The diversity indices of the birds of the Tilyar lake, Rohtak were measured from July,2017-April,2019. Birds were observed by point count method and data collection was done fortnightly. A total of 3061 birds belonging to 75 species were recorded. A stable population trend was exhibited by n=26 (34.67%) birds species while n=13 (17.38%) birds species showed unknown population trend. Out of total 75 species 46 (61.33%) were common and only 7 (9.33%) were rare species. The Indian Cormorant (Phalacrocorax fuscicollis) was the most abundant species whereas the Comb Duck (Sarkidiornis melanotos) and the Eurasian Thick Knee (Burhinus oedicnemus) were least abundant species in the Tilyar lake. The species richness as calculated by Menhinick's Index and by Margalef's index were 1.33 and 9.18 respectively. The evenness of lake's community was 0.88 with a species richness of 75. The Shannon-Wiener index and Simpson's Index (1-D) were 3.79 and 0.95 respectively. These biodiversity indices showed both species richness and abundance of bird species in the Tilyar lake, suggesting implementation of appropriate protective measures for the conservation of its avian fauna.