How DNA Is Rewriting North America's Bird Field Guides
Imagine spending years memorizing every bird in your field guide, only to discover that scientists have changed their names, rearranged their family relationships, and added new species you've never seen before. This isn't a birder's nightmare—it's the exciting reality of modern ornithology! In 2018, the American Ornithological Society (AOS) published its Fifty-ninth Supplement to the Check-list of North American Birds, a document that continues to revolutionize how we understand and categorize our feathered friends 1 . This annual update isn't just bureaucratic paperwork; it represents the cutting edge of scientific discovery, where DNA analysis and field observations combine to create a more accurate picture of avian biodiversity.
For bird enthusiasts, researchers, and conservationists, these updates are far from trivial. They shape everything from which species receive protected status to how we interpret bird behavior across continents.
The 59th Supplement alone added new species to the main list, changed English names that had stood for decades, and reorganized entire family trees based on groundbreaking genetic research 1 . This article will take you through the most fascinating changes, explore the science behind them, and introduce the tools that are helping scientists rewrite the bird book—literally.
At the heart of modern bird classification lies phylogenetics—the study of evolutionary relationships among species. For centuries, ornithologists relied on physical characteristics like beak shape, plumage patterns, and skeletal structures to classify birds. While these observations were remarkably insightful, DNA sequencing has revealed that looks can be deceiving in evolutionary relationships.
The 59th Supplement reflects this molecular revolution, with many changes driven by genetic analysis that shows how species are related on a deep evolutionary timescale.
When two birds look similar but actually evolved from different ancestors, scientists call this convergent evolution—and DNA helps untangle these relationships.
You might imagine that changes to the official check-list happen arbitrarily, but in reality, they result from a rigorous democratic process. The AOS's North American Classification Committee (NACC)—a group of leading ornithologists—evaluates scientific proposals throughout the year regarding bird taxonomy and nomenclature 2 .
The 59th Supplement to the AOS Check-list introduced several important changes that resonated through the birding community and scientific world 1 . These updates can be grouped into several categories:
The supplement added several new species to the main list, primarily through taxonomic splits where what was once considered a single widespread species was recognized as multiple distinct species.
New Species Added | Scientific Name | Former Classification | Reason for Change |
---|---|---|---|
Common Shelduck | Tadorna tadorna | Appendix species | New distributional information |
Chiriqui Foliage-gleaner | Automolus exsertus | Split from another species | Taxonomic split based on new evidence |
Morelet's Seedeater | Sporophila morelleti | Split from another species | Taxonomic split based on new evidence |
Table 1: New species added to the main list in the 59th Supplement 1
Perhaps the most noticeable changes for birders were the English name revisions. The Gray Jay became the Canada Jay, reverting to a historical name that better reflects its primary distribution and cultural significance 1 . Similarly, the Red-breasted Blackbird became the Red-breasted Meadowlark, a change that better reflects its evolutionary relationships.
Reverted to historical name reflecting primary distribution
Better reflects evolutionary relationships
One of the most significant changes in the 59th Supplement was the reorganization of several bird families and genera. For example:
"New families of storm-petrels (Oceanitidae) and suboscine passerines (Onychorynchidae) are added, a subfamily classification and a new linear sequence are adopted for the Accipitridae, and a modified subfamily classification and a new linear sequence are adopted for the Tyrannidae, all due to new phylogenetic data" 1 .
One of the most comprehensive studies behind the 59th Supplement's changes was the multi-year research into woodpecker relationships. The study that ultimately led to the major reorganization of North American woodpeckers followed a rigorous scientific process 1 4 :
Researchers gathered genetic samples from museum specimens and carefully collected tissue samples from birds in the field across North and South America
In the laboratory, scientists extracted and sequenced specific genetic markers that evolve at rates useful for determining evolutionary relationships
Using statistical models, researchers compared DNA sequences across species to build evolutionary trees showing how closely related different woodpecker species were to each other
The team then checked whether the genetic relationships correlated with physical characteristics
The results underwent rigorous evaluation by other experts before publication in scientific journals
The study revealed that the traditional genus Picoides contained birds that weren't each other's closest relatives. Instead, they belonged to distinct evolutionary lineages that had diverged millions of years ago 4 .
This finding necessitated splitting Picoides and resurrecting the genus Dryobates (which means "woodland walker") for species including the Downy Woodpecker, Hairy Woodpecker, and others.
