Which of the following is an example of gene flow?

~ a forest fire kills 50% of red-spotted chipmunks in a forest community
~ pollen from a yellow daisy travels across a stream and pollinates an orange daisy
~ a bird with blue feathers is less camouflaged in the rainforest than a bird with green feathers
~ mice with heavy coats are able to survive the winter better than mice with thin coats