Janet Patton, NDSU Central Grasslands Research Extension Center
Table of Contents
Spring is a fickle season. The temperature rises and the wind picks up. Next we are hit with freezing rain or wet snow. The few warm, calm days are teasers that remind us to tie up the winter work and get ready for the hectic but upbeat days ahead. The weather is in control!
As the sun moves north, crossing the celestial equator, the days become longer and the sunlight more intense. This marks the vernal equinox, which occurs this year on March 20th.
Spring is also the time of year when the apex of orbit, or the leading point of the earth as it moves on its path around the sun, is at its southernmost location. This orientation allows meteors which approach the Northern Hemisphere to move through the atmosphere at slower speeds and so are able to come closer to the earth’s surface before vaporizing. The result of all this? Three times as many fireballs, or bright meteors, are seen in spring than in fall. Bolides, fireballs that explode in flight, may also occur.
Two major meteor showers occur in the spring, although neither is spectacular. The Lyrids, which appear around April 21-22, are part of a young meteor stream, and the rate of 13-17 meteors per hour changes little from year to year. The Eta Aquarids (peak: May 5-6) are made up of debris from Halley’s Comet, and appear at an average rate of 20 per hour. Both showers radiate from the south or southwest in the predawn sky.
An interesting alignment of the planets can be seen from late March through early April this year. All five bright planets: Jupiter, Venus, Mercury, Mars, and Saturn, will be visible in the early evening sky. This arrangement of planets, like beads on a string, is the last for many years. Look for bright Venus towards the west near the Pleides.
North Dakota is blessed with “nearly continuous air movement” in the spring (Jensen, no date). April is, in fact, the windiest month of the year, with an average wind speed of 12.8 mph at Bismarck. This is due to uneven solar heating, which also causes the wind to be stronger in the afternoon than at other times. Unlike precipitation which can vary a great deal from year to year, the average wind speed in a given year differs from the long-term average by only 10% at most. In the spring, the prevailing winds at Bismarck are from the northwest.
March is known as a snowy month with an average of 8.7 inches of snow at Bismarck. This is due to low pressure systems that move into the area from Colorado causing blizzard conditions. By late March or early April, the first substantial rains occur, brought on by storms which track in a more northerly course than those of winter. This moisture comes from the Gulf of Mexico, and although spring rains are light, they are steadier than those of other seasons. Monthly precipitation at Streeter increases from 0.70 inches in March to 3.45 inches in June, the wettest month of the year.
March and April are transitional months with regards to temperature. Average monthly temperatures increase by 15° to 19° F. through each month. The average last date when below freezing temperatures occur is in mid-May, resulting in 110 to 130 frost-free days a year.
The Missouri Coteau is a portion of the Prairie Pothole Region, an area from Alberta to Iowa once covered by glaciers. The word “coteau” translates from the French as “ridge” or “high ground”. These rolling uplands with numerous wetlands are found in a narrow band running from Saskatchewan to South Dakota. They were formed by the deposition of thick glacial sediments at the southern margin of glaciers as recently as 12,000 years ago.
The Missouri Coteau is 300 to 500 feet higher than the Glaciated (or “Drift” ) Plain found to the east. The Missouri Escarpment is the border between these two areas. This slope was formed before glaciation, but the movement of the glaciers over and along the length of the escarpment made it steeper and straighter (Bluemle 1991).
The Coteau Slope is found to the west of the Missouri Coteau. This area has a natural drainage system that flows west and south to the Missouri River. The Coteau, on the other hand, has no natural drainage, that is, no streams.
