Spring migration is the movement of Purple Martins from their winter grounds in South America to their breeding grounds in North America and Canada. It is believed that there are three routes or flyways taken. One is the over land route that takes the martin over Central America and Mexico. A second is a route that crosses directly over the Gulf of Mexico. A third route includes the Caribbean Islands where it is believed that the martins fly from island to island until they reach Florida.
All three of these routes may be used, depending on what area of the United States or Canada the particular martin is headed for. Martins do not usually migrate in large flocks but usually fly in small groups or sometimes alone. Based on studies using geolocators by the PMCA, it was found that a female martin returned from the Amazon to Pennsylvania in just 13 days, flying at an average of about 358 miles per day!
The older martins, sometimes referred to as Scouts, will be the first martins to reach the United States. They are also referred to as ASY (after second year) adults. Scouts are martins that have nested the previous season(s) and are returning to their established nesting site. The martins that were born the previous year are called SY (second year) martins. They are also referred as subadults. The subadults complete their molt a few weeks later that the ASY martins and usually arrive about 4 weeks after. If you are starting a new colony, these are usually the birds you will be able to attract. This is why it is important to wait 4 weeks after the older birds have migrated through your area before opening your houses to decrease the establishment of invasive pest birds such as sparrows and/or starlings.