Bell’s Vireo

The Bell’s Vireo is a small, drab passerine found across central and southern parts of North America. Not much of a looker, these birds are mostly identified through their scratchy, fast song. They prefer low, bushy thickets near streams and rivers. They are difficult to observe as they nervously flit through the scrub. Bell’s Vireos do not stand out from other birds in their family, you can verify it’s them by comparing their size to the larger Gray Vireo. 

About Bell’s Vireos

This species does not show differences between males and females, where both are dull olive green. Populations show variation in coloration from brighter yellows and greens to plain grays. Bell’s Vireos search through low scrubby fields for scrumptious insects to feed on and can even hover to catch their meal. These neotropical migrant birds are of great interest to researchers due to interesting host-parasite interactions, making them an ideal species for conservation programs. Today, we will learn more about these tiny birds, covering topics like:

● Bell’s Vireo Photos, Color Pattern, Song
● Bell’s Vireo Size, Eating Behaviour, Habitat
● Bell’s Vireo Range and Migration, Nesting

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Bell’s Vireo Color Pattern

The word “vireo” refers to a green color bird, which is fitting for Bell’s Vireo. The plumages of males and females do not vary. They both have a dull olive greenback and a bright white lower wing bar. Bell’s Vireos have two populations that are slightly different in coloration; the Eastern population has a brighter white wing bar, and sometimes a fainter upper wing bar,  whereas the Western counterparts have a singular, fainter one. The Eastern population also shows hues of yellow in the birds’ flanks. While the Western population is more gray and dull green. They have a white eye-ring on the portion from the beak to above the eye, which is called the supercilium. This gives the appearance of highlighter eyebrows. The beak is a pale whitish brown and the little bird’s legs and feet are a dark brown or black. Their eyes appear black, noticeable due to the contrasting eye-ring.

The head and neck of the Bell’s Vireo fade from dull olive or yellow to a slightly more saturated shade on their back. Their wings are dull olive green, slightly darker brown, or black in some individuals. Overall, the Eastern population shows much more saturated, brighter colors than the population present in the West. Least Bell’s Vireos, are confined to California and are completely gray. They can get confused with the Gray Vireo, although they are smaller in size.  

The juveniles of this species can be identified by looking out for their whitish cheeks and forehead and greener tails. They mature quickly enough to participate in the next breeding season.

Description and Identification

This active bird is difficult to catch by the naked eye, using its small size and drab color pattern to effectively hide from any potential predators. Constantly hopping through dense vegetation, these Vireos move their tails in a bobbing, wagging, or flicking manner while foraging. They stay low in the scrub, staying about a foot from the ground but may look for food higher if need be. Considering their inconspicuous appearance, these birds are mainly recognized by their unmelodic calls, delivering a scratchy “tweedle-deedle-dum?” “Tweedle-deedle-dee!” has been described as a harsh jingling sound produced as if the bird’s mouth is full of rocks. Finding these birds in low bushes may be hard, but they are usually in pairs. 

Bell’s Vireo Song

Despite being songbirds, Bell’s Vireos calls are far from melodious; their discordant vocalizations are the key feature of identification. They produce a distress call when in danger, alerting other Vireos and other surrounding birds, working effectively as an alarm. The males’ lively calls occur throughout the spring, indicating their breeding season. They primarily sing a song with two distinct phrases, “tweedle-deedle-dum?” “Tweedle-deedle-dee!” where the first phrase goes up and the second down. Bell’s Vireos call in rollicking, jingling sounds, although only the males emit mating calls. 

Bell’s Vireo Size

These Vireos are on the smaller side of the family, measuring 4.5-4.9 inches in length. Their wingspan expands to 6.7-7.5 inches, showing a proportionate body with a round head. They weigh only around 0.3 pounds, their lightness, and size allowing them to be very active both in movements and calls. Their beaks are small and pointed which allows them to easily pick out insects from the thickets. Bell’s Vireos hop around on their thin, dark feet and perch on branches of bushes. When compared to the Warbling Vireo, the Bell’s Vireo has a slimmer body. Although they have a rounded head, when compared to another member of the vireo family, the Gray Vireo, the Bell’s Vireo has a flatter, less shapely head. 

Bell’s Vireo Behavior

Bell’s Vireos are agile and very active while foraging. They hop through the dense vegetation of lowland scrubs, and never halt on a branch for too long. They avoid the ground, opting to stick to the bushes even while foraging. Their flight pattern shows some undulation as they fly with rapid shallow wingbeats before gliding for distances of 10-15 feet before perching on a suitable branch. To aid them while catching their prey, they hover for a few seconds, giving them ample time to grab their meal. If a predator such as a snake tries to steal their eggs from their nest, the Bell’s Vireo
admonishes the culprit by calling a defensive song while flying at it. They also try to keep ants away from their nests by picking them out, although the ants are usually quick to come back.

To maintain their plumage, these birds ensure to bathe in nearby streams by taking a quick dip directly into the water. They may also prefer a quick shower by rubbing themselves against leaves that are wet from dew. They keep their beaks clean by scratching and scraping from base to tip on branches, while they scratch their heads with their feet.
 
