The Painted Stork Mycteria leucocephala is a prominent species of Indian heronries and wetlands. Given that this stork is listed as Near Threatened (BirdLife International 2001), it is worrying that its nesting ecology, especially the factors affecting nesting success, is poorly understood. While a relationship between rainfall and nesting intensity has long been known (e.g. Ali and Ripley 1987), this has not been investigated in detail. Previous observations have also indicated that many more individuals are present at colonies at the beginning of the breeding season than actually breed (Ali and Vijayan 1983), but this phenomenon has not been investigated further. To address these issues, we studied reproductive output, causes of nest failure, the number of adults in nesting colonies, and factors associated with yearly variation in nesting densities of the Painted Stork at Sultanpur National Park (henceforth Sultanpur), in Haryana, India. STUDY SITE Sultanpur (28°28′N 76°53′E, c.25 km south-east of Delhi) is located in a predominantly agricultural landscape, crisscrossed by irrigation canals (Fig. 1). The national park covers an area of 13,727 ha (Islam and Rahmani 2004) and includes as its core c.143 ha of low-lying marshes, which were notified as a bird sanctuary by the Haryana state government in 1971 (Kalpavriksh 1994). The dominant terrestrial vegetation in this area consists of trees of Prosopis juliflora, Acacia nilotica, Tamarindus indica and Azadirachta indica, and grasses such as Vetiveria zizanioides and Erianthus ravennae. Plants recorded in the marshy areas of the park include submerged vegetation such as Vallisneria natans and Ceratophyllum demersum, emergents such as Typha angustata, Saccharum munja and Cyperus rotundus, and surface vegetation such as Nymphaea stellata, N. nouchali and Ipomoea reptans (Kalpavriksh 1994). As a part of its management policy, the park authorities embarked upon a tree plantation programme during the 1980s. Several mounds were created in the lake and Acacia nilotica trees planted on them. There are now about 50 islands, including one large island (c.100×40 m) in the centre of the marsh (Fig. 1). Painted Storks nest on this island and on some smaller islands with canopy diameter <10 m, together with Indian Cormorant Phalacrocorax fuscicollis, Cattle Egret Bubulcus ibis, Black-crowned Night Heron Nycticorax nycticorax, Black-headed Ibis Threskiornis melanocephalus and Asian Openbill Anastomus oscitans (Urfi et al. 2005a). METHODS We visited Sultanpur once each in October and November 2002, and on an average of once per fortnight from August 2003 to December 2005. Painted Storks visit Sultanpur to breed between August and January and are typically absent in other months. We recorded the arrival date of Painted Storks each year by consulting park staff. Roost counts were made between 17h00 and 19h00, using binoculars (7×50) and a telescope (15×). A sample of nests (Table 1) was monitored on a regular basis during 2004–2005 from an elevated spot, approximately 50 m from the south-eastern edge of the heronry (Fig. 1). The nests were located on subsequent occasions by Nesting ecology of the Painted Stork Mycteria leucocephala at Sultanpur National Park, Haryana, India ABDUL JAMIL URFI, THANGARASU MEGANATHAN and ABDUL KALAM Figure 1. Map of Sultanpur National Park Haryana, India. Detailed observations of the main heronry (black oblong) were made from a point due south (marked ‘x’). The solid single line indicates the park boundary, the double line indicates paths, the dotted line denotes the edge of the marsh, and small circles represent islands. The top left inset shows the location of Sultanpur in relation to Delhi and the Najafgadh drain. The smaller inset (right) shows the location of Delhi within India. 150 SHORT NOTES Forktail 23 (2007)