Thursday, March 22, 2007

Purple Martin birdhouses western Washington

Volunteers who want to actually participate in a successful species recovery in western Washington are encouraged to consider participating in purple martin recovery locally.

First, some background on the bird. I recently saw a national poll of what gardeners people thought was the most helpful bird in their garden in the United States, and the people placed the purple martin at the top of the list. Apparently it is the only bird which actually has a magazine dedicated to it. East of the Rockies, apparently there are over one million birdhouses built for it to nest in.

The purple martin is the largest member of the swallow family, and like other swallows, very helpful in controlling aerial pest insects. This includes agricultural, backyard, and public health menace pests. Some people know of swallows value, but for those who don't, simply with the advent of Nile Flu being spread by mosquitoes, it is surpising that swallow enhancements in general have not become a priorty of government wildlife managers everywhere. Swallows are very helpful in controlling mosquito, aphid, and fly populations. Swallows, in nesting season, have also had a long history in discouraging crows around their colonies.

As far as the martins controlling mosquitoes, its a myth. Actually, I was taken in by the myth myself some decades ago, when I built my first martin apartment house. I abhor mosquitoes. But by the time I discovered that martins are not the big mosquito controllers, it was too late. I was already hooked on wanting to have these birds back around here.

Since a lot of others also would be interested to learn "What are they good for if they dont eat mosquitoes?" I perused a lot of resources. A lot of dietary studies have been done on martins, and a thousand bows to those who sifted through thousands of beakfuls of insects. Wow! Boy did they give us some answers. Of the many insects they do eat, some are beneficial and many are pests. They eat dragonflies, damselflies, moths, butterflies, midges, grasshoppers, june beetles, japanese beetles, wasps, flying ants, balloning spiders. the list goes on and on. But I left out one insect near the top of the list because that they eat a lot of this type of insect should convince a lot of people to go bang some boards and nails together for birdhouses.

Flies. Purple martins eat lots of flies. Ever lived near a farm with animals, like cows or chickens or horses or goats? Ever lived near a dump, or people who leave their trash can open, or an outhouse? Ever wondered where those maggots grew before becoming your flies, or where that flie was before it landed on your bbq? Ever been bitten by a horsefly or deerfly? Ever had a houseful of flies, or even a double digit invasion? Well. isnt that reason enough to want to have a resident fly control expert on premises?

Unfortunately, maybe ignorance is why the purple martin is relatively unappreciated in the Pacific Northwest, and this has contributed to its decline. West of the Rockies, purple martins are considered a separate subspecies than their eastern counterparts, and throughout this range are barely hanging on for survival. For one thing, they much prefer single nesting sites in loose congregations, instead of the apartment style birdhouse commonly used for the eastern martins. So enhancement for our local martins is more time consuming to participate in than for eastern martins. Also , due to low numbers, patience for years is the norm before colony nesting occurs. Rewards are worthwhile, not easily attained, but recovery at this time almost totally dependent on volunteer efforts. In the long haul, changing foresty and land management practices hopefully will supplant artificial nests with more natural nesting situations.

Like many local species, histories of Purple Martins are sketchy in the Pacific Northwest. Many local birdlovers have read that in the late 40s and 50s that purple martins would gather in a huge roosting flock in August at the south end of Greenlake in Seattle, gathering to migrate en masse to thier wintering grounds in Brazil. This flock, estimated at between 10,000 and 15,000 birds, reportedly would circle Puget Sound in late afternoon before settling in the large swamp at the south end of the lake. Some biologists are uncertain about this report, as hardly anybody was paying attention back then to martins, biologists included.

In the 50s and 60s, 3 things happened that many ascribe why this alleged flock vanished at Greenlake. First, the swamp, like wetlands througout the region, was drained, this one being replaced with various sports fields. Second, throughout the west, 2 new aggresive competitors for nests appeared, the English Sparrow and the starling. Third, pesticide use continued to diminish bird populations en masse, ampified by the switchover from chemical industries of WWII applications to the new Green revolution chemical applications. Pesticides have never much help to birds. Habitat change always affects species composition, and biologists are continuing to investigate how martins are affected.


By 1976, a survey only found 6 nesting pairs of martins north of the Columbia in western Washington. Further north, in British Columbia, in 1985, only 5 nesting pairs were noted.

Fortunately, a few volunteer birdwatchers througout the region stepped up to the plate to try and bring the martins back locally. They invested their own time and money in the martin's recovery. Governments have had limited knowledge, interests, and resources. As one bird survey person for the Washington Dept of Wildlife replied to me in 2005 on a dock in the San Juan islands, "Nobody is talking about purple martins on every street corner, like they are with the spotted owl or the marbled murrelet."

Fortunately, for the martin, it does have a few assets that many of our other local at-risk species lack. Besides its economic value, it is an exceptional flier to watch, and like other cavity nesting swallows, is often approachable to humans. Many of the other species at risk in our region are not as accessible, and even less is known about them. This inclued many seabirds, fish, and lepidoptera (moths and butterflies).

