Purple Martins: What A Trip!

Most people involved in Eastern Bluebird conservation house and help other native cavity nesters throughout the years. I view the Eastern Bluebird as an “entry bird” for those of us involved in the rather addictive bird conservation culture. My good friend, Darlene Sillick, has branched out to work with raptors at our local rehabilitation center. Dick Tuttle provides nest sites for American Kestrels, Prothonotary Warblers and Ospreys.

Madame WingNut has spread her wings to manage a number of Purple Martin colonies in central and northern Ohio. I have a passion for Purple Martins. In 2013, I provided weekly monitoring of 154 Purple Martin nest compartments at 5 different sites, fledging 439 Purple Martins. Here are Madame WingNut’s tips for attracting and managing Purple Martins:

Attraction

Habitat

The most important consideration in attracting Purple Martins is habitat. They require a relatively open area, preferably adjacent to a pond or lake. Purple Martins are aerial insectivores. Their diet is comprised solely of flying insects which they catch in flight. Consider all the mouths they will have to feed when rearing their young. Open habitat is needed for good insect hunting. Areas near water produce a lot of flying insects. There should be no trees taller than their housing for at least 40 feet.

Social Attraction

A few years back, I had the privilege of working the Ohio Bluebird Society booth at the Ohio State Fair with Michael Worley. Many of you remember Michael. He was a renowned Bluebirder, winning the OBS Blue Feather Award in 2007. This man knew his birds. He told me he had finally attracted Purple Martins after 30 years of trying. He had successfully employed the social attraction techniques of playing recorded dawn song and setting out Purple Martin decoys on the housing.

I was surprised as I had never used these techniques, but had no problem attracting them in areas with proper habitat. I theorize that I may have unwittingly employed another form of social attraction. Four of the sites that I monitor are located within Tree Swallow colonies. Tree Swallow colonies are established by installing boxes 25 yards apart in a grid formation or around the perimeter of a pond. I believe that the activity of their smaller swallow cousins has helped attract Purple Martins to these areas. Both species are aerial insectivores, but the Tree Swallow hunts smaller insects closer to the ground whereas the Purple Martin gleans larger ones in the higher realms.

Equipment

Housing

1. Design – Housing or gourds should be white. Providing a larger floor area of 7″ X 12″ is preferred for standard metal house compartments. Although I have Purple Martins using both metal houses and gourds, plastic Troyer gourds are my personal preference. The newer vertical gourd has a tunnel entrance that provides additional protection from avian predators. I place soft white pine needles in all compartments at the beginning of nesting season.
2. Inbox trapping – I am proactive when it comes to native cavity nest compartments, only installing boxes or gourds that have inbox traps available and at the ready. Non-native House Sparrows cannot be allowed to nest in a Purple Martin colony.
3. Starling Resistant Entry Holes – Non-native European Starlings can readily enter housing with standard round 2 1/8″ diameter holes. You can spend a lot of time using inbox traps to capture them or you can exclude them with Conley II entrances. I much prefer the latter. Purple Martins readily take to these entrances. The biology of their shorter legs and streamlined body allows them to enter while the European Starlings cannot (fun to watch them try though).

Pole and Mount

1. 

   Height – Housing should be raised 10 to 20 feet from the ground.

2. Vegetation – Keep bushes and vines away from housing to discourage climbing predators.
3. Baffle – The most common reason Purple Martins abandon colonies is depredation by predators. A climbing raccoon or snake will devastate a colony in no time and these predators can easily climb any wooden or metal pole. A good predator baffle is a must.
4. Pole design – Poles with a 2″ or 3″ square cross section are much preferred. Round cross section poles can cause parents to become disoriented if housing is not raised to proper compass point. If their compartment was originally facing west and housing is raised so it faces north, they may become confused as to whose young are which. You will not have this problem with a square pole.
5. Winch or pulley system – Colonies should be monitored every 5 to 7 days. This can only be accomplished with a good winch or pulley system. The cheaper telescoping poles are simply awful. I don’t know why they even sell these things.

Management

1. Timing – Housing should not be opened up until the first Purple Martins return. In Ohio, as a general rule, Purple Martins arrive the first week in April. This serves to reduce competition by other cavity nesting birds.
2. Competition by Native Cavity Nesters – In Ohio, Eastern Bluebirds and Tree Swallows establish nest sites before Purple Martins return. Keeping in mind the territory requirements of these birds, placing a nestbox or two within 15 feet of the Martin housing works well. Eastern Bluebirds and Tree Swallows start nesting in these boxes and then work to chase away any others of their species that show interest in the Martin housing when it is opened up. If native birds do show interest in Martin compartments, block these for a time and drive them to appropriate housing you have set out for them.
   Regarding Tree Swallow colonies, another theory of mine is that the intraspecies competition between Tree Swallows helps diminish the interspecies competition between Tree Swallows and Purple Martins. When you set out multiple nest boxes for Tree Swallows, they seem much more concerned with defending their box (and their mate) from other Tree Swallows than attempting to investigate the Martin housing.
3. Competition by Non-native Cavity Nesters – Starling resistant entry holes and inbox traps work well to eliminate competition. Repeated bait traps for House Sparrows can also be effective if needed.
4. Monitoring – Monitor compartments every 5 to 7 days. Keep good data and careful track of the age of the oldest young in the colony. Pre-fledging is a concern if housing is lowered after young are 22 days old. Purple Martins generally fledge after 28 days.
5. Nest Changes – Parasite loads are heavy in Purple Martin nests. I generally perform one nest change when young are 7 to 22 days old.
6. Supplemental Feeding – Setting out egg shells or mealworms is often done. I have not tried this, but training birds to come to a platform feeder sounds intriguing. People use slingshots or sturdy plastic spoons to flip mealworms or crickets to the birds, and then graduate to platform feeders. It is a bit like teaching an Eastern Bluebird to use a mealworm feeder, but with a different twist, or flip…
7. Clean Out – Unlike Eastern Bluebirds, Purple Martin fledglings will return to their housing to roost for a week or two. I leave housing raised and old nests in housing until Labor Day, waiting for migration. Housing should be closed up or stored for the winter.

September rolls around every year. I miss the friendly chortle and plaintive dawn song that regaled me for the past five months. The Purple Martins have left once again, migrating to their wintering grounds in South America. I just googled the air distance from my most northern colony in Put-in-Bay, Ohio to Brazil. That is 4339.76 miles folks! What a trip!

“Madame WingNut” is the pen name of a long-time Columbus Audubon member and volunteer.