The red-eyed vireo (Vireo olivaceus) is a small songbird found throughout eastern North America. This olive-green bird gets its name from its distinctive red eyes. Red-eyed vireos are neo-tropical migratory birds, breeding in North America during the summer months and wintering in Central and South America. As their name suggests, red-eyed vireos are known for their red eyes and their incessant singing. But where exactly do these birds make their nests during the breeding season? Read on to learn more about the nesting habits of the red-eyed vireo.
What kind of habitat do red-eyed vireos prefer?
Red-eyed vireos prefer to breed in deciduous and mixed forests across eastern North America. They are found in greatest numbers in moist, mature hardwood forests, especially those with an abundance of tall trees. Some key habitats include:
– Mature oak forests
– Floodplain forests
– Maple-beech-birch forests
– Aspen groves
Within these forest types, red-eyed vireos look for trees that are over 50 feet tall. They tend to avoid coniferous forests and open areas without significant tree cover. Edge habitat between forests and open areas can attract red-eyed vireos, provided there are enough large, mature trees present. In general, larger tracts of unfragmented, deciduous forest habitat have the highest densities of breeding red-eyed vireos.
Do red-eyed vireos build hanging nests?
Yes, the nests built by red-eyed vireos are distinctive. They construct pendulous, hanging nests suspended from a tree branch high up in the canopy. Their nests are cup-shaped and about 4-5 inches across.
Red-eyed vireos situate their nests anywhere from 6 feet to 50 feet high up in a tree. Oaks, maples, birch, beech, and ash trees are common nest sites. Nests are lashed to a forked branch and hung securely from spider silk, pine needles, strips of bark, grasses, and other materials. The outside of the nest is camouflaged with lichens, spider egg cases, and birch bark.
This hanging nest style helps conceal the nest and protect the eggs and young from predators. The nest’s position high in the canopy also takes advantage of the dense foliage up there. The pendulous structure sways in the wind, which likely makes it harder for predators to access.
When does nest building occur?
Red-eyed vireos time their migration and return to the breeding grounds based on optimal conditions for nesting and raising young. In spring, adults arrive on the breeding territory in April or May.
Males establish territories shortly after arriving. Then the females appear approximately a week later. Once a monogamous pair bond forms, the female begins constructing the nest alone in late May or early June.
She builds the nest over a period of 5-10 days. Red-eyed vireos may even reuse a nest from the previous season, repairing and refurbishing it first before laying eggs. Old nests make up about 30% of the nests used for breeding.
How many broods do red-eyed vireos have?
Red-eyed vireos are persistent nesters and can raise more than one brood per breeding season. The first brood is generally initiated in May or June. If this nest fails or the eggs don’t hatch, the pair may build another nest and try again.
Once the first brood fledges by late June or July, mature forests provide enough food resources for red-eyed vireos to breed again. The female initiates a second nest while the male continues caring for the fledglings from the first brood.
Second broods represent 30-40% of breeding attempts. Having two broods per season helps maximize reproductive success for red-eyed vireos. More broods mean more offspring and better odds some will survive to adulthood.
How many eggs do red-eyed vireos lay?
The typical red-eyed vireo clutch size is 3-5 eggs. On average, first clutches contain 4 eggs while second clutches are slightly smaller at 3 eggs. The female lays one egg per day until the clutch is complete.
Red-eyed vireo eggs are white with brown speckles concentrated around the larger end. The eggs measure approximately 0.8 inches long by 0.6 inches wide. Only the female incubates the eggs for 12-16 days before they hatch.
Red-eyed Vireo Clutch Sizes
| Clutch | Typical # of Eggs |
|---|---|
| First clutch | 4 eggs |
| Second clutch | 3 eggs |
Who incubates the eggs and feeds the young?
The female red-eyed vireo incubates the eggs by herself. She develops a brood patch, a bare patch of skin on her belly used to transfer warmth to the eggs. The female sits tight on the nest and rotates the eggs periodically.
Once the eggs hatch, both parents feed the nestlings. They forage caterpillars, insects, fruit, and other food to bring back to the nest. The chicks fledge from the nest 10-12 days after hatching.
Fledglings follow their parents around and beg for food. The male tends to focus on feeding the young while the female starts building a second nest. Juveniles become independent 3-4 weeks after leaving the nest.
Do males and females look alike?
Male and female red-eyed vireos appear nearly identical in their plumage patterns. They have olive-green upperparts, white underparts, a pale yellow wash on the flanks, and dark wingbars.
However, experienced birders can distinguish subtle differences between the sexes:
Identifying Male vs Female Red-eyed Vireos
| Male | Female |
|---|---|
| Brighter yellow flanks | Duller yellow flanks |
| Darker red eyes | Ruby red eyes |
| More distinct wingbars | Faint wingbars |
In addition to slight plumage variations, behavior can help identify the sexes. Only the female builds the nest and incubates eggs. Males establish territories earlier in spring and do most of the singing to defend their turf.
