The other day I was driving over a bridge in Two Rivers and was surprised to see the surface of the lower West Twin covered with a light green haze of algae. I was also told that the East Twin and Manitowoc Rivers are also experiencing similar blooms in their lower sections. For some reason, this is a very good year for growing duckweed.
Duckweed is an interesting little plant- the smallest flowering plant there is. The entire plant consists of a handful of tiny leaves which float on the surface of slow-moving or stagnant waterways, ditches, and ponds, with equally tiny roots that hang down. There are several species of plants in the duckweed family around here ranging from giant duckweed (which is still only ¼ inch across), lesser, little, and least duckweeds, and the even tinier water meal, which just looks like very small grains of green dust floating in the water. And yes, ducks do eat duckweed, although I think it grows as fast as it is eaten.
Duckweed produces very tiny flowers which are mostly unnoticed. More importantly, it reproduces by budding and fragmentation, producing tiny leaves which become new plants. In that way it can quickly colonize new areas.
So why is there so much this year? That’s a very good question. For one thing, duckweed grows abundantly where there are lots of nutrients in the water and we humans are really good at fertilizing our waterways. Nutrients include leaves and dirt that wash in with stormwater, lawn fertilizer, and any soil that is allowed to erode and flow into the rivers. Phosphorus is often a nutrient which limits growth of aquatic plants, and phosphorus accompanies soil that is washed into waterways. Tons of soil wash into the East and West Twins and the Manitowoc River thanks to human activity, and there are plenty of nutrients for duckweed to utilize. We are on pace for record precipitation this year, so there are lots of opportunities for nutrients to enter our river systems.
Duckweed also thrives in stagnant or low-flow conditions and I wonder if the high lake levels, which affect the levels of water and flow in the lower parts of the rivers, have reduced the relative water movement from the rivers to the Lake at the surface. There just isn’t a lot of vertical drop between the rivers and the Lake. For whatever reason, something about the flow of water in the lower parts of the rivers also seems to favor the duckweed.
Duckweed is a valuable part of the ecosystem, and they are native plants. Like so many aspects of life, too much is not necessarily a good thing. Although animals eat duckweed, it can become so abundant that it coats boats and makes water look less than inviting. It can also shade the lower part of the water column so that algae can’t grow below it, and when they die they consume oxygen in the process of decay, sometimes to the point of causing problems for animals.
A type of algae – the blue-green variety, is also found in some waterways and lakes and builds up an unappetizing scum on the surface. Blue-green algae scum can be somewhat multicolored and in it you can’t distinguish the flat, floating leaves or buds of duckweed. Blue-green algae can also be toxic to pets or cause skin rashes on people who come in contact, and you certainly don’t want to drink the stuff.
Soon, cooler temperatures will cause duckweed and other algae to die off, and generally in fall the water becomes clearer. In the meantime, we should think about how we can keep excess nutrients out of our rivers and lakes so that they look and support life better.
photo- from Wikimedia By Mokkie – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=31954009
As the season advances toward fall, our weather is more comfortable, even though we still experience the occasional rainy day. For many of us, it is our favorite time of year, and that opinion is largely based on the weather. And if the weather doesn’t remind us of the change of season, the birds do. Have you seen the thousands of nighthawks that have been migrating along the Lake these last several evenings? Many of these are streaming southward from their nesting areas in Canada- unfortunately they don’t nest on rooftops here anymore. Like us, they rely on the beautiful fall evenings for opportunities to migrate.
photo- Kirtland’s warbler by Joel Trick of the US Fish and Wildlife Service
We are standing now in the midst of a great ocean of living things. The tide is high right now, but starting to flow southward. Our location on the edge of a Great Lake in the middle of the continent is outstanding for wildlife watching, as animals funnel down the Mississippi Flyway. The nature center, busy as we were during summer, is ready to be literally buzzing with activity this fall.
