A Northwoods Almanac for March 31 – April 13, 2023
Hopkins Bioclimatic Law
With our Northwoods spring lurking somewhere over the southern horizon, the question is when we’ll see some of that warmth. Well, one way to get an estimate of when we can expect spring to arrive is via “Hopkins Law.” In the early 1900s, American entomologist Andrew Delmar Hopkins developed what he called the Bioclimatic Law, which hypothesized that phenological events in North America were shifted by four days for every 1° latitude north, every 5° longitude west, and every 400 feet of elevation increase.
Doing the math, (one degree of latitude is 69 miles and there’s 60 minutes in one degree of latitude), this means spring moves north at a rate of 17 miles per day. So, for example in Manitowish, we’re 250 miles from Madison. Divide 250 miles by 17, and that equals 15 days.
However, we’re also over 700 feet higher in elevation – Madison is 873’ and Manitowish is 1600’ – so we have to add another 7 days to spring’s march northward.
Thus, in Manitowish, we’re 22 days behind Madison in the arrival of spring. Tulips just blooming in Madison on April 1 will bloom up here on average on April 22.
The Bioclimatic Law was established through observation of the Hessian fly (Mayetiola destructor), an insect pest on many cereal crops. Hopkins proposed his rule of thumb to predict when wheat could safely be sown without risk of attack. Years later, Hopkins suggested that the Bioclimatic Law could be applied generally to many phenological events in plants, insects, and animals.
To be sure, Hopkins law is by no means universally accepted. One researchers writes, “The depiction of the relationships involved is too rigidly defined to fit the diversity that I have come to know in nature.” So, for instance, proximity to the Great Lakes throws the law off, as does proximity to mountains.
Nevertheless, Hopkins’ work continues to be cited almost a century later, and for mixed forest communities like where we live, one analysis showed that spring green‐up varies predictably along broad geographic gradients consistent with the Bioclimatic Law. The researcher does throw in the caveat that variation in timing at individual sites will occur with unusual temperature and precipitation events, so there are lots of exceptions.
All this is to say, hang in there. Cabin fever is running amuck, I know, but spring is near.
Sightings: American Goldfinches, Sharp-shinned Hawk, Pine Siskins
At our feeders in Manitowish, we are currently inundated with American goldfinches – 80 or so! They arrived in force about a month ago, and continue to enjoy the bounty of sunflowers seeds that we provide.
To complicate matters, however, a sharp-shinned hawk arrived two weeks ago, and is a frequent presence in the trees above our feeders. The birds scatter to the four winds whenever he/she is outed, usually by the alarm calls of the local blue jays, so we know to look for the hawk whenever the feeders are bereft of birds.
I have a devil of a time differentiating a sharp-shinned hawk from a Cooper’s hawk. They’re virtually identical, though a Cooper’s is substantially larger on average than a sharpie. But a female sharpie can almost be as big as a male Cooper’s (female raptors are larger than males), so size can’t always be used as a determinant. You have to use a combination of field marks to draw a conclusion, and even then, I’m seldom 100% certain. So, we may have an adult male Cooper’s, but that’s an ID differentiation that is meaningless to the birds at our feeders since both species avidly eat songbirds.
Meanwhile, the goldfinches are starting to molt, which clearly tells us spring is on the way. All birds molt at least once a year to replace weathered and/or worn-out feathers. Some only molt once a year, like blue jays, but others molt twice, the spring (breeding) molt usually resulting in more brilliant coloration in particular for the males.
Finally, a small flock of pine siskins showed up at our feeders on 3/20 after being absent nearly all winter.
Turtles Still “On Ice”
Our northern turtles survive the winter underwater either on top of the sediments or buried in them, but are also known to move around on occasion. Their body temperature goes down to around 34°F and remains that cold all winter long, which allows them to reduce the amount of oxygen they need. Once underwater, their lungs shut down, their blood oxygen levels drop to near zero, and they start to rely on cloacal respiration. The blood vessels around the cloaca (their butt) are able to take up oxygen directly from the water.
If oxygen levels drop very low, snapping and painted turtles can switch to anaerobic respiration, which does not require oxygen. This can cause lactic acid build-up, but they can deal with it because they've got a heavy shell with a lot of calcium and carbonates in it that neutralize the acids. So, the shell, in addition to offering physical protection, helps maintain their body chemistry while they're living underwater.
Sandhill Cranes Returning, and Time for The Crane Count
Sandhill cranes usually begin returning to our area by the first week of April. Like great blue herons, they return before the ice is off our lakes, often feeding along the shorelines of creeks and rivers that open well before our lakes.