By 2005, the nesting population in Washington had increased to about 400 pairs and over 300 pairs in B.C. Some may believe that our local occurence is back from the brink, but martins are yet a very vulnerable population and need all the understanding and help they can get. For instance, in their wintering grounds in Brazil, 50,000 martins were killed in a single pesticide incident in 1989. Such occurences are devastating for imperiled populations when they return to breed in North America.

If volunteers want to help this bird recover, there are a number of things they can do. First, learn about it. The web has much info on how to help them locally in their housing situation.

Second, after learning about it, try to enlist riparian zone landowners to allow and encourage martin housing. Well over 95 percent of the local recovery has occurred in nestboxes over water. Some believe that one of the reasons, starlings, a prime competitor, do not like to nest over water. Prime sites for nestbox placement is on piers, either old or new. So, encourage local marinas, public and private dockowners to allow martin cluster housing to be allowed on their docks. Martins prefer to defecate over water, so this should be noted to those who might object to this possible adverse impact.

Third, consider helping in other opportunities for martin enhancement. Many recovery individuals would like martins to become re-established in natural forest opportunities, like Garry Oak knotholes, old woodpecker holes, or beaver flooded wetlands that kill trees. In Colorado, our same western martin subspecies nests on average at about 25 feet high in cavities of large live aspen trees, preferring edge trees where the opening faces a meadow, and with freshwater nearby, often beaver ponds. Unfortunately, fire suppression is changing foresty character, and as confers invade aspen stands, suitabe nesting sites are declining.

Then again, we hope that our western martins are adaptable. Inland cluster housing is a long term opportunity for re-introduction, and might occur at both freshwater public and private ponds and lakes, not to mention private yards, community gardens, parks, skyscrapers, bridges, etc.

Our local martins have an interesting occurence. The first scouts show up in our region in early April, and after perusing the marinescape, generally show a strong site fidelity, setting up shop at last year's nesting site. In this way, colonies tend to increase over the years, as long as there are plenty of houses for returning birds. On the other hand, year-old and young birds may not have the same opportunities, and be candidates for beginning a new colony.

Most local martin nesting occurs from early June to early August, but houses should be up by early April, so the scout birds have had a chance to see it. Often, other species will nest earlier in the housing, and often there is competition for the housing, even later. It gets rather complicated, which makes nature study the fascinating dynamic world it is. Landlords are encouraged to evict English sparrows and starlings, but other tenants are generally best left alone. You might want to remove entry hole blocking twigs if the local house wrens have been active blocking up all cavities in the neighborhood. They are very territorial, and nest in only one of the cavities they frequent. Leave that one alone. Tell cowbirds and crows and jays to get lost, as some of them like to harass, parasitize or kill martins. Don't get too friendly with the neigborhood rodents or the weasel clan either.

Colony size varies from single pairs on up, with colony managers generally attempting to attain 5 or more boxes per site. Some locally successful managers claim the initial housing should offer a minimum 25 houses. Martins, like swallows in general, are much more successful in fending off predators when they have sufficient numbers to en masse drive daytime predators off their colonies.

The most succesful sites have the following charactersitics, (but dont let variances stop you, we are trying to encourage an adaptable nesting strategy) : As for nests, they are within 200 feet of human habitation, as martins have learned to believe that people help protect them. The houses are at least 5 feet higher than highest tide (if over water), and over at least 10-12 feet above ground if on shore or other inland site. The birdhouses are preferably placed higher than any other structures within 40 feet, and the site should be in the open. Tall trees, where a raptor might desecend from, should be 100 to 200 fet away minimum. The house entry should face to an opening, preferably to the north or east, to cut down on mid to late day overheating.

The colony is best if all houses are within about 50 feet of each other, maybe a few meters apart each and openings not facing each other. They can occasionally be on the same pole, or near each other, but they like it more if they have a little more space.

Both locally and nationally a variety of housing types have proven successful. Many colony managers prefer that a variety of housing options be presented, so that the birds adaptability to a variety of nesting situations is encouraged. The housing needs to be relatively easy to access, strongly built , well- ventilated, water resistant, and predator proof. Back east some colony sizes have actually diminished because of the weak construction of some of the most popular store-bought apartment style bird houses. Apparently owls, especially great horned owls, have torn them apart.


Perhaps the easiest housing to buy or make in western Washington is gourds, 8-12 inches in diameter. These gourds can be either natural or artificial, and improvements are led to such things as "Super Gourds". Surprisingly, in some martin nesting studies, gourds have sligthly been preferred over other housing types.

If one wants to build their own, heres some general specs. First, consider how you will attach and access the housing. Remember that it generally needs to be fairly high, so consider the ease of ladder access. If ladder access is easy, then the boxes can be secruely fastened permanently. If ladder access in not easy, then consider lifting the house with a pole and attaching it to a protruding large spike. One way to do this is to build a back wall that is 24 inches long, with the lower 16 inches open to the weather, with a couple of house-gutter drainpipe hoops screwed about 12 inches apart so that a pole can lift it upthe house by inserting the pole into to two hoops. A pvc pipe (a smaller one inside a larger one is stronger), or a peeled fir pole can be used to lift the house. At the top, a section of 1 inch pipe clamp (covered with hose so it doesnt shear in winds)) can be screwed to the house to make a hoop that goes over the spike. The spike should be about a 9-12 inch spike.

