No melting glaciers, but climate change is at the door

If persistent, unpredictable rain patterns — such as the one witnessed in Chennai this year — can interfere with the breeding time-table of resident birds to the point of sending their populations crashing

A common sandpiper on the wall around the Perumbakkam wetland. Photo: Prince Frederick 

Discussing the presence of climate change is fraught with the same risk as walking on eggs. Challenging weather patterns built into natural processes may sometimes get tacked on to the climate crisis. More often though, climate change would be present incognito, particularly where it cannot manifest itself dramatically. There may be no rapidly melting glaciers in Chennai, but there are other straws in the wind betraying global warming — notably the erratic weather patterns witnessed in recent times, particularly rainfall-related. The quick succession with which weather systems occurred in November in Chennai could just be the elephant in the room — one we are trying to make sense of, unfortunately with the perspective of those blind men. While forcing birds into adaptations, climate change may be flying alongside unnoticed for want of an attention-grabbing garb. There are avian studies from the west suggesting that some bird species are developing longer wing spans but shrinking in their overall size — in response to a rise in temperature and also the necessity of having to fly further for food. In our parts, there may be a paucity of studies about such avian phenomena, but the impact of erratic weather on birds cannot be denied. Here, V Santharam, ornithologist and director, Institute of Bird Studies & Natural History, Rishi Valley, fields questions from The Hindu Downtown on the subject.

Q: How deeply can erratic weather patterns impact resident bird populations? In Chennai, the breeding season of many significant bird species — including the spot-billed pelicans, the glossy and black-headed ibises — happen around the north-east monsoon and what do these patterns mean for them?

Santharam: There can be failure in nesting. It is not easy for the birds to change the breeding season overnight, because they depend on factors like light for the hormones to get activated. They might breed but by then, the insects might have finished their cycle and they might not get enough food for the young ones. Most of the insectivorous and also frugivorous birds time their breeding season in such a way that it coincides with the fruiting or the season

Unpredictability is the operative word

• Unpredictability is the operative word, says K A Subramanian, Officer-in-Charge, Zoological Survey of India, Southern Regional Centre, while describing the key manifestations of climate change.
• He explains: “What climate change brings with it is unpredictaility. It is not about more rains or less rains — the predictaility of the system becomes elusive. That makes it difficult for the birds, particularly when it come to timing their breeding. Because, availability of food cannot be predicted. There are organisims that can manage this unpredctability, and they will thrive. We however need long-term data to nail the connection. It is difficult to connect the dots at this point.”

when the insects are found in abundance. If they miss that window — when caterpillars are emerging — they may not have sufficient food to feed the young ones. Due to the differences in climactic conditions, there may be a lack of synchronicity — the insects might have finished their cycle early and the fruits might have come up early, and the birds could still be lagging behind. When they have young ones, they may not be able to feed them. Instead of fledging six or seven or even eight young ones, they may fledge only one or two. It may mean that the population is going to crash. They may lay fewer eggs; or may not go for a second brood — some species do that. Reduced clutch size in response to climactic changes may however be more noticeable in temperate than in tropical regions — because birds species from temperate regions have a bigger clutch size compared to those in tropical regions.

Q: Have you seen anything like that happening in our parts — in terms of reduced clutch size?

Santharam: It may not be apparent in tropical regions — because we have stable climactic conditions. Of course, we are experiencing unseasonal rains, but in terms of temperature and food availability, there may not be much of an impact as of now. I am not sure our universities are thinking about studying these problems. Studies about rainfall patterns have been done but these have not been correlated with bird populations.

Q: There have been studies showing that birds are shrinking in size but their wing spans are growing longer. Has it been noticed in any of the birds in our parts?

Santharam: I do not think we have done much work in this area. When trapped at bird stations, birds would have been measured and the data would be present, but I wonder if any analysis has been done. They are mostly doing measurements for migrants— which already have fairly long wings for them to take long migratory journeys. It would be interesting to find out if birds that normally do not migrate, are now slowly developing more pointed wings that could be useful in long-distance migration. Birds with rounded wings cannot fly much. Only when they have narrow, elongated and pointed wings are they able to fly long distances. This adaptation could be in response to global warming with resultant changes that impact food availability.

This is likely to happen to birds that are in extreme climatic conditions — those species that are in the northern hemisphere where winters can be harsh. It pertains mostly to birds found in the Arctic and sub-Arctic regions. Probably, species that do altitudinal migration can also be studied — there has been one research article that has suggested changes in their wing patterns.