1.   These birds generally overwinter in tropical regions.

2.   As a result, biologists say, in many tropical regions it is easier to cut a forest than to study it.

3.   Biologists say that in many tropical regions it is easier to cut a forest than to study it.

4.   A hurricane is an area of low air pressure that forms over oceans in tropical regions in either the North Atlantic Ocean or eastern North Pacific Ocean.

5.   Dengue fever is a viral infection transmitted by the aedes aegypti mosquito and is most often found in tropical regions of the world.

6.   El Nino occurs when trade winds slow in tropical regions of the Pacific Ocean, warming water temperatures off the coast of Peru and affecting weather around the world.

7.   El Nino, which occurs every few years, is characterized by slowing trade winds and warming water temperatures in tropical regions of the Pacific Ocean.

8.   El Nino occurs in tropical regions of the Pacific Ocean when trade winds slow, allowing surface temperatures in the Western Hemisphere to heat up.

9.   El Nino, a weather pattern that occurs every few years, is characterized by slowing trade winds and warming water temperatures in tropical regions of the Pacific Ocean.

10.   El Nino occurs when trade winds slow in tropical regions of the Pacific Ocean, warming ocean temperatures off the coast of Peru and affecting weather around the world.