Smallest Bird sanctuary in Bihar in terms of geographical area is -

Concept

"Smallest in terms of geographical area" asks for the protected area with the least notified extent (in square kilometres / hectares), not the one with the fewest bird species or the lowest visitor count. To answer, compare the official notified areas of the candidate sanctuaries and pick the lowest figure.

Application

Comparing the notified areas of Bihar's small bird sanctuaries from official and standard references:

Nagi Dam, at roughly 1.92 sq km, has the least notified area and is the standard answer for the smallest bird sanctuary in Bihar.

Cross-check

• Nakti Dam (about 3.33 sq km) is the largest of the three, so it cannot be the smallest.

• Barela Jheel (about 1.96 sq km) is very close to Nagi Dam, but its notified extent is slightly higher, so Nagi Dam remains the smallest by area among the choices offered.