Storks that serve the environment
When one talks about scavenging birds, the first name that comes to mind is the vulture. All vultures, including the very unique-looking Bearded Vulture and the giant condors (New World vultures), have earned quite a repute for being effective at disposing off carcasses, and in doing so, they also provide valuable ecological services to the environment. A more enlightened soul would go on to include opportunistic urban dwellers, such as crows, ravens and even Black Kites, but chances of storks being featured in the list of scavenging birds are highly uncommon. Yet, a unique group of storks have made scavenging their way of life.
Storks belonging to genus Leptotilos are certainly not considered beautiful birds. Just like vultures, they have scarce feathers on their heads and necks, contributing to their ‘ugly’ looks. This adaptation helps the storks in scavenging, as feathers would collect blood and other debris when a bird sticks its head inside a corpse to feed. But despite being well-adapted for scavenging, these storks also readily hunt small animals, such as frogs, insects, birds, reptiles and rodents.
Three species of storks belonging to this genus are found in South and Southeast Asia as well as Sub-Saharan Africa. All three species bear a very similar look, having dark upperparts, white underparts, standing on tall legs and equipped with long and thick beaks. In flight, these storks prefer to hold their necks in a retracted fashion, much like egrets and herons, rather than outstretched like other storks, most likely to support their heavy bills.
The Greater Adjutant (L. dubius) and Lesser Adjutant (L. javanicus) are found on the Asian continent, with the former being more restricted in its range. Both the storks prefer to live around marshes and wetlands and are threatened by habitat loss. The Lesser Adjutant scavenges to a much lesser extent than the other two members of the genus. Generally solitary in nature, the Lesser Adjutant is quite shy. It is a widespread bird, found throughout Southeast Asia, from India to Java. The Greater Adjutant, on the other hand, is probably the rarest stork in the world, having just three known breeding populations (two in India and one in Cambodia). In Assam, where you find the largest of the three breeding colonies, the big stork has taken to scavenging from garbage dumping sites.
The Marabou Stork (or sometimes called just Marabou) (L. crumerifer) is probably the most specialist scavenger among the three. It is also less dependent on wetlands than its Asian cousins, readily living in arid conditions as well. The massive bird is often found scavenging alongside vultures in the African savanna but will prey on smaller birds and other animals when an opportunity presents itself.
What made the storks scavenge in the first place is a mystery. But since the time ancestor of these storks took up to scavenging, it has undergone an extraordinary process of selective evolution, being the storks we see today. In this process, the storks did gain some traits similar to the vultures (like bare heads and necks). This is called parallel evolution; where two organisms have developed similar physical or behavioural traits, but do not share a common ancestor.
The scavenging storks represent a unique lineage of storks, but if nothing is done to protect them, we may soon lose at least one species very soon.
Cover Pic: A close-up of a Greater Adjutant stork shows the colourful, but bare, head and neck.
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