In a couple of weeks from now, most of the wetlands in Gujarat will be almost devoid of migratory waterbirds that have been busy swimming, up-ending, diving, wading and plunging in our wetlands in search of food during the winter season. A bird watcher used to spending time at a wetland since last December will not be tempted to visit the wetland again until next November/December. This is because lakhs of migratory and resident-migratory ducks (for example, Northern Shoveler, Northern Pintail, Eurasian Wigeon, Eurasian Teal, Gadwall, Garganey, etc) and shorebirds (such as stints, sandpipers, plovers, etc.) may have already departed from our familiar wetlands in the state and many others will be vacating them soon to rush to their breeding quarters in Europe, Central Asia and North Asia. For around five months of winter, starting in November/December, our wetlands had been playing the role of 'guest-houses' or 'resorts' for these feathered and winged 'foreign tourists'. They not only provided 'living rooms' to these 'foreigners', but 'dining halls' too. In fact, the 'dining hall' function of wetlands has been of prime importance for these feathered foreigners. Each winter, these migratory waterbirds visiting our lakes, ponds, irrigation reservoirs, waterlogged areas and riversides, find themselves in great need of energy which can usually be derived from fats (and other lipids), carbohydrates, proteins and fibres, all which come from 'yummy' plant and animal food provided by the wetlands. Of course, these birds do not decide if a particular food item (plant/animal) is 'yummy' based on its taste. After all, birds are not blessed with taste buds. Rather, they decide on the 'yummy-ness' based on their physiological demands, which further create specific nutritional requirement (in terms of nutritional/energy value). Interestingly, birds' physiological demands depend on the phases of their life cycle, which includes migration, moulting, nesting, etc. In other words, nutrition requirements shaped by physiological demands (which are further influenced by various phases of the life-cycle) of a migratory waterbird species decide whether or not a particular food item is eatable. Migratory ducks or other kinds of wintering migratory wetland birds, which we see in wetlands such as Nal, Thol, Wadvana, Gosa Bara-Mokarsagar, Khijadiya, Narara, etc. need a great amount energy to deal with the rigour of migration that may include travelling to great distances, harshness or vagaries of weather, harshness of the landscape over which they need to fly, etc. A migratory waterbird, before leaving its stop-over (refuelling) wetland site during the course of its journey, or one that wants to indulge in return migration, feed on items that help accumulate fat (and other lipids) and also provide carbohydrates. Of course, they also get proteins, but their major interest lies in fats and carbohydrates from the migration view-point. Fats function as a source of energy much required for flying thousands of kilometres. Fats and other lipids, unlike proteins, can be accumulated rapidly when food is favourably available and they can also be used rapidly when conditions to access new food resources are harsh. Some of the fat provisioning treats for waterbirds include plants such as paddy, millet, barnyard grass, switchgrass, sedges (nutlets), pondweed, buckwheat, etc and tiny animals such as crustaceans (gammarus, cladocera and anostraca), dipteran larvae (chironomid larvae), molluscs (pond snails), etc. A majority of these fatty treats are available from natural or man-made wetlands. Waterbirds derive carbohydrates mainly from seeds, agricultural grains (available in the fields surrounding wetlands), and tubers of wetland plants and to a certain extent, from invertebrates and leafy submerged vegetation. So, next winter, when you see a waterbird greedily foraging in a wetland, have some compassion for it. It might not be a glutton but simply trying to get some much-needed nutrition! The author is the founding editor of e-Periodical Jalaplavit, senior scientist and Ph.D scholar from West Virginia University, ketantatu1@gmail.com

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