Zoologists have been studying hundreds of species of birds on a massive 40-year project and have discovered that over the past 4 decades the same species of birds have shown drastic changes in their habitats, migrating patterns as well as their mating patterns as well, but even more striking is that each species of bird has also shown to be gradually shirking in size as well.
But it's not just birds, there are many other species of animals that have shown similar size reductions over the same period of time and from all over the world.
These scientists in this field of zoology have come to the conclusion that the reduction in size is a direct result of the rapid increase in global temperatures as animals don't need to grow as large in order to keep their core temperatures warm, and smaller sizes help with cooling.
There is a grim future if this trend continues as smaller bodies produce less offspring which can have a significant impact on ecosystems and food chains in nature.
Take a look at the video below by the YouTube channel: Vox on Why Some Animals Are Shrinking...