Recycled Freon Canisters

Nest structures made from these discarded metal canisters (2) have been used successfully at Federal Refuges in Iowa (Union Slough in particular) for the past 25 years. The USGS website provides plans for construction.

They are virtually maintenance free and will last over 20 years. The “all-in” cost is less than $5 each for assembly hardware.

MWDI raised concerns about Maryland’s more southerly latitude than Iowa and whether “our” wood ducks would use them. Most people we’ve spoken to have universally indicated that the plastic cylinders sold by Ducks Unlimited did not work.

2005 Research Projects & Results
In 2005, MWDI installed 6 canisters in 4 separate project locations in Maryland and conducted a heat test placing a box in the shade after cutting vent holes in it and painting it light beige. The spring was relatively cool that year and even in July, the inside temperature of the canister never exceed 96 degrees and the highest inside temperature was 7 degrees above the outside level. (106 degrees being the upper limit possible for egg survival.)

Of the 6 field canisters, 5 were used and 4 hatched. The unsuccessful nest was in full incubation with a normal clutch but the hen was overwhelmed by an ant infestation and abandoned the nest. Two canisters were placed in generally high use wood duck areas, representing new capacity in each project where placed. Of the others, two were in new project area and two in a moderate use region. This was most encouraging.

2006 Research Projects & Results
In 2006, 28 canisters were installed although only 18 were determined to be functional as nesting material had not been provided. Water conditions were also very poor and many canisters were in dry habitat that was typically flooded. Of the14 functional nests, 4 were used and hatched. In one project area, 2 new wood and 2 canisters were placed in the same wetland (although visually hidden from each other) and the wood ducks used the 2 new wood ones and not the canisters.

Conclusions
Field acceptance is still considered favorable although it is MWDI’s perception that, other things being equal, in new habitat use areas, wood ducks will prefer wood over metal if given a choice in the near term. Field trials will continue.

Manufacture using a plasma cutter will also be tested further as this seems to be the easiest way to cut off the tops and bottoms and cut out the entrance hole and bolt holes. Supply of canisters is not a limiting factor. MWDI has sources defined to make hundreds.

Heat Test

Heat Test Conducted
To independently analyze the heat buildup issue, Donny McKnight, of the Harford Christian School, agreed to establish a heat test under more controlled circumstances than that done by MWDI and to monitor a wooden box in the same environment. Donny’s results will be published soon. He has documented that heat buildup was not an issue limiting the prospective widespread use of recycled canisters in a shaded environment.

Pros & Cons Indicate Longer Term Evaluation Worthwhile
Freon canisters are harder to fabricate than wood boxes and they are not “traditional,” but they are very cheap and the maintenance benefits are such that longer term evaluation is considered to have real merit.