examples.

Normally, natural selection eliminates the least capable individuals from a population during hard times, and by our feeding them this winnowing may not take place. It may even boil down to helping individual birds to the detriment of the gene pool of their species. So when we make bird populations increasingly dependent on our handouts, we may be obliged to continue feeding them. Birds that normally winter in the tropics may take up residence at a feeder in the fall and not migrate south; they will probably be in trouble if the feeding is discontinued. Many birds (for example, Anna’s Hummingbird in the PNW) have probably expanded their winter range because of dependable bird feeding.

However, there is also a downside to bird feeding. Cats haunt the shrubbery and accipiter hawks visit from time to time; birds kill themselves against windows; and disease spreads readily at feeders. All of these sources of mortality are there without feeding, but the concentration of birds at feeders exacerbates them.
And then there is our subsidy of introduced species. I live next to a green belt in Seattle, with a nice variety of birds, but starlings often dominate the suet in summer and House Sparrows the seed feeders all year until a recent and surprising decline in both species in my neighborhood (lack of nest sites?). 

When Rock Pigeons visit, all too frequently, they easily displace native Band-tailed Pigeons. Millet feeders attract cowbirds, which parasitize native passerines, although cowbirds have also declined dramatically in Seattle. And don’t forget the gray squirrels and rats that compete with the birds (and eat their eggs). I don’t know any way to avoid this when feeding birds.

The feeding of waterfowl at parks is even worse, leading to the proliferation of semidomestic ducks and geese, as well as pigeons and sparrows. Diseases transmitted by these birds will of course infect wild populations. Birds of the native species are quite able to find their own food, but some of them become virtual beggars, a far cry from the traits for which we admire them!

It sounds as if I’m arguing against it, but in fact bird feeding at our homes is probably benign for most birds and furnishes much pleasure, as well as personal education, for us. There is also greater knowledge of the birds when their occurrence is recorded on Cornell University’s FeederWatch ( or  ebird ( In any case, the real favor I think we can do for birds is to fill our yards with plants that attract insects (just the opposite of the gardener’s strategy), bear edible fruit and bird-pollinated flowers, and/or furnish good nest sites. And lay off the pesticides.

Dennis Paulson

Tuesday, September 8, 2009

green darner, Washington state insect

Most states don’t have state insects, and most people in Washington state don’t know about our very own state insect! Do you know what it is? You probably do by now, having seen all the photos, but you may not know its name. It’s the Common Green Darner, Anax junius. This species is a member of the family Aeshnidae, suborder Anisoptera, order Odonata. This insect order contains the dragonflies and damselflies.

In 1997, a group of students at Crestwood Elementary School in Kent brought the idea of a state insect to the legislature. About 25,000 students from over 100 school districts statewide were asked to pick a state insect from among several contenders, and the dragonfly won in a landslide.

Male Common Green Darners are easily recognized by their green thorax and mostly blue abdomen. Females are similar, but the abdomen is usually greenish (rarely blue). Common Green Darners are the only North American darner in which the pair stays connected after mating and flies around in tandem while looking for places to oviposit.

Common Green Darners are among the best-studied of North American dragonflies. They occur all across North America, breeding in ponds and lakes from southern Canada to southern Mexico, as well as in Hawaii. They are known to be highly migratory throughout their North American range. Mature adults arrive rather early in spring at the north end of their range, often the first dragonflies to be seen in flight each year. They breed and lay eggs as long as they live, then die after a few weeks. Their eggs hatch and their larvae develop in the water through the summer.

In Washington, as elsewhere in the North, the larvae have grown rapidly in the warm-water environment and are ready to emerge from the water in August. There is usually a hiatus in summer where not many are seen, but then immature individuals, colored like adults but with a reddish-violet abdomen, become common. After their emergence, you can see their exuviae (cast skins) along the edges of wetlands everywhere.

The immature Anax very soon begin to head south. Obvious migratory movements are rarely seen in Washington, but farther south in California, Common Green Darners can be everywhere in fall. They move through the landscape in numbers, steadily heading south.

If you wander through Florida or southern Texas in September and October, Common Green Darners are ubiquitous. These are end points in the long migration, and by the time the migrants reach these lower latitudes, they have attained sexual maturity and are ready to breed. They do so, and – to make a long story short – their larvae mature through the tropical winter and are ready to emerge in spring. These spring emergers then head north to repeat the annual cycle.

