Multiple broods bolster red-winged blackbird population

One of the most abundant and well-known birds in North America is the red-winged blackbird. The descriptive name of the red-winged blackbird only applies to the male. The female looks like a sparrow with her drab brown coloring.

Female red-winged blackbirds resemble a sparrow more than their name

Typically male birds flaunt their brightly-colored feathers to attract females, but not red-winged blackbirds. The bright reddish-orange shoulder feathers (called epaulets or epaulettes) instead help the blackbird defend its territory.

In the military, an epaulet’s position, length, color and diameter on the bearer’s shoulder indicates the bearer’s rank. Similarly, the larger the blackbird’s epaulets, the more likely the blackbird will successfully defend its territory.

In studies, the epaulets of red-winged blackbirds were experimentally blackened and the males would subsequently lose their territory. However, black epaulets didn’t change the ability of the male to attract a female. 

The red shoulder feathers are called epaulets (or epaulettes)

Male red-winged blackbirds don’t try to attract only one female, they defend a large enough territory to attract numerous females. Male red-winged blackbirds are polygynous, meaning they will form breeding partnerships simultaneously with more than one female. Only two percent of all bird species are polygynous.

By defending a large, high quality territory with its large epaulets, the male can average five female partnerships. Though studies have observed a male partnering with up to 15 females. 

A high-quality territory is necessary for the male because he will feed the female while she incubates her three to five eggs. Incubation lasts 12 days on average and the nestlings fledge in two weeks. The short parenting time allows the female to have multiple broods each summer--up to three broods in some areas of the country. 

The female will build a new nest from grasses, cattail reeds and rootlets for each brood. Construction takes three to six days.

With nests often built over water, the fledglings are able to swim for a short duration in case their first attempts to fly land them in the water. As they become proficient aviators, they lose their swimming ability. 

Fledglings, nestlings and eggs are the most prone to predators, despite their location over water. Predators include raccoons, skunks, crows, owls, hawks, foxes, weasels, raptors and snakes. 

An unlikely predator for red-winged blackbirds are marsh wrens. Since marsh wrens and red-winged blackbirds share the same territory and food supply, they will eat each other’s eggs. 

Males can hide their epaulets with black feathers which they sometimes do when going through another male's territory

Both marsh wrens and red-winged blackbirds eat insects in the summer. Red-winged blackbirds feast on dragonflies, beetles, butterflies, moths and spiders. If the opportunity arises, they will also eat frogs, birds eggs (such as the marsh wren’s eggs), snails and worms.

When insects are not available, red-winged blackbirds head for grain fields. Large flocks of red-winged blackbirds gather in the fields to gorge on grain outside of the breeding season.

Between the abundant wetlands and grain fields across North America and the ability to produce up to three broods a year, the red-winged blackbird’s population is quite abundant--nearly 200 million strong across the continent.

Note: Published in the Bonners Ferry Herald on April 25, 2013.

No two rainbows exactly alike

Raining one minute and sunny the next, the ever changing weather of spring creates prime rainbow viewing opportunities. Just as no two snowflakes are alike, no two rainbows are alike. Rainbows can be bright, dim, a half-circle, a small sliver or be flanked by a secondary rainbow. 

Rainbows can be a small sliver under a storm cloud

The brightest rainbows occur when there are large water droplets, often during thunderstorms or heavy rainfalls. Red, green and violet shine the brightest in these rainbows. 

Rainbows with a weak red color indicate smaller water droplets and in a fine mist, only the color violet may be visible.  

Rainbows are an optical phenomenon created by sunlight and water droplets, visible only to those in certain locations. Rainbows form by light refracting and reflecting inside water droplets. 

Sunlight, while it appears white, can be separated into a spectrum of different colors: red, orange, yellow, green, blue, indigo and violet. The spectrum appears when the sunlight is refracted (bent), such as through a prism or water droplet. 

Rainbows can be very close to the horizon

Rain on gray, dreary days doesn’t produce rainbows because a key element is lacking--sunlight. Sunlight and water droplets are the two key components of a rainbow. The third is the viewer. 

To see a rainbow, the viewer has to be facing away from the sun and facing towards a rain shower (or waterfall with mist). A rainbow is visible because the sun’s rays of light are being reflected (just like an image in a mirror) inside the water droplets of the rain shower back towards your eyes. 

