The Evolution of the Plastic Purple Martin Gourd

Reprinted from: Purple Martin Update 7(4): 26-27
James R. Hill, III
Purple Martin Conservation Association

Plastic Purple Martin gourds have been on the market for the past 15 to 20 years and have proven to be very popular with both their feathered tenants and their human hosts. The reason for their popularity with landlords is that plastic gourds have several advantages over natural fruit gourds. First of all, plastic gourds last longer; they don’t crack from hot/cold, or wet/dry, weather extremes, and they don’t rot from fungal attacks. Second, they’re less fragile; drop a natural gourd on the driveway and it could split in half. Third, plastic gourds are low-to-no maintenance and come ready to hang; natural gourds have to be drilled, cleaned out, soaked in copper sulfate, sanded, primed, and painted, then resanded and repainted every few years. Fourth, because plastic gourds from a manufacturer are uniform in appearance, they are more aesthetic and acceptable in some communities than a cluster of nonuniform natural gourds. Finally, plastic gourds are less expensive to buy and maintain over the long haul than properly-prepared and equipped natural gourds. All of these features make plastic gourds far more convenient to use for busy martin landlords.

Over the years, numerous manufacturers have produced plastic martin gourds to meet the demands of the martin hobbyist. In the beginning, companies like Geauga Company of Chardon, OH, made the one-piece, blow molded style of gourd shown above on the far left. Typically, these were only available in a chocolate-brown color that the landlord had to paint white. Unfortunately, many landlords didn’t bother (or weren’t instructed to do so by the manufacturer) and the nestlings inside these gourds got too hot from solar absorption. Some companies now offer these small, one-piece plastic gourds in white, like Stalnaker Plastics of Warner Robbins, GA, and the Purple Martin Gourd Manufacturing Company of Sumter, SC., but they are somewhat translucent, which can cause inside temperatures to rise due to a “greenhouse-like” effect. Another drawback of these early plastic gourds is that they are only about 6" in diameter and weigh 8 to 10 ounces; a 10" to 12" natural gourd weighs 2 to 3 times as much, about 26 ounces. Being only 6" in diameter, martins tend to lay smaller clutches of eggs in these gourds, yet still suffer overcrowding. Being so light, these gourds also tend to blow around more in the wind. And being a one-piece, plastic container, nest observations and cleanouts are not very practical or convenient. Only the cost of these early models is attractive; they sell for about $1.75 to $3.50 a piece.

The next style of plastic gourd to come along was the two-piece, slot-opening gourd shown second-from-left, manufactured by Purple Martin Homes of Chattanooga, TN. These were 8&3/4" in diameter and weighed 10 ounces. The top and bottom halves snapped together with three tabs. To the best of our knowledge, these gourds are no longer on the market; martins tended to shun them because they were so translucent and because of the oversize (1&1/2" x 5&1/2") slot entrance, which martins dislike. These gourds did have the advantage over their predecessors of being easier to clean out at season’s end because they snapped apart.

The next plastic gourd on the scene was the two-piece, injection molded 8-incher manufactured by Carroll Industries of Madison, MS, (center of group photo). These are totally opaque (i.e., they let no light through their walls) and weigh 15 ounces. The snap- and screw-together seam runs top to bottom. They come apart for end-of-season cleanouts, but not for weekly nest checks. They retail for about $7.50 apiece. Up till now, Carroll Industries’ gourds have been the pinnacle of plastic gourddom (and have been the only plastic gourd offered by the PMCA), but lacking an access door, they prevented landlords from being able to conduct accurate weekly nest checks.

In 1996, Plasticraft Manufacturing Company, Inc., of Albertville, AL, introduced the 11-inch gourd pictured second-from-right in the group photo. It’s a 4-piece, injection molded piece weighing 23 ounces, connected with two screws. This gourd has several innovations borrowed from natural gourd users. It has a snap-in access door for nest checking and end-of-season clean out. It has a molded-in rain canopy over the entrance hole. It also has an adjustable vent cap that can be opened in hot weather and closed in cold. The cap covers two, large, 5/8" vent holes. The gourds are opaque and have ultraviolet inhibitors for long life in the sun. Plasticraft sells these gourds for about $7.00 each (plus $3.50 S&H), and also offers, as an option, an oval, starling-resistant entrance hole (3" x 1&7/32"), as well as blank doors for those who want to drill their own holes. I applaud Plasticraft’s offering of an optional starling-resistant entrance hole (the PMCA have been promoting them since 1993.) While starlings do not commonly nest in gourds, this option is a welcome one for those folks who do have starling problems. More research and testing is needed on starling-proof entrances, however, and it might be necessary to make some adjustments as these holes are refined.