The interesting land forms of the Missouri Coteau are the result of the action of glaciers and subsequent erosion. The glaciers were sheets of ice sometimes thousands of feet thick. Flowing southward, they picked up soil and rocks, reworking this material as they moved. Ridges known as “thrust masses” were pushed ahead of the advancing glaciers. These formations are from local sediments that were folded and/or lifted (Bluemle 1991). When the climate warmed and the glaciers began melting, huge amounts of materials were deposited at the stationary glacial margin. Mudflows in tunnels within the glaciers created ridges (eskers) which can be seen today. Some sediments were rearranged by melt water at the margin of the glaciers, leaving outwash areas of loose sand and gravel. As the glacial ice melted, the layers of debris covering the glaciers settled unevenly, forming hills. In some areas, the debris over the ice was so deep, providing insulation, that the ice took 3000 years to melt. This settling resulted in the “hummocky collapsed topography” (Bluemle 1991) of the Coteau with prairie sloughs between the hills. Glacial sediments in this area are 500 to 600 feet thick, and are the remains of several glacial advances. Glacial till forms rich soil, although in the case of the Coteau, hilly, rocky, and sandy areas were created as well.
Because there are no streams in the Coteau, the sound of running water here is very unusual. Rivulets from snow melt last for a few days or hours, and sometimes not at all during a very slow thaw. Drainage in this area is “unintegrated”, meaning without channelized surface flow, and the numerous potholes and wetlands can hold large volumes of water, release it slowly, and reduce flooding. Groundwater is recharged by some of these basins, and due to frozen ground in the spring, most of the water for recharge is from snow melt. Depending on topography and the underlying sediments, some basins are groundwater recharge areas which release groundwater, and others both collect and release groundwater (“through-flow” systems). Some basins, called discharge areas, simply collect water and lose it only by evaporation, thus becoming saline. The flow of water through prairie potholes and wetlands is beneficial because the process filters out contaminants and sediments (Kantrud et al. 1989).
The Missouri Coteau has a large number of semi-permanent wetlands (> 100/ sq. mi.) due to the underlying glacial landforms of terminal moraines and depressions left by large ice blocks. To the east, on the Glaciated Plains, the wetlands are shallow and more temporary in nature because they occur on more level ground moraine (Kantrud et al. 1989).
The surface of the soil may begin to thaw in late March, but the maximum depth of frost actually occurs in April, at about the 4½ foot depth. Warmer air temperatures allow the soil at the surface to thaw at the same time ground heat begins to thaw frozen soil from below. The last soil to thaw is at the three foot level, usually by May. At this depth, the soil reaches its maximum temperature in mid-August, two weeks after the surface soil has reached its peak.
Seeing the prairies and wetlands green up in the spring is always encouraging. This usually begins when mean daily temperatures reach about 45°F. Temperature is the most important trigger for plant growth, but sufficient day-length, moisture, and cold-period are requirements, too.
In April, the crocus or pasque flower (Anemone patens) is the first flower seen on the prairie, along with the first growth of the cool-season grasses. The crocus flower is interesting in that the petal-like sepals are shiny and curved and reflect sunlight to the center of the flower thus increasing the temperature within by 18°F over the air temperature (Collicutt 2001). This promotes pollen and seed development and also attracts pollinating insects. The flower also follows the path of the sun. After flowering, the fuzzy leaves emerge. The seeds are released by early June. The long tail of the seed has stiff hairs and twists when exposed to water, pushing the pointed seed into the soil. Sufficient moisture will allow the seed to germinate, otherwise the seed will become dormant until next spring. The leaves of the crocus plant die back by the time the grasses have reached their full height in mid-July. Crocuses are long-lived plants (50 years or more) with a woody taproot, and are well designed to avoid competition.
Other early flowering plants of the prairie include wild parsley (Lomatium orientale), common dandelion (Taraxacum officinale), prairie buttercup (Ranunculus rhomboideus), and yellow prairie violet (Viola nuttallii). The cool-season grasses like Kentucky bluegrass (Poa pratensis), green needlegrass (Stipa viridula), and smooth brome (Bromus inermis) do not begin blooming until June, but by then have put on 50% of their total growth for the year. The warm-season grasses begin growth in mid-May, with summer being their primary season of productivity.
Growth on woody plants is first seen in the emergence of willow and poplar catkins. Willow flowers are insect pollinated and benefit from the activity of the earliest bees and flies. With our short growing season, trees must leaf out quickly, first the box-elder, elms and chokecherry, and then ash.
