Bird nests range from simple to elaborate

Just when I think the robin can’t hold any more grass in its beak, it leans over and picks up one more piece before flying to a nearby tree. Without any guidance, the robin knows exactly what materials to collect to build its nest and how to construct its nest. 

Nests are not random creations because all birds of one species tend to build the same type of nest with similar dimensions and materials. For example, American robin nests are deep cups constructed of mud and grass usually in the fork or crotch of a tree. There are exceptions like robins nesting on rail fences or in wood sheds but you wouldn’t find a robin nesting on a gravel bar. 

A cedar waxwing nest is hidden from view

Birds instinctively know how to construct a nest and where to construct it. Nests can be as simple as a scrape in the dirt to massive aeries weighing two tons. No matter the nest, they all serve the same purpose--keep the eggs and hatchlings warm and safe from predators.

The simplest form of nest is the scrape which is a small area cleared for eggs. Scrape nests are used by most shorebirds, terns, many ducks, pheasants, quail and some falcons. Terns and killdeer make a scrape nest among small rocks and rely on the speckled eggs to keep them camouflaged from predators.

A simple type of nest is a cleared area for eggs such as this killdeer nest

Arctic terns lay their eggs among small rocks without any other material

Mallards also use scrape nests but often line it with grasses or other soft materials. Many birds line their nests with soft materials for the eggs and hatchlings.

However, some birds don’t even clear an area for a nest. Some raptors and owls just lay their eggs in a safe place, such as on isolated ledges or in small caves on a cliff. Their eggs are often pointed so they roll in a circle instead of rolling off the ledge. 

The most common type of nest is the cup nest. Most songbirds, hummingbirds and swifts build cup nests. Cup nests are built with pliable materials, such as grass, to make a well-insulated nest. Robin nests are a familiar cup nest as well as barn swallow nests. 

A cup nest that has fallen out of a tree

The middle layer of a robin’s nest is mud and is shaped just right by the female sitting in the partially constructed nest and rotating her belly around while the mud is still moist so it can be smoothed and shaped. 

Barn swallows also use mud to build their nests but their nests are made of mud pellets mixed with grass, straw or hair and then attached to a vertical surface. Collecting mud is no small feat and one barn swallow made more than 1,200 trips to construct its nest. Swallows then line the nest with feathers or hair. 

Hummingbirds build the tiniest of cup nests using fine plant material held together with spider silk. As if the small size wasn’t enough to make the nest hard to find, hummingbirds camouflage the outside of the nest with moss or lichen. 

Often cup nests aren’t seen until the leaves fall off the tree or shrub. Most cup nests succumb to the elements over the winter and some of the materials may be utilized the next spring when most songbirds build a new nest (though some birds, such as robins, may reuse their nests). 

Winter weather slowly deteriorates bird nests

Other types of nests are reused more often than cup nests, including those of eagles and woodpeckers. Look in next week’s column to find out about these nests and other types of bird nests. 

Caterpillars utilize a variety of tactics to stay alive

As a slow-moving, plump morsel, caterpillars are an ideal target for a predator’s meal. However, caterpillars still exist because they have developed means to escape detection from predators or ward off predators.

Black swallowtail caterpillars use black and yellow coloration to warn predators of their toxicity

The most common way caterpillars, like many other animals, escape detection is camouflage. Their camouflage makes it hard for even us to find them when they resemble twigs, bark, leaves, buds, flowers, fruits and tendrils. Larvae of several swallowtail butterfly even resemble bird droppings--something even birds won’t touch. Others bear false eyespots that resemble snake’s eyes or look like hair balls or small furry mammals.

Another way caterpillars escape detection is by not being exposed. They gain protection by living concealed lives within stems, roots, galls, seeds, wood and other plant tissue. Tent caterpillars build silk tents to help protect themselves from hungry birds. Tent caterpillars also find safety in numbers. 

On the other end of the spectrum are caterpillars that are brightly colored and say “See me!” The black and yellow stripes of the black swallowtail caterpillar are easy to spot in the garden but birds have learned to avoid them. The bright colors are a warning to alert predators of the unpleasant taste or toxicity of the caterpillar. Black and yellow are two of nature’s most widespread warning colors as demonstrated with wasps and bees. 

