Darwin noticed that birds that were good at finding scarce food in the winter had a better chance of survivng and producing offspring. what did he call his struggle for existence?

genetic variation will increase because of a new habitat and food source.

explanation:

glacial erosion, the picking up and movement of earth beneath a glacier, is also referred to as plucking. erosion and transportation of individual pieces of bedrock, especially large "joint block occur as a result of this glacial erosion. plucking is type of erosion in which rocks become frozen into the bottom and sides of the glacier.as the glacier moves downhill it 'plucks' the rocks frozen into the glacier from the ground.