The Darkness, Seclusion And Rustic Factor
From: Steve Kroenke, Tallahassee, Florida
Date: 12/26/01
Time: 5:17:28 AM
Comments
The Darkness, Seclusion And Rustic Factor
Brightness, visibility and slickness are everywhere it seems in the "inside world" of purple martin housing. Most modern purple martin housing seems to minimize the darkness and seclusion and maximize the brightness and visibility within the martins’ nests. This in part can be attributed to small nesting compartments with entrance holes placed around an inch above the bottom. There are slick, white plastic gourds that enhance the brightness of their interiors when light pours through the entrance holes. And of course, there are hundreds of thousands of those shiny aluminum compartments of the Trio houses scattered all over North America. Other commercial aluminum houses are painted white inside, including the Lonestar series. The sides and bottoms of both aluminum and plastic are slick and provide no rustic surface for martins to cling to and climb. And some martin house manufacturers even claim that martins prefer bright shiny compartments! Nonsense.
Okay, so why a discussion about the mysteries of interior light, darkness and roughness within purple martin housing and their possible relationship to martin nest site preferences? Do martins like it bright and slick? Or do they prefer it dark and rough? Maybe they are "swingers" and don’t care one way or the other? Sounds like we are talking about the secret personal life of martins! No, just exploring how such factors may or may not influence a martin’s, particularly the female’s, decision to nest in various housing types. Of course, no one knows for sure if such concepts are truly relevant, but they are certainly worthy subjects for further exploration.
So are you ready to "shed some light" on the darkness of martin housing interiors? Ready to "slide" on some "rough" surfaces?
Physics 101
There is a key law of physics in operation relative to the darkness/lightness dichotomy: light colors tend to reflect light, thereby brightening an area within a confined space while dark tones absorb light and reduce the brightness factor. So if you paint a room in your house white, the room will be brighter because any light striking the white wall will reflect back out into the area. In contrast, a room painted black or other dark color will be darker as the light molecules are absorbed by dark tones. This same situation will exist inside martin house compartments or gourds when light pours through entrance nest holes and strikes the interior walls, bottoms and tops. A shiny aluminum surface or white painted interior of a house compartment or gourd will be brighter than one that is darker in coloration. Physics 101.
Hole-nesting Birds Seek Darkness and Seclusion For Their Nests
For most hole-nesting birds, darkness and seclusion may mean survival while brightness and visibility may mean death. All these birds have one thing in common and it is not just breeding in a cavity. Most of their nests are constructed in relatively dark secluded areas, some of which can be a foot or more deep in dead tree cavities or even farther in bank tunnels. And why do they do this? There is a good reason for such a nesting arrangement. Predators. The darker and deeper a nest cavity is the less visible the contents are to the watchful eyes of hungry predators. And hole-nesting birds know this. Plus more secluded nests are better protected from rain soakings. You don’t see woodpeckers constructing their cavities only a few inches deep where their eggs and young are clearly visible from the outside. They dig them deep and their nest cavities are like black pits. Such nest cavities may be safer from predators. Additionally, these deep natural cavities have rustic interiors, so any birds nesting in them can easily climb up the walls.
The Purple Martin’s Past Was Dark, Secluded And Rustic
Before the advent of human supplied purple martin housing in eastern North America, martins nested in deep, dark abandoned woodpecker holes or similar natural cavities. The woodpecker cavities were vertically deep for the most part, sometimes as much as a foot or more. Such cavities provided the female martin in particular a dark and secluded place for her nest, eggs and young. Plus these nest chambers were rustic and provided a surface that allowed martins to cling to the sides and perhaps even "climb" up from the bottom to the entrance hole. And you need to understand an important aspect of purple martin nesting behavior: while the male chooses the territory, the female chooses the nest site and the females are far more selective than the males. She is seeking the safest and best nest for her young. The darkness and seclusion of a deep cavity perhaps gave her a sense of security as her nest was not as visible to hungry predators and provided some protection from their watchful eyes. One problem with nesting in abandoned woodpecker holes is that the nest bowl diameter tends to be relatively small. I have examined the insides of both red-headed and red-bellied woodpecker nest cavities and the bottoms tend to be oval in shape, often not more than 5 inches long and 3 or 4 inches wide. These cavities are a tight fit for a family of most birds.
