Black-headed Grosbeak (IMAGE) University of California - Davis Caption The black-headed grosbeak commonly summers in the Central Valley. A UC Davis study found bird diversity in the area was actually higher in the winter than in summer, highlighting the importance of protecting habitat for birds year-round. Credit Andrew Engilis/UC Davis Usage Restrictions Provide credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.