Feb 28, 2011

Quacking Frogs Get a Jump on Spring

I've always been an avid frog watcher. Even before the Spring Peepers’ chorus heralded the arrival of spring, I’d pull on my boots and go to still-icy pools to listen for the sound of Lithobates sylvaticus, the Wood Frog, kicking off the annual frog-breeding cycle.

Back then, this frog's scientific name was Rana sylvatica, but scientists recently decided figured out that it really belonged to the Lithobates genus. Of course, I had no clue about scientific names back then, so they were just Wood Frogs to me.
A young Wood Frog (Lithobates sylvaticus

Photo by MichaelZahniser

L. sylvaticus, a forest dweller, is the widest-ranging frog species in North America and appears the farthest north—all the way to the Alaskan arctic. Further south, it prefers higher, cooler elevations. In Virginia, it ranges from the upper Piedmont throughout the Mountain region, but also occurs in the northern part of the Coastal Plain.

During most of the winter, Wood Frogs hibernate under rocks, logs, or detritus in wooded areas. Their emergence from hibernation is triggered by warm spells that, in Virginia, can occur as early as January. At that time theys mass in shallow, short-lived pools for a frenzy of breeding that lasts only a few days. These vernal pools are formed from rains and thaws in winter and spring and dry up as temperatures rise and rains disappear.

How does the Wood Frog manage to survive breeding in the cold of winter? As author Elizabeth Colburn explains in Vernal Pool: Natural History and Conservation, “Within five minutes of the start of freezing, Wood Frogs accumulate high levels of glucose in the liver and leg muscles, subsequently releasing the glucose into the blood and other tissues, where it functions as an antifreeze.”
While other frog species can pull off the antifreeze trick in anticipation of winter, only L. sylvaticus can adjust to changes in the immediate temperature conditions. It can survive freezing for up for four weeks and is back to normal within hours of thawing out.

Medium-sized (1.5 to 3.25 inches), the Wood Frog is easy to distinguish from other Virgina frogs because of its black mask, which runs from each eye to above the foreleg. The rest of its body color ranges from pink to black.

The Wood Frog’s distinctive clacking call—likened to the “feeding call of the mallard” on the Minnesota Herpetological Society’s website—has earned it the nickname of “quacking frog.” The Handbook of Frogs and Toads of the United States and Canada notes that Wood Frogs give two, four, or six short notes in rapid succession that are “high and grating in character.” (Click here to hear the call.)
A pair of Wood Frogs mating
(pulled out of the water for the photo)
Photo by Cephas
Male Wood Frogs are so frenzied in their breeding that they actually have a secondary call to let males who have trapped them in a lusty embrace know that the object of their desire isn’t a female. The clacking can go on day and night when temperatures are right but doesn’t carry far.

In northeastern forests, wood frogs are numerous, with almost 5,000 recorded at just one vernal pool in Massachusetts, according to Colburn. During mating sessions, they can turn breeding pools black in an orgy of procreation. 

Each Wood Frog is extremely loyal to its natal pool (where it was born), with up to 85 percent returning to their natal pool to breed, bypassing other pools along the way. The remaining percentage disperses to nonnatal pools, ensuring genetic diversity. While the dispersing males may plop down in any shallow pool they find, females are pickier, refusing to breed in any pool with fish, the main predator of frog eggs.

A Wood Frog tadpole morphing into an adult 
Photo by Brian Gratwicke

Each female produces 1,000 to 3,000 eggs. Barring water that is overly acidic, dries up. or refreezes, or predation, the eggs’ rate of success in hatching out is high—80 to 96 percent, according to Colburn. Tadpoles don’t fare so well, with less than 4 percent usually surviving to adulthood. Wood Frogs prefer to breed in pools that appear very early and disappear fast, so they have to grow fast, becoming adults within 50 days.

Once the breeding is over, the frogs go silent and return to their small terrestrial home ranges (500 to 700 square feet) on the moist forest floor 1,000 or more feet uphill from their breeding areas. The breeding migration can be dangerous, especially across areas that have been cleared of forest—roads in particular.

Wood Frogs are voracious eaters, especially in the far north, where insects are around only briefly in the short summer. They chow down on ground beetles, crickets, bugs, caterpillars, other small insects, earthworms, snails, and spiders, and in turn are eaten by hawks, wading birds, snakes, and turtles, among other predators.