Do both parents sing?
The male red-eyed vireo is responsible for the incessant singing these birds are famous for. Males sing to attract mates in spring and defend territories year-round. One bird may sing more than 20,000 songs per day!
Each male has a repertoire of over 100 song types. Songs consist of a variable series of short phrases, with each phrase repeated two to six times in a row. The male’s frequent singing led to alternative folk names like “preacher bird.”
In contrast, female red-eyed vireos may sing just a few short songs on the nest when communicating with a mate or offspring. But they do not sing persistently on a territory like males do. The far more vocal male uses his endless songs to repel rivals and communicate pair bond status.
How do red-eyed vireos defend their nests?
Red-eyed vireos are not particularly aggressive birds, but they have some defensive strategies for protecting nests:
– Camouflage – The hanging nest is disguised with lichens and bark strips and situated high in dense foliage. This concealment helps avoid detection.
– Mobbing – If a threat gets near the nest, red-eyed vireos may harass predators in a group by diving and calling loudly. This mobbing distracts and drives intruders away.
– Nest guarding – Males stand guard near the nest and chase away other males intruding on their territory. Their vigilant presence helps deter some nest predators.
– Good sites – Building nests high in the canopy provides some protection from tree-climbing predators. Swaying nests are harder targets too.
Despite their efforts, many nests fail due to natural predation. Jays, crows, squirrels, and snakes commonly take eggs and young. But red-eyed vireos persist and often raise two broods per season.
Where are wintering and migration habitats?
Red-eyed vireos breed across eastern North America in summer but migrate long distances to spend winters in the Neotropics. They occupy a wide range of forest habitats in migration and on the wintering grounds.
Some key migration and wintering sites include:
– Lowland rainforests from Mexico to the Amazon Basin
– Forest fragments across the Caribbean
– Scrub habitat and woodland edges in Central America
– Mangroves in coastal regions
– Arid tropical forests in regions like Venezuela
Red-eyed vireos often join mixed flocks with other migratory songbirds while wintering. Their winter range spans over 4,500 miles between Canada and South America. Maintaining habitats along this entire migration route is crucial for conserving red-eyed vireo populations.
Red-eyed Vireo Migration Distance
| Migration Route | Approximate Distance |
|---|---|
| Canada to Central America | 3,000 miles |
| Central America to South America | 1,500 miles |
| Total one-way distance | 4,500 miles |
How do predators impact nesting success?
Many predators target red-eyed vireo nests, contributing to relatively low reproductive success. Only about 40% of nests successfully fledge young.
Common nest predators include:
– Blue jays – The most frequent nest predator, jays eat eggs and young.
– Crows – Very intelligent, crows raid nests opportunistically.
– Squirrels – Tree squirrels raid nests for protein-rich eggs and chicks.
– Snakes – Climbing rat snakes and others consume eggs.
– Domestic cats – an invasive species that threatens breeding birds.
– Hawks – Sharp-shinned hawks and Cooper’s hawks prey on adults and fledglings.
Nest predation is the main cause of nest failures, rather than weather, competition, or parasites. Building multiple nests per season helps compensate for frequent predation events.
How can we help conserve red-eyed vireo populations?
Although still common, red-eyed vireo numbers have declined over the last 50 years according to monitoring data. Habitat loss on the breeding grounds, wintering areas, and migration routes likely contributes to reductions.
Some conservation actions that could help red-eyed vireo populations:
– Protect mature, unfragmented deciduous and mixed forests. This provides quality breeding habitat.
– Promote sustainable forestry practices that maintain taller tree stands.
– Reduce predation pressures from jays, crows, and squirrels where possible.
– Preserve and restore wintering grounds and migration stopover sites.
– Support shade coffee or agroforestry plantations that offer habitat.
– Limit pesticide use, which reduces insect prey for vireos.
– Keep domestic cats indoors to reduce predation.
– Participate in citizen science nest monitoring programs.
With large habitat needs across a migratory range that spans continents, conserving the red-eyed vireo is a challenging but worthwhile endeavor. Sustaining healthy, productive forests remains key.
Conclusion
Red-eyed vireos are dedicated nest builders, constructing elaborate hanging nests high in mature deciduous trees across eastern North America each summer. Their specialized nests help protect against predators, while persistent re-nesting efforts maximize reproductive success. Loss of prime nesting forests could threaten red-eyed vireo populations in the future, but sustaining quality breeding habitat and reducing mortality factors across their range can support these prolific and beloved songbirds. With attention to their life history needs, the incessant songs of red-eyed vireos will continue gracing forests for generations to come.
