Global communities, particularly biodiversity conservationists, are observing World Migratory Bird Day today with the theme “Protect insects, protect birds”.
In February this year, the Convention on the Conservation of Migratory Species of Wild Animals (CMS) - a UN biodiversity treaty, brought out a landmark report which was an alarm bell as well.
The report pointed out a sharp decline of 40% in the migration of birds.
Climate change, deforestation, hunting and poaching were identified as some of the major reasons behind this.
For Bangladesh, the report seemed a warning as the country, for long, has been a host country for migratory birds.
Birds available in Bangladesh are categorised as resident and non-resident, with migratory avians mostly classified as non-residents.
The country boasts around 712 species of birds. Of them, 320 species are migratory. Some migrate to this land in the winter while some others stay year-round.
Bangladesh's strategic position in the Ganges-Brahmaputra-Meghna (GBM) basin, coupled with its tropical climate, renders it a crucial site for migratory guests, specifically waterbirds and shorebirds.
These birds adhere to specific routes, known as Flyways, between their breeding and wintering grounds for rest and replenishment.
Bangladesh lies within two major bird migratory flyways: the East-Asian Australasian Flyway and the Central Asian Flyway.
A study published last year revealed that Tanguar Haor - one of Bangladesh’s main wetlands for hosting migratory birds, is slowly losing some of the waterbirds.
Numerous news reports support the claim that hunting and poaching are among the common threats to migratory birds in Bangladesh.
However, the rampant use of insecticides, resulting in food scarcity of the avian species, should now be recognised as another major threat to the migratory birds.
Professor Md Anwarul Islam, a faculty at Dhaka University’s zoology department, and also chief executive at WildTeam Bangladesh, deemed the thoughtless application of toxic insecticides and pesticides for balancing the food chain of birds.
Birds feed on different types of food. Depending on their food habits, the birds are classified as frugivorous, folivorus, harbivorous, nectarivorus and insectivrous.
Whatever their food habit is, every bird depends on insects - at least for feeding their nestlings because insects are the best source of protein.
Invertebrates like flies, bees, snails, moths, or anthorpods like spiders, centipedes, millipedes and crabs are among the favourite food for birds.
A study published in the journal Science in 2020 states insects are in steep decline worldwide – 0.92% per year which translates to an average loss of 8.81% per decade.
Sajeda Begum, a professor of zoology at Jahangirnagar University, said, "Among the major reasons for the insect decline are the excessive use of insecticides, pesticides, and toxic fertilisers in agricultural fields."
As a technical reviewer, she contributed to the creation of the IUCN Red List of Birds in Bangladesh.
She highlighted that birds' reproductive cycles and chicks' health may suffer from toxicity after consuming surviving insects exposed to insecticides.
Many migratory birds fly from the North Pole, Siberia, Europe, parts of Asia, and the surrounding Himalayan areas.
Despite not using Bangladesh as their breeding ground, the abundance or scarcity of insects still matters to them.
"Migratory birds consume insects as protein, storing energy to prepare for reproduction upon their return to their original habitats." Another threat arises as many migratory birds, primarily aquatic species, shelter in wetlands and forage along shorelines, relying heavily on aquatic insects,” Professor Sajeda said.
"Toxic pollution in water bodies destroys aquatic insect populations, ultimately impacting migratory birds. We are aware that toxic elements from agricultural fields and industrial zones ultimately find their way into wetlands,” she added.
A study rightly revealed a lack of proper knowledge among pesticide users has resulted in widespread and excessive pesticide application.
17% of the respondents, who were mostly farmers, believed pesticides killed beneficial insects and animals, while 6% believed pesticide use was decreasing the number of migratory birds, the study stated.
United Nations’ Food and Agriculture Organisation (FAO) said that unregulated use of insecticides and pesticides can harm beneficial insects while polluting water sources, and contaminating soil, risking biodiversity and ecosystem health.
The positive news is that FAO, in March this year, officially handed over its recommendations on the pesticide rules to the Department of Agricultural Extension.
One can hope that the authorities concerned will strictly implement the recommendations for the sake of public health, conservation of the environment and protection of biodiversity.
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