So in this dragonfly, there are two alternating generations, one that emerges in fall in the north and flies south, another that emerges in spring in the south and flies north. Thus this species shows an amazing and unique migration pattern, unlike that of any other animal. At first glance, it seems something like the migration of Monarch butterflies, but it is actually somewhat different.

In Monarchs, northern adults that emerge from their chrysalis in the fall head south and winter in southern Mexico. These same individuals begin a northward migration the next spring, so in that way their migration is more like those of birds. But they stop and breed somewhere in southern US, then their offspring continue northward and do it again. There may be three generations of northbound migrants, then, as they emerge from their pupae late in the summer, the offspring of the northernmost breeders head south instead. There are indeed similarities to the darners in that more than one generation is involved in the annual cycle, and the northernmost breeding populations have a northbound and a southbound generation.

But it turns out that the darners have been varied in the evolution of their annual cycles. Larvae growing rapidly through the summer in Washington emerge in fall to fly south, seemingly the most common mode, while those growing more slowly are forced to overwinter as large larvae and emerge the next spring. Thus there is also a “resident” population of individuals with a life cycle more like other dragonflies, that is they fly during the summer and their larvae develop during the winter. It was hypothesized that these two populations might even show genetic differences because they didn't interbreed. However, recent studies have shown that the migratory and resident populations are genetically identical.

With global warming, the summer growing season should lengthen, possibly causing further variation in the life cycle of this interesting species.

Dennis Paulson

Tuesday, September 1, 2009

Dragonflies in autumn

Dragonflies are insects that love warmth, so the adults fly through the spring, summer, and fall and disappear in winter, overwintering in the larval stage in the water or as eggs in the case of a few species. The best month in which to see dragonflies in the Pacific Northwest is July, when the spring species are still around, summer species are in full swing, and the first of the fall species are appearing. By the end of August, when these photos were taken, the spring species are gone, the summer species are waning, and fall species dominate.

Certain groups are especially common in fall. The big blue darners (Aeshna) peak in August and September, when we see them in numbers at just about any wetland. The males are looking for females, and they alternate flying along the shore and hovering in one spot, occasionally dipping down into the aquatic vegetation to see if they can spot an ovipositing (egg-laying) female. When two males intersect, there may be a fierce chase. When a female is spotted, the male grabs her and mating takes place, usually up in the trees and often lasting an hour or more. The female will soon make her way back to the water and lay her eggs in plant stems or rotten wood.

Another common group in the fall are the meadowhawks (Sympetrum), members of the skimmer family (Libellulidae). These little dragonflies, most of them red, fly in numbers around just about all lentic wetlands. (Lentic = still, such as ponds and lakes; lotic = flowing, such as streams and rivers.) One species, the Cardinal Meadowhawk (Sympetrum illotum), flies throughout the summer and can be recognized by its very bright red color and orange-suffused wings with a dark streak at the base. This species breeds in permanent ponds and lakes, and a larva, after hatching from the egg, develops over the summer, goes into dormancy in the winter, then emerges as an adult the following spring. If it develops especially rapidly, it will emerge in the fall, and it thus has a bimodal flight season, common in spring and fall and less common in midsummer.

But most meadowhawks don't emerge as adults from the water until July or August, then fly well into October. Another very common species is the Striped Meadowhawk (Sympetrum pallipes), recognizable by its striped thorax. The individual shown here is a bright red female, colored just like a male, but other females are brown. This is another example of polymorphism, with red and brown morphs, and we can only speculate on the factors that cause the evolution of such color variation. This species breeds in temporary wetlands that often dry up during our relatively dry summers. The females drop their eggs while in flight around the edge of these wetlands, usually on dry ground. Then the wetlands flood over the next winter, inundating the eggs, and they hatch in early summer when temperatures are high enough. They develop quickly and emerge in midsummer, and the adults fly during the fall, repeating the cycle. Two related species can have quite different life histories.

Dennis Paulson

a day at the coast

Hello, all.

This is the first post from the Slater Museum of Natural History at the University of Puget Sound in Tacoma, Washington, USA.

These posts will be varied, but the theme is Northwest nature, information about natural ecosystems of the Pacific Northwest and their plants and animals. We encourage anyone with interest in this subject to join the blog and contribute to it. We also encourage civility and respect for the opinion of others. As most of our material will consist of facts rather than opinions, that should be easy!

