Effects of Migration Distance on Shifting Migratory and Breeding Phenology in Waders

Area of Science:

• Ecology
• Evolutionary Biology
• Ornithology

Background:

• Phenological shifts are common in migratory birds, with short-distance migrants often advancing breeding timing.
• Long-distance migrants may face constraints in advancing breeding due to later arrival.
• Quantifying phenological trends across species with varying migration distances under similar conditions is rare.

Purpose of the Study:

• To investigate phenological trends in arrival and laying dates of migratory waders in Iceland.
• To compare the phenological flexibility of short-distance versus long-distance migrants.
• To understand how migration distance influences breeding timing adjustments in response to environmental change.

Main Methods:

• Monitoring arrival and laying dates for nine wader species in lowland Iceland from 2007 to 2022.
• Categorizing species based on migration distance (wintering grounds proximity).
• Analyzing trends in arrival and laying dates over the 15-year study period.

Main Results:

• Waders wintering closer to Iceland arrived approximately 6 weeks earlier than those wintering further away.
• Laying dates differed by only 1-2 weeks between short- and long-distance migrants.
• Short-distance migrants advanced laying dates with minimal change in arrival, while long-distance migrants advanced both arrival and laying dates.
• A longer interval between arrival and laying in short-distance migrants facilitates earlier nesting in warmer springs.

Conclusions:

• Short-distance migrants exhibit greater flexibility in advancing breeding phenology, potentially by utilizing warmer springs more effectively.
• Divergent population trajectories may arise from differential breeding phenology adjustments in response to climate change.
• Further research on nesting success is needed to understand the costs associated with longer migration distances and later arrival.