Early August 2020, Carlton County, Minnesota

Estimating numbers of birds coming to your feeder is, of course, an inexact science. But we all know that there are FAR MORE BIRDS using your feeders than you see at anyone time.

The max I saw at my one Carlton County feeder at one time in early August was 9….and they were going through a quart every 48 hours. So by using the two methods below, I was likely hosting between 54 and 64 Rubythroats each day!

TWO METHODS for calculating hummingbirds at a feeder have been derived by hummer experts:

1. Multiply max number you see at one time by 6: This formula was arrived at by banders Nancy Newfield and Bob & Martha Sargent who arrived at this numerical factor after years of banding and color-marking hummers at feeders. Using this formula, I was feeding 54 hummers on any give day in early August.

2. Divide hummingbird nectar ounces consumed per day by 0.25: This “Consumption formula” was devised by North America’s preeminent hummingbird authority, Sheri Williamson, based on years of experience. Sheri arrived at 1/4 oz. per small hummer per day. I was going through 32 ounces in two days, so 16 ounces per day. That calculates to 64 hummers were using my single feeder each day. Crazy!

I have put Sheri’s actual blog post below: “Studies of field metabolic rates (the average rate at which an organism consumes energy as it goes about its daily life) indicate that small hummingbirds such as Black-chinned and Ruby-throated are going to need 45% to 50% of their body weight in sucrose (a.k.a. white sugar, the dominant sugar in the nectar of hummingbird flowers) to get through an ordinary day, so they would actually need 180% to 200% of their weight in a 25% sucrose solution.

A 25% solution is much stronger than most people use in their feeders. The generally recommended proportion is 1 part table sugar to 4 parts water by volume, which comes out to about 18% sugar by weight. Converting to this recipe, it would take approximately 250% to 280% of the bird’s weight in ordinary 1:4 feeder solution to meet each bird’s daily energy requirements.

So, how do you use these data to estimate numbers of feeder visitors? The simplest way is to convert grams to fluid ounces so that you can measure the volume consumed (you can even mark your feeder and estimate usage on the fly).

According to my postal scale, one fluid ounce of 1:4 sugar water weighs about 35.5 grams (approximately 20% more than its plain water counterpart). We’ll average the weight of the birds to 3.5 grams, or about 10% of the weight of a fluid ounce. Multiply that times by 265% for average consumption and we get 0.265 fluid ounce of 1:4 feeder solution per bird per day, which we’ll round down to 1/4 fluid ounce per bird per day. This multiplies out to around 32 smallish hummingbirds per 8 ounces of 1:4 sugar water, 128 per quart, and 512 per gallon. This is higher than the TFFBBB estimate, which is not surprising considering the differences between our figures for weight and consumption rates of the birds and weight/volume ratio of the sugar solution.

Of course, there are a lot of factors that can skew this already crude estimate. The amount of sugar water each bird consumes may be greatly reduced when natural nectar sources are available and greatly increased when the birds are under stress from cold, drought, courtship, fighting, nesting, and/or migration. A given volume will supply the needs of more birds if you make your feeder solution a little stronger than 1:4, as many people (myself included) do in winter and migration, and fewer if you make it a little weaker. Size figures in as well, so a given volume of sugar water will feed fewer Anna’s than Black-chinneds.”

—Sheri Williamson on her blog, Life, Birds, and Everything: Jan. 12, 2008

https://fieldguidetohummingbirds.wordpress.com/2008/01/12/running-the-hummer-numbers/

March 16, 2019

A couple weeks ago Bridget and the boys got to watch this same Bobcat (likely the same one) go up to our rabbit pen and paw at the hardware cloth enclosure. A great experience from 6 feet away. PS The rabbits are just fine.

This morning the Bobcat was sitting just 20 feet away from our house for about 30 minutes at dawn. She’d sometimes glance towards our two pet rabbits who are kept outside but didn’t go over to the pen.  I got to watch her just “sitting pretty” for about a half hour. Bridget woke up and she got great looks too. The Bobcat even “meowed” a couple times. So cute!

She eventually sauntered away in the direction of our cabin. Since we have free-range chickens, I decided to distract our feline friend the next day with some wild food. I found two road-kill Snowshoe Hare and a deer rib cage which I put out in the woods. One Snowshoe Hare was gone the next morning.

Neat experience. Hopefully she will eat some of the Wild Turkeys that come to our feeders…It is a favored prey of Bobcats. Skogstjarna, Carlton County, Minnesota. (I don’t really know if this is a female…but this Bobcat was fairly small and has delicate features so I will call it a “she”)

Bobcat (Lynx Rufus) at our home in Carlton County, Minnesota (March 16, 2019)

All photos taken through our living room window (uncropped!)

[Canon 7D with Canon EF 400mm f5.6 L USM lens; 1/25 of a second at f5.6; ISO 3200 (!); +1 ev; braced on dining room divider wall and shot through living room window]

Video taken at dawn. So cute when she “meows” a couple times. No audio.

Purrrdy the house cat watching a BOBCAT through our Living Room Window