Meet the White-eyes!

“Aegion of lemon drops with wings” is how Jason Gregg, in a 2026 article in Audubon, described a flock of Swinhoe’s White-eyes, Zosterops simplex, he saw in Southern California. The same could be said of its close relative, the Warbling White-eye, Z. japonicus. These gregarious, radiant, and active denizens of neighborhoods and forest edges in California and Hawaii, respectively, are the two species of white-eyes found in the ABA Area. Despite their abundance, their presence is relatively new. In Hawaii, Warbling White-eyes were introduced in the 1920s; see Robert L. Pyle and Peter Pyle’s excellent overview in The Birds of the Hawaiian Islands: Occurrence, History, Distribution, and Status. And it was not until the early 2000s that the similar Swinhoe’s White-eye colonized Southern California, marking a first appearance of any population-level significance in the New World; I am unaware of a formal publication on the species’ initial establishment here, but it is well attested in the eBird database.

Their shared genus Zosterops is widespread, spanning Africa to Australia and north to Asia, with their center of diversity across the many islands and islets of Oceania. Bas van Balen’s synopsis in Birds of the World illustrates how Zosterops began arriving at and speciating among these islands over two million years ago, resulting in 110 species in the genus today. Their amazing ability to colonize—earning the designation of a “supertramp” species from Ethan Linck, Sarah Schaack, and John P. Dumbacher writing in 2016 in Molecular Phylogenetics and Evolution (94 [A]: 113–121)—remains a distinguishing part of their identity. In a related vein, Luca Cornetti and six coauthors call Zosterops “the great speciator” in a 2015 paper in Genome Biology and Evolution (7: 2680–2691). Today, introductions in the ABA Area have demonstrated their potential to establish populations even in more temperate locations. The questions now are what the future holds for these two species and where they might spread next.

To understand the future of this genus in the ABA, we must first explore its past.

 

Three species of white-eyes have been established in the ABA Area. The first was the Warbling White-eye, in Hawaii, introduced to control insect pests by the Territorial Board of Agriculture and Forestry; see Thomas G. Lammers, Stephen G. Weller, and Ann K. Sakai’s 1987 paper in Pacific Science (41 [1–4]: 74–78) for details. In this benign, tropical-island environment, their numbers exploded. By the 1960s, they had become the most abundant birds in the archipelago. Pyle and Pyle, in their Hawaii monograph, report of the vagrancy of Warbling White-eyes to remote atolls—including five records from Johnston Atoll, 860 miles from the main islands. As is typical with invasive species, the overall Warbling White-eye population in Hawaii has leveled off and is perhaps declining, but the species remains abundant in all habitat types on the main islands of Hawaii. Additional information on the species’ general biology is provided by Sandra Guest Van Riper and Bas van Balen in their Birds of the World account.

The next introduction occurred in the 1970s, when the San Diego Zoo reported escaped Indian White-eyes, Z. palpebrosus. While the population initially grew to over 100 individuals, Valerie Van Way, writing in Proceedings of the Eleventh Vertebrate Pest Conference (41: 188–191) in 1984, describes that the California Department of Food and Agriculture eventually eradicated them due to concerns over competition with indigenous bird species. This successful extirpation recalls similar stories of Mandarin Ducks in Northern California and Budgerigars in Florida.

Finally, in 2007, Swinhoe’s White-eyes were reported in Southern California, likely arriving due to the illegal pet trade. Around 2013, the first breeding record was confirmed, and today white-eyes are common throughout Southern California. Their established range extends from Isla Vista in Santa Barbara Co. down to Ensenada in northern Baja California and includes recent advances to the Channel Islands, according to eBird reports. As of 2026, their range in California seems to be restricted by the Transverse Ranges, similar to the resident Allen’s Hummingbird. In addition to areas of provisional establishment, there are scattered records across the West Coast that likely reflect dispersers from this source population. Strays northward include a record at Morro Bay in San Luis Obispo Co., breeders in San Francisco Co., and even a few individuals in the Seattle, Washington, area, well attested in the eBird database. For a species that has been in the U.S. for fewer than two decades, its progress is incredible.

 

Part of what makes birds in the genus Zosterops so effective at dispersing is their favorable life history traits. They are able to have over three clutches per year, they are woodland generalists, and they have a flexible diet including frugivory, insectivory, and nectivory. For good treatments of the ecology of Swinhoe’s White-eye in its indigenous range, see van Balen’s Birds of the World account.

These preferences reflect white-eyes’ tropical origins, and the increased abundance of exotic plants in cities and parks in the ABA Area has allowed these species to spread farther into temperate regions, well noted in Jason Gregg’s 2026 Audubon article. This phenomenon is not unique to white-eyes, by the way; consider the dramatic range expansion east and especially north of Anna’s Hummingbird, caused in no small part by the species’ ability to adapt to urban environments. All white-eye species that have occurred in the ABA Area share this similar life history, as well as similar molt strategies and plumages. Identification
between them is easy in 2026, as they are currently allopatric in our area. However, their ability to expand to new areas presents possible challenges going forward.

But we’re getting ahead of ourselves. That’s because the first identification hurdle is distinguishing white-eyes from indigenous species.

 

In Hawaii, flocks of Warbling White-eyes in primary forest can resemble flocks of the indigenous amakihis and other Hawaiian honeycreepers due to their similar size and color. Small flocks of yellow birds moving through the misty treetops might require a closer look. In addition to visual similarity with indigenous honeycreepers, white-eyes can sound like indigenous species such as the amakihis and Apapane. And while the typical song of an amakihi is a junco-like trill, amakihis can also produce a “subsong” that consists of rambling chattering and warbles—similar to the warbling chatter of a Warbling White-eye. This can be distinguished from the song of the white-eye by its lower, reedier, and less-clear tones, combined with a lack of distinct phrasing. Apapanes give songs that are either (1) lower-pitched than those of white-eyes or (2) erratic high-pitched squeaks that do not form phrases. They can also give a descending call note similar to the white-eye call, but it is clean and not tinny.

