At a distance they are difficult to differentiate from other pelicans in the region although it is smaller but at close range the spots on the upper mandible, the lack of bright colours and the greyer plumage are distinctive.

The spot-billed pelican was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae.

[2] Gmelin based his description on "Le pélican des Philippines" that had been described and illustrated in 1760 by the French zoologist Mathurin Jacques Brisson.

In flight they look not unlike the Dalmatian pelican but the tertials and inner secondaries are darker and a pale band runs along the greater coverts.

A few birds from India are known to winter in the Gangetic plains but reports of its presence in many other parts of the region such as the Maldives, Pakistan and Bangladesh has been questioned.

The spot-billed pelican is not migratory but are known to make local movements and are more widely distributed in the non-breeding season.

In June 1906, C E Rhenius visited a colony in Kundakulam in Tirunelveli district where the villages considered the birds semi-sacred.

[10] The Sittang River in Burma was said by E W Oates to have "millions" of pelicans in 1877 and in 1929 E C Stuart Baker reported that they were still nesting in thousands along with greater adjutant storks: The whole forest consisted of very large trees, but a portion, about one in twenty, was made up of wood-oil trees, gigantic fellows, 150 feet high and more, and with a smooth branchless trunk of 80 to 100 feet.

I was out that day till 3 p.m., continually moving, and must have walked at least twenty miles in various directions, but never from first to last was I out of sight of either a Pelican's or Adjutant's nest.

From what I saw, and from what the Burmans told me, I compute the breeding-place of these birds to extend over an area about twenty miles long and five broad.This colony was however reported by B E Smythies to have disappeared between the 1930s and the 1940s.

[12] Another colony was discovered in 1902 at a village called Buchupalle in the Cudappah district, where these pelicans nested along with painted storks during the month of March.

[15][16][17] Due to habitat loss and human disturbance, the spot-billed pelican's numbers have declined and many populations in Southeast Asia (including parts of China[18]) are now extinct.

[21] Estimates suggest that increased protection has since enabled a recovery in their numbers and the status of the species was changed from vulnerable to near threatened in the 2007 IUCN Red List.

[29] The trematode parasite Renicola pelecani was described from the kidneys of a specimen of a Sri Lankan spot-billed pelican that died at the London zoo.