A Northwoods Almanac for 2/22 – 3/ 7/2013
Spring in the Air?
Though at the moment February continues to offer its normal menu of snow and cold, there are definite signs that spring is coming. Black-capped chickadees are singing their “Hey, sweetie” song more frequently and robustly, ravens are engaging in courtship flights (rolling and tumbling), bald eagles are coming and going from their nests, and if you have cardinals around as Don and Greta Janssen do in Woodruff, the males have begun to more ardently express their desires in song. Even the male pileated woodpecker that uses a dead black ash right next to our house as his favorite drumming tree is now hammering away with a greater frequency and duration, The competition for territories and mates is in its earliest phases, but birds everywhere are heeding the change in daylight, as are our early flowering trees and shrubs. We’ve still got to be patient until May for spring to arrive in full dress, but its first faint expressions are in the air now.
Common redpolls have earned their first name this winter – they have indeed been common, a phenomenon that typically occurs in alternating years. I’m always impressed by these diminutive birds, because they are true cold weather birds. They breed circumboreally, meaning they’re found in boreal regions of the Arctic from northern Scandinavia, Russia, and Siberia, to Greenland, Iceland, and the British Isles.
Their alternating irruption cycle is mostly driven by widespread failure in seed-crop production among spruce and birch trees, which forces them to winter farther south. But they don’t just wander straight south from their breeding grounds – some seem to go on long adventures. One redpoll banded in Michigan was subsequently recovered in eastern Siberia, while another redpoll banded in winter in Belgium was recovered two winters later some 5,000 miles east (89°) in Heilongjiang Province, China. The “why” behind such extraordinary migrations is hard to fathom.
Redpolls are highly acrobatic, feeding in trees on the outermost branches, and often hanging upside down while extracting seeds. They eat a lot – from 31–42% of their body mass each day, though given that they weigh less than a half-ounce, that’s not necessarily a lot of seeds.
As they eat, they store seeds in their diverticula – an expandable area of their esophagus – for later regurgitation, husking, and swallowing. Their diverticula can hold up to two grams of seeds, or about 15% of the bird’s body mass. This adaptation enables them to shelter in dense conifer cover while eating, a savings of significant energy at times of intense cold. This mass of stored seeds when digested provides over 25% of their daily calorie requirements in winter and can get them through a long Arctic night.
And those nights can be extremely cold – common redpolls in Alaska are able to survive at temperatures of -65°F, a figure topped by hoary redpolls, which can withstand -88°F. To survive these temperatures, redpolls employ a number of other strategies besides storing seeds in their diverticula. They retain heat by fluffing their feathers, an effective tool given that wild Alaskan redpolls have 31% heavier plumage in November than in July. Their plumage structure is also better for insulation than many other species.
They also know to remain inactive whenever possible to retain energy, and to seek shelter. In fact, they have been observed making roosting chambers in snow! They drop from a tree into the snow, and dig out a tunnel 10 to 15 inches long down to a chamber 2 to 4 inches below the snow surface. Then before dawn, they break the roof to depart, leave the roost, and start foraging, being active considerably earlier than other birds. They are even reported to be sunbathing at times, though I’m not sure how this is determined. (Do they sit in lounge chairs? Perhaps put on sunscreen?) I don’t know, but what I do know is that redpolls are remarkably adaptive, and we’re truly fortunate to have them at our feeders.
A number of people have emailed to say they have red crossbills now coming to their feeders, a species that Mary and I have never seen at our feeders in Manitowish (we’re jealous!). Their highly distinctive mandibles are curved and crossed at the tip, an unmistakable feature shared only with white-winged crossbills. The adult male is a deep brick red to reddish yellow (some even greenish) with uniformly dark blackish brown flight feathers, and a short, deeply notched blackish brown tail. The female, on the other hand, is uniformly olive to grayish, with a greenish-yellow breast and rump and a white throat.
Keep an eye out for these highly uncommon birds!
I often hear this response to what seems like relatively small increases in overall annual temperatures: “Why would 2 or 3 degrees warmer matter to anything? So what?”
Well, here’s a great example of “so what” – the mountain pine beetle, a native species that has never before been much of a problem. In the last decade, however, an exponential increase in the beetle population has occurred from the Sangre de Cristo Mountains in New Mexico to the Yukon Territory near Alaska, the result of which has been that the number of forest acres killed by these beetles is 10 times that of any previous epidemic recorded.
Long thought to produce only one generation of tree-killing offspring annually, some populations of these native mountain pine beetles now produce two generations per year, dramatically increasing the potential for the bugs to kill lodgepole and ponderosa pine trees. Because of the extra annual generation of beetles, there can be up to 60 times as many beetles attacking trees in any given year, an exponential increase. Each beetle lays 60 eggs and, since nearly all survive, each of those beetles goes on to lay 60 more eggs in the same summer, which means 3,600 more beetles.
Why has this happened? In the last two decades at the Mountain Research Station in Colorado, mean annual temperatures were 2.7 degrees Fahrenheit warmer than they were in the previous two decades. The number of spring days above freezing temperatures increased by 15.1 in the last two decades. Also, the number of days that were warm enough for the beetles to grow increased by 44 percent since 1970. It should also be noted that a serious prolonged drought has increased the forests’ susceptibility to the beetles.
The bottom line – warmer temperatures have given the beetle larvae more spring days to grow to adulthood.
Not only are the beetles expanding in all directions, they are expanding upward. In the last 25 years, the beetles have expanded their range 2,000 feet higher in elevation and 240 miles north in latitude in Canada.
So, what does a western beetle have to do with us? The Great Plains have long been considered an insurmountable barrier to the mountain pine beetle, but now some fear that the beetles could reach the Great Lakes region. The beetles are now between 60 and 120 miles from the nearest stand of jack pine, a species not previously acquainted with mountain pine beetles and which experimental evidence suggests that the beetles will thrive in. If the beetle hits the jack pines, nothing would stop it from plowing eastward into stands of eastern white pine and cruising south all the way to the loblolly pine forests of the Southeastern United States.
So, does a two or three degree average increase really matter?
The full moon, called by some tribes the “Snow” or “Hunger” moon, occurs on 2/25.
For planet-watching in March, after dusk look for Jupiter bright in the west, while Saturn rises in the east after 9 p.m. Before dawn, there’s not much to see until Mercury reappears low in the southeast around mid-month.
On 3/2, look later in the evening for Saturn about 3 degrees north of the moon.
March 6th marks the first day that our average high temperature again reaches 32 degrees, a figure we haven’t seen since November 30th. For those of you who think it’s always cold in the Northwoods, Minocqua averages 269 days with high temperatures above freezing every year.