In California, visual identification issues may arise with poorly glimpsed little yellow birds like goldfinches and warblers, with the Orange-crowned Warbler perhaps the biggest possible point of confusion. The Orange-crowned Warbler subspecies lutescens, found mostly on the Pacific Slope, has a bright yellow plumage that approaches the lime-green of Swinhoe’s White-eye. Additionally, migrant orestera Orange-crowned Warblers in the region can show white eye-crescents and a hooded appearance, both of which can suggest Swinhoe’s.

Larger issues can arise from vocal identification. Hutton’s Vireo is one of the notorious “mystery sounds” in the region—and often a source of confusion to visiting and even local birders. One of the vireo’s many vocalizations is an incessant descending buzz impressively similar to that of Swinhoe’s White-eye. To get an idea for the similarities, compare the audio and spectrograms of Bob McGuire’s recording of a Hutton’s Vireo from Napa Co., California (Macaulay Library ML192455), with Paul Marvin’s recording of a Swinhoe’s White-eye from San Diego Co., California (Macaulay Library ML259750111.

Microhabitat may be helpful. Hutton’s Vireos tend to be restricted to oaks. Swinhoe’s White-eyes, like Warbling White-eyes, are more generalist. Broadleaf vegetation is invariably present, with a mix of exotic plantings like eucalyptus and bottlebrush and indigenous trees like willow and ash. For a good treatment of the ecologies of both species in their indigenous ranges, see Nial Moores’s 2019 post to his Birds Korea blog.

Two other sources of possible confusion are the descending whistles of the desert-adapted Verdin and the slurred squeals of the protean European Starling. However, the relevant calls of both species usually lack the burry quality of the white-eye.

Back to field ID within the genus. Again, it’s not a problem for us in the ABA Area—yet. Many field marks are unresolved at the present time due to novel taxonomy, stemming in no small part from a seminal 2018 paper by Byran T. M. Lim and eight coauthors in theJournal of Ornithology (160: 1–16). A brief overview is given in Ted Floyd and Andrew Guttenberg’s treatment on pp. 372–373 in the recently published 8th edition (2025) of National Geographic’s Field Guide to the Birds of the United States and Canada.

Swinhoe’s White-eyes are generally slimmer and sleeker than Warbling White-eyes, with a brighter yellow forehead that contrasts with darker lores. The bill of Warbling averages larger and grayer. Pyle and Pyle, in their Hawaii monograph, note that the Warbling White-eyes introduced to Hawaii likely represent the northern Japanese subspecies, japonicus. Their variable flanks can be grayish to somewhat buffy, with the flanks of Swinhoe’s paler. However, flank coloration is weakly correlated with clinal differences in both species’ indigenous ranges.

Vocal differences are greater. Swinhoe’s White-eyes have a heavy, downslurred call, whereas Warbling White-eyes have a sweeter and thinner call. In addition, Swinhoe’s White-eyes generally sing with a simple, repetitious series of downslurred notes, whereas Warbling White-eyes produce a namesake jumble of warbles that are more complex than Swinhoe’s; the notes in the jumble sometimes ascend in pitch. In excited flocks, a common occurrence with white-eyes, the downslurred calls of Swinhoe’s stand out, whereas a general chattering is more evident with Warbling.

Other species are conceivable going forward in the ABA Area and deserve brief mention here. The extirpated Indian White-eye is brighter overall than Swinhoe’s and Warbling, approaching a lemon-yellow hue. Thus far, these three species of white-eyes are the only species confirmed to have occurred in the ABA Area, but other Zosterops white-eyes are possible. One candidate is the Lowland White-eye, Z. meyeni, from the Philippines, nearly identical morphologically to Swinhoe’s, but apparently with harsher calls. Hume’s White-eye, Z. auriventer, its range centered on Malaysia, shows a prominent yellow stripe from its vent to its breast; note that some Warbling and Swinhoe’s show this mark, but more weakly. Finally, the Sangkar White-eye, Z. melanurus—hailing from Java and Sumatra , and popular in the pet bird trade—is similar to the aforementioned species, but with significantly reduced hood contrast.

If you encounter a white-eye out of range in the ABA Area, try to get good photos—especially of the facial features. Audio recordings and behavioral notes could be very helpful, too.

Finding a vagrant is not a hypothetical. In Sept. 2025, Tim Carney found a Swinhoe’s White-eye in Baltimore, Maryland, associating with a migrating Magnolia Warbler; the record is well-supported by Carney’s eBird checklist, with excellent photos, audio, video, and field notes. Carney’s personal detective work yielded no reports of recent escapes in the region, and it seems exceedingly unlikely the Baltimore white-eye dispersed from the California source population due to sheer distance—although that is not inconceivable. And it has recently come to light that, a few years earlier, in Apr. 2021, David Gabay photographed a white-eye in Broward Co., Florida. Bill Pranty, an expert on Florida field ornithology, has determined that the bird cannot be identified to species. Nevertheless, the occurrence of any Zosteropssp. from Florida raises the prospect of rapid establishment there. Much of peninsular Florida is considered a tropical biome by the U.S. Environmental Protection Agency, well-poised, it would seem, to support one or more white-eye species.

Following similar logic, large cities such as Houston, Phoenix, and Mexico City are prospective starting points for the next white-eye establishment in North America. The story here is dynamic and unfolding before our eyes. For starters, there is much to be learned in Hawaii and California, where white-eyes already are now well established. But it would be well worth it to keep an eye on just about any stand of trees in the ABA Area or elsewhere in North America.