Thumb on the pulse of life: Phenology in the context of change

Refuge Notebook
The first bee bumbling on a willow catkin near the Russian River is a phenological event that happens every spring.

In springtime, we are aware of every subtle shift in bud size amongst the birch or the first flight of the mosquito. Spring is also the time when the fish begin to run. A traditional tale from the Kenaitze Tribe tells of a man listening for the song of a bird. “Tsik’ezlagh” sang the bird, a Golden-Crowned Sparrow. Then a gull began calling “be’quina” (it’s fish eggs), and the man went to where the gull was calling with his dipnet. He jumped into the water, and soon caught a king salmon. Everyone came down to the beach with their dipnets, and they marked the day. Some years the fish ran earlier, and some years later. The people knew that when the sparrow sang “Tisk’ezlagh,” the first salmon were running. 


Keeping an eye out for changes in our natural surroundings intuitively embraces the concept of phenology, the study of periodic plant and animal life cycle events and how these are influenced by seasonal and yearly variations in climate. The word is derived from the Greek word “phaino,” which means “to show or appear.” Ecologically, the term generally indicates a time frame for seasonal biological phenomena, such as date of emergence of leaves and flowers, the first flight of butterflies or the first appearance of migratory birds, the date of leaf coloring and leaf fall in deciduous trees, or dates of egg-laying of birds and amphibians.

Phenology also describes the study of biological events cycling throughout the year, or a reading of the “pulse of life.’’ Observing and documenting life stages of plants and animals have been traditional and necessary for humans throughout history. This ancient practice let people know when to plant crops, when to harvest, or when to hunt and fish. Phenological observations were key to successful hunting, fishing, gathering, and farming, and therefore survival, as the story of the Golden-Crowned Sparrow illustrates.

Phenological variations in the local flora and fauna may be important ecological indicators of change, or merely interesting anecdotal stories, depending on the scale and length of observations. Taken in isolation, phenological change does not tell us much. This past winter offered an exceptional volume of snowfall in this region (delightful to skiers and snowmachiners), while much of North America experienced a relatively mild winter. Observations from this spring may be quite different than “normal” trends.

Phenological records over time, however, can be a useful proxy for physical trends like temperature. Timing of ecological phenomena can be sensitive to small variations in climate, providing insight into long term climate changes. Observing long-term patterns is a lengthy tradition in parts of Europe. For example, grape harvest records have been used to reconstruct summer growing season temperatures going back 500 years. Trends over time help current vineyard managers make decisions on when and where to plant or shift cultivation in their vine crops to accommodate current and anticipated climate trends.

Phenological observations can enhance our understanding of ongoing climate change, which may have more pronounced or faster effects on species living in Alaska’s short growing season. Phenological changes may mean a narrower window for plant interactions with pollinators or dispersers.

Also, competition between plant species may be out of whack, disrupting the complementary relationship early spring versus later summer blooms may currently operate under. Species may have differing abilities to adapt to climate warming. Species with poor phenological adaptability may be stressed in periods of climate warming, leading to migration or extinction. Understanding the timing of seasonal events such as leafing or flowering can be critical for maintaining rates of survival and reproduction of plant and animal populations.

Because the range of seasonal temperature changes is magnified at higher latitudes, embracing an understanding of phenological responses may help frame our responses to change. Studies of phenological processes in Alaska and other near-polar sites have shown dramatic changes in various plant responses to a warmed temperature. Species are already responding by flowering earlier, leafing out earlier, returning earlier, or blooming before pollinators appear.

Right here in Southcentral Alaska, phenological monitoring shows that the migration window for some migratory birds has recently  expanded. Sandhill Cranes, Rhinoceros Auklets, Marbled Godwits, and Black-footed Albatrosses head south later in the fall, while a few, such as Greater Yellow-legs, are arriving earlier in the spring.

Green-up, or the date when vegetation leafs out, can be remotely monitored by satellite. Chorophyll, the stuff that makes plants green, can be detected from the MODIS satellite by examining normalized difference vegetation index values each spring. Green-up dates will presumably become earlier as the climate warms, and long-term trends can be detected by looking at sequences of satellite images over time.

Maybe you are waiting for the snow to melt, the fish to run, or the first song of the sparrow this spring. Each of these observations is part of our traditional ecological knowledge as well as part of our understanding of ecological change.

For more information, or to record your own phenological observations as a citizen scientist, read more at the USA National Phenology Network or Project Budburst websites: and

Dr. Elizabeth “Libby” Bella is an ecologist at Kenai National Wildlife Refuge. You can find more information about the Refuge at or


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