Have the signs of spring returned early this year in your community? Warm weather across many areas of the country for the last several weeks have hastened development of tree buds and certain flowers. Migratory birds have also returned north earlier than usual. On the other hand, the recent wave of cold weather across portions of the Upper Midwest would not be conducive to the onset of spring flowers.
Invariably, the lengthening daylight and higher sun angles should warm the air and ground, permitting the reemergence of spring foliage across the northern sections of the country. The onset of spring growth usually depends upon various climates and weather factors. While most events occur at about the same time each year, the specific date often varies from year to year. Farmers and others who work outdoors have long monitored the occurrence of certain seasonable events. Some records of the budding and flowering of plants and the migration of wildlife have been maintained for centuries in Europe and the Orient, and more recently in North America. In northern latitudes, the occurrence of the autumnal coloration of deciduous foliage and the dates for the freezing and "ice out" (or opening) of lakes have also been noted. Such an organized and systematic effort to monitor the well defined seasonal phases in plant and animal life is an example of phenology (a contraction of the word phenomenology), a scientific study of the influence of climate on the periodic annual phenomena of plant and animal life.
By comparing these phenological observations over a wide area, we can also monitor how these events move over time, responding to the seasonal changes in the sunlight with latitude. According to Hopkins Law (named for A. D. Hopkins, an entomologist with the U.S. Department of Agriculture during the early 20th century, and no known relation to this author), most phenological events tend to progress northward and upward in altitude during spring, while southward and downward in fall. A delay is also noted in the eastward direction. This empirical relationship suggests that the time for the peak flowering of a certain plant specie, would progress northeastward at a rate of 4 days per 1 degree of latitude and upward at 1 day for 100 feet of altitude.
Maintaining a phenological observation record can be a fun project. All you would need is a notebook that can be stored and used for future reference. Include as much information as you think will aid future groups in their analyses. This recorded information should include the date, overall weather conditions for the day and the some description of what you saw. Additional notes may be included. You may also wish to compare your observations with those made by relatives or acquaintances who live some distance from you.
When selecting events for observation, you should consider:
The most obvious phenological events occur in spring and autumn when changes in vegetation are most apparent. Phenologists have specific definitions to describe a number of phenomena, such as those pertaining to plants:
Wisconsin Phenological Society, 1977: Manual for phenological observers. Madison, WI. 20 pp.