If the sun is too high, the rainbow will be below the horizon and you won’t see it. Rainbows are only visible when the sun is low in the sky (morning and evening) for this reason. However, when in an airplane, it is possible to see the entire circle of a rainbow.

For a primary rainbow (the main rainbow), the sunlight entering the water droplet is bent and separated into the spectrum of colors. The individual colors then reflect off the back of the raindrop and bend a second time when the light exits the front of the raindrop. Each color refracts and reflects at a certain angle, which is why the color spectrum is always in the same order (red, orange, yellow, green, blue, indigo and violet). 

Additional colors beneath the violet of a primary rainbow are called supernumerary bows

From the millions of raindrops that create a rainbow, your eye only registers one color from each raindrop. As the colors leave a raindrop, only one color will be at the right angle to intercept your eye. 

Since red light is bent the least, it will always appear on the outside of the primary rainbow, while violet is bent the most and will always appear on the inside of the primary rainbow. 

However, on secondary rainbows (the rainbows that appear outside of the primary rainbow) the colors are reversed, with violet on the outside and red on the inside. The reversal is because the light entering the water droplet undergoes two reflections inside the droplet before exiting. 

The second reflection also absorbs some of the light’s intensity, so the exiting light is typically at one-tenth of the intensity of the primary rainbow. The resulting rainbow is also twice as wide.

The colors on a secondary rainbow are reversed with violet on the outside

While each color has a specific angle that it typically refracts and reflects at, some light rays deviate slightly. This deviation is what causes the lighter sky beneath the primary rainbow. These deviating rays are only seen beneath the primary rainbow because they exit the water droplets at a higher angle, which reaches your eye. 

On the other hand, the sky is darker between the primary and secondary rainbows because no internally reflected rays, even deviating rays, exit at an angle received by the observer. 

Basically, every raindrop is refracting and reflecting the same colors of light across the spectrum, but only one color from each raindrop will be at the correct angle to strike your eye.

 

Two people standing two feet apart would see two different rainbows because different colored rays are striking their eyes. Thus, every rainbow is truly unique because every person sees their own personal rainbow.

Note: Published in the Bonners Ferry Herald on April 18, 2013.

Spinning a web comes naturally for spiders

Without a single lesson, a young spider can build its own web. As the spider grows, so does the size of the web. 

While every spider can produce silk, only 85 percent use silk to spin webbed traps. The two-dimensional orb web is the most recognized web but others include sheet webs, funnel webs and cobwebs.

Orb webs need at least three attachment points but more attachment points are used if possible.

All spiderwebs are made of silk but not the same type of silk. Spiders can produce up to seven different types of silk, each with a specific purpose. Different silk is used to make egg cocoons, release draglines, wrap prey, and create different parts of a web.

A separate silk gland, located inside the spider’s abdomen, produces each type of silk as a liquid. The silk is drawn out of the abdomen by a leg, breeze or the weight of the spider dropping--it is not squeezed out like toothpaste. 

The act of pulling the silk makes it solid, not by contact with air (as demonstrated by spiders that spin webs underwater). Pulling the silk changes the orientation of the fibers and solidifies it.

Dew and rain can't dissolve a spider's web because the silk is insoluble to water. However, the silk will absorb water and swell.

Silk is pulled from the spider’s abdomen through spinnerets, each one connected to a different silk gland. A spinneret resembles a shower-head with multiple tiny spigots. As the silk emerges from the spigots as extremely fine strands, they combine into a single solid thread. 

The diameter of silk is extremely small--0.00012 inches for a garden spider. The average human hair is 0.0039 inches in diameter.

A spider can use between 65 and 200 feet of silk for one web. Spiders will often roll up and eat an old web to conserve protein, as they may spin a new web everyday if the web is damaged.

The average orb web takes approximately one hour to complete. Orb webs are constructed in a very systematic manner.

Orb webs are the most commonly recognized spiderwebs

To begin constructing an orb web, a spider will release a fine silk line into the breeze and wait, as if fishing, until the line touches and adheres to a nearby object. Then the spider will tighten the line and add more strands until the bridge thread is strong enough to support the entire web. 

