A changing world is taking a big toll on tiny birds

A tiny, dull-coloured, restless-looking leaf warbler flies from a garden in Europe to a forest patch in the Indian Himalayas, carrying hidden stories of environmental change and evolution.

“I love this genus,” says Tushar Parab, a PhD scholar at the Wildlife Institute of India.

His recent research explores what drives the distribution of Phylloscopus or leaf warblers – a widespread group of around 80 species – across Eurasia. The study highlights how natural and human-driven forces, from snow cover and elevation to soil moisture and urban lighting, influence where these birds are found. The findings could support conservation planning by understanding their habitat choices and limits to resist environmental change.

These tiny birds weigh just six to 10 grams, roughly the weight of a five-rupee coin. Yet, their role in ecosystems is outsized. “They need about 2,000 arthropods a day, but many birds starve in the winter,” says Trevor Price, an evolutionary biologist at the University of Chicago who has studied warblers in India for over five decades.

Found across Europe, Africa, and Asia, these “old world” leaf warblers seasonally migrate between temperate Eurasian breeding grounds and warmer wintering areas in South and Southeast Asia. The greenish warbler, for instance, breeds across Eurasia and when it’s winter there, spends its time almost entirely...

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