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Sunday, February 18, 2024

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!

Friday, January 12, 2024

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!   


Friday, December 15, 2023

Phenomenal Phenology


The color-changing and dropping of leaves is a seasonal process.

Defined as the study of cyclic and seasonal natural phenomena, phenology is critically important in relation to climate and both plant and animal life.  The timing of biological events can be shifted earlier or later by climate variations in temperature, precipitation, and sunlight. Events such as migration, egg laying, flowering, and hibernation are all influenced by these climatic factors.  

Early blooming plants support early spring-emerging insects.

While ecosystems are resilient enough for normal phenological variations, major shifts may indicate a change in normal climate patterns.  These shifts can give rise to larger problems, since all life is interconnected.  In many areas of the world spring events are occurring earlier and fall events are occurring later than they have in the past. But since not all species are changing at the same rate or direction, mismatches are bound to occur.  

Nectar-producing flowers need to bloom in time for migrating hummingbirds.

Flowers that bloom too early leave fewer nectar sources for migrating hummingbirds.  Early flowering also leads to earlier fruiting, which typically yields lower quality fruit for fruit-eating migrating birds.  Many bird species time their nesting and egg-laying efforts so their eggs hatch when insects are available.  The emergence of insects depends on leaf out of their host plants.  One seemingly subtle shift in plant phenology can change entire food webs.  

Nesting and egg-laying are timed to coincide with insect emergence.

Some examples of phenology studies that are easy to perform include the date of emergence of flowers and leaves, the first appearance of migrating birds, the first flight of butterflies, the dates of egg-laying of birds and amphibians, and the date of leaf color changes and dropping in deciduous trees.  Studies can be formal or informal, and while many citizen scientists note these kinds of changes over the years, imagine if hundreds of thousands of them standardize their recording techniques and enter their data into a database that anyone can access.  This describes Nature’s Notebook, a web-based monitoring program of the USA National Phenology Network ( 

Anyone can contribute to the USA National Phenology Network's database.

Nature’s Notebook’s vision is to “provide data and information on the timing of seasonal events in plants and animals to ensure the well-being of humans, ecosystems, and natural resources.”  Its mission is to “collect, organize, and share phenological data and information to aid decision-making, scientific discovery, and a broader understanding of phenology from a diversity of perspectives.” Scientists use phenological data for critical applications such as understanding the timing of ecosystem processes like carbon cycling, assessment of vulnerable species and ecological communities, and invasive species and forest pest management.  Phenological data are immensely useful indicators of change, so considering joining the movement to document the changes you see in nature’s calendar, and watch what happens!

Wednesday, November 8, 2023

Preparing for a Winter Feast


Pine Siskin feeding on Thistle

Gardens can be a source of delight even during the winter months, if created with native plants for wildlife in mind. As the weather turns cold and foraging becomes more challenging, home gardens can be a critical resource for many different species.  Planting layers of vegetation, from ground covers to trees, provides the food and shelter necessary to sustain wildlife. 

Since different species utilize different types of food, it is important to consider the fructivores, nut eaters, granivores, and insectivores.   Native berry producing trees and shrubs that persist into winter are numerous and include yaupon, possumhaw, southern wax myrtle, American beautyberry, flameleaf sumac, roughleaf dogwood, Virginia creeper, Texas persimmon, and rusty blackhaw viburnum.  Trees such as the native Texas Red Oak, Live Oak, Post Oak, pecan, and Arizona walnut provide highly desirable nuts.  

Southern Wax Myrtle Berries

Rusty Blackhaw Viburnum Fruit

Post Oak Acorns

Another valuable practice is to create areas that mimic the forest floor by leaving leaves, which allows animals places to forage for overwintering insects.  Raking, mowing, and blowing is detrimental to many species of moths, butterflies, snails, spiders, beetles, and dozens of arthropods (such as millipedes).  Many moths and butterflies overwinter in the egg, caterpillar, or chrysalis/cocoon stage and use leaf litter as winter cover.  If you must keep your non-native lawn free of leaves, carefully rake them into a pile in the corner or spread them underneath trees and shrubs as a natural mulch.

Just as important is the practice of leaving seedheads and not cutting or pruning back perennials until they begin to break dormancy in late February or early March.  Birds can pluck seeds from spent flowerheads, hollow stems can become nests for solitary bees, and overripe fruits can be left to fall to the ground for animals to find.  Several native plant species that should be left standing throughout the winter include purple coneflower, blazing star, fall aster, common sunflower, tall goldenrod, western ironweed, frostweed, Texas thistle, Turk’s cap, blue mistflower, chile pequin, pigeonberry, and white boneset. 

