There’s a good piece in the current (Jul-Aug) issue of Audubon Magazine on the chronic White-tailed Deer overpopulation problem. Ted Williams points out what is obvious to most wildlife ecologists: that deer populations are allowed to grow until they destroy the ecosystems they depend on.  Research is overwhelming and unequivocal: when deer are present in high densities, they alter the landscape so severely that plants disappear, some never to recover, setting off a chain reaction that echoes through the system, resulting in drastic reductions in biodiversity.  For example, the article states:

In Warren, Pennsylvania, a 10-year study by the U.S. Forest Service determined that at more than 20 deer per square mile, there is complete loss of cerulean warblers (on the Audubon WatchList as a species of global concern), yellow-billed cuckoos, indigo buntings, eastern wood pewees, and least flycatchers. … In heavily settled parts of Pennsylvania, where hunting pressure is light or nonexistent, it’s not unusual to have more than 75 deer per square mile.

The only realistic way to control deer populations is with guns. Like it or not. Contraceptives are expensive and ineffective for the management that needs to take place.  Trap-and-transfer is inhumanely stressful, and often fatal, to deer, and only transplants the problem somewhere else.  The problem with killing deer — either through increased bag limits or, in populated areas, with sharpshooters — is that a segment of the public does not want to or will not comprehend the ecological damage deer inflict and does not want them hunted.  In an interesting twist, described in this article, hunters are initially happy with increased hunting opportunities, but when the deer in an area “wise up” and become more elusive, and the density decreases to the point where the animals actually have to be hunted, rather than shot from a comfy seat, some hunters pressure game commissions to increase the herd.  Because hunters provide a disproportionate amount of funding for game commissions and state agencies that manage deer, their demands are often heeded.

This illustrates what I consider one of the most frustrating conservation dilemmas ecologists face, especially in urban areas: how to convince people that some species that are nice to look at must be controlled and managed, usually by killing some, so they do not do incredible damage to already strained ecosystem. In addition to deer, I encounter the same type of resistance to lethal management of Mute Swans and resident giant Canada Geese.  I’ll be visiting those issues in the future.

You rely a lot on your ears when doing bird surveys, especially in the summertime. Thick foliage obstructs views, females are tending nests or young, and unless they are singing from an exposed perch, males may be hard to locate as well. Listening carefully for songs or call notes usually allows a patient observer to verify an identification, or recognize a behavior that provides confirmation of nesting (in my case, for a state breeding bird atlas project).

Some birds you just hardly ever see, no matter how long-fused you are waiting around checking out the shrubbery. I’ve encountered several of these enigmatic species so far this breeding season. They are disparate, unrelated birds, similar only in their sneaky, furtive ways. Here’s a (figurative) look at one of these surreptitious species. (Part 2 here)

Yellow-billed Cuckoos (Coccyzus americanus) are forest ghosts, detectable by their guttural, hollow, just-downright-strange call: ka-ka-ka-ka-kow-kow-kow-kow-kowlp-kowlp. It’s hard to tell if they are near or far. There sure seem to be a lot of them around this year. I think this may be because they had a bumper year for reproduction in 2004 due to the emergence of Brood X of the periodical cicada in this region. Cuckoos specialize in large insect prey (and hairy caterpillars like tent caterpillars and gypsy moths), responding to an abundant supply by laying more eggs. They are not obligate brood parasites like Old World cuckoos. Usually, they raise their own young, but sometimes lay their eggs in the nests of other cuckoos, and occasionally other species. Prey abundance may trigger this behavior. Sometimes. Or not. This is a bird that doesn’t easily give up its secrets.

One aspect of cuckoo development is well-documented, however. The chicks have exploding feathers. Yellow-billed Cuckoos have one of the speediest breeding cycles in the avian world, only 17 days from the eggs hitting the nest to the young ones leaving it. A week after hatching, chicks are covered in long “pin feathers,” growing feathers encased in sheaths*. All at once, the feathers begin erupting from their sheaths and presto! The bird is fully feathered in about two hours. A correspondent to Bent’s Life Histories of North American Birds reported in wonder: “This process took place with such rapidity that it reminded me of the commotion in a corn popper or a rapidly blooming flower.”

When they know they are being observed, Yellow-billed Cuckoos tend to stop moving and arch their backs to conceal their white underparts. I have a lot of territory to cover doing my atlas work, so I have yet to even spend the time really trying to see a cuckoo, much less find a nest. But bursting baby feathers! Next time I hear the wooden notes of the Rain Crow, somewhere in the woods, I may try to stalk this skulking bird.

