Cassin's Vireo
A species of Vireos Scientific name : Vireo cassinii Genus : Vireos
Cassin's Vireo, A species of Vireos
Botanical name: Vireo cassinii
Genus: Vireos
Content
Description General Info
Description
Cassin's vireo (Vireo cassinii) is a small North American songbird, ranging from southern British Columbia in Canada through the western coastal states of the United States. This bird migrates, spending the winter from southern Arizona (the Sonoran Desert) to southern Mexico. The vireo is 11–14 cm (4–6 inches) in length, with a gray head, back, and flanks, and whitish underparts. It has solid white "spectacles" and white wing bars. The song, given persistently, consists of short, rough whistled phrases of several notes, spaced about 2 seconds apart. The phrases often alternate ending on a high note and a low note, giving an impression of question and answer. It prefers open woodlands of the western mountains and foothills. It is usually found in the middle to lower portions of the forest canopy, where it slowly and deliberately forages for insects among the foliage. Cassin's vireo builds a cup nest out of bark strips and down in the fork of a twig. It lays 2 to 5 white eggs with some brown spots. This species was formerly considered to belong to the same species as the plumbeous vireo and blue-headed vireo. At that time, this complex of species was referred to as the "solitary vireo". This vireo is named after the ornithologist John Cassin. 
Size
10-15 cm (4-6 in)
Nest Placement
Tree
Clutch Size
3 - 5 eggs
Incubation Period
1 brood
Number of Broods
12 - 14 days
Nestling Period
13 - 14 days
Feeding Habits
Cassin's Vireo primarily feeds on insects such as moths, stinkbugs, and ants, as well as spiders, with occasional consumption of seeds and small fruits, especially in winter. They forage in lower to middle tree levels, gleaning prey from foliage or catching insects mid-flight.
Habitat
Cassin's Vireo primarily inhabit a broad range of forest environments including coniferous, deciduous, and mixed woodlands, from sea level to elevations of around 8,000 feet. They prefer drier, open woodlands with essential trees like pines, firs, larch, and various hardwoods. In coastal areas, cassin's Vireo select oak forests, while inland they frequent pine and fir-dominated forests. Along the coast and into the suburbs, cassin's Vireo adapt to human modifications. In Baja California, they span from dry thorn forests to pine-oak cloud forests. Migration can see cassin's Vireo passing through diverse landscapes, such as shrub-scrub or subalpine forests. Wintering cassin's Vireo utilize a wide array of wooded habitats in Mexico, including riparian and mangrove forests, revealing their ecological versatility.
Nest Behavior
Both cassin's Vireo parents participate in nest construction, likely with site selection by the female. Nest building leads to egg laying and parental care, though specific timing and patterns are consistent with other vireos and not distinctly documented.
Nest Characteristics
Cassin's Vireo's nest is typically located in a fork near a branch tip, mid-level in medium to large trees. It's a bulky, cup-shaped structure, roughly 3.2 inches wide and 2.2 inches tall, constructed from leaves, grass, and moss, lined with plant fibers and hair. Distinguishing features include adornments of paper, lichen, spider eggs, and hornet nest bits on the exterior.
Dite type
Insectivorous
General Info
Feeding Habits
Bird Feeder Type
Platform
Sounds
Song
Recording location: Mexico
Song
Recording location: Mexico
Behavior
Cassin's Vireo exhibit daily activities characteristic of their species, starting with males singing upon arrival at nesting grounds to claim territory. While territorial disputes in cassin's Vireo are not well-documented, closely related species engage in countersinging and threat displays, suggesting cassin's Vireo may display similar actions, including feather ruffling, horizontal threat postures, and aerial pursuits. Males entice females by puffing up plumage and presenting nesting materials with distinct gestures. These birds are likely monogamous, with both partners sharing responsibilities of incubation and feeding of chicks. Post-fledging, families may congregate in mixed-species flocks, transitioning to a migratory lifestyle as seasons change.
Species Status
Not globally threatened.
Scientific Classification
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