Sounds of the Cranes: Behavioural ecology of complex duet vocalisations of Sarus in north Indian farmlands

Suhridam Roy


Sarus Crane is a fascinating bird species which inhabits the floodplains of northern India and is revered as an epitome of marital virtue and also as a sacred bird. They have a range of complex behaviours, and one such behaviour is duetting, where the male and female sing in coordination to form one unified song. It is not clear why they sing together, how duets look like and whether the structure of the duet is consistent across its distribution or not. No acoustic study has been undertaken for Sarus. So, in order to gain better knowledge on duetting behaviour of Sarus Crane, this study aims to elucidate duet structure of Sarus, its patterns of variation in space, and different ecological factors that may shape the duets of Sarus.

Sarus landscape

Sarus distribution was once spread throughout Gangetic floodplains and its documentation can be traced back to as early as 16th century Mughal dynasty. Sarus in Sanskrit means the “bird of lakes”. Research suggests that wetland availability is critical for young birds to survive. But due to attrition in wetlands and habitat alteration, Sarus distribution in India is restricted to several highly populated agricultural regions of north, west and central India. The breeding pair density changes across the distribution as a result of habitat quality and farmer tolerance. Our study sites incorporate three density classes: High (Uttar Pradesh), medium (Gujarat) and low (Haryana).Duet of Sarus

Duet of Sarus

By definition, duet is a piece of music sung by two individuals. There are 1627 different species of birds in the wild that perform duets. The existing studies are skewed towards songbirds and the function behind their duet songs. We know very little from non-passerine birds including different waterbirds who regularly perform duets. The mated pairs of Sarus Crane are known to sing loud trumpeting duets with associated physical postures, which stimulate awe to the observer. However, this wonderful vocal behaviour still remains unexplored.

Why study duets of Sarus?

Duets are reported to serve many critical functions in birds, such as territory defence, pair bond maintenance, signalling vigour to the rival pairs etc. But the functions are rarely tested experimentally in the wild for non-passerines. With ever changing landscape features due to anthropogenic interventions, there are ample evidences of behavioural modifications of wild birds. But, how complex behaviour such as duets are affected by ecological features such as territory quality, neighbourhood density, habitat composition and anthropogenic features such as roads, anthropogenic built up areas, is not yet tested. If duets are pair specific then it can also act as a way to identify individual pairs which may help in monitoring them.

What to expect?

Duets are not simple. They consist of different segments and these segments are strictly adhered by all Sarus Crane pairs. Pair mates coordinate their songs with each other, producing loosely or tightly coordinated duet. The mechanism of attaining the coordination is still a mystery.

The vast distribution of Sarus implies a potential of geographic variation of duets. Initial findings consisting of 101 pairs showed that pairs vary across north India in some features such as duet coordination, bandwidth and duration of duets. As expected, the coordination between pair mates and the duet bandwidth showed to increase with better territory quality.

We will sample more duets and use satellite imagery to deduce landscape classes and relate it with the duet structure. We will also run playback experiments to understand the primary functions behind the duets. It is still a long but intriguing road ahead to unravel the remarkable duets of Sarus Crane.

Sarus Crane is the tallest flying bird on planet, and possess a range of behavioural displays, used for an array of different purposes.