Well, here we go again, waiting for the latest snow episode to work its way out of our system. We have finally entered the stage where we are setting records- and definitely not the sort that most of us would choose to set. As of April 17th, the amount of snow for the month of April in Duluth sits at 25.5”, and falls under the all time record of 31.6” in 1950. We may cross that threshold tonight into tomorrow. We have also earned the snowiest Feb. Mar, and April in Duluth history at 70.4” breaking the former record of 68.5” again in 1950. The good news is that we are nowhere near the snowiest winter ever designation, in fact we have not made the top 5 (yet!), we are at 104.1” for the season compared to 135.4” in the winter of 1995/96. We really don’t wanna go there! I’m not sure how this rates up the Shore, but my guess is that it has been not quite this bad elsewhere. This winter has dragged on for a long time, and truthfully we haven’t seen one of these for -are you ready for this… nearly 30 years! However, we are still within the bounds of normal for Minnesota- tough as that is to swallow at this point. Time to do what we normally do- suck it up and go on about life.
In wracking through my brain to decide what to write about this week, I got to thinking about insects for a couple of different reasons, one, they are really some of the first brave pioneers to break out in the spring, and two, it’s about time to think about those Luna moth pupae that I have hanging in the garage waiting for warmer weather- more about them in a minute. So this week, let’s look ahead a little bit since springlike current events are summarily lacking at this point.
I guess it should be no surprise that the insects are some of the first things we see in the spring- there are after all over 900 thousand known species. Scientifically speaking, we know there have to be many, many more than that with estimates ranging from 2 million to 30 million possible species out there. As far as pure numbers and biomass, consider this: it’s estimated that there are approximately 200 million insects out there for every human on the earth and a whopping 300 pounds per pound of human. You can do the math- that’s a lot.
Insects can overwinter in any of their normal life stages- adult, egg, larvae and nymphs, or pupae. They are not hibernators- that’s a title reserved for the warm-blooded animal species of the world. As cold-blooded critters their body temperature is always fairly close to whatever the air or water temperature is where they live. They are very well equipped to survive winter by being able to reduce the amount of water in their bodies and producing a chemical called glycerol which is the insect version of antifreeze. So anytime it gets really cold, they just sort of stop moving, seek shelter and ride it out in a process called diapause.
It’s the adults that we see most often first in the spring, and even while it is still winter in the form of snow fleas popping around on the surface of the snow looking like a sprinkling of pepper on top of the snow on a warm day. Others that overwinter as adults include flies, honeybees, ladybugs, wasps, and the amazing first spring sightings of butterflies- which in our area of the world are beautiful black Mourning Cloaks. The one in the photo thanks to the National Park Service, is a little rough around the edges, which is not unusual since they take shelter inside logs or trees, and scrape their way out as soon as it is warm enough to move.
Fewer insects overwinter as eggs, a bit more risk involved here, eggs are not too tough, and can easily freeze, but if you are a preying mantis, this is how you get the job done. Many more overwinter as larvae or nymphs. The terrestrial species can do this in galls on plants such as willow, or goldenrod. The aquatic species such as dragonflies and mayflies stay underwater. In fact some of them spend a much greater proportion of their lives as nymphs than as adults. Often for dragonfly species it is several years as a nymph in the water, and even as long as seven years. Mayfly species hatch as adults and live a brief frenzied 24 hours: hatching, mating, laying eggs, and dying. As adults, eating isn’t on their agenda at all and consequently they don’t even have mouth parts.
Moths typically spend their winters as pupae in cocoons. I was walking at Hartley Nature Center the other day and saw what might well be a Luna Moth cocoon hanging in a tree. Good reminder of the Luna Moths I have hanging in my garage waiting out the winter. Luna Moths like adult Mayflies also spend their adult lives solely for the purpose of mating and laying eggs, and also are not equipped with mouth parts. So they make a brief appearance usually in early summer, lay their eggs which hatch still within the summer as young caterpillars and spend their time eating and growing, until they pupate (or form a cocoon) for the winter. Unlike many species of moths and butterflies, Lunas in Minnesota only have one generation per year. Further south they may have two, if the length of the warm season is long enough for two generations. So I will be settling my Luna Moth pupae in a safe and open place for hatching and pumping out their wings, and watching for that amazing transformation to take place. They will be taking up residence with me at Sugarloaf- so feel free to stop in and check on their progress. And in the meantime, spring has to burst for real at any point now- keep your eyes out for those rough around the edges Mourning Cloaks, and make your predictions for the first hatch of mosquitoes for the season. It really can’t be long now, it just can’t be!
