Requisite Night

 

Light pollution is nearly non-existent in Big Bend,
allowing for spectacular star-filled night skies.

Most environmentally-minded individuals recognize the more talked about threats to our native wildlife, such as habitat fragmentation/loss, invasive species, and climate change, but not as many are aware of the dangers posed by light pollution. Up until the mid-1800s, humans and animals lived under night skies solely lit by the moon. Electric outdoor lighting became common in the early 20th century, but its use spread quickly, and the global extent of modern light pollution became clear.  

By 2016, it was possible to measure nocturnal artificial light with the advent of a comprehensive global satellite measurement system. Researchers found that more than 80% of the world’s population lived under light-polluted night skies, or skies where the glow of artificial light is significant enough that the stars disappear from view.  In the US and Europe, it was found that 99% of residents live under light-polluted skies.

Light pollution exposes animals to many dangers, including predators, starvation, exhaustion, and disorientation. Artificial light, like roads and fences, can create barriers that fragment habitat.  Slow-flying bats avoid feeding in or passing through illuminated areas for fear of predators such as owls and other birds of prey. Artificial light near their roosts can also delay their emergence at dusk when their insect prey is most abundant.  If they never leave their roost since it always appears to be light, they can even starve to death.  

Artificial nocturnal light can also lure animals in and lead to their destruction.  Many species of migratory songbirds are attracted to brightly lit structures at night, circling them, sometimes colliding into them, or becoming disoriented enough to lead to a depletion their energy stores which ends in exhaustion and the inability to complete their journey.  In some bird species, artificial light at night interferes with their ability to use natural polarized light from the sky to calibrate their internal compass.

Artificial light at night attracts insects, like this Luna Moth, 
and can disrupt normal behavior patterns.

Light pollution is also one of the many factors contributing to the rapid decline of insect populations.  Moths and other nocturnal insects orient themselves by moonlight, and this instinctual tendency is interrupted by artificial night light, luring them in to fly incessantly around a bright light, causing exhaustion, exposure to predators, and the potential to miss courtship cues from mates.  This is especially true for fireflies, as artificial night light can cause them to alter or cease their mating flashes.  Studies have also shown that light pollution can harm diurnal insects like monarchs, who flit and flutter all night when exposed to excessive light when they should be resting, and causing them to be disoriented from their migration route.

Light pollution facts and some easy solutions.

Unlike other environmental threats to wildlife, simple solutions to artificial nocturnal light exist.  The best solution is to have no nocturnal lighting other than natural conditions. If a light at night is truly needed, the amount that spills into wildlife habitat can be reduced through dimming, downward shielding, or switching to motion-activated lights. Studies are also showing that lights in the warmer color tones are less disruptive than bright white lights.

Travis Audubon promotes the Lights Out Initiative for Austin.

Austin is one of several cities across the US that participates in the migratory bird friendly Lights Out Initiative, which asks residents to turn out all non-essential lights from 11pm to 6am every night during spring migration (March 1 – June 15) and fall migration (August 15 – November 30).  This is one of many ways we can prevent light pollution from overpowering our native wildlife. Turn out your lights when they are not needed, and welcome the requisite night!

Irruption Disruption

Pine Siskins often feed in groups or flocks

While many northern species of birds fly south through central Texas during fall migration, some species go no further, and spend their winters in the area. Our generally mild winters and higher availability of food sources are the reasons they stay, fueling themselves in the cooler months as they prepare for northward migration in the spring.  

This cycle is not always predictable, however, as there are a few overwintering bird species that are nearly absent in some years, and overly abundant in other years.  One such species is the Pine Siskin (Spinus pinus), a small finch-sized, seed-eating bird with a sharp pointed bill, short notched tail, and streaky brown overall with subtle yellow edging on the wings and tail.  They flash yellow wing markings as they flutter while feeding or burst into flight, and usually occur in fairly large, gregarious flocks.  Their wheezy twitters are a dead giveaway, and they will stay all winter near a dependable food source.  

