Falcons consist of many species such as the Peregrine Falcon, the Gyrfalcon, and the Apalomo Falcon. Although this is not an exhaustive list, these are the most popular falcons.  The name Peregrine Falcon means Falcon Wanderer. It is also known as the Duck Hawk. They have been recorded going 242 mph while stooping (hunting dive). Technically, this is the fastest creature on the planet. 
The name Gyrfalcon comes from the French word gerfaucon. Back in medieval Latin it was written as gyrofalco, and this is how we started using it for the scientific name. The name means vulture. It is the largest of all falcons. It is somewhat like the Common Buzzard.
The name of the Aplomado Falcon comes from an unusual Spanish word for "lead-colored". This Falcon is considered to be the medium sized falcon of the Americas. 
The Peregrine Falcon is about the size of a large crow. Peregrines are about the weight of a crow as well. They have a wingspan of 40 inches, and are known to grow to 15 inches long. Adult Peregrine Falcons have white faces with a dark black stripe on each cheek. Peregrines also have dark blueish grayish wings, and their backs are barred with black pale undersides. The female is bigger than the male and more dominant as well. With that, they also have dark black eyes without the white or color parts that humans have.
The Gyrfalcon is the largest among all the falcons. Its size is 60cm (about 24 inches), and its wingspan is 130cm (about 52 inches). The Gyrfalcon looks like a larger form of the Peregrine, but broader winged and longer tailed. The female is bigger than the male just like the Peregrine. This falcon flies at horizontal level instead of flying high and swooping down to catch its prey. The Gyrfalcons prey are mammals like Ptarmigans and Lemmings. 
The Aplomado Falcon is about the size of a small Peregrine, but at half the weight of it. They are very slender, long tailed, and long winged. The adults have dark blueish grey upper parts which goes well into the head. The upper breast is white, and on the lower breast there are black patches. Below these are the belly and thighs which are a cinnamon color. Its diet includes small invertebrates, insects, and lots of smaller birds. 
For Peregrines their eggs take about 33 days to hatch. The number of eggs that are produced are usually three to four. Both parents look after them and take care of them. Also, both the parents incubate the eggs. In the first six days the babies gain twice their own body weight, so the parents are consistently finding food for them. By the time they are three weeks old, they gain ten times their beginning body weight. After they are hatched the eyas (young falcons who have not left the nest) have a white down fur. They keep this for about four to six weeks. At this time they grow their feathers and start to learn how to fly. To get the young to leave the nest, the parents will bait them out with food. Then, by the end of the summer the falcons leave the nest and fly away to start a new area of their own. While they are still babies in the nest (about three weeks old), scientists will take blood samples, strap metal bands to their feet, and record their sex. These are all used to help the Peregrine to regain their species number. 
The falcons are an endangered species due to the pesticide DDT which people used in the 1960's and up to 1972. Scientists only found out in the 60's about this, so the pesticide probably was used long before that. When used, DDT would affect the falcons by thinning the egg's shell. After this would happen, when the falcons would go to incubate the eggs, the shell would break from the force. DDT was outlawed in 1972, not only in the United States, but it was outlawed worldwide. DDT did not only affect the falcons, but almost any fish and meat eating bird in the world. After DDT was outlawed, scientists started an Eastern Peregrine Recovery Plan in the United States. They started doing things such as checking for the chemical by taking blood samples, putting on tracking bands on the legs, and recording the sex of each falcon. 
Falcons very rarely make their own nest; they usually make them in another bird's emptied nest. Other times they will lay their eggs in cliff walls or outlets. The Peregrine Falcons used to live from west to east all over North America. Now they are slowly starting to reproduce all over North America again. The Gyr Falcons live in Arctic coasts and islands of North America, Asia and Europe. The Aplomado Falcons live in slightly warmer climates. They range from northern Mexico and Trinidad to Texas, and a little more locally to southern South America. These are the areas they used to live in, and are know starting to reproduce in these areas.
- Bird of Prey By Wikipedia
- Falcon By Wikipeida
- Peregrine Falcon Facts By The Division of Wildlife's Peregrine Falcon Management Program
- Aplpmado Falcon By Wikipedia
- Gyr Falcon By Wikipedia
- Peregrine Falcon By Wikipedia