Surveys of Calling Amphibians in North Dakota

Table 1

Table 1. Codes used for explanatory variables.

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Wind speed: Beaufort scale

     0     Smoke rises vertically (<1.8 km/h)

     1     Wind direction shown by smoke drift (1.8-5.5 km/h)

     2     Wind felt on face, leaves rustle (7.4-11 km/h)

     3     Leaves and small twigs in constant motion; light flag extended (12-19 km/h)

     4     Raises dust and loose paper; small branches are moved (20-30 km/h)

Cloud cover

     0     Clear or a few clouds (<10% cover)

     1     Partly cloudy (10-25% cover)

     2     25-50% cover

     3     50-75% cover

     4     Mostly coludy, fog, or mist (>75% cover)

Precipitation

     0     None

     1     Drizzle

     2     Light rain

     3     Showers

Moonlight

     0     None, new moon, or blocked by cloud cover; difficulty in seeing directly 
           in front of you without a light

     1     Some light from waxing or waning moon; not enough to comfortably navigate 
           in the dark

     2     Reasonably bright, near full moon, or light reflecting off clouds; able to 
           navigate, but not able to differentiate objects well

     3     Bright, full moon; able to see shapes of objects well

     4     Dusk; still enough daylight to see birds at station
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