The capital, which is a stopover for thousands of migratory birds, has been seeing a sharp decline in their numbers each year.

This time each year, hundreds of migratory birds from North Indian states, Siberia and Southeast Asia flock to Delhi’s wetlands such as Okhla Bird Sanctuary, Sanjay Lake, Yamuna river, NajafgarhJheel, HauzKhas Lake, and Shantivan.

However, their numbers have been declining and even this year only a handful made their way to Delhi.

Only 27 species have been recorded at the wetlands in Delhi and according to experts their population is less compared to last year.

For example, approximately 1,000 graylag geese were recorded last year in December compared to only 250 till now this month.

Similarly, 50 bar-headed geese were recorded in 2014, but, only 30 in 2015 in December.

Experts say that though the diversity is still good, the population is degrading, owing to global climate changes, along with local environmental threats and degrading habitat.

“This season approximate 27 species of winter migratory water birds diversity with lesser number/population has been observed at seven wetlands in Delhi,” said ecologist and bird watcher K Roy.

“Out of this diversity only large flocks of graylag geese at Okhla Bird Sanctuary; bar-headed geese at Okhla and NajafgarhJheel; Eurasian coot at Okhla, Northern shoveler at NajafgarhJheel, mixed flocks of brown-headed and black-headed gulls on river Yamuna and rest of the species in smaller number are recorded which used to be more in diversity and number in comparison to previous years,” Roy, who is the Asian Water Census (AWC) Delhi state co-coordinator for Wetlands International South Asia.

The AWC is a volunteer-based census and is conducted to record overall status of important wetland habitats, water bird diversity and population every year during mid winter. This year the census will be held from January 9 to

January 24.

The number of bar-headed geese, graylag geese, and black-headed gull, was comparatively more last year, Roy said, adding, some like tufted duck, ruddy shelduck, mallard, and pallas’s gull have not been sighted at all at the three major sites in the capital till now.

The observation of the number declining this December was done by Roy along with a group of volunteers.

“This is the most crucial time for water birds. But their migration started at a slow pace. The migration trends are changing and the birds prefer shorter distances to longer ones as they are finding similar climatic conditions at shorter distances,” the environmentalist said.