Behavior and Basics of a Purple Martin's Life
Section 1: Food and Diet - What do they eat?
Purple martins are insectivores who hunt their prey by hawking, a strategy used to catch insects during flight. Hence they mostly eat flying insects such as moths, butterflies, horse flies, etc., and their diet will change with the time of the year or the weather conditions on a given day. For example, they will feed low over the ground where insects are most likely to congregate on cloudy days. Whereas they can also be seen flying at altitudes as high as 300m to hunt on warmer days/nights (H.W.W, 2015). Such an example would be the high-catching noctuid moths who migrate in warm updrafts of wind during the nights in summer/fall. Also, a study in 2015 showed that fire ants may consist of a significant part of their diets. Hence they are well known for controlling populations of certain destructive insects. (Jackson, 2015)
Section 2: Breeding - Where and Whene Does it Take Place?
In a two bird relationship, right before the breeding season from late April to early May, males are in charge of establishing a territory consisting of many nesting sites (H.W.W,2015). These nests are either made in cavities of trees or artificial structures such as purple martin houses (made by humans). Cavity nests found in nature are usually made of three levels, each one with a distinct role:
Bottom floor: Usually made of twigs, mud, small pebbles, the bottom floor acts as a foundation for the structure.
Middle floor: Sometimes used to store extra food, the second floor is mainly grass and smaller twigs.
Top floor: The third floor is usually where the eggs are kept in a pile of leaves, and it is made of even lighter/smaller twigs and some leaves.
Purple martins are mostly known to raise only a single brood where the average clutch size is around four to six eggs. Females can only lay one egg a day, and the incubation of the eggs begins when the penultimate (second to last) egg has been laid. The process of incubating an egg usually takes around 16 days with the periodic help of the male. With that said, the hatching occurs over approximately 3 days; the fledgling (development of wings and feathers ready to fly) of the newborn chicks takes between 26 and 32 days. Once the chicks are ready to fly, they will receive support from their parents for another month before getting let go into the wild all by themselves. (H.W.W, 2015).
An example of an artificial purple martin house in Ottawa
Section 3: Distribution of Habitat - Where do Purple Martins like to Live?
Purple martins breeding habitats are primarily in open areas across the southeast region of North America. They prefer to live closer to humans since we make life a lot easier for them. This behaviour has made them a lot less independent, which has proven itself to not be helpful for them when humans aren’t around. However, not all subspecies are entirely dependent on us humans to stay alive. In fact, the Western purple martin subspecies are known to reside in natural cavities such as old woodpecker holes or saguaro cacti (Turner, 1989) and feed on slightly different insects. Since these two subspecies aren’t nesting in the same areas, this makes their distribution very patchy.
Section 4: Migration - Migration Process of the Purple Martins
When winter arrives in Brazil and parts of Peru, purple martins migrate to North America in a staggered fashion to breed during the spring. Earlier arrivals around January will be in more southern areas such as Florida or Texas. In contrast, later appearances in the southern regions of Canada start in April and come as late as May.(Eugene, 1990)
The arrival to breeding grounds can also be related to the age of the bird where:
Older Birds: Tend to arrive a month before the flock since they know from experience that arriving earlier will increase their chances of getting a better nesting site.
Male Birds: Tend to arrive before the females since it is their job to secure a breeding site for their family.
Younger Birds: Tend to arrive two months after their parents since they are a lot slower. Adults don't wait for the younger birds since they would not risk sacrificing a breeding ground for their future generations.
Purple martins also like to travel in huge flocks, known as roosts (Cornell Lab, 2021). These roosts tend to form around the start of July and end around the beginning of September. Most of the congregation areas are held in remote locations. They are all a group of a few thousand birds getting ready for the long journey south for the North American Winter. It is also important to note that the roosts are not specific to purple martins, but they may include any other species in the family of Swallows.
The Swallows tend to group up later at night and are often undetected. Only when the number of birds is very high can they be detected on the weather radar as a cloud that has appeared out of nowhere. The roosts primarily serve these birds as safety from predators and warmth from each others' bodies. (Fisher, 2017)