On a recent warm day after a rain and thaw, I donned my boots and headed for the wetlands along the Rappahannock River. I was disappointed by the silence there, but the winter has been unusually dry and cold, and no one else in my conservation network had reported hearing the distinctive clacking yet this year, either. However, with the recent warm spell and rain, I'm now hearing from my contacts that the quacking frog is back. With the late start and the short time they breed, there has to be a real frenzy of the little guys getting their groove on now.

Want to Help Our Frogs?
Amphibians of all kinds are under siege from changing climate and environmental degradation. A fun way to help monitor their health is to volunteer for FrogWatch USA. You just need an area with frogs that you can visit at least a couple of times a week from now through August. It only takes a few minutes to do the monitoring by ear and then enter the results into the Frogwatch online database. With only a few species in the Piedmont and western Virginia, it’s easy to learn all the calls.

The Virginia Herpetological Society’s website has sound recordings of native frog calls and lots of other good information, and the Virginia Department of Game and Inland Fisheries website has a breeding chart showing where and when each species breeds. VDGIF also offers a CD, Calls of Virginia Frogs and Toads, for $5.

Feb 22, 2011

Daddy Longlegs—Crawly but maybe not so creepy

[From my"Wild Ideas" syndicated newspaper column, January 2011]

Some people fear spiders in general — or are just sure that venomous Brown Recluse or Black Widow spiders are lurking in the dark corners of our houses waiting to pounce on us. The truth is that neither of these species is common in our houses and the arachnids that are more likely to be our housemates are innocuous ones commonly known as “daddy longlegs” because of their long, spindly legs.
The problem with the common name is that it is often used to refer to two different families of arachnids and even to an insect, the crane fly. Crane flies have wings and are insects, so that leaves us with the arachnids, cellar spiders and harvestmen.
A cellar spider
(Pholcus phalangioides).
hanging around in a house
Photo by Sven Siegmund.
Cellar spiders, also known as “skull spiders” because of the markings on their bodies, are in the family Pholcidae of the spider order, Araneae. The most common of these species in Virginia homes is a European immigrant, Pholcus phalangioides.
Harvestmen, like cellar spiders, are arachnids but belong to the order Opiliones. Harvestmen are well represented on the planet, with more than 6,400 species having been discovered worldwide out of a total that probably exceeds 10,000, according to Wikipedia. Determining which kind of harvestman is in your house is a task best left up to entomologists, since the variations among species can be extremely subtle.

Harvestmen can be differentiated easily from spiders in that their multi-sectioned bodies appear to have only one oval segment instead of the two of spiders. The eyes differ as well: harvestmen have a single pair of eyes in the middle of their heads, oriented sideways, while Pholcidae have the eight eyes indicative of their order.
Cellar spiders, like harvestmen, have long legs, but they appear more spindly and frail and are often askew, which makes these ethereal spiders appear drunk or dying. Like cobweb spiders, their webs are messy.
Cellar spiders are effective predators, preying on mosquitoes, small moths, flies, gnats and other insects that often end up in our houses, as well as other spiders, even those much larger than themselves. They’re also fond of woodlice, a tiny terrestrial crustacean commonly called a “pill bug.” When food is scarce, cellar spiders can turn cannibalistic.
I recently saw a cellar spider with a Marmorated Stink Bug trapped in its web. The spider kept touching the bug with its back two legs. I couldn’t figure out if the spider was trying to determine what it had trapped, was intrigued by the scent of this other exotic invader, or was trying to figure out how to get through the bug’s hard carapace to the feast inside. In any case, by the next day the stink bug was gone — probably having escaped rather than ending up spider food. When disturbed, cellar spiders often shake their webs violently to ward off predators.
A harvestman (Opilio canestrinii), probably a female
Photo by Pudding4brains.
Harvestmen do not spin silk, so don’t have webs. While they will occasionally eat small live insects, they mostly live off decomposing animal and vegetative matter.
Humans tend to have an uneasy relationship with spiders and their kin and can even be phobic about them. Maybe it’s because spiders are quick little predators that appear strange to us, are not exactly cuddly, can be aggressive and are in some cases quite venomous. We know so little about them, and there are so many of them, that we have a habit of spinning myths about them.
Take cellar spiders. Urban legend has it that they are the most venomous spiders on the planet, but that their jaws are too short or weak to bite through human skin. The television show “MythBusters” tested this myth by getting a spider to bite one of their onscreen reporters. The spider’s teeth did indeed manage to break through the skin, but the victim reported “nothing more than a very mild, short-lived burning sensation.” Researchers at the University of California, Riverside, back this up: “There is no reference to any pholcid spider biting a human and causing any detrimental reaction.” Some research shows that cellar spider venom is so weak it doesn’t even kill the tiny prey they normally use it on.
I used to freak out my friends when I was a little kid by letting wolf spiders crawl on my hands and bite me. I had the same sensation as that described in “MythBusters,” although the wolf spider’s bite was quite itchy after the fact. Harvestmen have no venom at all, but they do produce a harmless, albeit smelly, fluid when disturbed.
Harvestmen and cellar spiders are also decidedly nonaggressive. I’ve poked quite a few cellar spiders to see if they were alive, since they often look remarkably dead. Their only response was to shrink back a bit. And I’ve carried many a harvestman out of the house without them getting excited at all.
What isn’t a myth is that spider silk has antimicrobials in it, which makes sense, since spiders often catch prey that takes them a long time to consume, and antimicrobials preserve the nutrients. It is also hypoallergenic and so strong that the military is testing it for use in bulletproof vests.

