Milbert’s tortoiseshell butterflies in flight are a typical Manitoban sign of springtime. (JOHN GAVLOSKI)
As I write this, it is April 2, 2018. The weather in Carman this morning is -18°C and -27°C if you factor in the windchill. The ground is covered in snow. Where is spring you ask? Do not despair – there is hope. . .
The robins have returned! Some animals have started to return to Manitoba from their southern winter homes, and in the next few weeks there will be a lot of animals either retuning from the south, or coming out of their winter hibernations. In this month’s Incredible Creatures we will explore some animals that mark the arrival of spring.
When early-birds can’t get worms
I saw my first robin this year on March 24th. There were a couple of them in my crabapple tree. But there is still snow all over the ground, and no way any robin will be feeding on earthworms any time soon. So will these robins starve? What will they feed on until the ground thaws out and they can find earthworms? Did they do a bad job with the timing of their return to Manitoba?
Not all robins go to warm tropic areas to spend the winter. While many may head to the southern United States or Mexico, some will overwinter in the northern United States, in areas that are covered with snow in the winter. North Dakota and all but the northern part of Minnesota are in the ranges where robins can live year-round. And some may even stay year-round in the very southern parts of Manitoba, although this would not be common. Manitoba is just beyond their normal year-round range. Winter robins eat mainly fruits and berries. This will be the bulk of their diet until earthworms and insects (such as beetles and caterpillars) are available as food. So when they arrive in Manitoba and there are no earthworms to feed on, they will feed on fruits and berries.
If you travel to some of the more northerly year-round locations of robins you will not likely see an abundance of them like you do in spring and summer. They tend to hide out in the trees to survive the cold and winter storms. Since food is often sparse in the winter, the robins need to conserve energy by spending less time flying and hopping around in the cold. So even in some areas where they do overwinter they are considered a sign of spring because people only start noticing them when the weather gets nice and they are in yards seeking worms and other food as the weather warms.
A symphony of frogs
The calls of frogs are another sign of spring for many. The earliest frogs calling in Manitoba are the boreal chorus frogs, which can often be heard by early-April. And by mid-April the wood frogs may be calling as well. The call of Boreal chorus frogs resembles the sound of drawing your finger down the teeth of a comb. So if you hear that sound while out in the spring, it is boreal chorus frogs looking for a mate, not playing with their combs. Wood frogs have a call that sounds like short clacking or barking sounds, often compared to the quacking of a duck. From late April until mid-May you may hear the call of the northern leopard frog. Their call sounds like a long snore followed by a few grunts.
We only have eight species of frogs and four species of toads in Manitoba. So getting to know the calls of common frogs is not difficult. Should anyone want to learn to identify frog calls a good resource is The Manitoba Herps Atlas: http://www.naturenorth.com/Herps/Manitoba_Herps_Atlas.html. If you go to the heading “species info” the frogs are categorized separately under tree frogs (which includes boreal chorus frogs and three other species), frogs (the four species of true frogs; which includes wood frogs and northern leopard frogs), and there is a category for toads (also four species).
While many people associate spring with the arrival of birds such as robins, there are some early-emerging butterflies that can also be a good indication that spring and warmer weather are here. Butterflies such as Milbert’s tortoiseshell and the mourning cloak overwinter as adult butterflies and are some of the earliest butterflies you will see in the spring.
Milbert’s Tortoiseshell (Aglais milberti) is one of the more spectacularly-coloured early butterflies in Manitoba (see photo above). They hibernate as adults, often in small congregations, and are out flying early in the spring. They can be seen flying from April to October, and have two or three overlapping generations each year. Butterflies emerging from hibernation in the spring are usually quite pale and worn.
The adult butterflies feed mostly on sap, rotting fruit, and animal dung, but is also seen feeding on nectar from flowers. Look for them around the lilacs when the lilacs flower. Males drink mineralised moisture from damp ground, and pass the minerals to the females during mating. Larvae of this butterfly feed on stinging nettles.
The mourning cloak (Nymphalis antiopa) is a rich brown colour with creamy yellow borders. The blue dots along the wings help make this butterfly look quite attractive. The adult butterflies hibernate during the winter, often in tree cavities and underneath loose tree bark. Because they overwinter as adults they are able to immediately start mating in the spring. Mourning cloaks are powerful fliers, and have a lifespan of 11 to 12 months, one of the most extensive lifespans for any butterfly. They are known for their graceful gliding behavior. Adults may play dead if attacked by predators. These butterflies feed primarily on tree sap and rotting fruit, and only occasionally on flower nectar.
For butterflies that emerge early, feeding on things like sap and rotting fruit means that there is likely to be food available even when flowers may be scarce. Both the mourning cloak and Milbert’s tortoiseshell have been seen by the end of the first week in April in years with milder springs. This year it may be a bit later with the cool start to spring, but once the weather warms up these are 2 more signs that spring and warmer weather are here.
So enjoy spring and the bounty of animals and plants that will soon be emerging or returning.
The fields, ponds and forests will soon be full of sights and sounds that let us know that spring has arrived.
Incredible Creatures is a monthly contribution to provide information on some of the common yet often not well known creatures that we share space with in Manitoba and abroad.