Heralding the arrival of spring-summer season, the swallows distinguished from the martins and other smaller birdlife by their characteristic deeply forked tail appear in the city around the months of March-April when they almost immediately set to nesting.
"This is the third year in continuation that the swallows have raised a family in the ceiling of our shop," says 58-year-old C L Kandoi, who owns a shop on MG Marg here.
In 2009 the shop had four chicks, in 2010 there were another four and this year the shop ceiling is home to the nest of a swallow couple and five recently born chicks wait with their beaks open for their parents to fly in food.
"We have been living here in Sikkim for the past 130 years and our family has been running this shop for the past 50-60 years. Earlier swallows used to come and make their nests here frequently.
"After some time they suddenly stopped and now again over the last 5-6 years they have begun returning and nesting and in the last three years they have been hatching their eggs right here," he says.
He points out that it usually takes the eggs about 15 days to hatch, about another 15 for the chicks to learn how to fly and after a few days of practice, they take off.
Slicing through the air in graceful swoops and darts, snapping up unsuspecting midges and flies along the way, spiritedly pursuing aerial game only they'd know the rules of or simply perched meditatively on wires and edges of rooftops, this twittering avian life was once a familiar sight along the capital's MG Marg stretch.
While the swallows can still be sighted, their presence has dwindled among the bazaar residents. While earlier, they could be seen adding to the exuberance and bustle of the town in the thousands, over the past few seasons even a 100-200 count was hard to come by.
Gregarious by nature, the swallows are known to keep close to human habituations and civilizations and their local name ''gaonthali'' connotes this fact roughly translating as belonging to the vicinity of a village or ''gaon''.
This is most clearly manifested in their choice of location for the nest, which, over time, has travelled from overhanging cliff faces and caves to manmade structures like barns, bridges and dwellings which offer easy accessibility and are yet sheltered from weather and predators.
Also, their insect-feeding habits make them more tolerable to man, insectivores being beneficial to famers especially.
The mating season is usually from May to June-July during which they lay eggs at least twice and fly back to warmer climes towards the end of August