Birds in the Southwest are Molting Earlier

A Shift in Feather Replacement Schedules

Birds in the southwestern United States are altering their molting schedules, a critical part of their annual cycle. Researchers have identified significant changes, particularly in the fall molting season.

Key Findings from the Study

• Data Source: Bird banding data collected over 13 years in southeastern Utah.
• Focus Areas:
• Spring and fall molting seasons.
• Differences between males, females, and young birds.
• Results:
• Spring molting times remained relatively stable.
• Fall molting is starting earlier, indicating birds are replacing feathers sooner than before.

Climate's Role in Molting Changes

Several climatic factors influence these shifts:

• El Niño
• Temperature

• Rainfall

• Warmer temperatures can delay fall molting.
• Increased rainfall can prompt earlier molting.

Long-Term Trends

• This is the first study to examine long-term molting trends in North American birds.
• Over the past decade, birds in the western U.S. have been molting about one day earlier each year in the fall.