Or at least listen for a quiet series of little explosions, the repercussions of popping plumage.

*Pin feathers look kind of like aglets, which are the things at the ends of shoelaces.

I came across this attractive land snail while doing some gardening. I was curious, as usual.  For me, it doesn’t seem right not to know and understand the creatures sharing my property.  And while I don’t want to become too mollusk-oriented here, considering the slug post,  this one turned out to be too fascinating to not write about.

The snail is Cepaea nemoralis. It goes by many common names, Banded Wood Snail and Grovesnail seem to be the most frequently used.  I soon learned (and you’ll anticipate my next statement) that they are not native to North America. C. nemoralis and its sister species C. hortensis are from western Europe and have been widely introduced, often via plant materials but occasionally intentionally. They have been on this side of The Pond for about 150 years.

It turns out C. nemoralis is a remarkably well-studied organism because it is, I was intrigued to discover, one of the most polymorphic species of any known animal, possessing extreme intraspecific variation of mitochondrial DNA.

The polymorphism is readily apparent if you run across many of these snails. The base color of the shells may be various shades of yellow, pink, or brown, and the shells may be unbanded, or have up to five bands.  Bands may be complete, fused, or not fully pigmented (some handsome photos here).  To keep things straight, a shorthand has been developed to categorize shell color and pattern, beginning with a letter signifying shell color, and five digits to record the number of bands.  My snail would have the notation Y12345.  Had any bands been fused, they would be noted parenthetically, and split bands would be shown with subscripts. I don’t know how bands that change color along their length are recorded, nor the variations in the color of the shell’s lip, or the snails body — all of which are further examples of polymorphism in this gastropod.

What makes a snail — this snail — so variable? It turns out, a whole lot of things. In any given population of C. nemoralis, several factors may act together, and their relative importance will vary from site to site.  I found the classic paper on the subject, Polymorphism in Cepaea: A problem with too many solutions? both aptly named and a fine overview of the forces that influence polymorphism in Banded Tree Snails. Just a few examples:

Habitat: More structurally diverse habitats tend to have banded snail populations, while snails in more uniform habitats (grasslands, dunes) have fewer or no bands, thought to help in camouflage against predators.  Color of the base of the shell is also influenced by habitat, again facilitating camouflage. All the ones I’ve found in my garden are yellow with bands. I found this one in a shady wet woods.  Not only is the shell brown, so is the body.

Climate: Climate may influence shell color in two ways.  First, shell color helps the snails thermoregulate. Darker shells absorb more heat than light shells; therefore, yellow shells tend to predominate in hotter climates.  Rainfall also plays a role. Although most C. nemoralis have dark-lipped shells, populations with high percentages of white lips tend to be found in wetter areas.  In the same places, dark-lipped C. hortensis (the uncommon morph) are found in higher proportions.  Rainfall affects both these species in the same way (increasing the number of the less-common morph), but the mechanism is not known.

Conspicuousness — C. nemoralis is the most active of a suite of similiar species, making it more conspicuous to predators.  This may further influence the high degree of polymorphism in this species.

All this selective pressure is complicated by elaborate genetics, which I don’t pretend to fully understand.  I do know that since snails don’t move very far, they tend to mate with close, often related, neighbors, and that will cause the frequency of gene alleles to change over time. Looks like the sequencing of their DNA was completed fairly recently, so I’m sure more there will be even more interesting revelations on the evolutionary ecology of what Thomaz et al. called “a classic organism in ecological genetics.”

And I just thought I found a pretty snail, and wondered if maybe I could find something interesting about it.

Jones, J.S., B.H. Leith, and P. Rawlings.  1977. Polymorphism in Cepaea: A problem with too many solutions? Annual Review of Ecology and Systematics 8:109-143, with 201 references.

Terrett, J. A., S. Miles, and R. H. Thomas.  1996.  Complete DNA sequence of the mitochrondrial genome of Cepaea nemoralis (Gastropoda: Pulmonata). Jrl. Molecular Evol. 42:160-168.

Thomaz, D., A. Guiller, and B. Clarke. 1996. Extreme divergence of mitochondrial DNA within species of pulmonate land snails. Proceedings of the Royal Society Ser. B: 263: 363-368.

Kady has issues.  What most of them are, beyond her being a lazy diva, are unknown to us. When she is displeased about something, she decides it is not worth her time and energy to go down to the basement to use the box.  We have not been able to determine if her choice of alternate toilet locations — my office or my husband’s — is correlated with specific annoyance with one of us, or just equal opportunity contempt.  Anyway, my office has been the target lately.