The First Big Change - Indians And Natural Gourds
Then along came the Indians and natural gourds and the martins made their move. The interior color of a natural gourd, being used as a birdhouse, tends to vary somewhat but usually is a light to medium brown or beige often mixed in such tones. Some gourds may even have darker colored interiors. There may still be the dried papery light colored pulp that often clings to the sides. A natural gourd cavity is brighter inside than a deep woodpecker hole, but still retains the rustic inside and usually provides more "darkness" and "seclusion" than equivalent size white plastic gourds or aluminum houses. A natural gourd with a consistent layer of dried pulp coating most of the interior may be nearly as bright inside as the plastic gourds. A martin may be able to "climb" up the side of a natural gourd because the interior is rustic and provides good "toehold value". This can’t be done with slick plastic or aluminum. Natural gourds are in between the deep tree cavities and modern day housing relative to the darkness and seclusion factor. So, natural gourds were not a drastic change from cavities in dead trees. The darkness and seclusion factor was still very evident in natural gourds.
Aluminum, Plastic, and Painted Wood - Here Comes The Light, Visibility And Slickness
But oh how things have changed! Now days, commercial martin housing is not vertically "deep" and the entrance holes are around an inch above the bottom of the compartments, clearly exposing the insides. Commercial aluminum houses have shiny aluminum interiors or are painted white. In the small bright 6"x 6" cubicles of most commercial aluminum martin houses, the contents are easily seen when looking into the hole, much to the predator’s delight when seeking a meal. The sunlight just pours through the entrance hole and brightens up the interior as the shiny aluminum reflects and spreads the light throughout the nest chamber. Even the 6" x 12" compartments of the Lonestar houses are painted white and you can see to the back of the rooms. The same situation exists with many of the plastic gourds currently on the market. They tend to be bright white on the outside and the inside, and such an interior is brighter than a similar size natural gourd. On the Supergourd, the inside curvature of the rain canopy displays a prominent "semi-circle of light" right above the nest hole when you look through an access door. Again, light colors, particularly white, in a confined space reflect the entering light and spread it out thereby brightening the area; dark colors absorb the light and maximize the darkness. The plastic access door lids used for both plastic and natural gourds may let the light through to help brighten up the interior. Just holding up the lid to the sun and you may see your hand silhouette pressed against the outside of the lid’s top. And the interior sides of aluminum, plastic and many painted wooden houses are smooth and provide almost no "toehold value" for martins to cling to the sides. Shiny aluminum and white or light colored plastic are different in texture, feel, and in the way they enhance inside brightness of martin housing from the interiors of natural gourds and unpainted wooden houses. Wooden houses with white interiors would also maximize the brightness factor.
Rustic Factor May Not Be As Relevant Anymore
Since most modern day martin houses have entrance holes around an inch above the compartment bottoms, martins do not need to "climb" or "cling" to get out. The rustic component of the darkness and seclusion factor may not be that relevant now days. However, rustic texture may be more important for providing a solid toehold for greater "pushing power" and foot traction of a martin trying to slip into a tight starling resistant entrance hole (SREH) on a slick plastic gourd. A rustic texture does provide a better platform for nesting material and keeps the material from sliding around as much. I have seen this "sliding nesting material phenomenon" in my plastic SuperGourds. When the female martins would "spin" their bodies to create a nest bowl for their eggs, sometimes the female would "spin" to the bottom and reach the bare plastic. The nesting material just kept separating because it would not adhere to the slick plastic bottom. Perhaps a rustic interior has a more natural "feel" to a martin.
Forget Darkness And Seclusion - Maybe It Is Just Larger Size?
Does size really matter in the world of purple martin housing? There is a temptation to say expanding the dimensions of a nest compartment or using a larger diameter gourd increases the attractiveness value to martins. That is, the size of the interior is the key factor and independent of other variables. But is it size or is it increasing the darkness and seclusion factor? Maybe it is both. Larger natural gourds either hung vertically or horizontally are readily colonized by martins. Now they are larger in size, but they are also darker and more secluded inside. Larger house compartments are also popular with martins; but again, is it just size or the increased darkness and seclusion. The interrelationship between size and the darkness and seclusion factor is interesting. You can increase the size of a nesting compartment in a martin house but paint it white and it will still be relatively bright when sunlight pours through the entrance hole. And those 10-inch diameter SuperGourds, with their white interiors, are usually brighter inside than smaller diameter natural gourds with darker insides.
But Martins Have Adapted To The Light And Have Thrived
And yet, martins have readily colonized and thrived in the bright, visible and slick nesting compartments of commercial houses and plastic gourds. In one way, you can make the argument that humans have "forced" martins to adapt and nest in such housing because the commercial aluminum houses are probably the most common houses erected in the United States. If there is nothing else out there, then martins must accept what is available or perish.