As I drove in and parked this morning I was greeted by about 50 barn swallows perched on the overhead wire in the yard. They are usually gone by now, beginning their migration in mid-August. Perhaps our cold spring and summer delayed their nesting by a couple of weeks- there is still a nest with nearly grown young in our pavilion. Barn swallows, as delicate and graceful as they are, have a very long migration ahead- all the way down to central South America, fueled by insects they catch along the way. Up in Duluth at Hawk Ridge Bird Observatory, they are counting thousands of cliff swallows migrating past, along with other songbirds and a few bald eagles. The big hawk migration will happen in a couple of weeks. Later some of those birds, plus those moving from the U.P. and Canada via Sault Ste. Marie, will begin to show up here using the shore of Lake Michigan as a guide along with stars and even the Earth’s magnetic field. This morning at 4 am our dog woke me to go outside, and while standing and waiting under a beautiful clear, calm, starry sky I could hear the peeps of several of the thousands of songbirds migrating in the dark. The fact that they can do this, sometimes thousands of feet up and invisible to sight (but not radar), is almost unbelievable.
During the same period during the day, migratory insects are also on the move. I think most of us know that monarch butterflies travel to Mexico to spend the winter clinging to hemlock trees in certain mountains. Well, this seems to have been another good year for monarch reproduction in our area, and the latest generation of those plus monarchs from farther north are also traveling along Lake Michigan to the south in large numbers now. If you live close to the Lake and are very lucky, you may see a monarch roost in a tree in your yard. Sometimes dozens or hundreds of monarchs will roost in a group for the night, continuing their flight the next morning when things warm up. There have been at least dozens of monarchs in our butterfly garden and in the wildflowers near our building headquarters the last few days. Similarly, some dragonflies migrate, and if you are in a field with wildflowers, or perhaps just along the Lake, you may see hundreds of green darners either flying purposefully southward, or zig-zagging as they feed on smaller insects.
But these are just a few of the hundreds or thousands of species on the move right now, either migrating or getting ready for the coming seasons. Nature is in high gear, and interesting sights are all around us. It is a perfect time for children to be outdoors, and we’re also preparing for a thousand or so to visit on field trips. We do everything we can to give students a great experience outdoors on our trails (last year’s mosquito hatch was a challenge!) because we feel that is where they will learn the most. Our nature preserve is a huge classroom, and more and more research affirms the importance of nature-based outdoor education. Just this week I learned of studies which documented physical changes in the brains of students who were exposed to outdoor learning, and another in which researchers found that the positive emotions that one experiences outdoors are similar to those seen at Christmas, which is considered overall the happiest time of the year for most people.
So perhaps my wonder at the amazing workings of nature this time of year are very much self-centered. Perhaps I just want to re-experience the positive feelings of the Holidays. Well, there’s no better time of year than now, and if my desire for those good feelings results in my caring more and taking better care of nature, then I say “Merry Christmas”!
It’s about that time of year when clouds of winged ants can be observed flying in the sky or crawling over the sidewalks. This amazing sight, called “flying ant day,” occurs in late summer on a warm, humid and calm day, ideally after a rain.
Ants are social insects that live in colonies consisting mostly of female workers and a queen. Similar to their close relatives the bees and wasps, each worker has a job that is vital to the success of the entire colony. They care for the young larva, clean the nest, excavate more tunnels, guard the colony, forage for food and care for the queen.
Most ants do not have wings and only leave the colony when looking for food. However, once a year, the queen will lay eggs that will grow into new queens (princesses) and males (drones). The nursery ants feed these young a special food that allows them to grow wings. Once mature, these ants will fly far away from the home to mate. Flying a long distance helps to maximize the potential of mating with ants from different colonies. The long-winged princesses join the smaller drones in flight, in a courtship behavior called the “nuptial flight.” The queens will mate with several drones to ensure genetic diversity of her future colony. Amazingly, this is the only time a queen will mate. She retains all the sperm she needs from the nuptial flight and is able to lay thousands of eggs in her lifetime.
Shortly after mating, the drones die and the young queens find a suitable place to start a new colony. She will chew off her wings (it’s hard to dig a tunnel with huge wings) and excavate a chamber to lay her first eggs. The eggs hatch into larvae and she will care for them until they are adults. These new adults will then care for the queen and so a new colony begins.