Tall Goldenrod Seedhead

White Boneset Seedhead

Native grasses left to seed are also very beneficial, with clump-like vegetation at the base providing shelter from the cold and seedheads supplying food.  In early spring, the previous year’s leaf blades also provide necessary nesting material for many birds and small mammals.  The grass species to consider include inland sea oats, sideoats grama, switchgrass, big muhly, big bluestem, little bluestem, bushy bluestem, and indian grass.

Inland Sea-Oats Seeds

The colder months of the year are a good time to evaluate how well your garden provides a winter feast and haven for wildlife.  Helping our native animal species during the more barren months of the year by providing naturally occurring food and shelter helps to prepare them for a healthy and productive spring breeding season.

Sunday, October 1, 2023

An Abundance of Acorns

Texas Red Oak displaying fall color.

Texas is famous for its oak trees, with over 50 different species found in the Lone Star State.  Each of these oak species produce acorns, also called oaknuts or mast, which is a collective term for fruits or nuts.  The word acorn is related to Gothic term akran which has been interpreted to mean ‘the fruit of the unenclosed land.’  When oaks are dominant in the landscape, as they are here in central Texas, they play an important role in the ecology of the forest.

Acorns usually contain one seed enclosed in a tough, leathery shell, and have a cup-shaped cap or cupule. Depending on the oak species, acorns can take from 5 to 24 months to mature.  As a general rule, acorns mature in late summer, turning green to brown, and start falling from oak trees in September and October.  Acorns produced by trees in the red oak family (such as Texas Red Oak, Quercus buckleyi) take two years to mature, while acorns produced by trees in the white oak family (such as Bur Oak, Quercus macrocarpa) only take one year. 

Texas Red Oak Acorns

Some years, known as mast years, trees produce copious amounts of acorns with smaller crops in the years between.  Scientists have proposed a range of explanations for the mystery of what might trigger a mast year, but they do know that it is not resource-driven as annual rainfall and temperature fluctuations are generally much smaller in magnitude than the variation in the crop sizes of acorns.  Some scientists hypothesize that masting trees are trying to maximize pollination efficiency.  If these trees flower and release pollen at the same time in order to increase their chances of reproduction, since large amounts of pollen correlate with larger amounts of germination, they ultimately produce more acorns.  Large, occasional outputs of seeds like acorns appears to be more favorable than frequent, smaller outputs.

Bur Oak acorns are our largest acorns.

Boom and bust years of acorn production actually benefit oak trees from an evolutionary perspective, because acorns are an important, highly nutritious food source for many animals including squirrels, mice, turkeys, blue jays, pigeons, ducks, deer, and bears.  In a mast year, these animals can’t consume all of the acorns produced, so some are left to germinate and grow into future oak trees.  In leaner years, animal populations are kept in check so there are fewer animals to eat the acorns in the mast years.  Over time, a higher proportion of acorns survive to become oak trees.

Copious amounts of acorns are produced in a mast year.

Too heavy for wind dispersal, acorns need other ways to spread beyond the mother tree into a suitable area for germination.  Jays, squirrels, and some woodpeckers serve as the main dispersal agents, as they gather and hoard acorns in caches.  While they are remarkable in creating mental maps of their cache locations, these animals rarely eat every single acorn, so a small number manage to germinate and produce the next generation of oaks.

The Blue Jay is one of many species that cache acorns.

As autumn arrives and acorns mature and fall from our oak trees, think of the potential in the abundance of acorns produced.  As Henry David Thoreau once wrote, “Every oak tree started out as a couple of nuts who stood their ground.”  

Sunday, August 20, 2023

Cooling Conduct

Eastern Ringtail dragonflies obelisking

The unrelenting heat this summer has affected all living creatures, and while humans can escape into air-conditioned spaces, wildlife needs to rely on other ways to regulate their body temperature.  Often this is accomplished through different types of behavioral strategies acquired through adaptation, and some may seem quite odd until you understand the dynamics at work.

One of the most obvious behaviors (for humans at least), is sweating.  But many creatures don’t have sweat glands, or only sweat from their feet (like some canines), so they rely on panting instead.  In panting, animals breathe rapidly and shallowly with their mouths open, thereby increasing evaporation from the surfaces of their mouths.  This evaporation removes heat and acts as a cooling mechanism.  Panting is used by most mammals (like dogs) and many species of birds. While panting is effective at removing heat, dehydration is a risk so a nearby water source is important.  Birds may also spread their wings and body feathers to allow heat to dispel, and they have an elaborate breathing system that includes air sacs (in addition to lungs) to help them get rid of excess heat through panting.

