Friday, February 2, 2018

'Dig It — and They Will Come' by David McIntyre - guest blogger describes his backyard pond building process

David McIntyre, a friend and colleague of the Amphibian Foundation, was kind enough to describe his methods for building a successful wetland in his yard. By 'successful' we mean one that attracts and support native wildlife.
Take it away, David!

 'Dig It — and They Will Come'
If you are interested in attracting amphibians to your yard, the following method has worked for me:
1. Find an area with a high water table.
2. Dig.
I have to admit, when I set out to dig a pond on my property, I was thinking primarily of ducks, not amphibians. Back in the spring of 2005, I was planning to add a couple of ducks to my small poultry flock, and I thought they’d appreciate a bit of water to splash around in. I live on a long, narrow 1 1/2 acre parcel in western Massachusetts, and there’s an area across the middle that is thoroughly wet (saturated with water, particularly after it rains) for several weeks every spring. Any hole dug in this area in the spring quickly fills in with water, so I figured that if I dug a big hole, I’d have a pond for the ducks, at least during wet periods.
Peeper: I heard occasional spring peepers in my yard before I dug the pool, but their population has exploded since

This area was invaded long before I moved in by exotic yellow irises, Iris pseudacorus, and I had no qualms about removing them. Digging through the soggy iris sod, the heavy soil layer below, and the glacial till below that was slow going. Opaque muddy water replaced each shovelful of muck as I removed it, so I had to extract rocks by feel, and the only way to tell how deep I was digging was to measure with the shaft of the shovel. I started where I figured the center of the pond ought to be and worked my way out in a spiral, trying to go at least a couple feet deep throughout.
I had injured my back doing something equally foolish a few years earlier, so I didn’t try to dig for more than a couple of hours a day. As I recall, after only two or three days, with the “pond” only about 5 feet across, the first amphibian showed up: a wood frog, recently awakened from its winter freeze. By the time the hole was about 10 feet across, there were several clusters of wood frog eggs.
After a dozen years of occasional digging and maintenance, the vernal pool (most years it dries out completely for at least a week or two) is now an oval roughly 15 feet wide by 20 feet long, and perhaps 3 feet deep at its deepest. In addition to the wood frogs, four other amphibians regularly reproduce in the pool: spring peepers, gray tree frogs, green frogs, and American toads. Bullfrogs also take up residence every year, but because their tadpoles require more than a year to mature, and the pool dries out most years, they’re not often able to reproduce successfully.
Dry and wet: The vernal pool dries out completely most years (left photo), but it is at the bottom of a slope, and it refills quickly (right photo, after only a couple of rainy days).
Last spring I retired from work and started spending a lot more time observing life in the vernal pool. One day after the wood frogs had laid their eggs and returned to the woods, I noticed what looked to my semi-trained eye like a clump of spotted salamander eggs. After I located a few more clusters, I decided to bring a small cluster inside and try rearing some to find out for sure. I kept the first two larvae to hatch, returned the rest of the eggs to the pool, and for several weeks thereafter, I spent at least 45 minutes every day hunting in the pool for appropriate critters to feed the voracious salamander larvae. When they had absorbed their gills and changed to their adult coloration, I was able to confirm that they were indeed spotted salamanders.
New Spotted Salamander: One of the Spotted Salamanders I reared from an egg posed for a portrait on release day.

Perhaps because I was spending so much more time at the vernal pool in my retirement, I was able to add one more amphibian species to the list last year: one day I saw a pair of red-spotted newts mating, and later I often captured newt larvae while hunting for salamander food. In spite of daily visits to the pool, I only saw the adult newts a few times over the course of the summer, so it’s entirely possible that they’ve been around but evading my notice for several years.
For those whose interests extend beyond amphibians, the vernal pool has also attracted cattails (previously unable to get a foothold among the yellow iris), duckweed, all manner of insects and tiny freshwater crustaceans, snails, a young muskrat (briefly), a pair of mallards (also briefly, driven off by the unwanted attention of the resident drake), and the occasional great blue heron. 
Ostracod: The vernal pool produces many tiny crustaceans. Ostracods like these (about a millimeter long) were popular snacks for the newly hatched salamander larvae.

Dragonfly: Dragonfly adults and nymphs are among the more charismatic insects in and around the vernal pool.

A few years ago, a young snapping turtle moved in for a while; as the pool dried up, it became apparent that something was eating the tadpoles, and when all the tadpoles were gone (and the pool only a foot or so across), the turtle moved on. And last year, no fewer than three northern water snakes moved in for several weeks. They were skittish at first, but after a while, they became accustomed to my presence and stopped diving into the deep during my daily hunts for salamander food.
Water Snake: The northern water snakes that took up residence in the pool for several weeks in 2017 eventually became quite comfortable around me.

The primary suggestion I have for those interested in trying this themselves is to do most of your digging during the driest part of the year. It’s much easier to dig when the soil isn’t saturated with water, so if you’re sure your area is wet enough during the wet season (whenever that is in your area), you might want to postpone your groundbreaking until things dry out a bit.
Maintenance depends on your plans for the pool. Without any interference, I assume my pool would eventually fill back in, and the yellow irises would invade again, so every few years I dig some silt out of the deepest area. I find that 2 1/2 to 3 feet deep is deep enough to keep most vegetation from getting a foothold. I also dig out some of the vegetation that grows in the shallower areas, just because I like to be able to see to the bottom in some places. I don’t like to remove cattails (they’re in enough of a struggle around here with exotic grasses and the yellow irises), but I don’t want them taking over all the shallow areas, so when I’ve felt a need to dig them up, I’ve tried transplanting them to some other wet part of my property.
Note that while a vernal pool can be attractive when it’s full, it pretty much just looks like a mud puddle as it dries out, and some unenlightened people might not immediately see it for the wonder that it is. Also, if you have dogs, they may enjoy your vernal pool in a way that doesn’t exactly fit with efforts to keep your house clean. And although I haven’t noticed an increase in the mosquito population since I dug the pool (they didn’t seem to have any trouble finding places to breed in my wet back yard before the vernal pool), it’s not hard to imagine they could be an issue. As far as I’m concerned, though, the amazing spring chorus alone more than makes up for any shortcomings. 
Gray Tree Frog: Gray tree frogs contribute to a raucous evening chorus every spring.
The ducks did enjoy the pool for several years, but they ceased to be its raison d’etre long ago. “Mucking around in the pond” has become one of my favorite pastimes, and I can guarantee that on the first warm, rainy night in March or April, I’ll be out by the vernal pool watching for the return of any spotted salamanders that may have survived to reproduce another year.