Managing Purple Martin Colonies

Helping the birds that eat so many bugs

Written by Andi Pupke, Chesapeake Wildlife Heritage’s Education and Outreach Director

As spring arrived on the Eastern Shore of Maryland, the Purple Martin’s first tranquil call commanded our attention. We shared a sense of relief that winter was past and excitement that summer was on its way. The older male scouts reassured us that our old friends would once again return.

But the Martin’s call was also a reminder: 1) that houses needed to be cleaned and put up, 2) that Purple Martins rely on us for nesting cavities, and 3) that we must be active in caring for our Martin colonies.

Chesapeake Wildlife Heritage (CWH) has installed Purple Martin houses for more than three decades. During this time, we have had many moments of great success and a few tragedies. Through it all, our commitment to Purple Martins has remained strong.

CWH Education and Outreach Director Andi Pupke monitors a Purple Martin house on Kent Island.

Since 1998, CWH has restored more than 1,500 acres of wetlands, planted more than 850 acres of woodlands and planted upwards of 6,000 acres of native grasslands. CWH also helps private landowners manage habitat on their property and conducts research to benefit the Bay and its wildlife.

Nesting structures can be a valuable component of this work, and CWH’s Nesting Structure Program has provided them for a wide diversity of wildlife. The most popular structures are for Wood Ducks, Osprey, Bluebirds and, of course, Purple Martins. One thing we have learned is that nesting structures, including Purple Martin houses, need to be managed carefully.

Over the past 30 years of installing Martin houses, CWH has installed a wide variety of structures in various locations. We now favor one house design with a double compartment for each Martin pair that protects them from severe weather. All CWH-installed Martin houses are raised and lowered with a pulley system for easy monitoring, and each pulley system includes a predator guard that stops most snakes from making their way up the pole to the chicks.

When we learned that some Purple Martin landlords were having trouble with invasive House Sparrows, we researched better ways to install and maintain the Martin houses. This resulted in installing most Martin houses on docks over water and incorporating crescent-shaped starling-resistant entrances. House Sparrows do not like being over the water, but this does not hinder the Martins from using the nesting structure.

Once we had a good handle on managing the House Sparrow problems, we had to deal with owl attacks on the Martin colonies. Adding owl guards to all of the houses has proven effective at keeping the Martins safe from late-night owl attacks.

Predator attacks are not the only dangers to Purple Martins—the weather plays a huge role in the welfare of their population. Not only do Martins face treacherous weather throughout their long migrations in spring and fall, they can also experience bad weather once they reach their destination. Cold, wet springs can cause the demise of Martins who have depleted their body fat stores while traveling great distances to reach their breeding grounds. Martins feed on flying insects, so if it is too cold or wet for insects to fly, the birds have nothing to eat. The staff at CWH has spent many wet hours flinging crickets and mealworms into the air near a Martin colony trying to feed them. We have also cooked scrambled eggs and placed them on raised feeders for the Martins.

Purple Martins enjoy a dragonfly lunch.

On June 29, 2012, the area experienced a fierce derecho; a widespread straight-line wind storm that can cause hurricane-force winds, heavy rains and thunderstorms. We lost some chicks from a few of the Martin houses during this storm, but one site was in the direct line of the storm. The entire pulley system blew down, killing all 56 of the chicks and most likely some of the adults. We feared that a colony would not return the next season. It was a devastating loss, but happily, the Martins returned in the spring of 2013 to a reinforced nesting system. That colony has been thriving every year since the storm.

CWH also tries to be aware of insecticide use in the area before placing a Martin system. This hazard cannot always be controlled or known, as neighboring properties can be using insecticides that could harm the Martin colony we are trying to protect. Please be aware of insecticides being used on your and adjacent properties.

Many of our Martin landlords wanted their houses to be monitored throughout the nesting season but could not do the monitoring themselves. CWH responded by offering to conduct weekly monitoring as a management service and received a very positive response from the landlords. We began monitoring Martin houses for a few landlords in 2010, and the demand for this service has steadily grown. The CWH staff conducts weekly nest checks to maintain the health of the colonies, makes repairs to the houses, changes nesting material when needed and collects nesting data. At the end of the nesting season, we take down the Martin houses, clean them and store them for the winter. CWH sends each Martin landlord a summary of all data collected throughout the nesting season, including the number of chicks fledged, any predator issues and any repairs needed.

During the 2018 nesting season, CWH monitored 26 houses on 11 different properties that fledged 474 chicks. We will add at least four more houses and one new property to the monitoring list for the 2019 season. CWH is a member of the Purple Martin Conservation Association and use many of their educational materials.

CWH takes an active role in managing our Purple Martin nesting colonies. We help our fellow Purple Martin lovers attract and keep colonies, too. This work is helpful for Purple Martins and extremely enjoyable for the person who gets to spend so much time in the company of the Martins.

Martin Conservation Measures

According to the Wildlife Society Bulletin (WSB), the Purple Martin is experiencing a long-term decline. There is worry that their numbers will continue to diminish if humans don’t continue to provide housing for them.

A study published in the WSB found that Martins have very high nest survival in artificial housing, which makes Martin houses extremely important in conserving these birds. Texas Tech Assistant Professor Blake Grisham, an author of the study, noted that Martins have depended on mobile housing since European settlement – from gourds placed by Native Americans to modern houses such as those used by CWH. He also noted that Martin conservation measures are typically undertaken by older people and that younger generations must do their part to curtail the population decline.

To learn more about installing Martin houses on your property, call CWH at 410-822-5100.

Purple Martin eggs are pure white.
Three-day-old Purple Martin chicks are defenseless.
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