IntroductionPeople have been enjoying the

company of the acrobatic purplemartin for centuries. Their melodi-ous chatter and aerial displays are acouple of the reasons why so manypeople seek the company of purplemartins. Today, over one millionpeople across North America providehousing for purple martins.Unfortunately, many of these would-be purple martin landlords, for avariety of reasons, are unsuccessfulin their attempts to attract breed-ing martins. This fact sheetwill provide guidelines and rec-ommendations to maximizethe chances of successfullyattracting purple martins andensuring their return year after year.

Brief History of the PurpleMartin in North America

Did you know that purple martins livingeast of the Rocky Mountains only live inhuman-supplied housing? These birds areno longer seeking out natural nest cavities;however, this was not always the case.Before humans settled in North America,purple martins used cavities excavated bywoodpeckers or natural cavities found indead trees or cliffs. It is thought that thearrival of humans led to the purple martinchanging its nesting habits.

Purple MartinsFact Sheet 792

One explanation is that Native AmericanIndians discovered, perhaps by accident, thatmartins could be lured close to their villagesby hanging up gourds with holes cut out oftheir sides. Since then, thousands of purplemartin generations have slowly abandonedtheir natural nesting behaviors and havesought out human-provided housing. Thisprocess of slowly changing their ancestral waysis referred to as a “behavioral tradition shift.”

Because the martins were nesting closer tohumans, they likely had fewer predators.

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Also, the larger than normal nesting cavitiesallowed the martins to raise larger numbers ofyoung. For these reasons, it would have beenadvantageous for the fledglings to seek outthis type of housing the following season,upon returning from their wintering grounds.This arrangement is thought to have beenbeneficial for the people as well. Historicalinformation from the 18th and 19th centuriessuggests that martins may have acted as scare-crows by chasing vultures away from dryinghides and meats and driving crows from cornfields. We see evidence of this relationshipstill occurring today.

The Purple Martin MythIn many places across North America pur-

ple martin housing of various designs can beseen erected near lakes, bays, and swamps.Most of these houses are provided for mar-tins with the thought that they will con-sume a large number of mosquitoes.Research suggests that purple martins eatvery few mosquitoes, if any. One reason isthat the martin is too large of a bird to wasteits energy on small mosquitoes. For all thosepeople who hoped martins would curb theirmosquito problem, they should actually beproviding habitat for bats because bats, notpurple martins, consume large numbers ofmosquitoes. For information regarding howto attract bats to your area, read Fact Sheet791, “Got Bugs? Get Bats!”

This is not to say all those purple martinhouses should be taken down. On the con-trary, purple martins provide people withviewing enjoyment and also eat many agricul-tural and garden insect pests. Many of theinsects purple martins eat are well known pestssuch as stinkbugs, wasps, leafhoppers, cicadas,grasshoppers, horseflies, moths, and flyingants. Most of these insects may pose a threatto crops or gardens and the others may proveto be a nuisance to backyard gatherings.

The Purple MartinLandscape

Purple martins are aerial insectivoreswhich means they eat insects while in flight.Obviously it is easier for a purple martin tocatch flying insects in an area that has few

trees versus a forested landscape. For thisreason, people who live in areas with largeopen flyways such as wide open lawns, fieldsor pastures, ponds or lakes, are much morelikely to attract martins.

People fail to attract martins for many rea-sons, but the main reason is that tall treesare too close to the martin housing or theyard is too enclosed. As shown in Figure 1,purple martins require a minimum of 40' ofclear space around the housing. This areashould be devoid of trees, and shrubs orvines should not be allowed to grow upunder the housing. Also, martins like toperch on wires, but wires should not beattached to the housing and housing shouldnot be placed too close to over head wires toprevent squirrels from easily gaining access.

Even though purple martins prefer to bein an open area, they do not like to be locat-ed too far from humans. As mentioned ear-lier, they associate people with relative pro-tection from predators. Many purple martinpredators such as raccoons, snakes, hawks,and owls are not normally found close tohuman housing. For these reasons, it is rec-ommended that martin housing be placedno farther than 120' away from humanhousing (Figure 1).

