Photos and Text by Hope Batcheller
Recently-fledged Eastern Phoebes
Every May, birders pile out of their houses, headed for local migration hotspots. Come June, a few run Breeding Bird Survey routes while others keep an eye on local nests. By July, though, the chicks fledge, birds become quiet, and the binoculars go on the shelf. End of story, right? Wrong! Those fledglings must go somewhere and do something, but what exactly they do is largely a mystery.
Essentially nothing is known about fledgling behavior, identification, and vocalizations. Why is this, given the ubiquity of fledglings and the important role they play in monitoring breeding birds? Fledglings are young birds that have recently left the nest but are still dependent on parental care and feeding. The presence of fledglings is therefore an indicator of breeding success. Understanding this key stage of birds' lives could prove helpful for Breeding Bird Atlases and similar breeding surveys.
In 2007 I began a research project on fledgling warbler vocalizations. My first field season served to get my bearings and prepare for a more intensive effort the next year. Since only recording fledgling warblers was very limiting, I decided to expand my project to encompass all fledgling passerines. I received a grant from the Vermont Institute of Natural Science for the 2008 field season, which I used to purchase equipment. With the support of Carol Foss from New Hampshire Audubon and Lang Elliott (a professional nature recordist from Ithaca, NewYork), my 2008 summer field season was fantastic. I spent all of July (the northeast's peak time for fledglings) in the field, visiting a diversity of habitats across New England.
Of course, like any field work, there were ups and downs. The 2-inch-long Winter Wren fledglings at Pondicherry National Wildlife Refuge in northern NH…and later that day getting caught in a hail storm, three miles from civilization. A fledgling Eastern Towhee calling one foot from the path…and the construction noise in the background, making it impossible to get a perfect recording. The recently fledged Common Yellowthroat four feet away…that wasn't vocalizing. By the summer's end, however, I had recorded 35 species of fledglings, and learned much about their behavior to boot.
Fledglings are, arguably, the cutest possible research topic. They are also one of the most challenging. Sometimes they cooperate perfectly, but at other times they are nearly impossible to detect. Young fledglings often sit stationary, fluttering their wings and gaping widely when an adult brings food. Many are incapable of flight, leading concerned humans to believe they have prematurely fallen out of their nests. On the contrary, these young birds are safer when dispersed, rather than concentrated in the nest. The nest is a big, noisy, smelly target for predators. As fledglings age, they become more active and fledgling down is replaced by juvenal plumage. Older fledglings follow their foraging parents, begging constantly, and occasionally attempting to find their own food.
This punk Red-winged Blackbird is a stereotypical fledgling. Most young songbirds show a brightly-colored gape (fleshy area around beak) like this bird's, though this feature is gradually lost as the bird ages. Note also the downy plumage, short or non-existent tail, and klutzy perching posture.
Expert ventriloquists, fledglings of all ages are extremely difficult to locate, a trait which presumably helps them evade predators. Their vocalizations are generally short, repeated notes, but become faster whenever an adult brings food. For some broad examples, warblers' calls are usually a fast twittering, many sparrows have a soft "ticking", and flycatchers make a unique grating call when begging. Mimic thrushes (Gray Catbird, Northern Mockingbird, and Brown Thrasher) all have a high, thin fledgling call. Species within each genus are often noticeably similar when it comes to fledgling calls. As an example, several Dendroica warblers have a two-or three-note call, followed by a lower note. Most species have distinctive calls, which are identifiable in the field with practice.
As our understanding of fledglings increases, efficiency for Breeding Bird Atlases and similar projects will be vastly improved. Much information for such projects is currently lost simply because volunteers cannot identify fledglings. Further studies could also provide insight on call development, adult behavior, and species relationships. From a less scientific perspective, fledglings are awesome and something anyone can observe. Undescribed behaviors and vocalizations are happening all around us, if only we pay attention. Better keep those binoculars off the shelf next summer!
Hope Batcheller is 17 years old and lives in Petersburgh, NY. To listen to her recordings, and more information on fledglings, please visit www.fledglingguide.org.