Have You Been Myth-led?

Can you tell which of these statements
are true and which are false?

Reprinted from: Purple Martin Update 1(4): 11

James R. Hill, III

Founder, PMCA


1. False. This is perhaps the most widespread myth surrounding the Purple Martin. The number of mosquitos that martins eat is extremely insignificant and they certainly don't control them. In-depth studies have shown that mosquitos actually comprise no more than 0% - 3% of the diet of martins. This amount has been compared to the quantity a human would eat by riding a bicycle with his mouth open. Still, many martin landlords cling to this myth with religious fervor. Ironically, martins actually eat vast numbers of adult dragonflies and damselflies, the nymphal stages of which are the major aquatic predators of mosquitos. Theoretically then, by consuming mosquito predators, a martin colony should increase, rather than decrease, mosquito numbers. Despite all of this, a few martin house manufacturers continue to perpetuate and exploit this myth.

2. False. Most railings do little to prevent baby martins from tumbling off their houses. This is because very few nestlings actually "fall" from their houses. Instead, they are deliberately "knocked off" by aggressive older martins. When a baby martin ventures out of its compartment onto its porch, other colony members instinctively try to make it fly by physically colliding with it, regardless of whether or not the nestling is physiologically mature enough to fly. Railings do nothing to prevent this instinctive aggression by the other martins at the colony site.

3. False. Since gourds don't have porches, baby martins do not venture outside of them before they can fly. Therefore, they are far less exposed to the aggressive actions of other colony members, relative to nestlings in houses with porches. Nonetheless, gourds have gotten an unfair "bad rap" because many landlords don't paint them white to reflect the sun's heat, and baby martins will jump out of overheated gourds. Painted white, gourds are the safest, very best housing a landlord can offer.

4. False. The European Starling tends to avoid commercial aluminum martin houses because the size of the compartments falls just under its minimal floor-space requirements. It has nothing to do with bright, reflective walls. In fact, if you remove an interior wall partition from an aluminum martin house (thus doubling the floor space of a compartment), starlings will move right in. Nearly all commercial aluminum martin houses have compartments that approximate 6" x 6." Starlings prefer compartments slightly larger than this. Still, there are many records of starlings nesting in the 6" x 6" compartments of commercial aluminum houses.

5. False. Scientific tests conducted at the Mississippi State University by Dr. Jerome Jackson using sophisticated temperature probes have proven that martin nests in natural gourds and wooden houses stay cooler in hot weather, and warmer in cool weather, than do nests in aluminum houses. This only makes sense, considering that wood (and the wood-like walls of gourds) is a better insulator than metal.

6. False. No scientific testing has ever been conducted comparing the relative parasite loads of martin nests in wooden houses, aluminum houses, and gourds. The number of parasites a nest ultimately hosts is more dependent on the brood's health, vigor, and resistance, than it is on the type of material from which the compartment is made. Since all of the martin's nest-dwelling parasites are carried into the nest on the birds themselves (or fly or crawl in, in response to odors emanating from the nest) there is no logical reason to predict that there would be a difference in their numbers based solely on the material from which the housing is constructed.

7. False. Snakes and raccoons have absolutely no trouble climbing nearly any typical martin house pole regardless of its height, diameter, or material composition. Because one episode of predation from a pole-climbing predator can cause the total abandonment of a colony site, ALL landlords should use a predator guard on their martin poles.

8. False. While Purple Martins and House Sparrows may appear to share a martin house without much incident, House Sparrows severely limit potential martin nestings by clogging numerous compartments with their nesting material. They also have the nasty habits of building their nests on top of occupied martin nests, puncturing martin eggs, and pecking martin nestlings to death. There is also evidence suggesting that the nest parasites of House Sparrows transmit a blood parasite to the martins sharing their houses. For all of these reasons, it is not good management practice to allow House Sparrows to use ANY martin housing.

9. False. While it is true that martin "scouts" are the oldest and earliest returning martins, their early arrival serves no other purpose than to maximize their own chances of claiming the very best nesting sites at their former breeding spot. Once they have arrived, they do not return south for the "flock". Instead, they stay to defend their territorial claims against later arrivals. A martin "colony" is not an assemblage of birds that travels or functions as a flock. It is just a random aggregation of birds attracted to a favorable breeding site. Colony members arrive and depart independently of each other.

10. False. This is a very old "old wives' tale." Purple Martins will not abandon their nests if humans vertically lower their houses during the nesting season, or touch their eggs and young. In fact, landlords who periodically inspect their martins' nests actually raise more nestlings than landlords who don't, principally because they can see what is going on and can respond to problems more quickly and appropriately.

Copyright 1989 by Purple Martin Conservation Association. All Rights Reserved.

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