Through the Seasons - Phenology in the Northeast

Gilbert White's (1720-1793) pioneering field studies provide an introduction to phenology. See monthly tabs for videos.

The Swallows and Mr. White

It is, I find, in zoology as it is in botany: all nature is so full
that that district produces the greatest variety which is the most examined.

- White, G. 1887. The Natural History of Selborne. London, England: Walter Scott.

Phenology is the study of the timing of natural cycles and events and how these vary from season to season and from year to year. For many naturalists the annual progression of events is their appointments calendar and determines their daily rounds. For example Thoreau journal entry for Oct. 26, 1857 states, "The regular phenomena of the seasons get at last to be . . .the phases of my life. The seasons and all their changes are in me. I would have nothing subtracted. I can imagine nothing added."

swallow 1

The image of Celtic priest or Indian shaman calling back the sun on the winter solstice must have had powerful meaning for primitive societies. Indeed, the beginning of the sun's annual journey northward still connects many modern day naturalists with one of the most significant of natural cycles. Such recurring events, whether reflected in astronomical occurrences, climactic changes, or the behavior of various organisms, provide a framework for many of our natural history activities. A few such happenings have captured the attention of the public. The return of the swallows to San Juan Capistrano Mission is one well-publicized example. Each March 19th a group of curious Californians shows up in anticipation of the fabled return of the Cliff Swallows. That the observers are sometimes disappointed is not surprising. While we expect the timing of the solstice to be defined exactly, the swallow migration is a different matter. Perhaps the interesting point about the Californian phenomena is that the observer's behavior can be defined more precisely than can be the actions of the swallows. Sooner or later, however, the swallows do return, bringing with them the promise of a new spring.

swallow 2

It is not solely the swallows of Capistrano that are looked for each spring. For centuries, those with a bent towards nature and particularly we of temperate climes have urged our chilled bones out to this river valley or that lakeside in hopes of finding the first swallows of the year. These annual searchings are part of a more general affinity that has developed between mankind and various members of the swallow family (Hirundinidae). Several of the eleven species of North American swallows (this group includes the Purple Martin) have become familiar summer residents around our houses, garages, or barns. Here, they share the summer with us, calmly raising their families in our midst. The swallows' habit of eating a multitude of insects, many of which we consider noxious, has also endeared them to us.

Because of this proximity to man, swallows have long been the object of the naturalist's attention. The notions and theories that have evolved concerning this group of birds are many. The written record goes back at least as far as the third century before Christ. That preeminent naturalist-philosopher Aristotle turns out to be the source of much of this swallow-lore. In an attempt to explain the seasonal appearance and disappearance of the birdlife, Aristotle taught that while some species migrate to distant places, others, including the kite and the swallow, "simply hide themselves where they are" (p.600). What better way to pass the winter than to dive down into the mud of the pond bottom or burrow in the hillside? Aristotle presents the following evidence: "Swallows, for instance, have been often found in holes, quite denuded of their feathers, and the kite on its first emergence from torpidity has been seen to fly from out some such hiding-place" (ibid). Today these ideas appear curious and amusing. However, such lore was taught as truth for two millennia - not a bad record in the history of ideas.

Although Aristotle relied on much hearsay evidence, any reading of his work makes it clear that he was also an active observer. During one period in his life, Aristotle was a naturalist who did more than his share of field work. Unfortunately for the natural sciences, during the ensuing two thousand years, such field observation fell out of style. Up through the Middle Ages, natural history efforts were largely relegated to a combination of reworked Aristotle and a not too subtle dash of magic. By the seventeenth and eighteenth centuries, however, European and American naturalists had begun to reexamine nature in a more direct and realistic way. One of the pioneers of these fresh observations was Gilbert White.

G. White 1

Gilbert White (1720-1793) spent the major part of his life in the quiet, unremarkable parish of Selborne in the south of England. He became curate of Selborne in 1751, and his pastoral duties allowed time for frequent strolls about the countryside. In the course of these amblings, White made careful and detailed studies of the local plants and animals. He reported his observations in a series of correspondences, notably with the zoologist Thomas Pennant. Towards the end of White's life he was prompted to publish his letters and records in The Natural History and Antiquities of Selborne (1789). It has been this one publication that has secured for Gilbert White a privileged place among naturalists.

White lived at a time when Europe was experiencing a rekindled interest in natural history. The curate's perspective on the natural world was not, however, within the mainstream of this natural science renaissance. On the one hand the encyclopedic interests, represented by Buffon at the court of Louis XV, were attempting to catalogue and describe the entire natural world. All too often the emphasis was on the foreign and the remarkable. This resulted in a dilution of the level of understanding about many familiar plants and animals. On the other hand, the revolution brought about by Linnaeus and his Systema Naturae led inevitably to a preoccupation with morphology and classification, an evergrowing concern with names and lists, and ultimately to a ceaseless race to discover the rarities. Gilbert White was to take a different approach.

