Take the Local Wings and Learn to Fight… Climate Change
Reported by Isabella Lo
The 2nd longest cold weather warning in history, which lasted for 263.25 hours, was issued by the Hong Kong Observatory (HKO) in late January. For 9 consecutive days, the temperature had dropped below 10 degree Celsius.
The drastic drop of temperature is not the only sign of global climate change. The rate in average temperature rise and the frequency of extreme weather (i.e. torrential rain and cold surge) have been increasing over the past few decades.
Although the impact of climate change on Hong Kong citizens is not yet significant, it has in fact been affecting local ecology, more specifically, the birds.
“Bird watching was easier during the sudden cold spell,” said by Henry Lee Wing-him, a 20-year-old bird watcher, who noticed that birds can be more easily spotted during the coldness last month.
“On unusual cold days, the birds seemed to be less alert to humans. Some shy species even fed in exposed places where we seldom saw them appear on normal days,” said the bird watcher with 3 years of experience.
“The coldness brought birds from higher altitude to lowland in search of warmer habitat and food,” the amateur bird watcher explained, “this might be positive for us – birdwatchers, but not for the birds because they might become prone to predation by feral cats and dogs.”
The impact of extreme weather on birds is not limited on the species’ behaviour, but also on their physiology. Dr. Sung Yik-hei, a Hong Kong Baptist University lecturer and ecologist, believes the cold currents may significantly affect birds’ body conditions.
“Firstly, they consume more energy for maintaining body temperature, and less are remained for foraging.” Added by Dr. Sung, the possible decline in insects’ population under the coldness may also reduce food for birds.
In the long run, continuous and extreme cold weather may affect the birds’ survival rate.
“They may migrate less efficiently, or molt slower due to the less energy they have. These factors may eventually delay their migration timing,” said the ecology expert.
Unstable weather may trigger a series of consequences when birds’ migration or breeding timings are altered.
“When the birds return to their breeding ground after the winter, they may have insufficient mating time, or may delay laying eggs. They may also find insufficient food and this further affect their pullus’ growth,” Dr. Sung explained.
In Hong Kong, birds are more abundant in winter. Situated between the northern and southeastern parts of Asia, the city offers a stopover site for migratory birds on the East Asian-Australasian Flyway.
Mr. Kwok Chi-tai, a frequent bird watcher for more than 30 years, said he is worried about the possible decline of birds due to the warming climate.
“In the past, we could find Eurasian scops owl every two to three visits, now we cannot see one after 30 visits. Their departure time shifted in Northern China and Siberia, and less of them are coming every year”, said the 49-year-old man who watches bird every day in rural areas.
According to the Agriculture, Fisheries and Conservation Department, among about 500 bird species recorded in the territory, only 90 are resident birds that live and breed in Hong Kong in their entire lives, while the rest are migratory birds which travel to the city from northern breeding grounds during winter.
Dr. Pang Chun-chiu, a senior research specialist of Hong Kong Bird Watching Society said the migrants, composing the majority of local bird species, maybe more susceptible to warming climate or extreme weather than resident birds.
“Migrant birds experience less fluctuating temperature because they fly across countries to seek an optimal ground during winter,” said the bird specialist.
Apart from migrants, smaller birds may also be prone to extreme coldness, said Dr. Sung, “from the biological perspective, birds of smaller size may lose heat more readily.”
According to the sparrow survey conducted by Hong Kong Bird Watching Society, about 320,000 Eurasian tree sparrows reside in the city, spreading across all the territory’s 18 districts. Other commonly seen urban birds include Oriental Magpie Robin, Eurasian Magpie and Red-whiskered Bulbul, are all comparatively small in size.
Although there is currently no research data showing body condition, size or abundance of birds in the territory has changed under the warming climate, Dr. Pang said that a decline in wintering bird species in the territory is expected in the future.
Data from the Hong Kong Bird Watching Society shows that the number of Eurasian coots had rapidly declined from 3197 in 1991 to 48 in 2013. Meanwhile, zero Dalmatian pelican was recorded in the city during 2010-2012 after its population gradually reduced from 24 in 1997.
“Their original breeding ground, such as Northern China and Russia, may become warm enough for them to pass the winter now. Therefore, they no longer need to travel far to find wintering place,” he said.
Several researches from western countries showed that climate change can directly alter their abundance, distribution, behaviour, and even genetic composition of birds. It can also affect their migration or breeding timings through changes in temperature, rainfall and precipitation.
In 2017, nine out of 48 North American migratory songbirds species were unable to reach their northern breeding grounds due to delayed plant growth under temperature rise over 12 years, according to a Scientific Reports research.
Another study by the University of Edinburgh in 2016 also found out that birds are reaching summer breeding grounds on average about one day earlier per degree of increase in global temperature.
As the climate change intensifies at an accelerating pace, the above phenomena could also be found in Hong Kong which in turn reduce birds’ number and survivorship in the city.
While both Dr. Sung and Dr. Pang confessed that there is little we can do to directly overturn climate change, both scholars suggested protection and conservation of habitats are crucial to ensure the supply of nesting places and food resources for birds.
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