Our response in the past has been strategic placement of additional boxes in inconvenient places (for us), hand-wringing and heated discussions about what’s wrong with her, and my frequent personal schlepping of her to the main box, accompanied by much encouragement and praise for jobs well done.

Last night I took a shower and headed up to bed.  Kady was lounging at the top of the stairs, Mistress of the Landing. I decided it was probably a good time to take her to the box, and went to pick her up.  She did not want to be picked up.  She rolled on her back and grabbed my hand with her teeth and half-sheathed claws. This means, “Really, I prefer you not do that.”  There are more serious degrees of resistance, so I persisted, got my hands underneath her, and proceeded to tug at a cat with four sets of claws firmly embedded in the berber.  At that point, Sophie trotted upstairs, temporarily distracting Kady from her implantation, and I was able to hoist Her Fatness to my chest.  My bare chest.  She whined.  Now, I consider myself a fairly careful planner, and in fact this whole expedition to the box was, I thought, an example of farsightedess and forethought.  But at that moment, holding 12 pounds of squirmy, unhappy cat with nothing between her and I but…nothing…I realized this might not be one of my finer moments.

I headed downstairs.  As I passed my husband, who was on the couch, he looked at me wide-eyed. Not, I am certain, because the love of his life was going by nude and dewy from a shower, but at my profound bravery/foolishness being naked and carrying this cat, known to feel perfectly free to use her teeth and claws on her devoted parents.

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As a kid, I used to find caterpillars and raise them to adulthood. Nowadays, I don’t even see many caterpillars. Gone are the days, or so it seems, when every tomato plant had to be monitored for sphinx moth larva (“tomato worms”), dill was decimated by Black Swallowtail caterpillars, and each milkweed had its Monarchs-in-the-making. I especially miss seeing those impressive forest-munching machines, the silkmoth caterpillars (Saturniidae). Thirty years ago, most summers I could find Cercropia (Hyalophora cercropia) or Polyphemus (Anthera polyphemus) larvae, so big they were sort of gross and almost scary. Placed in an aquarium and kept supplied with a copious amount of fresh leaves, they’d balloon to three or four inches, and soon enough they’d spin a cocoon. The next spring I’d see the gratifying final result: a spectacular large moth (although some people find that, close up, their fat hairy bodies are still a little freaky). Here is a Polyphemus that I had the pleasure of welcoming into the world last week, courtesy of a friend who had raised some larvae he found in a more rural area.

Declines in silkmoths in the eastern U.S. are in part due to habitat loss and widespread, long-term pesticide use. Unfortunately, they are also victims of an introduced organism. Tachinid flies (Tachinidae) are a large family of parasitoids which feed on the larvae of other insects. Many are parasites of lepidoptera larvae. A non-native tachinid fly, Compsilura concinnata, was first introduced into North America 100 years ago (and up until 1986!) to control various pests, primarily (Lymantria dispar), themselves a non-native pest brought into the U.S. some 50 years before. Some tachinids are very host specific, but Compsilura proved to have quite catholic tastes and has been devastating to silkmoth larvae. Whereas parasitism of the target moths by Compsilura is generally around 5%, the mortality of silkmoth larvae in experiments at various densities was 52 to 100%. This research was done by University of Massachusetts-Amherst entomologist Jeff Boettner. Compsilura is also known to parasitize many other species, including swallowtail butterflies and other species that I see fewer of in my wanderings.

I don’t intentionally set out to find some subject that allows me to harp about introduced species in this blog. Working in an urban environment, if an interesting organism is not introduced itself, it’s a native organism that is impacted by a non-native one. It is often said that urban ecosystems are simplified ones, and that is true to a great extent — they tend to have less biodiversity and are often dominated by generalist species. But it seems that each time I delve into the life history of some bird, insect, or other creature that crosses my path, I am reminded of the complexity of all ecosystems, and the tangled web we weave when we tinker with the components.

UPDATE: Last night (9 June) while standing at dusk at a marsh awaiting a calling Common Moorhen, a Cercropia moth flew out of the woods and across the marsh. It was the first one I’ve seen in over 25 years!!

UPATE #2: Check out my first Promethea moth.

Boettner, G.H., J.S. Elkinton, and C.J. Boettner. 2000. Effects of a biological control introduction on three nontarget native species of saturniid moths. Conservation Biology 14:1798-1806.

Jeff and I went through the same undergrad program at the same university. Not only is he a great guy, but he is one of the rare scientists to gain respect and funding and publish in major journals even though he does not have a graduate degree. This makes him somewhat of a hero in my book.