Feb 18, 2011

Video on Burrowing Owls

Burrowing Owl (Athene cunicularia)
Photo by Pete Wallace
What a hoot! Check out this video, just featured on NPR's Science Friday. Burrowing owls are ground-dwelling and diurnal. Not native to Virginia, occurring in open areas in the West and Florida, but I wish they were. Great eyes, and a lot easier to observe than their nocturnal cousins.

Feb 17, 2011

False Spring

Today was the kind of day that made me want to come back to Virginia after years in on the Northern Plains, where winters were so brutally cold that the brief Chinook in January was not enough to dissuade me of the thought that the winter would never end. When the Chinook came, there usually was so much snow on the ground that it hardly brought thoughts of spring.

In Virginia, on the other hand, we're usually treated in February to springlike weather that can actually bring out the Wood Frogs, if an even earlier brief stretch in January hasn't already done the trick, and give more than a hint of the spring to come. Sure, we can still get pounded by three feet of snow in March,but by then we know we're over the hump, that spring will surely follow.

Today was the second day into this year's false spring. Temps in the 70s, and bugs flying through the air. In walking through a stretch of forest that is normally filled with vernal pools, which in turn should have been full of Wood Frogs making their frenzied attempts to breed in the brief warm stretches that pop up this time of year. But it's just too dry - no vernal pools. The last snow, less than six inches, has quickly disappeared into the parched winter ground or run off to join the Rappahannock River somewhere downhill.

Barred Owl (Strix Varia)
Photo by Sterren
That doesn't mean the woods was without life. A Barred Owl flew past me, and settled high in a tree down the trail aways. I got out my binoculars to make sure of the ID, and we stared at each other for quite a while until it decided it was better to find another stretch of that forest to rest in before going on its nightly hunt. It's passage stirred up a variety of woodpeckers, who sounded the alarm throughout the forest.

A few wasps were also out enjoying the weather and a pile of feathers that used to be a Titmouse, but that was about all.

The day was so warm that I'd left my windows open at home to air out the house and ended up keeping them open until well into the evening. As the full moon came up, it drew me to the deck to a perfect night—a few clouds slowly drifting by the moon, a gentle breeze, and temps still hanging in the sixties. If I hadn't had a deadline, I might still be out there.

Feeding Wild Birds in Winter—What's best for them and you

[From my"Wild Ideas" syndicated newspaper column, December 2010]

An evening grosbeak (Coccothraustes vespertinus)
at a tube feeder filled with sunflower seeds
Photo by George Gentry/U.S. Fish and Wildlife Service
You like birds. You want to see them up close. You’d like to help them survive through the winter. For any or all of these reasons, you’ve decided to feed your wild feathered neighbors, but doing it so that you and the birds get the most out of it can be complicated.