Woody plants, with all their years of evolutionary adaptations, are good indicators of when to plant gardens. The Hidatsa people, planting on the bottomlands of the Missouri River, observed the wild gooseberry plants. This shrub was the first to leaf in the spring, and in early May, when the bushes were almost in full leaf, it was time to plant corn. This planting took nearly a month, followed by squash and beans. The sunflowers, by the way, were planted as soon as the soil could be worked in April.
Other traditions state that cool-season vegetables such as peas and lettuce should be planted when the lilacs begin to leaf out, corn when the oak leaves are the size of a mouse’s ear, and cucumbers and squash when the lilac flowers fade.
My favorite indicator of spring is the call of the frogs. The male chorus frog can be heard “chirping” like a finger along a comb, in small, shallow wetlands from early April to mid-June, even before all the ice has melted. This non-climbing tree frog is tan to gray or green, with three dark stripes down its back. The chorus frog is the smallest frog found in North Dakota. It breeds in ponds in early spring, and the tadpoles develop into froglets 40 days after hatching.
Northern leopard (or meadow) frogs are more common and also emerge in early spring. Their call is like a deep snore, or someone rubbing a balloon. These green to gray frogs usually have dark spots. With their long legs, they can leap five to six feet. The eggs hatch in ponds after five to seven days, and froglets may be seen in late July or early August. Some tadpoles may stay in deep ponds and metamorphose into adults the following summer.
Toads emerge a little later, in May. The Canadian toad prefers the wetlands; the Great Plains toad, the drier grasslands; and the Woodhouse’s toad, either habitat. These toads breed in spring or early summer following a heavy rain. Eggs hatch in three or four days, and the tadpoles become toadlets in 40-50 days. The Canadian and Great Plains toads have a trill-like call, sounding like a riveter. The Woodhouse’s toad sounds like a sheep.
Tiger salamanders maybe silent, but they have endearing smiles. Ranging from 6”-12” long, they are the largest land-salamanders in the world. During rainy periods in spring, they crawl to deep ponds for mating and egg laying. After 20 days, the eggs hatch into gill-bearing larvae, and after another 60-100 days, the larvae are mature enough to leave the water. Some larvae may remain in the pond to emerge the following spring, and others may remain neotenic, i.e. in the larval stage, their whole life, though still able to breed. They eat invertebrates while in the water, and almost anything while on land. Salamander larvae are an important food source for white pelicans, grebes, herons, gulls, and cormorants. Their numbers have been down in our area recently due to a virus outbreak which also affects frogs, and perhaps due to spring cold snaps as in April 1997, as well.
The Missouri Coteau in North Dakota is home to only a few reptiles, which makes them easy to learn. The western painted turtle emerges from sloughs in April or May. This dark-back turtle has a black central patch on the underside, with red and yellow markings. Yellow stripes are found on its head and neck. These turtles nest in June, laying 5-15 eggs, and the young turtles hatch in ten weeks.
Two species of garter snakes occur here. The red-sided garter snake is dark with yellowish stripes and red bars along its sides. These snakes den together in the winter in “hibernacula”, or caves below the frost line. Up to 10,000 snakes have been reported in one location. The plains garter snake also has three stripes: the center one orange or yellow, and the side stripes bluish–green, along with a double row of dark spots between the stripes. Both species eat frogs, worms, insects and minnows.
Two unmistakable small snakes are also found in our area. The smooth green snake is 14”-20” long and bright green above and white below. Its postmortem color is an unnerving blue. The red-bellied snake, 8”-10” long, is light to dark brown with a red to salmon-colored underside. Three light spots are found on its nape. Both snakes eat worms and insects.
The plains hognose snake is a secretive snake of sandy areas in the mixed-grass prairies. This snake is 16”-25” long, brown with dark blotches and an upturned snout. It is most active in the early morning.
