As summer draws to an end, Purple Martins are preparing to start a long migration ahead.
Capable of travelling thousands of miles, these are resilient little birds.
This article explores the migration patterns of Purple Martins, the importance of particular roosting sites and how you can help them.
Read on to discover more about the migration patterns of Purple Martins.
What Are Purple Martins?
No, not little purple aliens on Mars – an honest mistake from any dyslexic birder like myself.
Instead, Purple Martins are a type of passerine songbird native to North and South America.
While females are white, grey and brown, adult males have dark blue-purple plumage with an iridescent sheen.
They are related to swallows and both groups belong to the family Hirundinidae.
They are aerial hunters, swooping up insects on the wing.
For me, martins and swallows are as synonymous with summer as an ice cream on the beach is.
However, it’s not their beautiful plumage or summer sightings that makes the Purple Martin so special.
Perhaps the most remarkable characteristic of this bird is its long-distance migration patterns.
Where Do Purple Martins Migrate To?
Purple Martins are long-distant migrants.
In the summer months, Purple Martins breed in the temperate regions of North America.
They are most populous in the eastern USA, in states such as Texas, Florida, Pennsylvania, Alabama and Louisiana.
They can also be found, although in much smaller populations, in western United States in mountainous regions of New Mexico, Arizona, western Colorado, and Utah.
As winter approaches, they migrate south towards the Amazon Basin in South America.
Non-breeding populations of Purple Martins can be found in Brazil, Bolivia and Peru, with the majority of birds spending the non-breeding season in Brazil.
After spending a few months in South America, they begin the journey back to North America.
A single Purple Martin can travel thousands of miles in one season – upwards of 10,000 miles.
The Significance Of Purple Martins In Brazil
In Brazil’s Rio Negro, a small island, known locally as Ilha do Comaru, can be found.
At just 12 acres, the island isn’t large.
However, between the months of February and April, the island plays host to approximately 250,000 Purple Martins – making Brazil’s Ilha do Comaru one of their largest known roosts.
But size alone isn’t everything.
What makes this particular roost in Brazil so special is the pivotal role it may play in the long-distance migration of these birds.
Scientists hypothesize that Comaru could be the staging ground – a place where migrant birds stop to rest, drink, and eat – for many of the 9.3 million Purple Martins that funnel from South to North America.
Why Do Purple Martins Migrate?
Purple Martins, along with many other long-distance migrants, migrate to pursue warmer climates.
While their summer breeding grounds offer a surplus of food for fledglings, winter conditions are harsh.
If they do not leave, freezing temperatures or high-intensity storms will most likely kill juveniles, and adult Purple Martins alike.
In regions with stable climates, food can typically be found-year round.
However, where there is food, so too are there predators.
So, to maximize food intake while decreasing predation risk, migration seems to be a sensible option.
Where do Purple Martins Roost?
Purple Martins begin arriving in North America in early spring. However, older adults may arrive as early as late-winter.
Nest building, courtship, copulation and egg laying follows.
Adult Purple Martins start laying eggs in late April or May, while subadults – younger adults that have fledged the previous year – may begin nesting later in the summer, typically in June or July.
After hatching, fledging occurs. During this time, both parents will continue feeding the young for up to two weeks.
Finally, the new juvenile Purple Martins, together with adults and subadults, begin congregating at roost sites.
Often, roosts are chosen on their proximity to water; as this provides ample opportunities for drinking, bathing, and foraging on abundant insects
More and more flocks of martins gather at these roosts to spend the night.
After roughly 4 weeks, groups of Purple Martins begin leaving roosts to start their migration back to South America.
In Brazil, many of this species roost in urban and suburban areas. Roosts can be found in small parks or human-made structures such as bridges and pipes.
North America’s Largest Purple Martin Roost
The largest known Purple Martin roost in North America can be found on Bomb Island.
Located on Lake Murray in South Carolina, Bomb Island is just 12-acres of land.
Despite its size, Bomb Island is the roosting site for hundreds of thousands of martins every summer.
Some estimates suggest as many as one million Purple Martins roost here!
The best time to see these birds on Bomb Island is from late June through early August, with the highest number of birds appearing from mid-to-late July. The birds are most active during the early morning or evening.
The size of the roost can be so large, it is often picked up on weather radars.
How You Can Help
Besides a few scattered populations, most Purple Martins in North America need hollow structures to nest.
Historically, natural cavities, such as tree holes, offered perfect nesting conditions.
However, with an exploding human population, deforestation soared and nesting trees were lost.
At the same time, competition with introduced species – such as the aggressive European starling – also lead to population decreases.
As a result, Purple Martins have become near 100% reliant on human intervention. Which seems almost ironic.
Are we humans completely responsible for this change in nesting behavior? Or did these birds make an informed choice to switch to human-made structures? Honestly, I’m not sure.
What I do know is that for a Purple Martin to successfully nest in North America, especially in the East, they will most likely need a human-made structure.
The most common structures are “condomoniums” – a specific birdhouse designed to house multiple bird families in separate compartments. This is vital, as the roosts of these species are highly social.
However, bird houses aren’t the only solution.
An easy, and often much cheaper, option is to hang hollowed-out gourds – a tradition dating back to Native American tribes.
Final Thoughts
Purple Martins are the largest member of the swallow family in North America.
They breed in North America and migrate to South America for the winter. A round-trip migration for these birds may be as long as 10,000 miles.
The majority of Purple Martins go to Brazil during winter, with many stopping off at the small Brazilian island of Ilha do Comaru.
In North America, they roost in large colonies – the biggest containing up to an estimated one million birds.
This swallow species is reliant on human-made structures to nest. You can help by erecting specific bird houses or simple, hollowed-out gourds.
