Tree Species used for nesting

Introduction Mangroves 
A variety of plants are seen putting up luxuriant growth in this inter tidal habitat. These species are endemic to the area and are called mangroves. Some species occurring outside  the inter tidal environment are called associates of mangroves. As many as 62 species of mangrove & its associates are found in Bhitarkanika Sanctuary. The mangrove are specialized plants which can tolerate inundation and salinity. Their adaptation to salinity condition is by preventing high concentration of salt, entering roots and secreting salts from their leaves. Mangrove seeds germinate on the trees, before they are disseminated. They grow a spear like hypocotyle, which when dislodged, gets embedded into mud and develop anchoring roots. Many mangroves have stilt root, which are aerial and acts as anchoring structure to withstand wave action.

Some mangroves have inverted wedge like projections on the ground from the underground root system, called pneumatophores. The plants breathe in oxygen through the pores of pneumatophores during prolonged time of submergence of the root system.

The mangrove is highly fragile eco-system as the essential factors for the maintenance of the system are fresh water influx from adjoining land and tidal inflow from the sea. Changing the regime of either factors, whether in quality or quantity is likely to affect a corresponding change in the mangrove system. In Bhitarkanika the water salinity exhibit a gradual change from near fresh water to very saline condition, thus the vegetation has evolved and adopted to withstand wide salinity gradients. Some plants have specialized to thrive in narrow limits of both low and high salinities. It is therefore likely that plant diversity would be fabulous here. Spatial diversity is seen to be of high order. However, evenness component appear to be low based on cursory observations. High diversity of plant communities is reflected in high diversity of animal life, noticeable so at least in avifauna.

Detritus is the principal energy source in the mangrove eco-system. This is the degraded product of mangrove litter, broken down by host of bacteria, fungi and protozoa to tiny protein-rich organic matter, which is then absorbed in clay particles. The Detritus feeders e.g. shrimps, prawns, nematodes and forage fish like grey mullets, mud skippers, through several cycles of ingestion, exhaust the nutrient laden detritus. Many fishes and crabs feed either directly on detritus or on detritus feeders. Large game fish (Bhekti for example) feed in detritus feeding fish. The off shore waters having a mangrove coast line also benefit through the out dwelling of nutrient laden detritus. Mangroves, therefore have a great ecological and economic value through its contribution to the detritus food chain, supporting rich estuarine and adjacent marine fisheries.

Sheltered water of mangrove provide nursery grounds for commercially harvested prawns and shrimps, which breed only in the sea. Several fish come to the estuary to breed viz; Bhekta and Hilsa. Prosperous fisheries on a sustainable basis is important to the economy of the people living around mangroves. About one lakh people depend directly and indirectly on fishing in undivided Cuttack and Balasore districts. Mangroves play a pivotal role in alleviating the economic condition of local Fishermen community.

Mangroves have been called as "Land Builders". The roots of mangrove secret an acid, which modifies the coarse particles into finer ones and help in soil formation. The tangles of stilt root also help in sedimentation of particulate matter. Networks of mangrove roots provide firm anchorage to the coast line and also river bank & effectively arrests river bank and coastal erosion and helps control flood damage. It exercises a moderating influence in the cyclonic wind. Severe periodic cyclones contribute to the shrinkage of mangrove vegetation.