BOSTON (AP) — Bird watchers in Massachusetts are beginning the annual Christmas Bird Count to collect data used by conservation biologists to study the long-term health and status of bird populations.

This is the 115th year the bird count has been conducted. It will continue through Jan. 5.

Each count takes place in an established 15-mile wide diameter circle. There are 34 geographic count circles where bird surveys are done in Massachusetts.

When combined with other surveys, the Christmas Bird Count provides a picture of how bird populations have changed over the past 115 years.

Each count circle is coordinated by a count compiler who works with teams of volunteer birders to ensure that beginning birders are grouped with more experienced birdwatchers.