So is there even an issue here to discuss? Does it really make any difference? Do martins prefer the darker secluded interiors of natural gourds or unpainted, rustic wooden houses or do they prefer the brighter compartments of modern day plastic gourds and aluminum houses? And maybe martins really don’t "care" one way or the other?
There Is Still Something Here To Explore More Thoroughly
I am guilty of having an inquisitive mind and like to "meddle" in martin behavior and biology. I am not satisfied with generalities and like details. So I am highly intrigued by the darkness and seclusion factor’s possible influence on a female martin’s selection of one type of housing over another for her nest. A further exploration of the role of rustic interiors, darkness and seclusion may yield insights into improving the attractiveness of current housing and particularly helping those folks who are experiencing year after year of failures to establish a martin colony. We should always be in a research and explorative mode of operation. Keep a pioneering spirit! Never pass on a chance to look at a subject in detail and question so called "standard practices". Insight is gained through taking chances at times and perhaps delving into subject areas that are often given just cursory reviews. I am amazed how much I have learned over the years about purple martin behavior and how much I didn’t know! Sometimes, I have to re-think or completely change a viewpoint because I learn something new through research, detailed observation, or insights provided by other martin landlords.
Are There Any Formal Research Studies?
I am not aware of any research studies that have been done to test the darkness, seclusion and rustic factor independent from other variables like size of compartment/gourd, type of housing, and housing design configurations. Sometimes multiple factors are so interrelated that you can’t extrapolate one from the other with any true precision or reliability. The relationship between size and darkness/seclusion is a good example. In fact, several factors may jointly operate and produce a combined effect. Drawing definite conclusions one way or another require objective data that has been carefully collected and analyzed using scientific methods.
However, all that said, we can still look at and consider anecdotal or just "common sense" viewpoints. If we can see significant trends or make consistent observations over a period of time, then we may be on to something that can be further explored on a more scientific level. Backyard observations from serious martin landlords have an important place in purple martin colony management and can lead to significant improvements in housing designs that ultimately benefit martin survival.
Possible Indications Of The Importance Of The Darkness, Seclusion and Rustic Factor
One possible indicator that martins may prefer darker, secluded and more rustic nesting interiors comes from reviewing occupancy levels recorded in various housing types. This involves studying martin housing preferences during various stages of the nesting season such as territory establishment by the males, female selection of the male and his territory, and the female’s ultimate choice of a site for her nest, eggs, and young. Do the territory seeking males gravitate toward one type of housing first? Most importantly, do the mate seeking females consistently select males occupying a certain kind of housing and stay to breed?
Huge Natural Gourd Colonies
There is no question about it. Natural gourds are perhaps the most attractive housing you can use, particularly in parts of the Deep South. Research by the PMCA has shown that natural gourds are highly attractive to martins. These colonies can be enormous in size, often over 100 pairs. But you can’t say this is because gourds are rustic, darker and more secluded inside. Just shows that there may be something to it, but not a direct correlation as there are only natural gourds in the colony, and there is no comparison with plastic gourds or houses with lighter interiors. However, if an area contains both natural gourd colonies as well as colonies of other housing types, you can compare occupancy levels and see if there are any patterns. But again, you really can’t say for certain how much effect, if any, the darkness, seclusion and rustic factor is exerting on the martins’ preference for one type of housing over another. Other factors could be involved, too.
Colonies Offering A Variety Of Housing
What about colonies using a variety of housing? Are there differences in martin preferences among houses and gourds? If so, can you narrow the selective criteria to the darkness, seclusion and rustic factor? Are natural gourds with their darker interiors more attractive than equivalent size plastic gourds with light insides? What about houses? Are houses with unpainted interiors or ones painted dark more attractive than ones that are painted white or are aluminum? Many of these questions can only be reliably "answered" in controlled studies where controls are in place to minimize or eliminate other variables that could also influence martin preferences.
From what I have read, observed and heard from other martin landlords, when martins are offered a choice of a variety of housing, martins generally, but not always, select natural gourds more often. This has always been the case in my colonies and I have used natural and plastic gourds, as well as commercial and homemade aluminum and wooden houses. My natural gourds were nearly always occupied first and in my largest super colony no martins would nest at the site until I added natural gourds. The martins shunned the fancy aluminum houses with the bright, visible interiors for years. So many factors come into play and rarely does a multi-housing colony site have scientific controls in place to minimize the influence of other variables. But it is still interesting that natural gourds, with their dark, secluded and rustic interiors, are so attractive to martins when compared to other housing.
