At Famed Walden Pond, Spring Is Coming Earlier Than In Thoreau’s Day

 By Richard B. Primack

 

“I would rather save one of these hawks than have a hundred hens and chickens. It is worth more to see them soar.” -- Henry David Thoreau in his Journal.

 

The detailed record of bird sightings and phenological observations around Concord, Massachusetts—from Thoreau’s notes 170 years ago to today’s studies by local bird enthusiasts and our research group—provides a key to studying how climate change is affecting bird migration.

 

Figure 1.  Yellow warbler collecting a caterpillar. Sam Zhang/Macaulay Library

The most important finding yielded thus far is that birds are not arriving earlier now than they did in the past. It appears that birds are not nearly as responsive to a warming climate as are trees, wildflowers, and insects. This could potentially lead to a phenological mismatch, and negatively impact the populations of migratory birds that miss the first early pulse of insect emergence. 

 

Figure 2.  Plants are showing a strong pattern of earlier leafing out and flowering in the spring. The response of birds is not as strong or consistent. 

This work is presented in the Spring 2023 issue of Living Bird (April 5, 2023): LINK