Monarch butterflies advertise their distastefulness with their black and orange coloration. They obtain this distastefulness during their larval stage when the caterpillar eats milkweed and retains the toxins. 

Caterpillars can either obtain their toxicity from the plants they eat or they can manufacture the toxic compounds themselves.

Bristles and hair protect some caterpillars from predators

If taste isn’t bad enough, one caterpillar wards off predators with its bad breath! The tobacco hornworm dines on nicotine-containing plants and as a result has bad breath which keeps predators at bay. 

Predators also tend to pass over caterpillars with hair or bristles--who would blame them. While some caterpillars are just hairy, like the woolly caterpillar, others have spines and barbs. Some caterpillars have urticating hairs which are hollow hairs that discharge a painful irritant when broken. The urticating hairs even cause irritation on curious humans. 

Some caterpillars use multiple tactics, such as hair and colors, to deter predators

Bristles and hair also deter parasitizing insects from laying eggs within the caterpillar and then upon hatching eating the caterpillar’s insides. The hair and bristles act as an armor against these insects since they seek out the caterpillar by smell. 

If smell, coloration, bristles and hair don’t ward of predators, caterpillars often resort to thanatosis--playing dead. Have you ever touched a caterpillar and it has fallen to the ground? The caterpillar is playing dead and is hedging bets that if it remains motionless on the ground it may go undetected. 

Caterpillars exhibit a wide array of physical, chemical and behavioral tactics to avoid being eaten. However, predators keep adapting their search techniques to these tactics and help keep the caterpillar population in check.

Spring wildflowers bring first splash of color

As the weather warms, signs of spring are everywhere--green grass, emerging larch needles and spring wildflowers. The burst of color from spring wildflowers is a welcome sight after winter. 

There are several wildflowers to look for as the snow melts and the days become warmer in North Idaho, most notably the western trillium, western spring beauty, violets, yellow bells and yellow glacier lilies. 

Yellow glacier lilies and western spring beauty

Whether they bloom in early, mid- or late April depends on the weather but these five are usually the first wildflowers emerging. Depending on elevation, however, they can be found as late as midsummer in the high mountain meadows. 

These five wildflowers are the beginning of a palette of color that will paint the woods, mountain meadows and hillsides over the next several months.

Western white trillium (Trillium ovatum)

The western white trillium is one of the first wildflowers to emerge in the woods which is why it is often called the wake-robin. 

Western white trillium

The ‘tri’ in trillium is one way to remember the identifying characteristics of the trillium since all the major parts come in three-- three leaflets, three sepals and three petals. The single white flower sits above the three broad leaves and the three green sepals alternate with the three petals. After fertilization or as the flower ages the petals turn pink.

Trilliums add a splash of color to stream banks, open and deep woods, and other moist shaded areas. 

The petals of the trillium turn pink with age or fertilization of the flower

Western spring beauty (Claytonia lanceolata)

Soon after the snow melts on open, moist grassy slopes, the spring beauty will emerge. The white dime-sized flower sits atop a two- to six-inch tall stem. Pink veins adorn the five petals that are notched at the tip. 

Western spring beauty

While they may be pretty, the spring beauty is also an important spring food source for black bears, grizzly bears and burrowing rodents. Each plant has a carbohydrate-rich corm (a spherical portion of the stem underground about the size of a marble) that these mammals dig up and eat. 

A spring beauty with intense pink veins

Violets (Viola sp.)

Violets are another small flower that add color to moist woods and meadows. All violets have five petals with one petal developing into a spur-like pouch.

There are several species of violets in the region identified by the flower’s color. The stream violet (also called the yellow wood violet or yellow violet) is yellow. The round-leaved violet is lemon-yellow to gold. The Canada violet is white with a yellow base while the kidney-leaved violet has pure white flowers. The early blue violet ranges from blue to deep violet.

Round-leaved violet (Viola orbiculata)

Yellow bell (Fritillaria pudica)

As the name implies, the yellow bell is a small, bell-shaped yellow flower that droops from the stem. The yellow bell is also called goldcup or yellow fritillary. The yellow bell appears in meadows and open woods including open ponderosa pine forests. 