Springtime weather affects the emergence of invertebrates. Rain and wind reduce the feeding and mating activities of flying insects, which can lower the number of larvae available to young waterfowl. Temporary wetlands contain a wide variety of invertebrates: crustaceans, annelids (worms), gastropods (snails), aquatic insects and the larvae of terrestrial insects like dragonflies and damselflies. These are important food sources for birds, fish, and amphibians. Most mosquitoes hatch from shallow pools of rainwater and snowmelt.
Ticks appear in mid-April, looking for a meal. The sub-adults feed on rodents, while the adults feed on large mammals. Their method of crawling up a grass stalk or leaf edge and waving their front legs is known as “questing”. They detect a potential host by sensing carbon dioxide, heat or movement.
One sure sign of spring is the arrival of migrating birds. About 100 species stop in North Dakota on their way to northern nesting grounds. Shallow, temporary wetlands warm up quickly in the spring and are soon populated with insects and crustaceans, important food sources for both migrating and early-nesting birds. These ponds are valuable stopovers for shorebirds that nest in the arctic and sub-arctic. Pasture and croplands are also used by migrating species for foraging.
Mallards and pintails are among the first nesting birds to arrive (in mid-March), and they prefer the temporary wetlands including those in cultivated fields. Giant Canada geese are also early nesters. This is the only race of Canada geese to nest in North Dakota, but others may been seen during migration. More permanent and deeper sloughs are used by both dabbling and diving ducks. These ponds are the last to open in the spring, and may support many species of birds, especially if more shallow ponds dry out in a dry spring.
Most ducks are philopatric, that is, they return to their place of birth. Courtship and pairing usually take place at the wintering site and the male follows the female to her home ground. Since the location was successful due to safe nesting and rearing sites and a good food supply, it is logical that the female would return to it. Some duck species have a strong need to return home (diving ducks, gadwalls and mallards), while others are more flexible, especially those dabbling ducks, like blue-winged teal, that use ephemeral, shallow ponds. Other birds commonly nesting in Coteau wetlands include: herons, coots, grebes, willets, sandpipers, marbled godwits, snipes, Wilson’s phalaropes, American avocets, killdeer, red-winged blackbirds, and black terns.
Another early arrival to our area is the western meadowlark. These birds prefer lightly to moderately grazed grasslands. The male arrives in late March to set up a nesting territory with a “bragging post” from which he can sing, facing the sun. From here he can defend his 3- to 15-acre territory and also woo a female. The males compete with song and may threaten one another with an upward “bill-tilt” and a “fluff-out”. The meadowlark song is complex, with double-notes, warbles and gurgles, said to sound like “Have you planted your wheat yet?”. Males learn from one another, resulting in regional variations. Singing stops once nesting begins. The female meadowlark nests on the ground, making a waterproof dome of grasses over the nest. If a male is heard singing in mid-summer, it may mean that the pair is ready to start a second brood.
The drumming and hooting of the male sharptail grouse can be heard in April. At display areas called “leks,” males gather at sunrise to show their dancing skills and attract females.
Spring is a good time to look for owls. Three species are found year-round in North Dakota: great-horned owl, eastern screech-owl, and short-eared owl. Two more arrive in April: burrowing owl, and long-eared owl. Although owls are not frequently seen, they are stand-outs and their distinctive calls may be heard most often in the spring or fall.
The male Richardson’s ground squirrel is the first to show up in late March, followed by the females in early April, and the Franklin and thirteen-lined ground squirrels in April or May. Meadow jumping mice emerge in April, while the western jumping mice appear in May or June.
Many mammals breed in winter (coyote, fox, skunk) and the young are born in spring. A few (badger, long-tailed weasel, least weasel) mate in late summer or early fall and the embryos begin to develop, but implantation is delayed until February or March. The young are born two months later. In some species of bats, mating occurs before hibernation but fertilization is delayed until spring. The young are born in summer. All of these adaptations insure that the young are born and reared at the optimal time of year.
Spring is the optimal time for rejuvenation, even if it lasts but a short while. We must stop and take in the warm sunshine of the lengthening days and the sight of new green plants before we hurry on our way. Don’t miss it.