The birds spend their winters in Central America and can be found in a variety of habitats, from central Costa Rica to the deserts of southeastern Sonora, in western Mexico. In the spring, they prepare to migrate thousands of miles to the conifer forests of the Mountain West, flying through grasslands, deserts, and occasionally, suburban yards. As global climate change causes spring to start earlier, birds such as western tanagers are arriving at their destination after what’s known as “green-up