The birds have been seen circling above the lake, perching in old trees and diving into the water to hunt for fish, drawing attention from residents and tourists.
Many visitors stopped to photograph the scene, viewing the return of wild birds as a positive sign for the lake’s ecological environment.
Wildlife experts said birds from the heron family can adapt well to urban areas if there is sufficient food, large trees for nesting and limited disturbance from noise.
The appearance of large numbers of waterbirds around Hoan Kiem Lake suggests the area continues to maintain suitable ecological conditions, they added.
Experts also noted that the seasonal transition period is when many bird species move in search of feeding or breeding grounds. Some flocks may only stop temporarily, while others could remain longer if conditions are favourable.
