Why non-native species like the golden-backed weaver and monk parakeet need to be dealt with before they spread elsewhere.

Synopsis (headphones recommended): In our first audio trail of Singapore’s nature spaces, The Straits Times explores the ins and outs of creatures in these places with those who know them well.

Listen to birdsong at the Kranji Marshes with the president and vice-president of freshly hatched conservation group Bird Society of Singapore Keita Sin and Movin Nyanasengeran who take ST journalist Ang Qing around one of the largest freshwater marshes here.

During a two-hour walk, they experience a morning at the remote park, which is home to more than 170 birds in north-western Singapore.

They banter on all things bird-related, from ‘parrot politics’ to the mounting threat of invasive bird species to Singapore and South-east Asia.

This comes as the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services reported in September that more than 3,500 harmful invasive species have cost the global economy at least US$423 billion (S$576 billion) a year. And the annual expense has quadrupled every decade since the 1970s.