There had been an "amazing rise in small finches", Mr Bashford told Today.
BBC: NEWS | UK | Fewer birds spotted in UK gardens
2.
The survey had been "extremely well supported... even in the most built-up areas where you might not expect people to watch birds, " Mr Bashford added.
BBC: NEWS | UK | Fewer birds spotted in UK gardens
3.
Co-ordinator Richard Bashford told BBC Radio 4's Today programme "a lack of food for the chicks" was causing the fall in the number of house sparrow sightings.
BBC: NEWS | UK | Fewer birds spotted in UK gardens