Pine Siskin showing the yellow edging on wings and tail

Pine Siskins range widely and erratically across North America every winter in response to seed crops, and flocks may monopolize your feeders one winter and be completely missing the next. In the winters when Pine Siskins are abundant, the phenomenon is referred to as an irruption.  In the bird world, irruptions, broadly defined as sudden changes in population density, refer to the movement of northern-wintering bird species to the south in years of low food availability. However, some recent bird banding studies suggest that some pine siskins fly west to east while others fly north to south in search of winter food.

While fairly common, the overall population of Pine Siskins is difficult to estimate due to their unpredictable seasonal movements.  However, this species is considered to be in steep decline, with an estimated 69% decline in numbers from 1966 to 2019.  Natural threats include predation by outdoor domestic cats, squirrels, hawks, and jays.  Man-made threats include pesticides, mineral deposits from salts used to melt ice and snow, outbreaks of salmonella from unsanitary feeders, and forest clearing.

Pine Siskins will quickly empty your feeders!

Winter flocks of Pine Siskins can be aggressive around food sources, often trying to disrupt and challenge feeding competitors by lowering their heads and spreading their wings and tail. They may even lunge toward and pick fights with other seed-eating birds such as Lesser Goldfinches and House Finches. Keep an eye on your feeders this winter and you just may witness this irruption disruption, when flocks of these birds can eat you out of house and home!

Odd Ducks

Waterfowl in winter's morning mist on Lady Bird Lake.

Wintertime is the perfect time to look for ducks in central Texas.  Several species that breed far north of our state’s border return to Texas in the colder months to feed in our unfrozen freshwater lakes and rivers.  From the Old English ‘duce’, the word duck is a derivative of the verb meaning to duck or dive, or bend down low as if to get under something.  It best describes the way many ducks feed, by upending or diving under the water in search of a wide variety of food sources, such as small aquatic plants, grasses, fish, insects, amphibians, worms and mollusks.

Most ducks fall into either the dabbler or diver category.  Dabblers feed on the surface of the water, and sometimes on land, while divers disappear completely beaneath the surface and forage deep underwater.  In general, divers are heavier than dabblers, which gives them the ability to submerge more easily, but they often pay the price by having more difficulty when taking off to fly. 

While there are several species of ducks that are commonly found in central Texas winters, those that are more rarely seen usually occur singly or in small numbers.  These ‘odd ducks out’ include species such as the Hooded Merganser (Lophodytes cucullatus), Redhead (Aythya americana), and Cinnamon Teal (Anas cyanoptera).

A pair of Hooded Mergansers (female behind, male in front).

The Hooded Merganser is an uncommon diving duck that is found on forested wetlands, rivers, and backwaters. The male has a black bill and head, with a large white head patch that is conspicuous and fan-shaped when the elegant crest or hood is raised.  His black and white breast and back gives way to chestnut sides.  Females are generally browner, including their bushy crest, with some white only in the wing feathers.  Hooded Mergansers are one of the few species of ducks that nest in tree cavities rather than on dry ground near water, and the females may start scouting for next year’s tree cavity at the end of each breeding season.

A handsome male Hooded Merganser with his crest on full display.

The Redhead is a locally common diving duck, with the male having a rounded chestnut head, black breast, and smoky gray back and sides.  The female is tawny brown with a mostly slate bill with a pale band bordering a black tip.  The male’s bill is similarly patterned, but is mainly pale blue instead of slate.  Redheads prefer ponds and lakes with open waters, and sometimes winter in large flocks called rafts.  They fly faster than most ducks with a rapid, shallow wingbeat, and are sociable ducks that are usually found feeding with other duck species in a mixed flock.

Redhead ducks are aptly named.

An overall cinnamon color distinguishes the male Cinnamon Teal from the rich brown of the female, but both have a teal blue forewing patch.  The male also has a white face crescent and a vertical white flank patch.  Cinnamon Teals are dabbling ducks that can be sometimes be found on quiet marshes, ponds, and lakes in winter, typically near the edges of vegetation.  Males molt soon after breeding, but regain their rich reddish plumage by midwinter. While this species is not endangered, its population is declining due to pollution, recreational hunting, and the loss of wetland habitat.

Cinnamon Teal prefer wetland habitats with emergent vegetation.

The next time you venture out to a lake, river, or pond this winter, check the water’s edge and scan the flocks to see if you can spot one of Austin’s odd ducks!