Modified Trio Houses - A Clue That Darkness And Seclusion Are Important
The Trio aluminum martin houses are probably the most common commercial ones around. Martins will colonize in these houses and breed successfully. However, something interesting occurs when you start messing with the insides of the houses. When the Trio houses are modified to create double nest chambers, any martins selecting these houses, invariably build their nest in the isolated, darker and secluded compartment that is AWAY from the entrance hole. It is important to understand that the actual nest compartment has NOT been enlarged and is still only 6" x 6" in dimensions. What has been created is a "no bird foyer" that martins enter first through the entrance hole. This area is open to light and highly visible. Then, another entrance hole is cut in one of the room dividers to the nest chamber, so the actual nest area is secluded and not flooded with as much light, thereby making it darker. If brightness and visibility were not issues, then martins would also probably nest in the "foyer" area of these double nest chambers. But they don’t. So the darkness and seclusion factor may be the key variable in operation here.
Okay, So What Does All This Talk About Darkness, Seclusion and Rustic Interiors Mean Now?
Purple martins are hole-nesting birds and they seek out the nest sites that may offer the safest place for their offspring. Their babies are the parents’ genetic legacy and continuation of the species is what it is all about. Keeping their young away from predators is a primary concern. So, breeding in a dark and secluded place makes the nest and young less visible to the eyes of hungry predators. If given a choice or opportunity, martins may instinctively gravitate toward gourds and houses with interiors that maximize darkness and seclusion and minimize brightness and visibility. This is particularly true of the females that select the nest site. Perhaps the "darkness and seclusion" factor is in the purple martin’s genes. The rustic component doesn’t seem to be as relevant now days since martins in Eastern North America no longer nest in deep abandoned woodpecker holes.
So what does this imply for martin housing? Well, it may imply nothing, but it sure makes me wonder. I do believe there is a darkness and seclusion factor in operation here and female martins in particular may "consider" this when they are reviewing the territories of males. The attractiveness of natural gourds and the obvious preference of martins for double-chambered house compartments may be strong anecdotal evidence that female martins are seeking nest sites that maximize darkness and seclusion. The females may be doing this so that their young are not as visible to predators and other dangers.
But Lets Just Not Talk About It - Lets Experiment
Okay enough talk, should we consider making changes in our plastic gourds and aluminum houses to enhance the darkness and seclusion factor? Sure we should, at least try it on a small scale and see what happens. Lets be pioneers for this upcoming martin season and explore the concepts of darkness, seclusion and maybe rustic interiors. You never know, there may be something to this. Those martin landlord wannabes who have tried and tried and tried might finally be successful. What do you have to lose?
I’m Doing It
Well, I have talked a lot about it so I am going forward. I plan to conduct a limited test of the darkness and seclusion factor for this upcoming martin season and I hope other folks will give it a try, too. Unfortunately, martins are declining in numbers in my immediate area and I’m not sure what next year’s population will look like. But I still plan to conduct a small study and see what happens. Here is my plan:
I will have the following colony make up for 2002: 40 plastic SuperGourds on two Lonestar gourd rack systems, 20 per pole; 20 natural gourds on a Lonestar gourd rack system; one 14 room Lonestar aluminum house; and two Trio aluminum castles (pre-modified 24 rooms) each converted into 12 room houses with double nest chambers. This will comprise 98 possible nest sites.
All gourds and house compartments will have artificial nests composed of cut up pine needles with a nest bowl of dry oak leaves. This makes a fairly good replication of a natural martin nest. My experiences have shown that martins prefer gourds/houses with intact nests.
All access lids to the SuperGourds have been painted black on the inside to eliminate any possible light penetration as some of the lids on my gourds did allow this to occur. The outer perimeter of the rain canopies will be painted white to eliminate the "semi-circle of light" around the top area above the entrance hole from the inside of the gourd. This portion of the SuperGourd's plastic does not appear to be that opaque or is semi-opaque. The only direct light source I want for the gourds is the entrance hole.
At least ten SuperGourds will be painted a medium or dark brown on the insides to somewhat mimic the coloration of the natural gourd interiors. The key here is to reduce the brightness factor as much as possible from light entering through the nest hole. Remember: dark colors absorb light. I will do the best job I can in painting the insides through the access doors, but may not be able to achieve a full coverage. To create a rustic texture on the inside, I may sprinkle sand or perhaps sawdust on the wet paint. I am not sure if this will work well, but will at least test it. These modified gourds will be randomly scattered through the two gourd poles containing the SuperGourds. I want to see if martins will select the "darker" interiors over the "brighter" ones and particularly what gourd the females ultimately choose.