These updates are made possible by a generous donation from David and Rosemary Good.
Watch the Radar!
Well, I’m crossing my fingers and hoping that we are finally done with the snow, snow, snow Apri land have moved on to the spring April . We still have a few days left, and as we know, anything can happen, and has this month! But the warmer weather should be with us for at least a few days. Time for that spring bird migration to really pop!
So how will we know when it really pops? We should start seeing new birds for one, but there are other ways beyond looking to see what is new in the neighborhood. Turns out that we can watch weather radar. Really, radar? Yup, really radar. But before I get into that, a little background information would be a good thing to help it all make sense.
Some species of songbirds fly incredible distances twice a year. Many of these, are called neotropical migrants. This means bird species that nest in Canada or the US and then fly to Mexico, Central America or even South America for the winter. There are thought to be about 200 species of birds that make these lengthy migrations. Many of these birds are warbler sized. So how big is a warbler? In general, much smaller than your clenched fist and can weigh as little as the equivalent of a dime and a quarter in your pocket! So here’s an example- we banded a Blackpoll Warbler on the 22nd of September of 2012, at Sugarloaf. It weighed about 11 grams, or about 2 quarters in your pocket. This bird travels from our area or even further north to Northern South America for the winter, a migration that can range from 2,500 to 5,000 miles for a single bird. That’s a long ways for a bird to travel- how do they manage it?
It turns out that there is definitely some strategy to all of this. Most songbirds migrate at night. This is done for a variety of reasons. For many, it could be a way to avoid predators, who generally fly during the day. It’s cooler at night and since flying generates heat, it is somewhat easier to regulate the amount of energy needed. Nearly all songbirds are daytime feeders, so think about it, if you migrated all day- when would you eat? If they migrate at night, they can rest and eat during the next day(s) to regain their strength for the next round of flight. There is not a lot of space for energy storage in the form of fat, and the energy they consume is quickly burned in the process of flight.
Songbirds like the Blackpoll Warbler can fly at speeds generally somewhere in the range of 10-30 miles per hour. 30 mph seems slow to those of us used to driving automobiles but imagine doing that on your own steam! Blackpolls are also unique in the migratory warbler world. They typically migrate to the southeast rather than directly to the south, which means that their migration to Northern South America always includes a long non-stop flight over the Atlantic Ocean. On average it takes them about 3 days to make this roughly 2000 mile journey, meaning that they have to travel about 660 miles per day. To put that in human terms, imagine you were running 4 minute miles- you would need to maintain this speed for 80 hours straight!
Most songbirds are not quite that extreme but it can take from a few weeks to as long as 4 months to complete their migration. There is a difference in length of time spent in migration from fall to spring. Fall migrations seem to be a little more leisurely, while spring migrations tend to cover distances more rapidly, especially as they get closer to their nesting region. Small birds like Blackpoll Warblers are definitely impacted by the wind. Winds are usually stronger at higher altitudes than at the surface of the earth and most songbirds fly in the range of 500 to 6000 feet about the earth. When they are able to take advantage of the wind at their back they tend to fly at higher altitudes. Flying into the wind will generally have them flying at lower altitudes.
So where does the weather radar fit in all of this? Well it turns out that masses of birds tend to take advantage of the same optimal conditions and move together, so much so that they are actually visible on weather radar. Peak times seem to be from roughly an hour after sundown to the maximum just before midnight and a gradual decline in the hours after than until dawn. If you know how to look you can track the radar yourself. But an easier way is to check with a website (woodcreeper.com) that keeps track of this for us. Our snowy April has definitely kept the bird traffic into Minnesota to a slower pace. In fact the storms of this week actually showed some birds in Iowa and Wisconsin doing reverse migration to the south earlier in the week. The best day of the early part of the week was in the early hours of April 21. See composite image below that summarizes the nights traffic. The birds are the round blobs showing over areas with radar, the darker the blue, the more birds moving. Weather systems tend to be darker than the birds- in this case, greener and more drawn out rather than round- see the system in south Florida for comparison.
www.woodcreeper.com
During the other days of this week there has been virtually no motion to the north in Minnesota. The latest image from the early hours of April 26 is below. Yahoo, there was movement last night, so we should be beginning to see some new birds today! Be on the lookout!
www.woodcreeper.com
These updates are made possible by a generous donation from David and Rosemary Good.
Resources:
www.woodcreeper.com
http://nationalzoo.si.edu/scbi/migratorybirds/fact_sheets/default.cfm?fxsht=9