Some years I don’t catch many Tennessee Warblers, but this year seemed to be a good year for them. Their populations surge and wane with outbreaks of spruce budworms (Choristoneura fumiferana) on their northern nesting grounds. The budworms tend to be cyclical, and Tennessee Warblers are one of a suite of warblers that are considered spruce budworm specialists; others include Cape May Warbler (Dendroica tigrina) and Bay-breasted Warbler (D. castenea). During budworm outbreaks, Tennessee Warblers will increase their clutch size — laying up to eight eggs rather than three or four — and occur at higher densities in response to this abundant prey.

Tennessee Warblers winter from Mexico to Venezuela, often on shade coffee plantations. Trees in the genus Inga are common overstory trees in coffee plantations, and important to wintering Tennessee Warblers. In addition to eating insects, the warblers are nectar thieves, stealing nectar from the flowers by piercing the base of the blossom, thus getting away with the goods without pollinating the plant. The birds also utilize other tree and shrub species in winter and during migration in the more conventional, stick-your-head-in-the-flower manner. Their faces, then, may become stained with red or orange pollen.

The majority of Tennessee Warblers, 97%, breed in Canada’s boreal forests. In fact, according to the Boreal Songbird Initiative:

• 53% of warbler species, 80% of the waterfowl species of North America, and 63% of the finch species breed in the boreal region.
• For nearly 100 species, 50% or more of their entire breeding populations occur in the Boreal.
• Over 80% of the North American populations of 35 species occur in the Boreal.

The boreal forests are so crucial to so many of the breeding birds of North America that several organizations have begun working on education, advocacy, and conservation for the region. In addition to the aforementioned Boreal Songbird Initiative, there is the Heart of the Boreal Forest, and the Boreal Forest Network. All take donations! The public can also help by purchasing paper products that are not made from wood harvested from boreal forests.

Likewise, many of our North American breeding birds are dependent on shade-grown coffee plantations, so you can also help by drinking shade-grown coffee.

When Tennessee Warblers pass though my neck of the woods, I am totally immersed in the richness and promise of a Midwestern spring. Tropical coffee plantations and northern boreal forests seem distant, but this little olive bird with a gray head is a perfect representative of both of these habitats, and reminds me how important they are to the continued spectacle of migration.

Olive birds with gray head, part 1 here.

When you do field work in an urban area, you come across a lot of trash, most mundane, some startling, and some kinda funny.  Yes, indeedy, this eating utensil was in fact at the intersection of two trails.

The amusement value of flatware in the forest pales in comparison with an item my friends and I found one year doing a Christmas Bird Count. Top honors for Most Unexpected Piece of Trash goes to the lifelike latex, uh, "marital aid" discarded (thought-provokingly enough) in an industrial area on a busy bridge over a river, which we were scanning for waterfowl.  We counted it as "dickey bird sp." at the tally that evening.

“The soft color tones combine to make a most charming picture of pleasing loveliness. He appears to be a well groomed aristocrat among birds.”

So Life Histories of North American Birds author Arthur Cleveland Bent described the Blue-headed Vireo (Vireo solitarius), one of my favorite birds. It is the first vireo to arrive here in spring from southern U.S. and Latin American wintering grounds. Not only are these vireos beautiful, but they are feisty, as the little guy working my finger demonstrates (the bird below was a more cooperative). This species was once called the Solitary Vireo, but in 1997 was split into three species: Blue-headed, Cassin’s (V. cassinii) and Plumbeous (V. plumbeous). It is the only eastern vireo to make extensive use of coniferous forests across the northern U.S. and Canada. This may be tied to its early spring arrival, which is prior to the leaf-out of most deciduous trees.

Blue-headed Vireos have an interesting behavior: the males construct “courtship nests.” Although usually rudimentary, they are thought to impress potential mates. These nests are often built in conifers, and tend to be abandoned when breeding nests are built. Male Blue-headed Vireos also help build the breeding nest, and they incubate the eggs as often as the female, behaviors that are unusual among songbirds.

Population trends of Blue-headed Vireos are stable or increasing. But all is not well in their northern forest homes. An introduced aphid-like insect pest, the Hemlock Woolly Adelgid (Adelges tsugae) is killing hemlocks in forests of the eastern U.S., and it is advancing at a rate of about 15 miles/30 km per year. This Asian insect harms hemlocks by sucking sap from young twigs, thereby retarding growth, and eventually weakening and killing the tree. The biological impact of the destruction of hemlock forests is significant. This excerpt from a Nature Conservancy document summarizes:

“Hemlock trees are ecologically important and provide a unique environment. T. canadensis is a long-lived conifer, and its stands form a cool, damp habitat with low light levels in the understory. These dense stands possess a very different microclimate and unique species composition from the surrounding, more open forests. These forests are normally stable and resistant to plant invasions. The loss of forests will greatly affect the microclimate and soil conditions. Large-scale hemlock die-off will affect species diversity, vegetation structure, stand environmental conditions, and ecosystem processes.”

