We are asked this question from time to time, prompted by caring customers who heard from a friend or read on the internet, that one must always stick to the 4:1 ratio for making nectar as anything other than that can cause hummingbirds harm.
Backyard Bird Shop cares deeply about our birds and wildlife and has found nothing to substantiate this claim with scientific research. Our recommendations are based on those made by Cornell Lab of Ornithology, a respected bird and wildlife authority.
You can find the following information from Cornell Lab of Ornithology at the link below.
“The sugar content of natural flower nectar varies, and is roughly comparable to sugar water mixtures ranging from a quarter to a third cup of sugar per cup of water. During hot, dry weather, when hummingbirds risk dehydration, it’s best to make your mixture no stronger than a quarter cup of sugar per cup of water. But during cold, rainy spells, making the mixture a bit stronger, up to about a third cup of sugar per cup of water, will not hurt your birds and may help them.”