Although Plasticraft’s product is a major leap forward in gourd design, it has some features that could be improved. First of all, the canopy is placed about 1&1/4" too close to the entrance hole. Anyone who has seen a martin sitting in the entrance hole of a gourd knows that their heads stick up much higher than Plasticraft has allowed for in their canopy placement. Martins using these gourds have to duck down in a crouched position to sit in the entrance hole.

The innovative, snap-out access doors on these gourds take a bit of getting used to. In order to keep owls from pulling these doors off, the manufacturer has fashioned them in a way that requires a bit of “muscle” to release the pull-up release tab. This tab is located inside, 1&1/2" below the bottom of the entrance hole, and could get buried under the mud dam martins build at the front foundation of their nests.

Plasticraft’s vent cap slides up 1/2" to reveal two ventilation holes. I doubt landlords are going to want to open and close those caps frequently (i.e., open during hot days, but closed during cool nights and before every approaching rain storm), but they might be valuable during heat extremes. The two vent holes point straight up and are exposed to blowing rain. There are only two drainage holes in the bottom of the gourd, each just 11/32" in size. This is inadequate, although purchasers could drill additional drainage holes. Finally, since this gourd is a 4-piece product with three separate seams, another concern is that rain water might leak through the seams. As the Plasticraft gourds have only been on the market one season, it's premature to draw any conclusions at this time.

Introducing the SuperGourd®. The PMCA will soon begin shipping the next generation in plastic gourd evolution: the SuperGourd®, a 10" plastic gourd shown in prototype form on the far right of the group photo on the previous page (also see photos on this page and the back cover). The SuperGourd® is the first martin housing to be designed and developed by a Hirundinologist, an ornithologist specializing in Purple Martins. It is a single-piece gourd with a molded-in, threaded access port, covered by a standard 120 mm threaded cap. This port is 4&1/4" in diameter, large enough to admit a human hand even while holding a fat nestling or a handful of wood shavings. The cap has a liner that renders it and the access port totally watertight. Landlords merely twist the cap off to do nest checks, band babies, do nest replacements, and end-of-season cleanouts. Because of the access port’s high, 45-degree viewing angle, nest contents are easily visible during nest checks. The SuperGourd® also has a large, molded-in rain canopy that doubles as a perching platform. Not shown in these photos of this prototype are a series of corduroy-like ribs on top of the canopy’s center that give martins the grip they need to perch. The canopy is placed high enough above the entrance hole to allow the perfect amount of head clearance for hole-perching martins. The SuperGourd® weighs approximately 26 ounces, the same as a natural gourd its size, so not only does it look like a natural gourd to a martin, but it also has the feel of one, too. It has six 5/16" drainage holes and having a one-piece body, there are no seams to potentially leak. The SuperGourd® is blow molded in a white (sun reflecting), opaque, high-density polyethylene plastic, with ultraviolet inhibitors added for long life.

The SuperGourd® is an attractive alternative for those landlords too busy to grow, paint, and modify natural gourds. The SuperGourd® has all the advantages of a natural gourd, but will cost less than a properly-prepared and equipped natural gourd, and has the added benefits of long life, low maintenance, and easy, weather-tight access. Price and shipping date of the SuperGourd® will be announced in Update 8(1).

James R. Hill, III, is founder and Executive Director of the PMCA. He is also the designer and producer of the SuperGourd®. This gourd is the culmination of his 17 years researching the needs and nesting preferences of martins, and it’s the realization of a decade-long dream for him.

Copyright 2001 by Purple Martin Conservation Association. All Rights Reserved.

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