Chestnut-sided Shrike-Vireo

The Chestnut-sided Shrike-Vireo, also known as the Honey-browed Shrike-Vireo, is a distinguished member of the Vireonidae family, and is likely the largest within this avian group. It is a bird of vibrant contrasts, with a bright green back and predominantly white underparts, accented by the rich chestnut flanks and chest band that give it its name.

Identification Tips

Adults of this species boast a slate crown and nape, with golden-yellow eyebrows that may extend to the lores at the bill base. Their black eyelines thicken towards the gray nape, and they have white cheeks, thin black malars, and a white throat. The legs are pink, and the irides are yellow. Sexual dimorphism is present, with females exhibiting paler plumage and less pronounced chestnut coloration.

Habitat

The Chestnut-sided Shrike-Vireo is a specialist of humid pine-oak forests, thriving in montane habitats.

Distribution

This species ranges from central Mexico, including Jalisco and San Luis Potosí, down to southern Guatemala. It is a bird not commonly encountered, preferring the tropical and subtropical forest zones, typically above 1,800 meters in elevation.

Behaviour

Territorial by nature, these birds maintain territories that can exceed 4 acres. Males are known to engage in countersinging and even physical combat. When agitated, they may raise their crown feathers and occasionally fan their tails.

Song & Calls

The song of the Chestnut-sided Shrike-Vireo is a complex, multi-pitched whistle that ascends quickly before descending less harmonically. Calls include a hoarse chatter, and their vocalizations can be heard up to 400 meters away, making them a key method for detection.

Breeding

During the breeding season, males sing more frequently, especially during nest-building in May. Both sexes participate in creating cup nests in trees, usually around 7.5 meters above the ground.

Similar Species

While there are no similar species mentioned, it is important to note the sexual dimorphism that can help distinguish males from females.

Diet and Feeding

The Chestnut-sided Shrike-Vireo forages for arthropods within the leaves and epiphytic vegetation, occasionally consuming larger prey which they beat to death in the branches. They may also partake in frugivory and are most active in foraging during the morning and late afternoon.

Conservation status

Currently classified as Least Concern, the Chestnut-sided Shrike-Vireo has a stable population estimated between 20,000-50,000 individuals. However, they are vulnerable to habitat fragmentation, with studies suggesting a minimum habitat size requirement for their presence.