By Ty Fitzmorris
The coldest season has come round again, and the wilds have entered the depth of their quiescence. But though the nights are at their longest now — the longest of the year is on Dec. 21, the Winter Solstice — the coldest (and, for many species, hardest) parts of the winter are still to come. December is slightly warmer and bears a bit less rain and snow than January, when the days will be already growing longer again. This lag between the darkest and the coldest times is a result of an interaction between the thermal qualities of the air masses in the atmosphere and the thermal mass of the landscape — the air holds its temperature long after incoming solar radiation has declined, but now begins to lose its heat to the rapidly cooling land. It is for this reason that the warmest parts of the summer are typically after the Summer Solstice, and that the coldest parts of the winter are after the Winter Solstice.
As a result of low temperatures and lack of sunlight, plants and insects now enter the depth of their winter diapause, when almost no activity is to be found. These two groups are the primary food sources for almost all of our species, so their somnolence brings extreme hardship for birds and mammals, the two groups that remain most active. Only the most resourceful and innovative can find food during this time, and often creatures are more desperate because of this. Predators, such as Cooper’s Hawks, Sharp-shinned Hawks, Coyotes, and Bobcats, become more daring in their attempts to catch small birds and rodents, and as a result prey species become more adept at avoiding their predators. Many birds band together into mixed-species foraging flocks, while rodents spend more time in near-hibernation in their dens after storing food for the last several months. Larger herbivores, such as Mule Deer and Pronghorn, live off of stored body fat for the next few months, and stay on the move to avoid predators. For all species this season is the time of highest overall mortality.
Even in this darkest time of year the astute observer can find the first glimmerings of spring. In the lowlands and deserts a few insects and relatives will appear on sunny days — harvester ants maintaining their colonies and gathering seeds, Mourning Cloak butterflies flying in river bottoms, and wolf spiders hunting for other small arthropods in leaf litter. Our deciduous trees, though leafless now, have begun swelling at their leaf-buds, growing what will become their spring flowers and leaves, while some, such as the Arizona Alder, grow their entire pendant flowers. Female River Otters are nearing the end of their pregnancies, and moving towards their dens, while Black Bear wait in their hibernacula, also about to give birth. As in the great never-ending cycle of birth, growth, mating, dispersal, and death, the darkness of winter enfolds the seeds of spring.
A Very Brief Survey of What’s Happening in the Wilds
• Pine Siskins, Red Crossbills, and Cassin’s Finches may appear from the north during especially cold years, often finding and flocking with House Finches and Lesser Goldfinches. This behavior helps migratory species learn the distribution of food in places with which they are unfamiliar.
Visit: Spruce Mountain Loop, Trail No. 307.
Ponderosa Pine Forests
• Dark-eyed Juncos arrive in force from colder lands to the north and join with Bridled Titmouse, Mountain Chickadee, Brown Creeper, and several species of nuthatches to form mixed-species flocks. These species stay together for months, and apparently gain protection from having many eyes of different types looking for predators. They avoid competing with each other by dividing up the microhabitats of trees — look for Juncos foraging on the ground, Chickadees in the tips of branches, nuthatches foraging in a downward spiral around trunks, and Brown Creepers foraging in an upward spiral.
Visit: Schoolhouse Gulch Trail, No. 67.
• Bushtits are very active when the weather is calm. These tiny, mouse-like birds are distinctive in that they forage in large flocks, but the birds trickle from one tree to the next in a slow but continuous stream, chiming continuously with beautiful calls. Once they have landed these birds search each tree assiduously, gleaning many thousands of insect larvae, thereby keeping many insect species under control.
• Several species of harmless spiders move into human dwellings, the most obvious of which is the Giant Crab Spider (Olios giganteus), which can often be seen running on walls and ceilings. These spiders are non-venomous, and can easily be relocated to the outdoors by carefully trapping them under a cup so that they aren’t injured.
Visit: Little Granite Mountain Trail, No. 37.
• Raccoons spend long periods, up to three weeks at a time, in their dens. Dens are typically in trees, though in the higher elevations Raccoons may excavate burrows. Dens can sometimes be found because of nearby latrines, large deposits of scat. This year’s young stay in the den with their mother for their first winter.
Visit: Tin Trough Trail, No. 308.
• Hawks continue to migrate from the north, escaping colder temperatures. Look for Swainson’s, Rough-legged, and the very rare Northern Goshawk.
• Gunnison’s Prairie Dogs (Cynomys gunnisoni) begin their winter hibernation deep in their underground tunnels, to emerge again in March or April. This is the smallest species of prairie dog in North America and the only one in the Mogollon Highlands, and is one of the most important of all species in maintaining the health of our grasslands. Their burrows both oxygenate and nitrogenate soils, which fertilizes grasses and forbs. Prairie dogs are also important sources of foods for many other species, such as hawks, snakes, and Black-footed Ferrets. They are a “keystone species” in that they are one of the species that forms the basis of their ecosystem.