I'm writing about a trip to the outer coast of Washington on 30 August 2009. Netta Smith and I wanted to get out of the house and see how the coastal bird migration was faring. It turned out there wasn't much migration going on, at least at most of the places we visited. We drove to Westport first, all the way at the end of the road around the marina to check out the breadth of Grays Harbor with our spotting scope. Out in the middle there were vast flocks of birds, underscoring the value of coastal estuaries for marine life. There must be a lot of prey out there to support hundreds, maybe thousands, of Brown Pelicans, Double-crested Cormorants, California and Heermann's Gulls, and Common Murres, all fish-eaters. There were also smaller numbers of Western Gulls, Pigeon Guillemots, and Rhinoceros Auklets on the relatively calm waters of the harbor. Heavy cloud cover made for gray sky and water, but visibility was good.

Small numbers of Brandt's and Pelagic Cormorants were roosting on channel markers and rock jetties, perhaps the beginning of the large numbers that arrive from the south each fall. No ducks, loons, or grebes were seen; they are yet to come. The only shorebird present was a welcome one, a juvenile Wandering Tattler (PHOTO) that probed among the rockweed. This bird is a far-journeying species that breeds in the Alaska mountains and winters on islands of the South Pacific, north to Hawaii and California. They pass along the Washington coast in small numbers every spring and fall, enhancing the sound of the ocean breaking on rocky shores with their loud, ringing calls.

Below us on the same rocks were scattered ochre seastars (Pisaster ochraceus), one of the dominant intertidal invertebrates in Pacific Northwest coastal waters. This is a polymorphic species, occurring in orange and purple morphs. We noted that the orange ones were very conspicuous, even below the water, but we didn't see the purple ones until the waves receded, exposing them, and even then we had to look quickly, as they blended with the rocks and algae. Why is the species polymorphic? Why are the purple ones more common here, when the orange ones are more common in Puget Sound? Does it have anything to do with their conspicuous to potential predators? One thing that Mother Nature bestows on us is a never-ending series of master's and doctor's research topics!

We headed for the ocean beach south of Westport. In some areas, driving on the beach is permitted, and that's a great way to see birds. Unfortunately, as our population has increased, too many of us are doing this now. We were shocked to see how many people were scattered along the beach. There were no shorebirds (sandpipers and plovers) at all, but there were roosts of hundreds of gulls of three species (Western [PHOTO], California, Heermann's) all along. As we would approach one of these roosts to try to get some photos and check for rare species, more times than not one or more people would walk right up to the birds, scaring them away. More often, a frolicking dog or two would do the same, and it was obvious that the resting gulls were irresistible to people and dogs alike. "Oh boy, let's go scare up those birds." If this was an opinion blog, I would relate in no uncertain terms what I thought of those people! Sharing the beach is great, but this wasn't sharing. Imagine just sitting down on your favorite couch to relax and digest your dinner, and someone comes running through the living room and says "up, up, up," so you walk around the house three times and then sit down again. Within a minute or two the pest comes again, and the scene is repeated. Some of the flocks were disturbed so often that I wondered, not for the first time, how birds and other wildlife will manage in the long run to coexist with our own species.

After this frustrating experience at several beach-access points, we motored down to Tokeland to look for the large roosting flock of Marbled Godwits and other shorebirds that are often present at the marina. Perhaps for the first time ever, there was not a single bird present. Other birders who we encountered had seen none of them earlier in the morning, and we arrived right around high tide, when the birds should have been roosting. But it was a low high tide, with plenty of mud flats in Willapa Bay still exposed, and why roost when you can feed? Shorebirds in migration feed until they are stuffed, laying down fat deposits all over their bodies, and after a few days of this, taking off on the next stage of their flight, often hundreds or even thousands of miles. They can burn their fat for "food" as they fly, and the longer they fly, the lighter they get!

Shorebirds are the world's best optimizers when it comes to feeding. A sandpiper's bill may actually be probing the substrate as it is coming to a landing, and they never stop probing, as long as there is a bit of room in their stomach. Many species have sensitive nerve bundles called Herbst corpuscles in little pits on their bill tip, and they can feel the wiggle of a worm or the curve of a snail as they probe the sand or mud.

Our final stop of the day was at Bottle Beach State Park on the south side of Grays Harbor, and that's where the migrants were. Flocks of hundreds of Western Sandpipers flew to newly exposed mud flats as the tide receded, and scattered among them were Semipalmated and Black-bellied Plovers, Whimbrels, Greater Yellowlegs, and other species. The sun never came out this day, but there were just enough birds that we headed home with a sense of accomplishment. Of course the birds were the ones accomplishing.

Dennis Paulson
Nature Blog Network