Saunders's Tern (Sternula saundersi)

Rare breeding resident of coastal waters, estuaries, lagoons, and other wetlands in the dry zone coastal areas. It breeds from May to June in small colonies, with dispersed nests in shallow scrape above tide line on mud or sandbars and in sand-dunes, along the north-western coastline.

Chinese Pond-Heron (Ardeola bacchus)

Very rare vagrant bird with few sight records in Sri Lanka. It breeds in Assam and Burma to Eastern China and Manchuria and in the Andaman islands. Non-breeding and immature Chinese Pond-Herons are indistinguishable from the common resident Indian Pond-Herons. However, during the breeding season, the Chinese Pond-Heron's distinctive maroon-chestnut head and neck make identification easier. As a result, all recorded sightings of this species in Sri Lanka have occurred at the end of the migratory season. 

Chinese Pond Heron was first time recorded in Sri Lanka by Dieter Zingel (Germany) on 30^th April 1995 at Deberawewa (Hoffmann, T. W., 1996). Later on sight record(s) available by Rex. I. de Silva from Negambo Lagoon (Kotagama S. & Ratnavira G. 2017: 258)

There is also a observation of two birds with photographic evidences on 16th May 2020 by Thishan Jeevaka Perera at Halmillagolawa Wewa, Saliya Wewa, Puttalam, according to the Ceylon Bird Club notes (https://www.ceylonbirdclub.org/the_ceylon_bird_club_news.php)

Recent observations reported in the eBird with photographic evidences

1) A single bird with breeding plumage by Alexander Cherinko at Flooded Fields near Rekawa Beach, Tangalle, Hambantota on 25th April 2021
2) A single bird with breeding plumage by Edmundas Greimas Sigiriya Water Garden, Dambulla, Matale on 8th April 2024
3) A single bird with breeding plumage by Tharaka Dhananjaya, Ashan Tharaka Piyasinghe and Osanda Dissanayake at Anavilundawa Bird sanctuary on 4th April 2025.

References:

• Hoffmann, T. W., 1996. Ceylon Bird Club Notes 1995. Loris, 21(1), 16-18.
• Kotagama, S., Ratnavira, G. 2010. An illustrated Guide to the Birds of Sri Lanka. Field Ornithology Group of Sri Lanka, Colombo

Great Knot (Calidris tenuirostris)

 Rather rare winter migrant to tidal mud-flats, lagoons and salt-pans of dry zone coastal areas, mainly in the northern part of the country.  It lives as solitary birds or as small flocks and feeds by probing. Great Knot breeds in north-eastern Siberia. 

Red Knot (Calidris canutus)

Rare winter migrant to mud and sand flats as well as the borders of lagoons and estuaries of the dry zone coastal areas. Even though very gregarious birds, both in feeding and flight, in Sri Lanka it is most likely to be found as solitary individuals or as flocks of 2-3 birds. Red Knot breeds in  far northern lands. 

Terek Sandpiper (Xenus cinereus)

 Rather uncommon winter migrant to lagoons, estuaries, tidal creeks, saltpans and mudflats of lowland coastal areas, mainly in the dry zone. It lives as solitary birds or as few to several scattered birds, usually associating with other sandpipers and plovers. It feeds on various small shore-line animals and has a habit of  carrying them to the water edge and washing them before swallowing. It breeds in the high north of Europe and Asia.