While far from being foolproof, here is how you can estimate how many Hummingbirds you have coming to your feeder or feeders. If you want to be compulsive about it, you need to establish what kind of hummers you have at your feeders and whether they are fattening up for their migration. Since most of our readers are in North America and since it is late August, you can safely assume that your hummers are fattening themselves up now. It is a long way across the Gulf of Mexico and there is no where to land and rest. Accordingly, Hummingbirds who make the trip fatten up before departing. They will utilize all the extra calories on the trip and arrive a couple of days later dangerously underweight. They’ll do the same next spring when they return.
A Hummingbird eats almost exactly its body weight in 25% sugar solution each day. They also need protein which they get primarily from the insects they consume. So, if you are east of the Mississippi and are feeding Ruby-throated Hummingbirds here is the data. A Ruby-throat getting ready to depart for its wintering grounds will weigh about 5.5 grams. This is almost double its body weight from when it arrived in the spring, about 3 grams. Therefore, each Ruby-throat you have now is probably consuming about 5 grams of nectar from your feeder each day. All you have to do to calculate how many you have feeding is divide the total weight of the nectar you feed in grams by 5 grams and you’ll have a pretty good estimate of how many birds you are feeding.
Unless, of course, you have no idea how many grams of nectar you are making. We certainly didn’t.
We could, I suppose, make you look it up so – as they tell us as kids, “You’ll remember it longer if you look it up.” – or we could just tell you. Since we are shamelessly trying to build readership at our new blog, we don’t think it is safe to try your patience so we’ll just tell you that a 32 ounce feeder contains 946 grams of water. Rounding up to account for the weight of the dissolved sugar, let us assume a 32 ounce feeder contains 1000 grams of nectar. An eight ounce feeder would contain 250 grams of nectar. Assuming an average hummingbird weight of 5 grams in the autumn you would be feeding 25 birds if you are feeding 8 ounces a day. Or 50 birds for 16 ounces or 100 birds for 32 ounces or 200 birds for 64 ounces. More or less. Unless our math is wrong. Or unless the 1973 study of hummingbird consumption is wrong.
This seems like a high number to us and we would love to hear from anyone who has any different methods for determining how many hummingbirds are feeding. We’d like all the help we can get. We’ll do another post of other ideas.
This information comes from an excellent book by Dan True entitled Hummingbirds of North America. We think this is his website. We will try to confirm that and post the results. (Actually, Mr. True – who has made an appearance at this blog once before as the curator of the film of the Greater Roadrunner killing the rattlesnake – failed to tell us how many grams there are in an ounce of water or nectar. He “misoverestimated” our knowledge of the weight of water in grams. But I have loved the man since I was a little boy watching his weather forecasts so I forgive him.