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 (www.usanpn.org). 

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!

Breeding Beauties

White-eyed Vireo nest, a sign of spring

As the fickle winds of  spring come in from  the south, they usher in several  species of birds  that spend the warmer months  in Central Texas.  Most of these species overwinter in Mexico, Central America, or South America, and their arrival in  our  area  signals  the start of the  breeding season.  Most notable  are the  Summer Tanager,  White-eyed Vireo,  Western Kingbird, and Scissor-tailed Flycatcher.

Summer Tanagers (Piranga rubra) are medium-sized, chunky songbirds with big bodies, large heads, and thick, pale, blunt-tipped bills.  Mature males are the only birds in North America that are completely red.  The female and immature males are bright yellow-green, which makes them harder to spot in the forest canopy. These birds prefer to stay fairly high in the trees, often in willows, cottonwoods, and mesquite along creeks and streams.  They prefer to sit still then fly out to catch insects in midair.  They are especially fond of bees and wasps, beating them against a branch once they are caught, but they may also forage on berries and fruits near their forest habitat.  Males have a sweet, whistling song, much like an American Robin.

Summer Tanager, male

Like most vireos, White-eyed Vireos (Vireo griseus) are small songbirds with compact bodies and thick, slightly hooked bills.  They have yellow spectacles around their white eyes, yellow-washed sides, gray head, white throat, and two white wingbars.  They prefer areas that are scrubby and thick with vines and other vegetation, staying hidden in the understory where they glean caterpillars and other insects. Their song is distinctive, rapid and harsh, sounding like ‘Spit. And see if I care. Spit.’ While only the males sing on their breeding grounds, both males and females have been found to sing on their wintering grounds.  They bathe by rubbing their bodies against dewy foliage in the early morning, or by quickly dipping their backsides in a pool of water.

White-eyed Vireo

Oddly often found in parking lots with Live Oak trees, Western Kingbirds (Tyrannus verticalis) are fairly large flycatchers with gray heads, broad shoulders, whitish chest, lemon yellow bellies, heavy straight black bills, and medium-length black tails with white outer tail feathers.  They prefer open habitats, often perching on power lines, fences, and in trees, waiting to hawk insects from the air.  In fact, their breeding range has been expanding as an unplanned result of humans planting trees and installing utility poles in open areas.  Their territory defenses include lots of wing-fluttering and a long series of squeaky, bubbling calls.  Paired males and females work together to defend their territory, which shrinks as the breeding season progresses.

Western Kingbird

Few birds are as graceful to watch as Scissor-tailed Flycatchers (Tyrannus fortificatus).  These elegant, slender birds are gray overall with salmon-pink flanks and underbellies, stout black bills, blackish wings, and long, forked tails they use to sharply twist and turn midair to catch insects.  Interestingly, Scissor-tails are known to use many human-made products in their nests, including pieces of cloth, paper, string, and even carpet fuzz and cigarette filters.  These items can account for up to 30% of the weight of the nests.  In late summer and early fall, these flycatchers gather to form large, bickering flocks and migrate together back to their wintering grounds.

Scissor-tailed Flycatcher

Scissor-tailed Flycatcher, showing its' namesake tail