There is currently no way to manage for Hemlock Woolly Adelgid in a forest setting. Hemlocks can act as keystone species in an ecosystem, and the Blue-headed Vireo is just one of the creatures that relies on the health of hemlock-dominated woodlands.

I hope through good science and with some luck we will find a way to halt the progress of the adelgid. It is hard for me to imagine welcoming spring without the appearance of the Blue-headed Vireo, a special bird, moving through trees just unfurling new leaves, singing its lazy, repetitive song, beguiling me with its pleasing loveliness.

Another installment in Things One Finds Under Rotting Logs. It still surprises me that I lived for decades, including a long childhood (not yet complete) spent thoroughly exploring the yard and neighborhood and its more secretive non-human denizens, before I encountered Limax maximus, the Leopard Slug (a.k.a., Spotted Garden Slug, Great Grey Slug, or Giant Garden Slug).

Slugs are, of course, not hard to come by, especially if you are fond of hostas in your landscape. I found my first L. maximus not under a log or munching a hosta, but moving purposefully (albeit slowly) down the trail in front of me. Although nicely camouflaged with dark brown stripes and spots on a tan background, it was hard to miss at about four inches long. For such a lowly creature, it was quite glorious! How had I overlooked them?

As is my habit, I went straight to the books. I learned that L. maximus is not native to North America, but yet another of the throngs of organisms “brought over by European settlers.” Whew. One envisions armadas of arks making their way across the Atlantic in colonial times. Anyway, the Leopard Slug belongs to the family Limacidae, or keelback slugs. These types actually have vestigial, clear shells encased by their mantles, having not slithered their way so far along the evolutionary path as to have completely lost their shells.

Much of the research that has been done on Limax maximus centers around physiological studies such as neurological responses and olfactory processing. However, I did find a couple of intrepid researchers who were working on something more practical, the development of slug slime into an adhesive. Even better, these were high school students, and they won an award for their work. I’m sure if they stick to it, they will make fine scientists one day.

I didn’t find much compelling about L. maximus natural history. The usual slug stuff; they don’t live very thrilling lives. EXCEPT when it comes to sex. The accounts of their mating habits — which I found described as “spectacular”, “remarkable”, and at a minimum “interesting” — piqued my curiousity, and the photographs…well, let’s just say I spent the next few years seeking out slug sex. This, it seemed, was something I needed to see for myself.

Leopard Slugs are hermaphrodites, with each individual possessing schizophrenically-named organs such as an ovotestis and spermoviduct. Reproduction, however, does involve two individuals, which ultimately both lay eggs.

Courtship (if lower animal foreplay can be called that) begins with a long session of mutual licking. Apparently this stimulates the copious mucous production necessary for the next step. The slug pair eventually suspends from a single intertwined mucous string up to eighteen inches long, heads down, twisting and spinning as if in a ballet. Finally, from the head region, the male organ is extruded from each slug. It’s hardly penile-looking, but rather an opalescent, ice-blue organ which also intertwines as the two exchange sperm in a process that can last up to two hours.

Years went by, and I began to wonder where all these slugs were coming from, as I had still not seen any mating. Then one day I was walking into work and found two Limax maximus suspended from their slime cord right on the post in front of my building, not a place I had thought to look. I took a series of photos, including this one, while I and my appreciative, like-minded co-workers looked on.

Although I run across (or accidently walk upon) these handsome gastropods fairly often, I only witnessed slug love this one time. I’m glad that I decided not to disdain such a humble creature, and remained on the lookout for their amour. I don’t know in what context early U.S. Attorney General William Wirt said, “Seize the moment of excited curiosity on any subject…for if you let it pass, the desire may never return, and you may remain in ignorance.” I’m sure it wasn’t in reference to slugs, but nevertheless, I couldn’t agree more.

Left: The resemblance between the Leopard Slug and Kady the Bed Leopard has not gone unnoticed.

UPDATE (right): While walking in a swampy woods today, I found a large shelf fungus (Polyporus squamosus, I think) loaded with Leopard Slugs. Here’s a 21-slug salute!