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Amateur Naturalist: The Remarkable Hummingbird

on August 11, 2019 - 10:41am
A Broadtail: How much sugar water does it sip in a day? Photo by Bob Walker
Los Alamos
July and August represent the peak for summer and a peak for hummingbirds.
Three species are particularly common:
  • Broadtail;
  • Rufous; and
  • Black chinned.
Some monitoring at a yard with two feeders results in up to eight or 10 being seen at the same time. They are circling and jockeying for position at the feeders. The rufous hummingbird is particularly territorial and tries to chase other hummingbirds away from the feeders. This must become frustrating for a rufous when trying to chase away up to nine other hummingbirds that are arriving at the same time. It becomes even more complicated if another rufous arrives and wants to control access to the feeders as well.
The three species weigh from about 3.1 to 3.7 grams or an average of 3.4 grams. This is slightly more than a tenth of an ounce. They are remarkable in other ways in addition to their small size and weight.
The beating of their wings is a blur of motion, approaching 70 beats a second. This is equivalent to 4,200 beats per minute. Their heart rate has been measured at 1,260 beats per minute and up 250 breaths per minute.
These figures reflect a very high metabolic rate. Their annual migration to Mexico provides another perspective. They will fly for approximately 30 days when migrating across New Mexico. This is 300 miles or 10 miles per day. They may fly another 300 miles to be in the northern part of Mexico for the winter, or a total of 600 miles. How many of us are prepared to walk a round trip of 1,200 miles each year?
The two sugar water feeders provide yet another perspective. Each of the feeders holds a cup of water and needs to be filled twice a day. This means the hummingbirds are sipping four cups, or 32 ounces, of sugar water each day. This is equivalent to 907 grams of sugar water being consumed by birds that weigh an average of about 3.4 grams. Mathematics implies that 267 individual hummingbirds (907/3.4) are coming each day to feed. Is it plausible that 267 hummingbirds are sipping their weight in sugar water each day?
Suppose instead that a single hummingbird is coming to the feeders 5 times each day. This suggests that 53 (267/5) hummingbirds are coming to the feeders repeatedly throughout the day. This is a more plausible number, considering that up 10 hummingbirds have arrived repeatedly. However this creates a new issue. This implies a hummingbird is sipping 5 times its body weight in sugar water each day. Is this plausible? Can you imagine a 100-pound human drinking 500 pounds of water each day?
The calories in the sugar provide yet another perspective. The 32 ounces of sugar water contain 4 ounces of sugar. Each ounce of sugar has the equivalent of 111 calories. Some math conversions show that 53 hummingbirds would consume 2.1 grams of sugar or 8.4 calories per bird each day. If this is proportioned to a 100 pound human, then a human would consume 118,871 calories each day. The actual daily calorie intake is about 2,000 to 2,500 calories.
So consider the remarkable metabolism of a hummingbird the next time you see one. Also consider what is implied when a hummingbird feeder is sipped dry in half a day.
A Rufous beating its wings. Photo by Bob Walker
A group of hummingbirds gathering at feeder. Photo by Bob Walker