Green Imperial Pigeons - An unfamliar Diet - Eating Moringa Leaves
Apr 24 2016
Bsc, PDIP -GIS
One morning while I was doing some birding around our field house at Wasgamuwa, a couple of Green Imperial Pigeons on a Moringa tree (Moringa oleifera) caught my eyes. I observed them closely using my binocular and noticed that they were eating fresh leaflets of Moringa. Green Pigeons(Teron spp) and Imperial Pigeons (Ducula spp,) feed almost entirely on fleshy fruits. Although I knew some species of columbidae forage on buds and leaves as a supplementary diet, this was the first time I observed Green Imperial Pigeons eating leaves. I took some photographs of them before they left the tree for my records.
This initial observation led me to observe them for a while in Wasgamuwa to learn more about their feeding habits. After following them for a while, I did not find them eating any other leaves from any of their fruit-eating trees except eating Moringa leaves as the popular morning diet of theirs.
Usually early morning they fly onto Moringa trees, often in couples and sometimes in small groups comprising 5-6 birds. They perch on high branches on arrival and walk on branches to find young leaves. According to my observations they prefer young leaflets of the compound leaves. I have never observed them eating old (yellow coloured) leaflets. They use their beak to pluck the leaflets from the compound leaf and rotate their heads in great flexibility to reach the leaves. Sometimes they are acrobatic, like parakeets, holding on firmly to branches by their feet to reach young leaves.
In general, leaves are low in energy and nutrients and leaves are full of cellulose which takes a long time to break down. As a result of this leaf eating birds (folivores) have longer and heavier digestive tracks. In turn these leaf eating birds have become bulky. Birds need high energy and light body weight for flight. Hence, amongst birds, leaf eating is the least popular feeding habit. Of all bird species folivores comprise only around 3% and of which only a few are obligate leaf eaters.
The Hoatzin, is the only obligate leaf eating flying bird, with major adaptation to process it’s leafy diets. Like in some mammals, the expanded foregut of Hoatzin allows microbial fermentation of its leafy diet. By adapting for the leafy diet Hoatzin has lost its flying capacity greatly compared to other birds.
Frugivores like Pigeions, generally have either a small gizzard and a large liver or a short intestine, as an adaptation for improved digestive efficiency. Therefore they are not morphologically adaptive to eating leaves.
"Why do these frugivores pigeons eat leaves, specially Moringa leaves?", I kept on wondering.
Moringa leaves are used in poultry industry as a supplementary diet. The main reason for that is, they are rich in protein and also it contains vitamins (A,B and C) minerals and oxycarotenoids .It has also been proven that providing Moringa leaves to chickens, boosts egg production. Pet owners feed "Canarios", Parkeets and Finches with Moringa leaves and Moringa leaf powder. The moringa leaf powder is sold commercially as a all-natural nutritional supplement.
Apart from Green Imperial Pigeons, I have observed Rose-ringed Parakeets eating Moringa leaves few times, but they are not regular visitors to Moringa trees like Green Imperial Pigeons.
Even though I am not exactly sure why Green Imperial Pigeons eat Moringa leaves, I guess they turn to alternative food sources where they can get much required amino acids (proteins), vitamins and minerals since most of the fruits that they eat are generally low in proteins and low in other nutrients and Moringa leaves are rich in those nutrients.
To end this note, can I make a request from all of, - if anyone of you have observed other pigeons or other birds eating leaves can you kindly share your observations and also to record and share your future observations.
Aukland University of Technology