Martins that nest within this zone have agreater likelihood of successfully raisingyoung. Also, if the housing can easily beseen, the martin landlord is more likely towitness and repel predators.

As seen in Figure 1, an excellent place forpurple martin housing is on a dock or pier.The other requirements still hold true in thisinstance. Purple martin housing works bestwhen 10 to 20 feet in the air. Monitoringand maintenance are keys to successfullyattracting and keeping martins, so yourhousing should be easily reached by a ladderor lowered for periodic nest checks andcleaning (this will be discussed in moredepth in following sections).

Purple Martin HousingOptions

Cavity nesting birds in general will nestin a wide variety of houses if the hole andcompartment sizes are compatible withtheir needs. The purple martin is no excep-

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Figure 1. Ideal purple martin housing locations.

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tion to this fact. Martin housing comes in awide variety of shapes, sizes, materials, andcolors. Fortunately, the Purple MartinConservation Association has engaged inmany years of research that gives us clues asto which types of housing are the most pro-ductive for martins.

One of the most important requirementsof purple martin housing is the necessity ofraising and lowering the houses. If housingis simply erected and forgotten about, disas-ter will likely occur. Other species, especiallynon-native species, may take up residence inyour martin housing and may be very hardto manage. Housing placed on a retractableor telescoping pole is optimal for monitoringand maintenance of the housing. Regardlessof the pole design, easy access to your mar-tin housing is imperative.

James Hill, founder of the Purple MartinConservation Association, conducted a studyof 15 years of data collected on 2,729 activepurple martin nests. The data that were ana-lyzed looked at three different types of hous-ing including wooden houses, natural gourds,and aluminum houses. Gourds were clearlythe most productive in larger clutch size andnumber of fledglings. Second were woodenhouses and the least productive type of hous-ing was aluminum. Differences in productivi-ty of the different housing are probably bestexplained by the size of the individual com-partments in each type of housing.

When providing housing for purple mar-tins, we should not overlook the size of thehousing compartment. Martins will be moreproductive in larger housing compartments,regardless of the overall housing design. Inthe study mentioned above, the gourds hadthe largest amount of space and the alu-minum houses on average had the smallest

amount of space. Cavity nesting birds ingeneral prefer larger nest compartments oversmaller, when given the choice. Female cavi-ty nesting birds often adjust the size of theirclutch depending upon the size of their nestcavity. Often, the larger the nest cavity, thelarger the clutch of eggs. These findings alsohold true for purple martins.

Regardless of the housing design, the floordimensions for each compartment should bea minimum of 6"x6". Larger compartments(7"x12") are preferred by the martins andalso provide increased shelter and protectionfrom rain and predators. The height of thenesting compartment can be 6" to 7". Largecompartments are preferred not only bymartins but European starlings as well. Inorder to prevent starlings from nesting inmartin housing, different shaped entranceholes can be provided (Figure 2). Entranceholes should be placed 1" above the floor.The preferred entrance hole size is 21⁄8",although martins will accept holes from 17⁄8"to 21⁄4." When purchasing or constructingmartin housing, other amenities such as ven-tilation and drainage should be considered.Each compartment should have drain holesthat will also aid in ventilation.

If your martin house has not been success-ful, check the dimensions. If the dimensionsare not correct, try modifying it to properspecifications. One modification that can bemade is by removing compartment dividersto double the size of the compartments. Inaddition, porch dividers can be added to helpkeep males from claiming more than onecompartment and to prevent nestlings fromwandering to other compartments where theycan get lost and die or steal food fromyounger nestlings, causing them to starve.

What color should purple martin housingbe? White seems to be the best color for acouple of reasons. First, it is thought thatthe hole opening contrasts the best against awhite colored exterior. This contrast makesthe entrance holes easier to spot while mar-tins are flying by looking for potential nest-ing sites. Also, white houses do not get toohot in the middle of the summer, thus pre-venting nestlings from overheating.