Then the spider makes a separate loose thread between the first two attachment points and moves to the middle of this thread. From there, the spider will attach a new thread and drop down to a lower attachment point, making a “Y” in the process. The “Y” makes the first three spokes of the web. 

From the hub (middle of the web), more spokes are added at precise angles, which are measured by the spider’s legs. The spokes of a garden spider’s web are 12 degrees apart. The bridge and spokes are made of non-sticky silk.

Once all the spokes are completed, the spider will start in the middle and add a temporary spiral outward. This spiral is a non-sticky guideline for when the spider returns to the center making a permanent, sticky spiral. 

As the spider returns to the center, it will eat the temporary thread while laying down the sticky thread in a spiral. At each spoke, the spider will dab the thread against the spoke and give it a tug so that it breaks up into a line of sticky beads. 

A spider waits in the middle of its web

The sticky spiral is terminated before the spider reaches the center, so that the spider has room to move in the middle. 

When finished, the spider will either settle in at the hub or sit nearby with a “signal thread” held by a front leg to stay in touch with the web. The signal thread enables the spider to feel the vibrations of a captured insect. 

Web-spinning spiders are in contact with silk threads virtually their entire life without a single lesson on how to make it work. 

Note: Published in the Bonners Ferry Herald on April 11, 2013.

Mourning cloak butterflies first to flutter around

Spring is full of firsts--the first robin, the first flower and the first butterfly. Not necessarily in that order though. The first butterfly is often fluttering around before the first flowers bloom or even emerge from the warming soil.

Emerging from under a piece of loose tree bark or from a crack in a rock on a warm spring day is the mourning cloak butterfly. Just as turtles bask in the sun to warm their bodies, the mourning cloak butterfly will crawl out and open its wings to the sun to warm up. 

The mourning cloak’s dark wings enable it to absorb heat from the sun’s rays on warm late winter days. 

Mourning cloak butterflies often look tattered in the spring because they are one of the few butterflies to overwinter as an adult

Mourning cloak butterflies are one of the few butterflies to overwinter as adults (anglewings also overwinter as adults). 

Like many other species in the spring, the first order of business is to find a mate. The males will perch in a sunny spot in the afternoon and wait for a receptive female. 

After mating the female will lay eggs on a twig of a host plant--willows, cottonwood, aspen, paper birch, hackberry or elm trees. Once hatched, the caterpillars will live communally in a web and feed together on the leaves of the plant. 

The caterpillars are black, covered with tiny white dots and marked with a row of large orange spots along its back. The two-inch-long caterpillar also grows several rows of black spines. 

Unlike a turtle’s shell that grows with it, a caterpillar’s skin doesn’t stretch as it grows. Thus, the caterpillar molts (sheds its skin) several times before pupating. The last molt a caterpillar undergoes produces a pupa. 

When a mourning cloak pupates, it will create a chrysalis to undergo metamorphosis. After 10 to 15 days (fewer days if warmer), an adult butterfly will emerge, typically in June or July. 

The undersides of the mourning cloak’s wings are cryptically colored. The grayish black pattern that appears like dark tree bark helps protect the butterfly from predators.

Even though the mourning cloak butterfly is one of the longest living butterflies at 10 to 11 months, it doesn’t flutter around the whole time. The butterfly enters hibernation in both the summer and winter. 

After emerging as a butterfly, the mourning cloak will feed briefly before finding a sheltered spot to estivate until autumn. Estivation is the summer equivalent of hibernation to avoid heat and the lack of moisture. 

Then in September, the mourning cloak butterfly will emerge once again to feed and store energy for winter hibernation (known as diapause in insects). Mourning cloak butterflies prefer to feed on tree sap and occasionally on rotting fruit and flowers. Tree sap is more readily available in early spring than flowers because the sap begins to rise in the trees. The sap will ooze out of damaged areas, including sapsucker holes.

Then as the day length becomes shorter the butterfly will find its winter hiding spot and produce an antifreeze that prevents it from freezing solid. 

The mourning cloak then waits in a suspended state until the first warm days of spring when it can emerge, bask in the sun and be the first butterfly in the woods.

Note: Published in the Bonners Ferry Herald on April 4, 2013.