Visit: Mint Wash Trail, No. 345.
• Waterfowl of many different species, including Pintail, Ruddy Duck, American Widgeon, Gadwall, Green-winged Teal, Shoveler, Canvasback, and Bufflehead, have arrived in our lakes by the thousands, and are easily observed as they feed from now until early spring. Rare birds, such as loons, ibis, some goose species, and several kites, appear in the lakes in midwinter, blown off course by winter storms sometimes thousands of miles away. Notice that some species dive while others “dabble,” or upend. The divers tend to feed in the deeper areas, while the dabblers stay closer to shore. It is partly because of the importance of Willow and Watson lakes near Prescott to North American waterfowl that they have been recognized as Important Bird Areas by the National Audubon Society, which affords them some protection. Both Watson and Willow lakes, however, carry extremely high levels of chemical and biological contaminants, and the effects of these on waterfowl are relatively unstudied.
Visit: Willow Lake Loop Trail, off of Willow Creek Road in Prescott.
• Some very few last native flowers persist, such as Desert Marigold (Baileya multiradiata) and Cliffrose (Cowania mexicana), providing nectar for a few species of butterflies, native bees, and flies.
• Kit Foxes, the smallest and most furtive of our foxes, begin their mating season.
Visit: Agua Fria National Monument.
Average high temperature: 51.7 F (+/-4.2)
Average low temperature: 21.9 F (+/-3.5)
Record high temperature: 78 F (Dec. 2, 1926)
Record low temperature: -9 F (Dec. 24, 1924)
Average precipitation: 1.66” (+/-1.63”)
Record high precipitation: 6.96” (1965)
Record low precipitation: 0” (10.2 percent of years on record)
Record high snowfall: 46” (1967)
Record daily precipitation: 3.13” (Dec. 30, 1951)
Source: Western Regional Climate Center
• Dec. 7: New Moon at 12:20 a.m.
• Dec. 13: Geminid Meteor Shower at its peak after midnight. This shower is considered to be the brightest and most numerous of all of the meteor showers of the year, with 60-120 visible meteors per hour. The waxing crescent Moon will not compete with this extraordinary meteor shower, since the Moon will set shortly after sunset, leaving excellent conditions for viewing even the most faint meteors. This meteor shower is one of the youngest observable from Earth, only appearing in Earth’s skies in 1860, and growing brighter and more numerous until now. Over the next 100 years this shower will fade to relative inconspicuousness.
• Dec. 15: Mercury at Greatest Western Elongation. The smallest planet in the solar system is at its most visible now in the morning sky, within the hour or so before the Sun rises.
• Dec. 21: Winter Solstice at 3:23 p.m. The Earth is at one of its two yearly extremes with regard to the angle with which the poles face the Sun. The Northern Hemisphere is tilted at its maximum away from the Sun, causing what we experience as the shortest day and longest night of the year, while in the Southern Hemisphere the opposite is true. Every day after this one, until June 21st, 2019, the days will get slightly longer (at higher rates around the equinoxes), while the nights get shorter. Interestingly, however, this is not the day of the earliest sunset and latest sunrise — those fall on Dec. 3 and Jan. 7, respectively.
• Dec. 21: Ursid Meteor Shower. This usually small shower periodically undergoes a dramatic increase, from its usual 5-10 meteors per hour to over 100 meteors per hour. While astronomers are not decided on the cause of this periodicity, it seems that it happens every eight years, next expected in 2023. The nearly full Moon will wash out many of the fainter meteors, but the brighter ones will still be visible, and will appear to radiate from Ursa Major (the “Big Dipper”).
• Dec. 22: Full Moon at 10:49 a.m. Notice that this full moon passes directly overhead toward midnight, much higher in the sky than the sun was at noon yesterday (or tomorrow, for that matter). The underlying reasons for this are complex — at the Winter Solstice our position on the Earth is leaning its furthest away from the Sun, so the Sun will be at its lowest in the sky at noon. But when we rotate around to midnight (where we’re facing directly away from the Sun) the Moon will be high in the sky, since our position on Earth is aimed more directly at it. By contrast, today at noon in San Rafael, Argentina (which is exactly as far south of the equator as we are north of it) the Sun will be at its highest of the year, and the full moon 12 hours later will be at its lowest.
Ty Fitzmorris is an itinerant and often distractible naturalist who lives in Prescott and is proprietor of the Peregrine Book Company, the Raven Café, Raven Sound Studio and Gray Dog Guitars, all as a sideline to his natural history pursuits. He is also the Curator of Insects at the Natural History Institute. He can be reached at Ty@PeregrineBookCompany.com with questions or comments.