The latest invention in purple martin hous-ing is the SuperGourd, a synthetic, extra-largegourd that has a nest inspection/clean-out

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Figure 2. Starling Resistant Entrance Hole

access port on the side. The SuperGourd’sone-piece body has no seams, so no rain willleak in, and six 1⁄4-inch drain holes provide arapid exit for any rain that blows in throughthe entrance hole. The SuperGourds can beeasily mounted on a variety of poles or can bepurchased with a telescoping pole and ready-made mounting arms.

When Should I Open MyHousing in the Spring?

The time to open your housing dependson whether or not you’ve had martins in thepast. The first martins arrive in Maryland inmid to late March. Landlords that have pre-viously had nesting martins can open theirhousing at this time. However, if you are anew landlord trying to attract martins forthe first time, this would be four to fiveweeks too early to open your housing!

The reason that previously successful land-lords can start when the birds arrive is thatthe birds are what we call “site-faithful.”Adult martins exhibit a behavior known assite fidelity, meaning once they have bredsuccessfully in a location they will return tobreed in that same place year after year aslong as the housing is available and properlymaintained. Site fidelity means that themartins will return to your housing everyyear and will actually wait around for you toopen it up. In fact, if you wish, you canleave the entrance holes on your houseclosed up until the martins return and landon the housing. This can help prevent nestsite competitors from becoming establishedand can save you a lot of work pulling outstarling and house sparrow nests. While thesite fidelity of adult martins is strong, theyprobably won’t wait more than two to threeweeks for their housing to be opened up, sobe sure to open the housing as soon as thebirds arrive and start landing.

Yearling martins, the ones that you canhope to attract as a new landlord, do notarrive until four to five weeks after the firstbirds are seen in your area. If you havenever attracted martins, do not open yourhousing until four to five weeks after thefirst martins arrive. If you have not hadbreeding martins in the past and you openyour housing too early, you invite instant

occupation by competing species. Thesespecies will prevent the housing from beingoccupied by martins and it will be very diffi-cult to eliminate them once they becomeestablished. In contrast to the informationabove for adult martins, new landlords hop-ing to attract martins to unoccupied housingshould never leave entrance holes pluggeduntil the martins arrive. Yearling martinslooking for new housing need to see openentrance holes in order to recognize a poten-tial breeding site. If other species are tryingto nest in the housing, a minimum of a fewcompartments should be left open on eachside of the house to attract the attention ofpassing martins.

How Do I Attract andKeep a Martin Colony?

The two keys to attracting and keeping asuccessful martin colony are monitoring andmaintenance. Martins are dependent onhuman-provided housing and they can begreatly aided by human management. Don’tbe afraid to engage in “hands-on” manage-ment of your martin colony. Data suggestthat active and involved owners can increasethe success of their colonies by almost twotimes and certainly reduce the risk of sud-denly losing an entire colony.

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Walk under your housing daily, payingcareful attention to items dropped on theground. These dropped items can provideclues to what is happening in your housingunits. Particularly look for signs of preda-tion such as dead nestlings, plucked feathers,wings, or owl feathers. Early detection of apredator problem can save you from losingan entire colony, if dealt with promptly. Ifyou find a live nestling that has fledged pre-maturely you can use the data from yourweekly nest checks (see below) to return thenestling to its proper compartment.

Far from causing martins to abandon anest-site, weekly nest checks can greatlyimprove the success of your martin colony.Ideally during the egg-laying stage you shouldcheck the nests every four to five days. Thisregular nest check will allow you to deter-mine the clutch-initiation date and thereforeexpected dates of hatching and fledging.After egg laying, check the nests every five toseven days unless your daily walk-undersindicate a reason to be concerned (see above).Number each of the compartments and keepcareful records of each daily walk-under andweekly nest check. Keeping careful recordsnot only allows you to understand thedynamics of your martin colony, but can alsohelp you detect predation problems, returnyoung to the proper nest, and determinewhether missing young have fledged or diedfor some reason. During nest checks youshould be on the look out for potential prob-lems and remove from the nests any non-native nest-site competitors such as starlingsor house sparrows.