First and foremost, Gilbert White was interested in the native flora and fauna of his parish. He never had to go far to find those things which interested him most. Instead of treating this parochial limitation as a handicap, White found his oyster shell to be all he could ask for: "It is, I find, in zoology as it is in botany: all nature is so full that that district produces the greatest variety which is the most examined" (p. 54). White's observations were detailed and often recorded information new to science. He distinguished three species of willow wrens (now, leaf warblers of the genus Phylloscopus) solely on the basis of song - a novel approach to bird identification at the time. Among other topics, White studied ectoparasites in birds, ballooning in spiders, and the migration of frogs. If not content with certain explanations he had read, Gilbert White would find out for himself. Being suspicious of Virgil's suggestion that echos were harmful to bees, White used a speaking trumpet to create his own echos around a beehive. After carefully observing the actions of the bees, he concluded that Virgil's idea was without merit.

Perhaps as important as any of his specific observations and records is the framework within which White perceived the natural world. For the curate of Selborne, nature was an integrated and interrelated whole. The relationships and dynamics of the natural community were important features to define. In a word, White was interested in ecology. The ecological model for nature study has come of age in the twentieth century. In the work of Gilbert White we sense a similar perspective held more than two centuries ago. Speaking of the local cattle he states that (they) "retire constantly to the water [ponds] during the hotter hours... drop[ping] much dung, in which the insects nestle; and so supply food for the fish, which would be poorly subsisted but from this contingency. Thus Nature, who is a great economist, converts the recreation of one animal to the support of another" (p. 23).

But White was not a man outside his own culture. His views on nature also echo the contemporary (18th century) perspective. Nature's "economy" was merely a reflection of the Creator's divine plan, and foremost in this plan was a utilitarian attitude towards the natural world. All plants and animals had been put here for man's use; he only needed to sort out their proper functions. White was to spend his life studying nature and hence, indirectly, the divine plan.

Among the curate's favorite subjects were the "birds of passage." White kept careful notes of arrival and departure times, nesting dates, and seasonal status of the various species. And this brings us back to the swallows, for these received Gilbert White's special attention. The following passage illustrates his interest in this group.

The hirundines are a most inoffensive, harmless, entertaining, social, and useful tribe of birds; they touch no fruit in our garden; delight, all except one species, in attaching themselves to our houses; amuse us with their migrations, songs, and marvellous [sic] agility; and clear our outlets from the annoyances of gnats and other troublesome insects. [P. 150]

swallow 3

White followed these birds from their appearance in spring through their nest building, egg laying, raising of young, and fledging, to their disappearance in the fall. One part of their life history, however, puzzled the curate. Did species such as the house martin migrate or hibernate? Gilbert White was, two thousand years later, still dealing with Aristotelian lore. In a somewhat uncharacteristic fashion, White made one of the same mistakes that his predecessor had; that is, he relied on hearsay. In a letter to Thomas Pennant he states, "I acquiesce entirely in your opinion - that, though most of the swallow kind may migrate, yet that some do stay behind and hide with us during the winter" (p. 36). White's actions, however, indicate that he was not entirely satisfied with this explanation. Several times he mounted expeditions to the countryside to gain proof for these ideas.

In some former letters I expressed my suspicions that many of the house-martins do not depart in the winter far from this village. I therefore determined to make some search about the south-east end of the hill, where I imagined they might slumber out the uncomfortable months of winter...and observing that no martins had appeared by the 11th April last; on that day I employed some men to explore the shrubs and cavities of the suspected spot. [P. 251]

To White's disappointment, no martins were roused from their torpor. Ironically, it was White's methodology of field work and first hand observations that ultimately would dispel the folklore of swallow hibernation.

Gilbert White's reputation did not suffer from these adventures. In fact, during the nineteenth century a cult of sorts grew up surrounding his life and work. Darwin and other important naturalists of his day made pilgrimages to Selborne to honor White. The curate's writings had an important influence on many distinguished naturalists including those in America such as Henry David Thoreau. A tradition of careful observations and recordings of local floras and faunas was established by Gilbert White and continues to this day. Over one hundred editions of The Natural History of Selborne have been printed. The book's influence on natural history writing has been significant, and it will, no doubt, remain a standard on the naturalists' bookshelf. The curate of Selborne has achieved a preeminent place in the tradition of natural history studies.

Note: On December 29, 1946, Edmond C. Jaeger, while on a field trip to the Chuckwalla Mountains of California, found a torpid poor-will within a small opening of a rock wall. Further studies documented the first known case of hibernation in an avian species.

Richard K. Walton September 1985


  • * Peattie, D. C. 1936. Green Laurels. New York, N.Y.: Garden City Publishing Co., Inc.
  • * Terres, J. K. 1980. Encyclopedia of North American Birds. New York, N.Y.: Alfred A.Knopf.
  • * Thompson, D'A. W. 1910. The Works of Aristotle Vol. IV Historia Animalium. Oxford, England: Clarendon    Press.
  • * White, G. 1887. The Natural History of Selborne. London, England: Walter Scott.
  • * Worster, D. 1977. Nature's Economy. San Francisco, California: Sierra Club Books.