The Bird Hide at The Bagh, Kanha National Park

A passerine is any bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or songbirds, passerines are distinguished from other orders of birds by the arrangement of their toes (three pointing forward and one back), which facilitates perching. Various Passeriformes (perching birds) are commonly referred to as warblers. They are not necessarily closely related to one another but share some characteristics, such as being fairly small, vocal, and insectivorous.

India is home to two warblers that are hard to tell apart, the Green Warbler (Phylloscopus nitidus) and the Greenish Warbler (Phylloscopus trochiloides). As the names suggest, green warbler is brighter in colour, and the underside is much more yellow. It has one strong and one faint wing bar, especially in young birds, while the greenish warbler is greyish-green above and off-white below with a single wing bar.

The warblers are insectivores and highly territorial. The Greenish Warblers, originally from the Himalayan foothills, generally found in Central and Eastern Himalayas, migrate southwards during winter seasons. Some of the Greenish Warblers have been found thousands of miles away in Central Asia and as far as Europe during summer months, but roost exclusively in the Indian sub-continent during winters.

The Green Warblers populate the tropical south of the Indian sub-continent more than the Greenish Warblers. But there are huge tracts of overlap and during the moulting season it becomes hard to tell the Greenish and Green Warblers apart, that is where the trisyllabic and disyllabic bird call comes into importance. Our expert birders at The Bagh, Bharatpur and The Bagh Kanha can help you identify the subtle difference in the bird calls as well as the wing bars.

Although not more than a fistful in size, the Warblers can be highly territorial. The calls change from continuous territorial songs claiming turf and short calls warning intruders, growing silent during the moulting. Their fidelity to the territory, returning to the same patch of canopy year after year is a marvel.

Just before the migration as the monsoon ends and the grey skies turn blue with chill filling the air, the Greenish Warblers get very active, gorging on insects putting on a few grams of fat to their body weight in anticipation of their voyage of thousands of miles. The Green Warblers are more ubiquitous in South India and Greenish Warblers are seen all across the sub-continent.

The male and female come together during mating season, working together to raise the young ones. When they migrate for the winter months, the males and females separate, holding their own territory and defending it against each other.