Yellow bell

As a member of the lily family, the flower is three-parted. Like most lily species the petals and sepals of the yellow bell are so similar that the flowers appear to have six petals.

The yellow bell also has a starchy corm sought after by grizzly bears, black bears, pocket gophers and ground squirrels.

Yellow glacier lily (Erythronium grandiflorum)

Painting mountain meadows with a carpet of yellow after the snow melts is the yellow glacier lily, also called the snow lily, fawn lily, dogtooth violet and avalanche lily. The yellow glacier lily is often found at the edge of retreating snowbanks taking advantage of the moisture. Often the glacier lily is intermixed with the western spring beauty.

The single golden-yellow flower droops down with the petals curving backward and the red or yellow anthers hanging below.

Mountain meadow filled with glacier lilies

Yellow glacier lily

Great blue herons more than excellent fishers

Standing motionless in stagnant water, a great blue heron’s head suddenly reels forward into the water and emerges with a small fish. Great blue herons are known for being excellent fishers. Their stealth and lightning-fast strike enable them to sneak up on prey. 

A great blue heron is poised to strike prey with its S-shaped neck

Several features help herons forage effectively. Their long legs enable them to wade into deeper water than other shoreline birds. They can stand still for long periods of time waiting for a fish to come into range or walk very slowly to stalk prey. 

When a fish is within range, their S-shaped neck allows them to quickly strike prey. Specially-shaped vertebrae allow herons to curl their neck in preparation to strike or while in flight (a helpful identification characteristic). 

For their impressive size of 38 to 54 inches tall, great blue herons only weigh five to six pounds

Depending on the size of the fish, the heron strikes in one of two ways. For small fish, herons grab the fish between the mandibles of its bill. For large fish, herons stab the fish with their sharp bill. They then shake the fish to break or relax the sharp spines before gulping down the fish whole. 

Despite their narrow-looking neck, herons can swallow large fish. Since they swallow fish whole, herons regurgitate the solid waste (bones, scales) in the form of pellets similar to how owls regurgitate pellets. 

Another adaptation for eating fish is the special feathers on their chest to help clean fish before they eat them. Herons rake the powder down feathers with their feet to shake off a powder that causes fish slime and oil to clump. This enables the heron to brush off the clumps with its foot before eating it. Herons also rub this powder on their belly feathers to repel swamp slime. 

Even though herons are known as excellent fishers, their diet is highly variable. They also feed on frogs, salamanders, snakes, small birds, small mammals, crayfish, dragonflies and grasshoppers. One study in Idaho found that voles comprised 24 to 40 percent of a heron’s diet. Voles are a major potion of a heron’s winter diet because the shallow, calm water they feed in is often frozen. 

Herons look for food, such as voles, in grassy areas

Their variable diet is one reason the great blue heron is the most widespread heron in North America. In some areas the heron resides year-round but in northern areas herons migrate south unless there is a reliable food source. 

Whether they are permanent residents or migrants, great blue herons are noticeable in the spring when they are nesting because of their noisy ruckus. Herons are solitary when they hunt but they nest in colonies. The heronries can include up to 500 nests in areas with plentiful food and nesting sites but typically range from a few to several dozen nests. 

Herons build their nests high in trees if trees are available otherwise they build them among grass on islands. In Idaho and Montana, herons favor cottonwood trees along rivers and lakes but they will also nest in the tops of ponderosa pine and willows. 

Heronries can consist of a few nests to several hundred nests

They build large, stick platform nests with the male bringing material and the female placing the items. Herons will often reuse nests and the oldest nests are the largest--sometimes up to four feet across. 

Like most animals, herons are most vulnerable when young with 69 percent dying before they are a year old. Eagles, raccoons, bears, turkey vultures and red-tailed hawks are a few predators of great blue heron young. If a chick or an adult is killed within a nesting colony the other birds will often abandon the colony. 

Once the young fledge, they return to the nest to be fed for up to three weeks, placing great demand on their parents’ fishing skills.