North American birds are getting smaller

Since 1978, North American birds have become smaller, with scientists examining over 70,000 dead birds from 52 species that crashed into Chicago skyscrapers. A study in Ecology Letters found a 2.4% reduction in leg bone length and a 1.3% increase in wing length in 49 species. These changes may be a response to climate change, as birds evolve to have wider wingspans for migration. Animals tend to be smaller in warmer regions to carry less heat and larger in colder areas to conserve warmth.

What was the primary focus of the study conducted on North American birds?

• The impact of skyscrapers on bird migration patterns

• The change in size of birds over several decades

• The diet of birds in urban environments

• The nesting habits of birds in Chicago

Which journal published the study on bird morphology changes?

• Nature

• Science

• The Journal of Ornithology

• Ecology Letters

What percentage increase was observed in the average wing length of birds?

• 0.5%

• 2.4%

• 1.3%

• 3.1%

Why might birds have evolved to have wider wingspans according to the study?

• To enhance their ability to escape predators

• To improve their hunting skills

• To compensate for smaller body sizes and aid in migration

• To better navigate urban environments

How do animals in warmer regions typically differ in size compared to those in colder regions?

• They have longer lifespans

• They are smaller to carry less heat

• They are larger to conserve warmth

• They have thicker fur