It is time for the Purple Martins to build a nest and raise their young. The process has begun and in 50 - 60 days young Purple Martins will be taking wing.
As the season progresses I am monitoring nest cavity temperature of my ChirpyNest housing in comparison to the Troyer horizontal gourd (THG). The THG is a plastic cavity and is arguably the most popular artificial nest gourd available to Martin landlords. Many landlords add additional venting to this gourd in order to make the cavity more hospitable to the nesting martins. The THG I am using has this additional venting in the lid of the access port.
Since April 1, I have been monitoring the internal temperature of three nest cavities in comparison to each other and the outside air temperature. These readings are logged and will be added to a spreadsheet at seasons end. I am using two, dual thermometer units, designed for greenhouse use, that record the maximum and minimum daily temperature. Each cavity has a temperature probe placed just above a pine needle nest bowl of the cavity it monitors. The cavities are labeled
CN-1. A typical ChirpyNest cavity
Air - The air temperature shielded from the direct sun.
CN-2. A ChirpyNest cavity that for the month of April has the Ventilation channel taped in order to study the effectiveness of the ventilation system.
Troyer Horiz. - A lid vented THG.
Last year I conducted this same type study but on a smaller scale. This season will give me a longer term analysis of the effectiveness of the ChirpyNest system. Results of last year’s study can be found here.
Above is an example of a reading from 11:50 on April 17. The readings at that time were as follows.
CN-1. 73.2 degrees
CN-2. 77.5 degrees
Troyer Horiz. 80.0 degrees
Air 72.8 degrees.
From this reading the standard ChirpyNest cavity is 6.8 degrees cooler than the plastic gourd yet only 4/10 of a degree warmer than the air temperature. Even the ChirpyNest cavity with the vent channel blocked is 2.5 degree cooler than the plastic gourd.
I anticipate this cooler ChirpyNest cavity will prevent pre-mature fledging and I have replaced all my plastic gourds with the ChirpyNest for 2019.
While temperature is the measuring factor, overall ventilation is what I see as the key to the improved cavity environment. Think about being in a poorly ventilated room versus one that is ventilated. That is the thinking I have applied. Openings in the bottom of the plastic gourds are blocked as soon as a nest is built and any flow through ventilation comes from the front opening. The ChirpyNest ventilation flows from below the nest tray and does not get blocked with the building of the nest.
The nesting season is under way. Time to enjoy the Purple Martins.