Re: PMCA info about using cedar in Martin houses
From: Louise C - Edinboro PA
Date: 5/30/00
Time: 12:16:36 PM
Comments
Here’s the Purple Martin Conservation Association’s position and history on cedar shavings. The PMCA conducted a four-year study to determine the effects of nest parasites on the reproductive success of Purple Martins. Over the course of the study, 2 identical martin houses placed 15 feet apart were monitored. Each year, one house was treated to remove all parasites from the nests, and the second house was left untreated as a control. The results showed that the treated house fledged almost twice the number of young as the control house. Clearly, one way to help martins was to reduce the number of nest parasites, without exposing the martins and their nestlings to any potentially harmful substances, such as Sevin. (Sevin may work beautifully in the short term in reducing nest parasite populations, but research suggests that its continued use will result in long-term toxicity that may affect breeding success in the birds. In other words, it will get rid of the parasites now, but the birds will suffer from poor reproductive rates later on.) It’s important to remember that the goal we all have in mind is to help the martins fledge as many healthy young as possible, not to eliminate every last nest parasite. Lice spend their entire life cycle on the birds; the targets here are fleas, nest mites, blowfly larvae, and bedbugs, all of which take blood meals from the birds, and spend most of their time burrowed down in the nest debris. The simplest and most direct method of controlling nest parasites is nest replacement (removing all nest material about 10 days after young hatch. Replace with bed of clean dry shavings or pine needles. Put nestlings back in nest. This one replacement may be sufficient to knock parasite numbers down for the rest of the nestling period, but in areas where blowflies are a problem, a second replacement when young reach 17-20 days old may be necessary.) The PMCA tested the martins’ preference, and found they prefer a compartment or gourd that contains shavings or other nest material to an empty compartment. So the purposes of using cedar shavings are, to provide insulation against cool spring weather, to save the martins time by giving them a prebuilt nest, to repel nest parasites, and to allow for nest parasite control, via nest replacements. The PMCA has used cedar shavings for six years (this will be the seventh year), other landlords (Andy Troyer, for one) for nine years, with 2000 being the tenth year. No ill effects have been observed in the young or adults. Andy did find, however, that cedar shavings significantly reduced blowfly parasitism at his site. We will continue to test cedar shavings, and other types of bedding. For all of the purposes listed above, though, (except parasite repellency) any type of wood shavings will do just as well as cedar. Hardwood shavings, such as aspen or poplar, are suggested by a US Fish & Wildlife health center; shavings from treated lumber and hemlock are toxic to birds, and should not be used. The wildlife health center could not find any data on problems from the use of cedar shavings in bird boxes. Aspen shavings are the only wood shavings product approved by the FDA and EPA for use by humans and animals. EPA data also confirmed that cedar shavings may be effective in repelling blowflies. When questions arose about the safety of cedar shavings for martin nests, we researched the topic as thoroughly as we could. Both the Environmental Protection Agency, and a wildlife toxicologist at the US Fish & Wildlife Lab in Patuxent, MD, found no data showing cedar shavings were toxic or harmful to birds. They commented that the only way to determine toxicity for sure was to do specific tests, exposing Purple Martins to vapors from cedar shavings, then destroying the birds, and analyzing them for signs of reaction to the cedar. No one has done such tests, but they did find cedar listed as being effective as a blowfly repellent. The EPA reported that cedar is exempted from registration as a pesticide as it poses no risk to people or the environment, unlike naphthalene, Sevin, etc. Contrary to what has been published on other forums, Naphthalene (the compound in moth balls) is not a component of cedar shavings. What is found in cedar is Cedrene and Cedrol. Extracts from cedar (and other softwoods, such as pine) are in the broad category of aromatic or volatile compounds such as hydrocarbons (naphthalene, which is classified as a phenol, is also a member, but a distinct compound), cedrene. Symptoms of overexposure to cedar shavings include respiratory tract infections, sneezing, and discharge from eyes/nostrils. We have observed none of these symptoms at the PMCA site, nor have other landlords using cedar reported them Another factor to consider is that we place cedar shavings in compartments in early April, just when the martins are due to return here. By the time the first young hatch in June, and vapors from the shavings have long since evaporated. We have suggested that landlords can use aromatic cedar in the house to begin with, and use other types of shavings, or dried pine needles, for changes after the young have hatched. Nestlings would be more susceptible to any vapors than the adults, so this method would minimize nestling exposure to any irritants from the shavings. But for one-time use early in the season, cedar shavings would be thoroughly aired out by the time the young hatch. But, PMCA research participant Andy Troyer uses fresh aromatic cedar shavings on all his nest replacements, as do other landlords, and have experience very good success rates. Reproductive success and return rates from PMCA-monitored sites strongly suggest that cedar shavings do not cause problems. Used in conjunction with nest replacement at some sites, and with one time use early in the spring at control sites, we have documented 95.5% success rates (hatch to fledge.) This is a statistically significant higher than average success rate for our region. Furthermore, since all nestlings and many adults at PMCA-monitored sites are individually color banded, we have been able to collect data on the survivorship of nestlings returning to their natal area as subadults the following spring. These rates (20-30% of the nestling Purple Martins that we banded are observed back as subadults) also strongly suggest that the use of cedar shavings is not having any ill effects on the birds. The return rate is twice the published norm return rate of banded young to their natal site. Also, throughout their evolutionary history, Purple Martins have nested in cedar trees, pre-adapting them to any potentially-harmful vapors. It is not a bad thing to be cautious about using new materials or management ideas. Our goal, ultimately, is to impact the martins in a positive way. Based on the data the PMCA has been collecting, using cedar shavings and nest replacement are resulting in higher than average success rates. We will continue to collect information on cedar shavings, and to try new ideas. This year, we are planning to use soft, dried pine needles in 1/2 the compartments, on the recommendation of Dr. Thomas B. Dellinger, who has found they maintain a better nest bowl shape than shavings, and that they drain more quickly after a rain. Offering compartments with both cedar shavings and pine needles will allow the PMCA to compare results, and share them in the Update and other forums for martin enthusiasts.
Louise/PMCA
