During an investigation, sam observes the number of hummingbirds that come to his large bird feeder at different times of day. he fills the feeder to the top the first day and counts the number of birds at 6 a. m., noon, and 6 p. m. over ten days. what are the independent and dependent variables in sam's investigation? the number of birds is the independent variable, and time is the dependent variable. time is the independent variable, and the number of birds is the dependent variable. the type of bird food is the independent variable, and the number of birds is the dependent variable. the number of birds is the independent variable, and the type of bird food is the dependent variable.