Seven rooms of the Lonestar house will be painted a medium or dark brown, too. The Lonestar house has four sides and each side will have modified compartments. These nest rooms are 6" x 12" in dimensions.
Nothing will be done to the insides of the natural gourds or the Trio castles. These gourds are "naturally" dark, secluded and rustic. The Trio house interiors have already been modified into double nest chambers, so the seclusion and darkness factor has been addressed. The natural gourds are painted white and are from 8 to around 10 inches in diameter.
This is by no means a scientific study, but may yield some interesting observations regarding purple martin nest site selections. I’m looking forward to giving it a try. If other folks would try something similar, then maybe we can collect enough data to at least give us a better foundation to assess the influence, if any, of the darkness, seclusion and rustic factor.
Suggestions To Enhance the Darkness, Seclusion And Rustic Factor Of Plastic Gourd And Aluminum Martin Housing Interiors
For those folks who are interested in incorporating the darkness, seclusion and rustic factor in their plastic gourds and houses, here are some ideas you may want to consider. Maybe try it on a few gourds or house compartments. Again, no one knows for sure if martins are influenced one way or the other. But if you are having difficulties attracting martins, then this might help. However, it is undeniable that most cavity nesting birds seek dark and secluded areas for their nests to perhaps hide their young from predators. This may just apply to martins as well. Here are some suggestions:
(1) Make sure any plastic access lids on your natural or plastic gourds are not permitting sunlight to enter. Hold the lid up to the sun or a light and see how "bright" the underside of the lid appears. Can you see the silhouette of your hand pressed against the top of the lid? If so, paint the inside of the lid black or other dark color to block out the light.
(2) Paint the insides of your white plastic gourds a darker color such as medium to dark brown to somewhat replicate the interior color of an equivalent size natural gourd. Again, dark colors absorb light while lighter colors reflect and spread it.
(3) If you are using SuperGourds, you may want to eliminate the "semi-circle of light" from the interior of the rain canopy that appears above and around on the inside of the entrance hole. This can be done when you paint the gourd insides or you can paint the outer perimeter of the rain canopy.
(4) Coat the wet painted interior surface of the plastic gourds with sawdust or sand to create a more natural texture. This action may reduce the "sliding nesting material phenomenon" that sometimes occurs when the female martin "spins" to create her nest bowl in a plastic gourd. She may literally be sitting on the bare plastic when the material continues to separate and slide. The nesting material may better adhere to a rustic surface.
(5) Create double nest chambers with existing Trio and similar aluminum houses. The action greatly increases the darkness and seclusion factor and martins invariably nest in the nest chamber that is a WAYS from the entrance hole.
(6) If you do not modify your aluminum martin house that has the 6" x 6" dimension compartments to create double nest chambers, consider painting some of the room interiors a dark color, like medium or dark brown, to maximize the darkness and seclusion factor. Even if you are using deeper nests, such as those in the Lonestar series, you can create a darker and more secluded environment by painting the inside rooms a darker color.
(7) Add an artificial nest to your gourds and house compartments to create a close replica of a "natural" martin nest. Such nesting material will absorb light rays and help increase the darkness and seclusion factor. I use cut up dry pine needles in about 4 or 5 inch lengths to create a solid foundation. Then I add a handful of dry oak leaves to a depressed bowl area at the back of the nest compartment or gourd.
(8) Add "tunnel" extenders to the entrance holes of plastic gourds. You are attaching PVC pipe pieces of various lengths, usually 3 or 4 inches, to the gourd entrance holes. These tunnels can be either straight or "angled". This creates considerable seclusion and darkness in the nest chamber, as sunlight does not directly enter the nest hole. Terry Washburn has experimented with this concept and reports good success. And I just wonder if it is because the nest area is darker and more secluded which may mean for the female, safety from predators? Be sure to visit Terry’s website for more information about his innovative creations: http://www.iocc.com/~twash/srehsolutions.html
Purple martins are similar to other hole-nesting birds in one critical way. They seek out nest sites that will offer the best chance for their young to survive and not be eaten by predators. To keep their nest and young protected, martins may instinctively choose when available those sites that maximize darkness and seclusion and minimize brightness and visibility. We might be able to increase the attractiveness of current aluminum houses and white plastic gourds through darkening the interiors and creating double nest-chambered compartments. Lets keep the light out.
Steve Kroenke Tallahassee, Florida
