Something subtle has been happening in the skies above North America for decades. The V-formations of geese, the first flutter of warblers through the backyard, the return of the robin to the front ...

As the weather gets chillier, birds are migrating, many crossing New Hampshire on their path to warmer climates. Hundreds of thousands of birds — warblers, tanagers, sandpipers, sparrows, hawks, even ...

Bird species are shifting to higher elevations over time, likely in response to climate change. The red line represents the mean elevation of birds, which has moved uphill after 20 years. Many bird ...