A molting Northern Cardinal, panting and spreading its wings to cool down

Some birds, such as some species of vultures and storks, will voluntarily defecate on their legs to cool down.  Since bird poop is mostly liquid, it works by having an evaporative cooling effect, much like sweating.  As the poop dries on the bird’s legs, the heat is carried away and it brings down their body temperature.  Pelicans, herons, doves, owls, quail, and nighthawks, can employ gular fluttering, vibrating the muscles and bones in the throat and exposing moist throat membranes to the air, which helps regulate temperature by increasing evaporation.

Insects, like most all creatures, can also maintain a stable body temperature in at least a portion of their bodies through some interesting behavioral means.  While many insects need some heat to warm up their flying muscles, many will adjust/reduce their activity levels or seek out shady spots to handle extreme heat.  Dragonflies, for example, will often obelisk while perched in the midday hot sun, or point the tip of their abdomen directly up at the sun.  It is believed that this behavior reduces the heating effect by reducing the amount of surface area exposed directly to the sun’s rays.

Checkered Setwing exhibiting obelisking as a cooling behavior

When temperatures soar, four-legged animals such as squirrels, marmots, rabbits, bears, and even dogs and cats will lie flat on their stomachs on a cooler surface with their arms and legs stretched out from their bodies.  This behavior is called splooting, and it is thought that since their bellies have less fur and lots of blood vessels, they can dissipate the heat and absorb some of the coolness from the surface.  Also known as frogging or pancaking, splooting can take on various forms: the full sploot (all four legs out), the classic sploot (one leg tucked underneath the body while the other is kicked back), the side sploot (one leg tucked under the body and the other kicked out to the side), and the reverse sploot or toolps (when the animal lays on its back with its legs in the air)!

Fox Squirrel in a full sploot on our back porch

Regardless of the method, we all have to find some form of cooling conduct that allows us to survive until temperatures fall and (hopefully) the rains begin once again.


Saturday, July 15, 2023

Black and White All Over


The white patches on the black body of this Cottonwood Borer
are actually areas of pubescence or short, dense hairs.

Colorful things typically catch our eye, but the patterns formed by black and white can often be the most striking.  In nature, these patterns can be achieved through contrasting chemical pigments or structural elements such as scales or pubescence (or hairs).  While somewhat rare but not uncommon, these distinct black and white combinations are particularly striking in three native beetles, the Cottonwood Borer (Plectrodera scalator), the Texas Click Beetle (Alaus lusciosus), and the Texas Ironclad Beetle (Zopherus nodulosus haldemani).

The Cottonwood Borer is an unmistakeable, robust, elongate beetle with a shiny black body up to 1.6 inches long, and irregular, contrasting markings of white pubescence.  It has long, black antennae and prominent spines on the side of the pronotum, or the plate-like structure that covers all or part of the thorax. As an adult it is most active in summer, feeding on leaf petioles (stalks) of cottonwoods, willows, and sycamores, and is often found near the base of these trees.  Its' larvae bore into the base of the tree, living under the bark, and require 2 to 3 years to reach maturity.

Cottonwood Borer, from above

Present in Central, South, and East Texas, the Texas Click Beetle, up to 2 inches long, has distinctive, large, round black eyespots its pronotum, usually encircled in white.  White markings made of scales on its black body are clumped and patchy rather than evenly dispersed, and can sometimes look faintly yellowish.  Its common name comes from the fact that they possess an unusual clicking mechanism, whereby a spine on the prosternum (the underside of the thorax) can be snapped into a corresponding notch that produces a violent click that bounces the beetle into the air.  It is mainly used to avoid predation but can be useful when it needs to right itself.  Its species name means ‘dim-sighted’, and it can be found under loose tree bark.

Texas Click Beetle

The Texas Ironclad Beetle, a nocturnal beetle up to 1.5 inches long, has a distinctively round pronotum and raised black bumps or knobs on a white body.  It has a phenomenally strong exoskeleton, very thick and hard, in part due to its interlocking elytra or wing covers.  As such, it cannot fly but will play dead for long periods of time if touched or disturbed.  Also called Haldeman’s or Southwestern Ironclad Beetle, the Texas Ironclad Beetle is endemic to East and Central Texas, and it is active as early as March and into late October.  It has been associated with dead or dying pecan, oak, and elm trees, and has been found feeding on lichen.  Each part of its scientific name has relevance; zopher comes from Greek and means ‘dark' or 'dusky’, nodulus comes from Latin and means ‘little knot' or 'knob’, and haldemani refers to Horace Haldeman (1820-1883), one of the first to concentrate on collecting insects in Texas.

Texas Ironclad Beetle

The next time you see a beetle that is black and white all over, take a closer look at these fascinating creatures.  You just might find them to be as interesting as their more colorful cousins!