It helps to stabilize the nestbox from swinging by attaching a couple lines near the bottom of the backboard, crisscrossing them as they come down the pole using galvy nails as cleats running around them . High winds swaying the boxes during nesting season apparently can cause less egg hatching success. Boxes left up year round often can get blown off their spikes, so it's probably a good idea to take them down if you can after the nesting season.


The house itself should be, on the inside, about 6 inches wide, by 6 to 8 inches high, and 10 to 13 inches long. It is long so a predator has a hard time reaching in to the nestlings. There should be a few square inches of ventilation up high inside, like 3+ 1/2 inch holes each side , and a half inch hole drilled interior of each corner for drainage of any rain water that gets in.

The housing doesn't need a steep roof, in fact some people use almost flat sheet metal. Due to wind possibly tilting the house, some tilt so water doesnt get inside via the wallss or door is important.

Often pieces of chicken wire with cut ends pointed skyward are atop the exterior roofing, to discourage gulls and other predator birds from sitting atop the house and picking off martins as they come and go. It is helpful to have a 2-3 inch wide porch, but no entry stick. A couple 1/4 to 3/8 inch twigs can extend out about 18 inches from the side of the house so martins can perch while coming and going.

The entry hole should face away from where the house is fastened, so that climbing predators have a harder time getting in. Raccoons, rats, squirrels are discouraged by sheet metal wrappings at the base of the pole.

In order to maintain the box, an easy access is necessary. This can be done by hinging the door on one of the walls. Often the walls are better to hinge, because of ease of access from a ladder or such. Whichever section opens, a handy way to make the access is to hinge it on galvy nails opposite each other about 2/3 of the way up on the sides. Make this hinged section as the last piece , and make it so that is it slightly smaller than that opening, so it doesn't extend and become obstructed on any side.

The door dimensions are critical in order to discourage house sparrows and starlings. It is better to make the opening rectangular than oval, in order to discourage upright walking starlings. The door opening is 1 3/16 inch to 1 1/4 inch high. It is 2 3/4 inch wide, and flush to the floor. Also above the door is fastened a piece of trim to double the wall depth (construction adhesive helps hold this small piece of wood) a 3/4 to 1 inch thick piece of wood. This creates a deeper opening which starlings don't like. Double - check these dimensions before putting up the house, and shim or adapt the door opening to comply if necessary.

The door top and bottom should be smooth so it doesn't rub on the birds as they come and go. I like using rough-cut 1 inch red cedar, but some houses are made with plywood. The thicker wood is heavier to lift but easier to fasten together. I also like using screws where possible, as they hold the box together better if it falls or gets banged around. They are more expensive thna nails or staples, but hold the house toghter better.

I personally like to salvage old shakes or shingles and use this for roofing and siding with a barrier of tarpaper in between. This gives the house an old look, which improves esthetics for skeptics of artificial housing . I have made some permanent-to- one-place houses simply with some old strong shakes, and made a double roof, each facing a different way. A friend makes birdhouses popular with swallows by putting a bottom and top on a hollowed-out trunk or limb, about 6-10 inchees diameter, hanging it from trees with a section of wire. Since gourds work for martins, something like this might also work for martins. Also, a creative type might be able to build unique houses from slabbed out sides of milling done at local or portable sawmills, taking advantage of this free material.

To help make the nest more attractive, small bunches of dry grass or straw or pine needles work great. Maybe about 1 cup worth of stuff per nest. Nothing longer than a couple inches which can entagle Martin legs. You can cut it up with scissors. Adults are vulnerable to predators when collecting materials on the ground, so it helps to give them a head start on nesting material. No treated wood stuff, or sawdust, sprayed vegetation, or stuff which compacts. As a final touch, maybe create a small mud dam 3/8 inch high an inch or two inside the front door. Supposedly martins like to do this anyway, to help shed rainwater, so apparently this is an attractive enticement.

As a final note, in case you haven't guessed, I am a beginner at attracting martins, and although I've had lots of various species use birdhouses I have built, I have yet to get my first martin tenants. I have had lots of viplet green swallow tenants over the years. Of course, I didnt even see my first martin for the first 30 years I lived in Washington state. With this in mind, I encourage interested readers to please consult numerous other resources on the web to learn more about our western martins. Here have been simply some the basics. I certainly appreciate comments or help in developping more of a strategy. Also, if you do start getting martins in houses you build, or see them around in somewhere in western wash, please contact me if you dont know who else to report your experience too, and I will pass on the info to the real martin enhancers, in case they dont know about it already.

Sometimes hammers and nails can come in handy.

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