Demand-Resource Mismatch Explains Body Shrinkage in a Migratory Shorebird.

Area of Science:

• Ecology
• Climate Change Biology
• Evolutionary Biology

Background:

• Observed declines in animal body sizes prompt debate on links to climate change and Bergmann's rule.
• Direct temperature effects are unlikely drivers; food constraints during development are a potential cause.
• Migratory shorebirds, like the red knot (Calidris canutus canutus), exhibit body size changes.

Purpose of the Study:

• Investigate if red knot body size decrease is linked to developmental plasticity during chick growth.
• Examine the role of food availability and timing mismatches on breeding grounds in the High Arctic.

Main Methods:

• Combined datasets on body size, food availability, and diet from 2003-2021.
• Utilized stable-isotope ratios in feathers to infer chick diet composition.
• Analyzed breeding timing, snowmelt dates, and resource availability on Arctic breeding grounds.

Main Results:

• Crane fly (Tipulidae) contribution to chick diet declined significantly.
• Earlier snowmelt advanced crane fly emergence, but red knot breeding timing did not adjust.
• This created a resource-demand mismatch, resulting in slower chick growth and smaller final body sizes.

Conclusions:

• Increasing resource-demand mismatches, linked to climate warming, drive body shrinkage via developmental plasticity.
• This causal chain offers a potential explanation for widespread body size reductions in animal populations.
• Highlights the impact of climate change on trophic interactions and wildlife physiology.