Posts tagged ‘slow motion video’

Jaeger Attacks: Lake Superior, Wisconsin Point

Parasitic Jaegers migrate through Lake Superior in spring and fall. We often see them harassing gulls in mid to late September off of Duluth, Minnesota’s Park Point and Wisconsin’s Wisconsin Point. Long-tailed, Pomarine and Parasitic can all be seen here, but Parasitic Jaeger is the most common by far. They will somehow single out an individual Ring-billed Gull that it feels has a crop full of food. I suppose they can see the full crop. Then they perform the bird equivalent of a aerial “dog fight” and scare the gull into coughing up its last meal. The jaeger can often catch the regurgitant in mid air!

You will see a successful “hunt” in this video. By the way, “jaeger” is “hunter” in German.

These attacks were filmed in mid September off Superior, Wisconsin’s Wisconsin Point with the Panasonic GH5 at 180 fps.

60 Hummers at my one feeder?!

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/