White-eyed vireos are small, stocky vireos measuring 12.7 cm in length, with a 19 cm wingspan and weighing 11.5 g. They have dark olive backs, with darker, almost black wings and tails. They have two white wingbars and white to yellow edges on the primaries. The nape is gray and borders an olive-colored head. One of the most defining features of this vireo are the bright yellow "spectacles" that include the lores and surround the eyes. True to the common name, another identifying feature is the white irises they develop as adults. They have whitish throats and bellies with pale yellow sides. Beaks and legs are black. Juveniles have dark irises which will stay this color until they are two years old. Juveniles may also be identified by white "spectacles", an entirely pale gray head and overall paler plumage. Males and females of this species look alike. (Sibley, 2000)
White-eyed vireos are Neotropical migrants, meaning that they perform seasonal migrations and inhabit both North and Central America during different times of the year. During the breeding season in the spring and summer months, these birds inhabit the southeastern United States and northeast Mexico. The northern extent of their range stretches from southern Iowa, across southern Michigan and to southern Massachusetts. They travel as far west as eastern Nebraska, Oklahoma and Texas. They are year-round residents along the southeast coastal United States from South Carolina to Texas, and also down through the east coast of Mexico. White-eyed vireos also overwinter in southern Mexico, Belize, Guatemala, Cuba, the Cayman Islands and the Bahamas. (Hopp, et al., 1995; Sibley, 2000)
White-eyed vireos prefer brushy habitats defined by a dense understory layer, and generally located near a water source. They often inhabit abandoned agricultural fields that have lain fallow for 20 to 50 years to allow for adequate shrubby, successional vegetation to grow. White-eyed vireos are frequently found in thickets alongside marshes and are one of the most common bird species in the Central Everglades. (Ehrlich, et al., 1988; Gawlik and Rocque, 1998; Hopp, et al., 1995)
Like all vireos, white-eyed vireos are monogamous, meaning one male and one female pair together to breed and raise young. Males establish territories and females will visit several and eventually select a suitable mate. There are no specific courtship displays, but pairs appear to court each other for several days during which time they forage together with the male closely following the female. Pair bonds seem to last only one season. (Ehrlich, et al., 1988; Hopp, et al., 1995)
White-eyed vireos breed once a year during the breeding season which lasts from late April to early August. Once pairs have formed, they begin searching for a nesting site which is usually less than 1 m from the ground in dense shrubs. The female selects the site, while her mate follow close behind. They usually select a suitable, forked branch where they can construct a suspended, cup-shaped nest. Both participate in nest building and they collect spiderweb silk, twigs, bark strips, and grass to incorporate into the nest. This process takes 3 to 5 days to complete. The female typically lays 4 eggs, and will lay one per day starting 1 to 3 days after the nest is complete. Like most vireos, the eggs are white with brown to black spots. Incubation is done by both parents and will last 13 to 15 days. After the young hatch, they will leave the nest after 9 to 11 days and will be brooded by their parents for an additional 23 days at most. White-eyed vireos can breed during their first spring, though not all are successful. (Ehrlich, et al., 1988; Hopp, et al., 1995)
After selecting a suitable nesting site and constructing a secure nest for their young, both parents participate in incubating the clutch. When they hatch, the young are altricial, meaning they lack feathers, have eyes closed and are immobile. After hatching, the helpless young require constant feeding and brooding, again by both parents. Male and female white-eyed vireos develop brood patches, which are featherless patches on their stomachs that can provide the most warmth to their eggs while the parents sit on the nest. Parents continue to feed and care for their young after they have flown from the nest. The young rely on their parents for up to 23 days after leaving the nest. (Ehrlich, et al., 1988; Hopp, et al., 1995)
Lifespan for white-eyed vireos is currently unknown. Adult survivorship ranges from 15 to over 57% depending on environmental conditions. First year survivorship is unknown. Possible causes of mortality include nest predation and severe weather. (Hopp, et al., 1995)
White-eyed vireos are mostly migratory birds that perform two annual journeys: north to the North American breeding grounds in the spring, and south to the wintering grounds in Central America in the fall. Non-migratory populations remain year-round in southern coastal regions of the United States from South Carolina to Texas, and also along the Gulf Coast of Mexico. Although white-eyed vireos make long-distance journeys at night, like many migratory birds, it is a diurnal species for the remainder of the year.
White-eyed vireos are highly territorial birds and remain so even throughout the winter and against other species. Males exhibit territorial behaviors against other males during the breeding season. On their wintering grounds, both males and females may defend small territories and are particularly defensive of their preferred food source, Bursera trees. However, during migrations this species may be seen in flocks with other white-eyed vireos as well as other species. (Greenberg, 1992; Hopp, et al., 1995)
Territory size for white-eyed vireos ranges in size from 0.14 to 1.3 hectares. (Hopp, et al., 1995)
White-eyed vireos rely heavily on acoustic and visual forms of communication. The primary call of this species has an explosive quality and may be described in words as "quick-with-the-rain-check." Both the first and last notes are short and sharp, while the middle notes are a rapid warble. This song is given by males during the breeding season to establish territory and attract females. Fledgeling males learn their father's song very early in life, and may begin mimicking his call as early as one month after leaving the nest. Young white-eyed vireos may also develop some elements of their song by mimicking their neighbors. Both males and females give a harsh chattering call in response to predators or in territorial encounters between males. Within a mated pair, both also give short 'pik' contact calls to each other when nearby. Adults and nestlings that are several days old will emit a harsh squeal if captured and handled by humans (during banding) and likely serves to startle a predator or alert a mate.