Cranes are socially monogamous, often with long-term pair bonds, so most return already mated. In our area, they typically select nest sites in or near seasonally flooded (non-woody) wetlands, while avoiding forested uplands. The presence of shallow water with emergent aquatic vegetation is very important. The nests are constructed of a mound of aquatic vegetation, grass, mud, sticks, and moss.
Once the eggs are laid, they share incubation duties equally during daylight hours, but only females incubate at night; thus females perform about 70% of the total incubation.
The annual Midwest sandhill crane count takes place on April 15. In 2022, over 1,200 people in Wisconsin participated, their effort resulting in a count of 11,513 cranes. In Oneida County, 41 sites were observed by 51 counters, with 153 cranes tallied.
If you’re interested in participating in Oneida County, email Bob and Jan Dall at janbobdall@gmail.com, or call 715-401-3214.
For Vilas and Iron counties, email Hannah Gargrave at the North Lakeland Discovery center at hannah@discoverycenter.net, or call 715-543-2085.
Sandhill cranes have had an incredible recovery over the last 70 years. Only a dozen pairs were known to occur in Wisconsin in 1936, but through various concerted conservation efforts, now an estimated 90,000 thrive in the Eastern United States.
By the way, counting is actually very easy – the hard part is getting up early! So, if you are worried that you don’t know enough to participate, it’s really rather simple to listen for their exceptionally loud unison calls, and jot down when you hear them. That’s fundamentally all there is to it.
2023 Great Backyard Bird Count
The 2023 Great Backyard Bird Count in February exceeded all expectations. Organizers estimate that more than 555,000 participants from 202 participating countries made the latest count the best ever. Participants reported 7,538 bird species and uploaded more than 151,000 photos, videos, and sounds. The highest number of checklists submitted came from the U..S., with India second, and Canada third.
Colombia took the crown as the country with the most species reported, with a mind-boggling 1,293. Ecuador and India followed, both reporting more than 1,000 species. The U.S. ranked tenth with 669 species.
In Wisconsin, 134 species were reported on 4,807 checklists from all 72 counties.
IPCC Report
The Intergovernmental Panel on Climate Change, or IPCC, recently issued a report that marks the conclusion of an eight-year, international effort to analyze the best and most current scientific understanding about climate change. It synthesizes a voluminous amount of research on everything from the physical science of the world’s climate system, to the vulnerabilities of economies and ecosystems, to ways of reducing the impact of global warming and building resilience.
Here’s the bottom line: Without major policy and behavior changes, the average global temperature is likely to rise above the internationally determined benchmark of 2.7°F above pre-industrial temperatures, likely within the next decade. Scientists estimate that’s the point beyond which climate disasters may risk irreversible damage to Earth’s ecosystems.
The report is crystal clear about the cause: “Human activities, principally through emissions of greenhouse gases, have unequivocally caused global warming. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred. Human-caused climate change is already affecting many weather and climate extremes in every region across the globe.”
Here's the final kicker if we choose to not act: No matter what we do now, temperatures will continue to increase because greenhouse gas emissions are cumulative. Think of the atmosphere as a bucket – what we put into the air 50 years ago is still there, and what carbon dioxide that we continue to put in will be there for another 300 to 1,000 years. Other heat-trapping gases, such as methane, have shorter lives, but they cause greater increases in temperature.
So, what do we have to do? We literally have no choice but to limit human-caused global warming to net zero CO2 emissions. Please remember that net zero does NOT mean we don’t emit any more carbon – that’s impossible. It means instead that we figure out how to remove carbon from the atmosphere at the same rate we are emitting it, and that IS possible.
See the report for yourself: https://www.ipcc.ch/report/sixth-assessment-report-cycle/. This is the very best science the world has to offer. We all owe it to our children and grandchildren to actually read it and not play politics.
Celestial Events
For planet watching in April, look after dusk for brilliant Venus high in the west, and for Mars high in the southwest.
Before sunrise, look for Saturn rising in the southeast.
The full moon – the “Awakening/Grass Appearing/Maple Sugar Moon” – occurs on April 5, and we’re up now to 13 hours of sunlight. Who knows – the snow may actually start melting!
The average date for ice-off in the Minocqua area is April 17, so we’re getting close.
Thought for the Week
“The more you watch the river, the more you understand what it means to apply the adjective “alive.” And it’s in those ways, just with regard to the river, the birds, or other components of the place that we separate out and name, that you begin to get an understanding of what this place is . . . The place itself is not all that important. It’s your intimacy with the place that’s really important. You can learn about God anywhere is what it comes down to. You just have to pay attention.” – Barry Lopez, Syntax of the River
No comments:
Post a Comment