You can just buy a bag of mixed bird food from wherever and stick it in any old feeder, but you’re unlikely to attract all the native species overwintering in your area and could even endanger the ones that do come. Think first about which species you want to attract, how many feeding stations fit within your budget and your willingness to maintain them, and where they will be located.

Every bird species has its food preferences, and some commercial mixes have seeds in them that they may not eat and that may even discourage wanted birds and attract unwanted ones. Corn will more likely attract unwanted nonnative species, such as weaver finches (a.k.a English sparrows) or cowbirds, and can get wet easily and become dangerous for the birds that do eat it.

Milo (sorghum), the little brown seeds in many mixes, is not preferred by any species in our area, according to National Bird-Feeding Society (NBFS) director Dr. David Horn. White proso millet, also often in mixes, will attract birds who feed close to or on the ground—such as quail, doves, juncos, sparrows, and towhees—but will likely go untouched if it’s in a tube feeder higher up.

If you’re only going to use one kind of feed, black-oil sunflower is best because of its high fat and protein content. According to the National Audubon Society’s website, hulled sunflower seeds are consumed by the widest variety of bird species, including jays, red-bellied woodpeckers, finches, goldfinches, northern cardinals, grosbeaks, chickadees, titmice, nuthatches and grackles.

Finches, redpolls, juncos, doves and pine siskin love Nyjer® (Guizotia abyssinica) seed. Often mistakenly thought of as thistle, it’s actually cultivated in Asia and Africa and belongs to another plant family.
A pair of Northern Cardinals
(Cardinalis cardinalis) at a feeder
Photo by Ken Thomas

If you want to use a seed mix to attract more species to one feeder, how about making your own? Use seeds that suit the birds you want to attract and the location and type of feeder you want to use. Shelled sunflower seeds, peanut hearts, and safflower seeds make a good mix that leaves less mess and is easier for softer-beaked birds to eat. (However, “hit-and-run” birds with tougher beaks, such as chickadees, enjoy hauling off larger or unshelled seeds to feast on in private.) You can use the various types of seeds separately to attract specific species.

Not all birds are seed eaters. Mockingbirds prefer raisins and berries, and bluebirds may come calling if you put out meal worms. For many birds, especially woodpeckers, suet is hugely popular because of the high fat content.

To get a variety of bird species, have feeders at different levels, with food matched to birds who feed in those zones. The ground, or a flat feeder not more than about five feet off the ground, is more likely to attract doves, northern cardinals, juncos, and sparrows. Doves won’t visit tube or hopper feeders—those that release seed when birds hop on them, but cardinals may visit both feeders they’re large enough. Chickadees, titmice, woodpeckers, and finches will feed higher up and do fine with most types of feeders.

Many species don’t like to be crowded or will gang up and take over, so spreading out feeders horizontally keeps everybody happy and also helps prevent spread of disease. Salmonella and other diseases, along with seed that has gone rancid or moldy, can be a problem, so it’s really important to dump out old seed and keep feeders clean. A mild bleach solution is recommended by most bird organizations.

Water is often more important than food for birds, so have that available, too. And you’ll need to protect the feeders from bears, squirrels, dogs, cats, and other nonbird marauders.

The quality of the seed processing can vary, according to Horn. How do you know which brands are best? Horn says the Wild Bird Feed Industry, a trade association, has set quality standards based on purity, test weight, maximum moisture, mold, odor, insect infestation and damage and heat damage.

“Not all seed producers who belong to the organization meet the standards, and not all producers who meet the standards belong to the organization,” Horn says, but he still suggests looking for WBFI’s logo on bird-feed packages.

What about the use of pesticides or herbicides in the growing process? I haven’t found any information on that and neither has Horn. However, he did point out that, since most of what ends up going to the bird-feed market is initially aimed at human consumption, the type and amount of chemicals (if any) used in the growing process should be the same wherever the feed ends up.

If all this doesn’t seem worth the rewards of seeing lots of different birds in your yard, you can just keep it simple and scatter a small amount of bird food around on the ground early in the day so that it’s gone before nocturnal nonbird foragers come calling. Change the locations regularly to avoid the spread of disease. To learn more about wild birds and feeding them, check out the following websites: Audubon, NBFS, and Cornell Lab of Ornithology’s “All About Birds” website.