Final answer:
Johnny can determine the preferred birdseed of cardinals by conducting an experiment with various birdseeds as the independent variable and the cardinals' seed choice as the dependent variable, collecting and analyzing data to support or refute the hypothesis.
Step-by-step explanation:
To determine which kind of birdseed cardinals prefer, Johnny could set up an experiment with different types of birdseed and observe which one the cardinals select more frequently. An experiment to test this would involve several feeders, each with a different type of seed. The independent variable would be the type of birdseed offered, as this is what Johnny changes or controls. The dependent variable would be the cardinals' seed choice, measured by the amount of seed consumed or the frequency at which cardinals visit the feeders.
Johnny's hypothesis might state: If cardinals prefer a specific type of birdseed, then they will visit the feeder containing that seed more often than feeders with other seeds. To accurately measure this, Johnny would need to ensure that other factors, such as feeder location and time of day, are controlled, meaning they do not change throughout the experiment.
Johnny would collect data on how often cardinals eat from each type of birdseed and could use video cameras to record their behavior remotely. He would analyze this data to determine preference. The results would either support or refute the hypothesis. The experiment should be repeated to verify results and to ensure reliability.