Light pollution bird survey begins
8 January 2014 Last updated at 16:53 GMT
The British Trust for Ornithology (BTO) is asking the public to take part in a survey to assess the effect of light and heat pollution on garden birds.
The charity is asking people to get up before sunrise (about 08:00 GMT) on Thursday 9 January, to monitor their garden bird feeders.
Participants should record the times at which they see up to 10 different species arrive.
This project is a follow-up to the charity's 2004 Shortest Day Survey.
Clare Simm from the BTO explains why the team wants to focus on light pollution.
Video journalist: Victoria Gill