White-eyed vireos also use body postures and behaviors to communicate, which may be done with or without calls. Alert, anxious individuals may perform exaggerated neck movements or wing flicks. These movements likely serve to intimidate predators or territorial intruders. Other warning behaviors include pecking at a nearby perch or their own feet. If the threat does not retreat, these vireos will perform an aerial attack.
Diets of white-eyed vireos vary seasonally, as they are primarily insectivorous (eat insects) during the breeding season and frugivorous (eat fruit) during the non-breeding season. When foraging for insects, these vireos often perch motionless and tilt their heads to visually locate and watch prey before acting. This is a foliage gleaning species, and after locating a prey item it will capture prey by hovering, hanging, lunging or picking insects from plants. Caterpillars are preferred prey items, but white-eyed vireos may also consume flies, spiders and their egg cases, damselflies, mayflies, beetles, cockroaches, stink bugs, leafhoppers, bees, ants, and wasps, and grasshoppers.
During the non-breeding season, white-eyed vireos consume a wide variety of insects but are mostly frugivorous. This species has a very strong relationship with gumbo-limbo trees that live in Central America. White-eyed vireos eat the berries of these trees and will spread the seeds after digesting the fruit portion. Unlike many species, white-eyed vireos establish territories during the non-breeding season and gumbo-limbo trees are often aggressively guarded. Across wintering regions, white-eyed vireos may consume the fruit of sumac, dogwood, poison ivy, pokeweed, and waxmyrtle as well as wild grapes.
Specific predators of white-eyed vireos have rarely been documented. Most predation occurs during the breeding season as eggs and nestlings are abundant and make easy prey. Hypothesized predators include snakes, mice, chipmunks, blue Jays, raccoons, skunks, and opossums. There is very little evidence for predation of adults, but one case has been documented of adult capture and consumption by a short-tailed hawk in Florida.
When predators are near a nest, the white-eyed vireo pair will emit harsh, rapid chattering. Adults will also peck at their perch or feet which may precede an aerial attack if the intruder does not retreat. (Hopp, et al., 1995)
White-eyed vireos serve as predator, prey, and seed dispersant within the ecosystems they inhabit. This species is largely insectivorous, particularly during the breeding season. These feeding habits likely have a significant impact on local insect communities, especially caterpillars which are the preferred prey. During the non-breeding season white-eyed vireos consume mostly fruit and are likely important seed dispersants for many plant species. White-eyed vireos have a strong relationship with one fruit-bearing species, gumbo-limbo trees, and is the primary seed dispersant for this tree species. White-eyed vireos remain highly territorial during the non-breeding season and are known to aggressively defend Bursera simaruba plants in particular. The eggs and young of white-eyed vireos are also prey for a variety of predators. (Greenberg, et al., 1995; Hopp, et al., 1995)
There are no known adverse effects of white-eyed vireos on humans.
White-eyed vireos have no known economic impacts on humans.
The International Union for Conservation of Nature and Natural Resources (IUCN) currently considers white-eyed vireos to be of least concern. This is due to the large population size, current increasing trend in population numbers, and relatively large geographical range. Although stable now, this species may be threatened by habitat loss in the future. The shrubby habitats that white-eyed vireos prefer are often easy targets for human development including urbanization and conversion to agricultural fields. ("Vireo griseus", 2009; Hopp, et al., 1995)
Rachelle Sterling (author), Special Projects, Tanya Dewey (editor), University of Michigan-Ann Arbor.
Birdlife International. 2009. "Vireo griseus" (On-line). IUCN Red List of Threatened Species. Accessed June 07, 2011 at http://www.iucnredlist.org/apps/redlist/details/146454/0.
Bradley, R. 1980. Vocal and territorial behavior in the White-eyed Vireo. The Wilson Bulletin, 92/3: 302-311.
Ehrlich, P., D. Dobkin, D. Wheye. 1988. The Birder's Handbook: A Field Guide to the Natural History of North American Birds. New York, New York: Simon and Schuster.
Gawlik, D., D. Rocque. 1998. Avian communities in bayheads, willowheads, and sawgrass marshes of the Central Everglades. Wilson Bulletin, 110/1: 45-55. Accessed March 30, 2011 at http://elibrary.unm.edu/sora/Wilson/v110n01/p0045-p0055.pdf.
Greenberg, R. 1992. Ecology and conservation of neotropical migrant landbirds.. Washington, DC: Smithsonian Institution Press.
Greenberg, R., M. Foster, L. Marquez-Valdelamar. 1995. The role of the white-eyed vireo in the dispersal of Bursera fruit on the Yucatan Peninsula. Journal of Tropical Ecology, 11: 619-639.
Hopp, S., A. Kirby, C. Boone. 1995. "The Birds of North America Online" (On-line). Vireo griseus. Accessed March 30, 2011 at http://bna.birds.cornell.edu/bna/species/168.
Sibley, D. 2000. The Sibley Guide to Birds. New York: Alfred A. Knopf, Inc..