Remember the pots we used to hang on the walls of our houses? The ones with a small hole in the middle. Sometimes we see a particular visitor calling it home with its small family. But soon enough, we may never see this visitor again. The visitor is none other than the House Sparrow/ගේ කුරුල්ලා (Passer domesticus) and its future doesn’t look promising.
It may sound strange. Some of us still may see the house sparrows around. Even the IUCN (International Union for Conservation of Nature) has listed the house sparrow as a Least Concern species. The house sparrow’s global population is secure, but in Sri Lanka, they are considered to be extinct in 18 districts. Not only in Sri Lanka but many other places in the world are experiencing a decline in this sparrow population.
What could be the cause of their decline? Researchers in Sri Lanka suspect that insect repellents are the main cause, especially the fumes from mosquito coils. Although this suspicion is still under research it is estimated that pyrethroid chemicals contained in these fumes can affect the calcium metabolism of these birds once they get inside the respiratory system. This leads to the weakening of the bones, muscles, and nerve functions. Even worse, this affects their reproductive health as well. For instance, degraded calcium metabolism means softening of eggshells and even a phenomenon called egg binding where the eggs get stuck inside the reproductive tract of the females.
The drop in Sri Lanka’s house sparrow population did not start recently. It has been happening since the 1970s when Malathion, another mosquito combatant, was sprayed around.
Living close to human residences, the house sparrows have a higher risk of being exposed to these changes compared to other birds. Needless to say, the use of pesticides in general is a main threat to house sparrows, just as for many other birds.
Just as for many other species, habitat loss is another main factor behind the house sparrow’s demise. The decline of vegetation affects the house sparrow as well. However, house sparrows also reside a lot in urban areas. The old buildings in Sri Lanka’s cities, which had many small openings provided ideal locations for these birds to nest, but now as these buildings get replaced by modern architecture the sparrows may lose the space they had.
Ironically, one country’s threatened species is another country’s invasive species. Although the house sparrows are facing a decline in their native range from Europe, and Northern Africa to Asia, here in New Zealand they are thriving. They were initially introduced here from Europe to control agricultural pests but ended up being considered pests themselves.
House sparrows are very adaptable and intelligent creatures. In New Zealand it is observed that these birds have the habit of stealing sugar packets from cafes, ripping them open, and eating the content, giving the definition of bird brain a whole new meaning.
If New Zealand has too many house sparrows and Sri Lanka has fewer of them, why can’t we ship them? The practical implications of catching these tiny birds aside, shipping of live animals poses a real threat. That is, there’s a possibility of shipping novel diseases and pathogens and exposing the native population to them.
What could be the worst thing that could happen if the house sparrows go extinct, other than listening to their cute chirping and watching their interesting behaviour? No matter how tiny and insignificant it may look, the house sparrow also plays an important role that benefits the ecosystem. They are seed dispersers and occasionally they grab an insect or a grub that affects humans negatively. It is also considered an Indicator Species, which means the presence or absence of these creatures can determine the health of the environment.
We should understand that even the smallest of creatures serve a purpose in this world. So, it is important to nurture them as well.
Photo Credit: Kathy Büscher & Luna Wang
By Thulitha Abayawardana – Auckland