Ants are very impressive insects. Trap-jaw ants generate the fastest motion recorded in the animal kingdom, closing their jaws at speeds up to 143 mph. In comparison, the fastest land animal is the cheetah, which can sprint about 75mph. The strongest ants are the Asian weaver ants, which can carry more than 100x their own weight. The most venomous insect in the world is the harvester ant, which has venom 23 times stronger than venom in a bee’s sting. Leafcutter ants construct giant nests in the tropics. Scientists excavated an empty nest that was 538 square feet and went 26 feet into the ground. The ants had to move 40 tons of soil to construct the nest. In human terms, this is the equivalent of building the Great Wall of China.
Ants are interesting to learn about and they also play an important part of the ecosystem. They help control insect pests, decompose trees, aid in nutrient recycling and are an important food source for birds and other animals. I think they are fascinating creatures and I look forward to flying ant night.
photos- an ant colony in an old stump, and a winged ant, from Wikipedia
Late summer is a season of abundance. Birds, butterflies, wildflowers, mosquitoes- so many things seem to be at their peak now. For gardeners of either the cultivated or wild variety, the proof of their efforts is on display, and I think its been a very good growing year.
I am a very lazy gardener, and I think way too much. In my shabby looking garden beds, which do not compare well with those in the butterfly garden at the nature center, I tend to evaluate the merits of the various plants that have volunteered to grow without my intention. Is it being used by bees or butterflies? Will it provide berries or cover that helps birds? I prefer native plants, but a few non-natives, if they don’t take over, add variety to the mix. And so through this ridiculous self-dialogue I end up with less order and more variety than I would like.
One way to skirt the issue is to use plants which are attractive, native, and very vigorous on their own. Sometimes they behave as bullies and take over an area, but because they are natives and likely to benefit insects and other animals, I don’t feel quite so bad about letting them have their way.
I have areas around my house in the country which are old fields. They are populated by whatever plant or seed was around to take advantage of some bare ground. These are often non-native, well established, and have an enormous store of ungerminated seeds in the soil around. Planting directly into such a place is usually a waste of time and seed. But sometimes, with a little mowing, smothering with plastic, or careful use of herbicide (not to excess), these tough customers can be persuaded to give up some space. If especially tough native plants can be introduced there, they stand a chance of becoming part of the species mix and will improve the value of land to wildlife greatly. It doesn’t always work- sometimes their are just so many tough weeds and their seeds are just too much competition. But sometimes, even with a little preparation, one can change the biological landscape in a really positive way.
What plants to use? I’m just going to highlight two that worked well in my old field- wild bergamot and false or oxeye sunflower. Bergamot is one of the many members of the mint family, has aromatic leaves (used in Earl Grey tea), and a kind of messy lavender flower, or cluster of flowers. The individual flowers are tubular, and must contain a wonderful-tasting nectar because bumble bees with their long tongues and hummingbirds seem to be drawn to them in numbers. Bergamot is an aggressive perennial, and once established on a wide variety of soils seems to persist and spread well, muscling its way into a community of non-natives.
False or oxeye sunflower is another easily grown wildflower. It prefers dry, sandy soil but I have had good luck growing it even on more loamy sites as long as they aren’t too wet. It is about the same height as bergamot, 3 feet or a bit more, and it also attracts hummingbirds and some pollinating insects. It’s probably not as valuable as bergamot, but it is a good addition and is easy to grow. It is a short-lived perennial that seeds itself into new areas. Also, it’s yellow color just looks nice alongside the lavender of bergamot.
These two plants really grow well in some challenging spots I’ve worked on and there are many sources for seeds and plants. Right now around my yard they’re full of bumblebees and butterflies, which is what I was hoping for. And its the same at the wildflower plantings at Woodland Dunes. As time goes on one can add more species for diversity, but given the state of things, I think it’s important to do what we can now, even if the effort isn’t perfect. Its so important to at least move in the right direction.