The chestnut-sided shrike-vireo (''Vireolanius melitophrys''), sometimes called the honey-browed shrike-vireo, is a species of

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

in the family

Vireonidae The vireos make up a family (biology), family, Vireonidae, of small to medium-sized passerine birds found in the New World (Canada to Argentina, including Bermuda and the West Indies) and Southeast Asia. The family contains 62 species and is d ...

, and probably the largest member of the entire family. A widespread species of subtropical and tropical moist

montane forest Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures lapse rate, fall as elevation increases, causing the ecosystem to stratify. This stratification is ...

s, this species is found from

Jalisco Jalisco, officially the Free and Sovereign State of Jalisco, is one of the 31 states which, along with Mexico City, comprise the 32 Political divisions of Mexico, Federal Entities of Mexico. It is located in western Mexico and is bordered by s ...

and

San Luis Potosí San Luis Potosí, officially the Free and Sovereign State of San Luis Potosí, is one of the 32 states which compose the Federal Entities of Mexico. It is divided in 59 municipalities and is named after its capital city, San Luis Potosí. It ...

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

in the north to southern

Guatemala Guatemala, officially the Republic of Guatemala, is a country in Central America. It is bordered to the north and west by Mexico, to the northeast by Belize, to the east by Honduras, and to the southeast by El Salvador. It is hydrologically b ...

Taxonomy and systematics

One of four species within the genus Vireolanius. The exact relationships of ''Vireolanius'' to other members of Vireonidae are not fully resolved, but it appears to be one of the basal groups within the New World Vireonidae along with '' Cyclarhis'' possibly '' Hylophilus''. Within the genus ''Vireolanius'', the chestnut-sided shrike-vireo appears to be the outgroup with respect to all other shrike-vireos. Two or three subspecies are recognized, depending on the taxonomic list being used. The type specimen of ''V. m. goldmani'' is alleged to be an immature of ''V. m. melitophrys'', in which case it should be considered a junior synonym of ''V. m. melitophrys''.

Description

Size

One of the largest species in Vireonidae, with a length of and a mean body mass of . Sexes are of similar sizes. Only one other population of Vireonid reaches this size - the

Cozumel Cozumel (; ) is an island and municipality in the Caribbean Sea off the eastern coast of Mexico's Yucatán Peninsula, opposite Playa del Carmen. It is separated from the mainland by the Cozumel Channel and is close to the Yucatán Channel. The ...

rufous-browed peppershrike The rufous-browed peppershrike (''Cyclarhis gujanensis'') is a passerine bird in the vireo family. It is widespread and often common in woodland, forest edge, and cultivation with some tall trees from Mexico and Trinidad south to Argentina and U ...

''Cyclarhis gujanensis insularis''.

Plumage

A striking bird, adult chestnut-sided shrike-vireos have bright green backs and largely white undersides punctuated by their eponymous chestnut flanks that meet in a chest band. The head is characterized by a slate crown and nape, golden-yellow eyebrows that sometimes reach the lores at the bill base, black eyelines that are thin near the bill and thickest where they meet the gray nape, white cheeks, thin black malars, and a white throat. The legs are pink, and irides are yellow. Chestnut-sided shrike vireos are sexually dimorphic, unlike most species of Vireonid which are monomorphic (with the exception of the black-capped vireo ''Vireo atricapillus''). Females can be separated from the males by their paler plumage and reduced chestnut coloration.

Vocalizations

The song is a complex, multi-pitched single-syllable whistle that quickly ascends in pitch with multiple harmonics before a longer, less harmonized descent, often given in repeated succession with pauses between whistles generally lasting between 0.7–1 seconds. Calls consist of a hoarse chatter, similar to many other species of Vireonid. A relatively difficult to observe species, vocalizations have proven to be one of the best ways to detect chestnut-sided shrike-vireos, with songs audible up to away. Six primary vocalizations have been described by Barlow & James:

Distribution and habitat

A humid pine-oak specialist, this species is restricted to montane habitats from central Mexico (

and

) to southern

. It is nowhere common, having one of the lowest relative abundances of any medium-sized songbird in Oaxacan pine-oak forests. In all regions, it is confined to tropical and subtropical forests zones, mostly above . In San Luis Potosí, this species is found principally between to in elevation. Similarly, a study in Jalisco only recorded this species above , with most birds found between and the highest elevations of the study area, .

Behavior and Ecology

Territoriality

Chestnut-sided shrike-vireos will maintain territories of up to or more. Males will often countersing, and will even engage in physical combat, latching on to each other while calling and beating each other with their wings. When agitated, birds will often raise their crown feathers and occasionally even fan their tails.

Vocal Behavior

Male chestnut-sided shrike-vireos sing the most during the nest-building phase of the breeding cycle in May, and show reduced vocal activity during the non-breeding season. Song bouts are usually approximately a minute in length, delivered with the body held between 50 and 80 degrees above the horizontal and the bill held perpendicular to the body, and delivered with as few as ten minutes between song bouts in the breeding season. Birds will respond to playback, and give a variety of contact, distress, and territorial calls depending on the situation (see Vocalizations above).

Food and Feeding

Forages for arthropods (including

caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder ...

wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...

grasshopper Grasshoppers are a group of insects belonging to the suborder Caelifera. They are amongst what are possibly the most ancient living groups of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago. Grassh ...

s, bugs,

spider Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...

s, and

beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...

s) primarily in the leaves and

epiphytic An epiphyte is a plant or plant-like organism that grows on the surface of another plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphyt ...

vegetation in the inner foliage of trees. Large arthropods, over approximately , will be beaten to death in the branches and sometimes held in the feet and dissected with the bill. Birds will less commonly eat vegetation and engage in frugivory. These birds prefer to stay in the mid-height of the tree but sometimes moving almost to the ground and up into the higher portions of the vegetation. Forage alone or in pairs, these birds are most active in the morning and late afternoon, often methodically moving from perch to perch approximately at a time. Occasionally joins mixed-species flocks.

Nesting

Both sexes create cup nests in trees usually about above the ground using vegetation such as grasses.

Threats

Vulnerable to habitat fragmentation, with a study from

Oaxaca Oaxaca, officially the Free and Sovereign State of Oaxaca, is one of the 32 states that compose the political divisions of Mexico, Federative Entities of the Mexico, United Mexican States. It is divided into municipalities of Oaxaca, 570 munici ...

indicating a minimum habitat size of for the species to occur.

Status

This conservations status of this species is presently considered Least Concern, with a stable population estimated between 20,000-50,000 birds and a global distribution less than .

References

{{Taxonbar, from=Q537579 chestnut-sided shrike-vireo Meso-American montane bird species Birds of Guatemala chestnut-sided shrike-vireo chestnut-sided shrike-vireo Taxonomy articles created by Polbot Birds of the Sierra Madre del Sur Birds of the Trans-Mexican Volcanic Belt