Some CommonManagement Concerns

Below are some common management con-cerns that martin landlords must deal with.These recommendations apply not only forcurrent martin landlords, but prospective land-lords should also take them into account whenattempting to start a new colony.

Nest-site competitors: The success of a mar-tin colony relies on active control of nest-sitecompetitors. Successful landlords with mar-tins who allow their housing to become over-run with aggressive nest-site competitors,such as starlings and house sparrows, can lose

their martin colony. There are two basictypes of nest-site competitors, native speciesand non-native species.

If desirable native species (such as treeswallows, eastern bluebirds, or house wrens)try to take over your empty martin housing,temporarily plug all the holes and provideappropriate single-unit housing elsewhere onyour property. Reopen your martin housingonly after the other species has accepted thealternate housing.

Non-native species such as starlings andhouse sparrows represent a significant threatto martins and other native species. Nestingstarlings and house sparrows will preventyearling martins from choosing your newhousing and if allowed to occupy existingmartin colonies, will fill nesting compart-ments, break martin eggs, kill nestlings andeven adult martins. Allowing these non-native species to invade existing colonieswill lead to greatly decreased colony successand possibly colony abandonment or lossthrough attrition.

Steps to ControlNon-Native Birds

1. Starlings and house sparrows should bemanaged by a repeated lowering of thehouse for nest tear-outs (martin eggs arewhite, while starling eggs are blue andhouse sparrow eggs are speckled brown).

2. Starlings and house sparrows may betrapped or shot (legal for these non-native species).

3. Starlings can be further excluded by usinghousing with starling resistant entranceholes (SREH’s, see Figure 2), which areaccepted by martins but normally not bystarlings. SREH’s are particularly recom-mended for housing with the larger 7” x12” compartments, which are moreattractive to starlings.

4. You can also minimize starling and housesparrow problems by storing your martinhousing inside over the winter and avoid-ing opening it too early in the spring (see“When Should I Open My Housing in theSpring?” above).

Predation: Martin housing is susceptibleto a whole array of aerial and climbing

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predators including raccoons, squirrels,snakes, hawks, owls, and crows. One suc-cessful nest predator could wipe out yourentire colony or cause the abandonment ofyour site. Do not attach wires to your martinhousing, especially if they lead to trees,buildings, or the ground. Climbing preda-tors such as squirrels can use these wires toaccess your colony. All poles (whether woodor metal) should be equipped with baffles orpole guards to prevent climbing animalsfrom using them to raid your colony. Even arat snake can climb an unprotected pole anddestroy an entire colony.

Here are two ways to deter aerial predators.1. To guard against aerial predators, martin

housing should have compartments thatare at least 6" x 6", but preferably 7" x12". Adults and young may be able toavoid the reach of predators in compart-ments that are 12" deep.

2. You can also design or purchase a housethat includes internal predator baffles oryou can attach owl guards (available com-mercially) to the outside of your housing.Owl guards are wire cages that you attachto the outside of your martin housing likea protective birdcage. These owl guardsshould also help if hawks or crows areraiding your housing.

Nest parasites and pesticides: Insects suchas blackflies, blowflies, nest mites, fleas, andmosquitoes can become so prevalent insidethe nesting compartment that they lead toreduced reproductive success or even inextreme cases total nesting failure and aban-donment of the colony. Nesting materialshould be removed and replaced on the sec-ond and fourth nest checks after hatching oras often as needed due to parasite loads.Nests should be replaced with a 1" to 2" bedof soft wood shavings, dried grass clippings,or dried pine needles. Make a shallow bowlin the material and place the nestlings backin the nest. The application of freshwaterdiatomaceous earth (DE) underneath thenest is also highly effective and can be usedonce the nestlings are seven to 10 days old.The DE scratches the carapace of insect para-sites causing moisture loss and death, but issafe for both humans and birds. The use ofinsecticides in the nesting cavity (such as

Sevin®) is controversial and should definite-ly be avoided when techniques such as thereplacement of nesting material and the useof DE are effective.

