Giving finches colorful feathers
If you want to have the sexiest house finches on the block, you can try this little experiment: Put a little finely chopped carrot peel, shredded carrots or sweet potatoes out near your bird feeder.
These vegetables are rich in the carotenoids house finches need to produce redder feathers.
Biologists have provided these foods to house finches in experiments to increase their redness, and apparently the birds loved them.
The time to try this is in the late summer and early fall when the finches are going through molt, dropping all of their old feathers and replacing them with new ones.
Dietary carotenoid pigments are most important when they are growing this new set of feathers.
Once the feathers are produced, their color doesn’t change until they molt the next year.