Although drab and small in appearance, these birds are feisty and fierce when it comes to mating. During the breeding season, they form monogamous pairs through a seemingly violent courtship where the male flies at the female, sometimes vocalizing a chum call. The three-part courtship, consisting of a greeting, pouncing, and a leap-flutter, is closely associated with the construction of a nest. The greeting consists of both the birds crouching a couple of inches apart while one of the birds slicks back their feathers while the other puffs them up. Pouncing consists of the female fanning and depressing the tail feathers while emitting a rapid call. The male lunges at the female with an open beak. Finally, the leap-flutter involves the male fanning their tail feathers, leaping nearly a foot vertically, fluttering, and then perching. If the courtship is successful and complete, the birds may copulate.  The nesting season is often a busy affair for Bell’s Vireos as they try to drive away birds of other species that try to lay eggs in their own nests. 

Bell’s Vireo Diet

These tiny birds are insectivores that feed on a range of insects found in the bushes. Not picky eaters, these vireos eat caterpillars, bees, wasps, stinky bugs, weevils, and some spiders. They might even favor a few berries. Bell’s Vireos pick out their food from the branches and leaves of vegetation. They don’t forage on the ground. They prefer bigger insects over smaller ones during the breeding season in spring. 

Bell’s Vireo Habitat

Found in the brushy, lowland scrub of the Midwest and Southwest North America, Bell’s Vireos prefer riparian locations. They inhabit dense vegetation that is characteristic of the second stage of an ecosystem’s succession of species. They prefer natural landscapes. A liking for younger bushes, they live in mesquite, woodland, scrub oak, green ash, and other dense brushlands. They are attracted to open waters and often nest at streamsides and coastal banks although they move away to more upland vegetation when wintering. 

Range and Migration

Bell’s Vireos typically live in riparian woodland scrub in North America, sticking to the central and southern parts of the continent. Their migration is restricted to within the continent as they travel to inner middle areas of North America and the Pacific coast during winter. Typical of neotropical migrants, their migration is complete. They leave around August to September for their winter journey and return by mid-March although they reach the northernmost nesting areas by May. Migration mostly takes place at night. 

Bell’s Vireo Lifecycle

After the elaborate and harsh courtship and nest construction, the female lays 3-5 eggs and both birds incubate for approximately 2 weeks. The younglings once hatched are fed by both the parents and eventually leave the nest after 11-12 days. The offspring are still fed by the parents for the next 3 weeks, by then the juvenile can start to forage for itself. These Vireos can mature to participate in the breeding process in the next season after their birth.

Nesting

Once a monogamous pair is bonded, the female leads the male to search for suitable nest sites. Short flights that are close to the ground allow the pair to forage at each site. While the female stops to check forked branches, the male sings loudly. The male then defends the nesting site by singing incessantly, often in low shrubs and saplings on a horizontal twig. The nest construction is a joint venture as both males and females hang a cup made of weeds, grasses, bark, and plant fibers, bound with spiderwebs. The inside of the nest is cozy with feathers, moss, and finer grasses. Interestingly, these birds embellish the outside of their nest with spider egg cases.

Anatomy of a Bell’s Vireo

The Bell’s Vireo is a rather small, slim vireo with a proportionate body. They have a slightly rounded head, with a short and pointy beak. Their wingspan is a little longer than their length, allowing them to flit and hop through thickets tirelessly. 

Final Thoughts

Usually, a common bird in North America, Bell’s Vireos are now becoming scarce in places they were before. The loss of their preferred waterside habitat of streams or rivers has reduced their population, although the International Union of Conservation of Nature has listed this species as Least Concern. It is endangered in Southern California. As these birds are seen in the secondary stages of a succession of ecosystems, they are a key species in conservation programs. Some land development authorities plan their schemes while also trying to protect the habitat of this species. 

A characteristic of the Vireo family, Bell’s Vireo is parasitized by Brown-headed Cowbirds which lay their eggs in the Vireos’ nest, hoping to outsource the work of incubation and feeding nestlings. Learning about this interesting strategy and Bell’s Vireos defense and behavioral patterns could reveal new lessons on the interdependence of species within an ecosystem. Their puny appearance is nothing but a mask to their tireless and territorial activity, surprising researchers with their unique courtship pair-bonding. This greenish passerine also does an incredible job by maintaining insect populations and is a valued member of the ecosystem. The Bell’s Vireo is a lesson to all birders that
appearances aren’t everything!

Ornithology

Bird Watching Academy & Camp Subscription Boxes

At the Bird Watching Academy & Camp we help kids, youth, and adults get excited and involved in bird watching. We have several monthly subscription boxes that you can subscribe to. Our monthly subscription boxes help kids, youth, and adults learn about birds, bird watching, and bird conservation.

Bird Watching Binoculars for IdentifyingBell’s Vireos

The most common types of bird watching binoculars for viewing Bell’s Vireos are 8×21 binoculars and 10×42 binoculars. Bird Watching Academy & Camp sells really nice 8×21 binoculars and 10×42 binoculars. You can view and purchase them here.

Bell’s Vireo Stickers

Stickers are a great way for you to display your love for bird watching and the Bell’s Vireo. We sell a monthly subscription sticker pack. The sticker packs have 12 bird stickers. These sticker packs will help your kids learn new birds every month.

Bird Feeders ForBell’s Vireos

There are many types of bird feeders. Bird feeders are a great addition to your backyard. Bird feeders will increase the chances of attracting birds drastically. Both kids and adults will have a great time watching birds eat at these bird feeders. There are a wide variety of bird feeders on the market and it is important to find the best fit for you and your backyard.

Bird Houses ForBell’s Vireos

There are many types of bird houses. Building a bird house is always fun but can be frustrating. Getting a bird house for kids to watch birds grow is always fun. If you spend a little extra money on bird houses, it will be well worth every penny and they’ll look great.