Cleaning your housing: Keep your housingin good repair. Store it inside during thewinter to minimize weathering and to pre-vent undesirable species from taking up resi-dence. Before storing your housing, removethe nests and scrub the housing with a 10-percent bleach solution. Rinse and allow thehouse to air dry before storing it permanent-ly for the winter.

Orienting housing after a nest check: Aftereach nest check, great care should be takento return the housing unit to the sameheight and orientation. Purple martins rec-ognize their nesting compartment by itscompass orientation, height, and relativeposition. If you fail to return the housing toits original position, adult martins will enterthe wrong cavities. Havoc ensues and caneventually lead to many young and possiblyadults dying and the permanent abandon-ment of the colony. Use alignment markson the house and poles to ensure that thehouse is returned to the same height and ori-ented in the same compass direction asbefore the nest check.

Providing extra housing and changinghousing: Ultimately you should strive to cul-tivate a sustainable colony of martins. Thismeans providing at least 24 to 30 total hous-ing compartments and trying to build acolony of at least 12 to 15 breeding pairs.Having at least two different housing unitsalso reduces the risk of a disastrous eventeliminating your entire colony. Never sud-denly replace your housing from one year tothe next. Housing should be replaced over atwo year period by erecting the new housingadjacent to the old housing and ensuringthat at least some martins use it. Once mar-tins have nested in the new housing do notmove it to the site of the old housing, eithereliminate the old housing or replace it withnew housing.

ReferencesInformation was adapted from the follow-

ing Purple Martin Conservation Associationpublications:

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Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, University of Maryland, College Park,and local governments. Thomas A. Fretz, Director of Maryland Cooperative Extension, University of Maryland.

The University of Maryland is equal opportunity. The University’s policies, programs, and activities are in conformance with pertinent Federal and State laws and regulations onnondiscrimination regarding race, color, religion, age, national origin, sex, and disability. Inquiries regarding compliance with Title VI of the Civil Rights Act of 1964, as amended; TitleIX of the Educational Amendments; Section 504 of the Rehabilitation Act of 1973; and the Americans With Disabilities Act of 1990; or related legal requirements should be directedto the Director of Personnel/Human Relations, Office of the Dean, College of Agriculture and Natural Resources, Symons Hall, College Park, MD 20742.

Attracting Purple Martin

by

M. Allan DalyMaryland Cooperative Extension

Elijah GoodwinOrganismic and Evolutionary Biology

University of Massachusetts

Reviewers

Jonathan KaysNatural Resources Specialist

Maryland Cooperative Extension

Robert TjadenNatural Resources Specialist

Maryland Cooperative Extension

Dr. Don KroodsmaBiology Department

University of Massachusetts

P2002

Figures were reproduced with permission from PMCA.

The PMCA’s Best Martin Management Tips:Purple Martin Update 8(1), 1997, p.10.

Attracting & Managing Purple Martins: 1995PMCA.

Ten Reasons Why People Fail to AttractPurple Martins: Purple Martin Update 2(3),1990, p. 28

Twelve Reasons Why People Lose TheirPurple Martins: Purple Martin Update 2(4),1990, p. 28.

Standards for Purple Martin Housing: 1995PMCA.

Helpful Hints for Martin Landlords from thePMCA: 1995 PMCA.

Additional Resources Purple Martin Conservation AssociationEdinboro University of PennsylvaniaEdinboro, PA, 16444Phone: (814) 734-4420Fax: (814) 734-5803Email: pmca@edinboro.eduWeb: www.purplemartin.org