Former Classification | New Classification | Common Name |
---|---|---|
Picoides pubescens | Dryobates pubescens | Downy Woodpecker |
Picoides nuttallii | Dryobates nuttallii | Nuttall's Woodpecker |
Picoides scalaris | Dryobates scalaris | Ladder-backed Woodpecker |
Picoides borealis | Dryobates borealis | Red-cockaded Woodpecker |
Picoides villosus | Dryobates villosus | Hairy Woodpecker |
Table 2: Woodpecker species that underwent genus changes in the 59th Supplement 1
This reorganization wasn't just academic—it helped scientists better understand how woodpecker adaptations evolved across different continents and time periods. The new classification reflects a more accurate evolutionary history, showing how similar-looking species on different continents actually represent independent evolutionary innovations rather than close relationships.
Modern bird classification relies on an array of specialized tools and techniques that allow researchers to uncover relationships invisible to the naked eye. Here are some of the most important "research reagent solutions" in the taxonomist's toolkit:
High-tech machines that read the exact order of nucleotides in DNA samples
Polymerase Chain Reaction instruments that amplify tiny DNA samples
Chemical solutions that isolate DNA from feathers, blood, or tissue samples
Computer applications like BEAST, MrBayes, and RAxML that use statistical models to build evolutionary trees from genetic data
Software like Raven Pro that visualizes and analyzes bird vocalizations, often revealing differences between similar-looking species
Carefully preserved bird skins, skeletons, and tissue samples that provide physical reference and genetic material for study
Online repositories like GenBank (for genetic sequences) and Macaulay Library (for bird sounds)
Fine nets used to safely capture birds for measurement and sample collection
High-quality audio equipment used to document bird vocalizations for analysis
Essential tools for observing and documenting bird behavior and field marks
You might wonder whether all these name changes and reclassifications really matter beyond scientific journals. The answer is a resounding yes—these updates have real-world implications for both bird enthusiasts and conservation efforts.
The birding community relies on accurate classification to identify species and maintain accurate life lists. When species are split (like the addition of Morelet's Seedeater in the 59th Supplement), birders might discover they've seen a new species without traveling anywhere new—what was once considered a population of White-collared Seedeater is now recognized as distinct 1 .
The AOS recognizes this impact and works to provide resources for birders to stay current. They maintain an online checklist that incorporates all changes, allowing easy access to the most up-to-date information 2 . Additionally, organizations like the Institute for Bird Populations provide standardized species codes that are updated annually to reflect taxonomic changes, ensuring that birding data remains consistent and valuable for scientific use .
Accurate taxonomy is essential for effective conservation. When a widespread species is split into multiple distinct species, conservation priorities may change dramatically—what was once considered a secure population might actually be a threatened species with limited range.
The 59th Supplement's recognition of the Chiriqui Foliage-gleaner (Automolus exsertus) as distinct from other foliage-gleaners, for example, means this bird now has a more limited geographic range and may require different conservation strategies 1 . Similarly, splits in the Sporophila seedeaters help conservationists design more targeted protection plans for grasslands in Central and South America.
"Subspecies that reflect biological diversity play an important role in flagging the attention of evolutionary, behavioral, ecological, and conservation biologists" 2 . Even when subspecies aren't included in the main checklist, they remain important for understanding biodiversity and targeting conservation efforts.
The Fifty-ninth Supplement to the AOS Check-list of North American Birds represents far more than a simple list of name changes. It embodies the dynamic, ever-evolving nature of science itself—our continuous effort to better understand the natural world through observation, technology, and analysis. Each annual supplement builds upon previous knowledge, incorporating new findings that refine our understanding of avian relationships.
As genetic sequencing technologies become more sophisticated and accessible, we can expect even more revelations about bird relationships in coming years. The AOS North American Classification Committee will continue to evaluate new evidence and incorporate it into future supplements, ensuring that our official checklist reflects our best current scientific understanding 2 .
For bird enthusiasts, these changes shouldn't be viewed as inconveniences but as opportunities to deepen our appreciation for avian diversity. Each taxonomic revision tells a story of evolution, adaptation, and discovery—reminding us that the natural world still holds many mysteries waiting to be uncovered.
So the next time you hear about a bird name change or classification update, remember that it represents years of research by dedicated scientists striving to better understand our feathered friends. In the words of the committee, these decisions are made carefully, following established procedures to ensure "the biological reality and practical utility" of our classification system 2 —helping both scientists and bird lovers alike appreciate the incredible diversity of North America's birds.