When seated at my desk, I have a nice view of the hills that surround Monterey. I often see hawks and hummingbirds and I marvel at how evolution has created two such different birds, and I do not mean just in terms of their size. It turns out that the fact that they both are seen in the same vicinity near my home is not an accident. What researchers have found is that hummingbirds nest under hawks because that protects them from their main predator, the Mexican Jays.
Hawks don’t prey on hummingbirds or their nests—there’s not enough meal in a hummer to be worth the effort, apparently. (“The hawk by weight is about 190 times the size of a hummingbird, so it’s basically the same reason that if you want to catch a fly, you don’t run after it,” said Greeney.) But not only are hawks not a threat—it seems they may actually protect hummingbirds from their predators, Mexican Jays.
…When they cross-referenced the GPS coordinates of hummingbird and hawk nests with the locations where jays were foraging, they expected to see “a big circle around the hawk where the jays just never went,” said Greeney. Instead they discovered that while jays do forage close to hawk nests, they do so at higher altitudes than normal, staying above hawks that typically hunt from above then swoop down on their prey. Greeney found that hummingbirds build their nests under the hawks’, in a “cone-shaped space where jays never go, right around the hawks.”
The hummingbirds’ strategy seems to work. And their nesting success depended not just on proximity to hawk nests but also on whether the nest was within the jay-free cone Greeley and his researchers were able to define.
To watch hawks in flight is to see pure grace in action. They hardly ever flap their wings, instead gliding along and using wind currents and updrafts to keep them aloft for long periods with the minimum of effort, just the occasional tilt of the wings to change direction. They are wonderful examples of energy-conserving flight.
This article describes some of the interesting things about hawks.
Hawks, like most birds, are tetrachromats having four types of colour receptors in the eye. These give hawks the ability to perceive not only the visible range but also ultraviolet light. Other adaptations allow for the detection of polarised light or magnetic fields.
…Hawks are known for their unique mating season. The method the hawk uses to reproduce is different from most. The male and female will fly together in a circular motion. Once they reach a certain height, the male will dive toward the female and then they will raise back to the height again. The two birds will repeat this until finally the male latches onto the female and they begin to free-fall down to earth. In one year, a female hawk will lay about five eggs. Both the male and the female will cater and take care of the eggs for about a month until they hatch. The male and the female create their nest before the mating season and improve it together during the nesting season. The two birds usually make their nest prior to mating. Some species of hawks tend to be monogamous and stay with the same mating partner their whole lives.
Hummingbirds are fascinating for a different reason. While hawk flight is so energy-efficient, hummingbird flight seems to be the opposite. Their wings beat so fast that they are a blur but it enables them to do vertical takeoffs from rest, shooting straight up into the air, and to hover in mid air. Needless to say this uses up a huge amount to energy.
This article lists 25 interesting facts about hummingbirds. Here are some.
An average hummingbird’s heart rate is more than 1,200 beats per minute. In comparison, a human’s average heart rate is only 60 to 100 beats per minute at rest.
…A hummingbird must consume approximately one half of its weight in sugar daily, and the average hummingbird feeds five to eight times per hour. In addition to nectar, these birds also eat many small insects and spiders, and may also sip tree sap or juice from broken fruits.
…A hummingbird’s maximum forward flight speed is 30 miles per hour. These birds can reach up to 60 miles per hour in a dive, and hummingbirds have many adaptations for unique flight.
…A hummingbird’s wings beat between 50 and 200 flaps per second depending on the direction of flight, the purpose of their flight, and the surrounding air conditions.
It is incredible that such a tiny bird can achieve such high speeds.
The products of the evolutionary process never cease to amaze.
You should see hummingbirds dive bombing cats. They are going the whole 60 mph in a dive and pull out inches from the cats. Ive watched cats flee in terror from a couple of hummingbirds who were feeding from the feeders in our yard. No cats within at least fifty feet in the open. Amazing stuff.
It’s not just hummingbirds that are in the consume approximately one half of its weight […] daily category. A number of smaller animals like mice are similar (though their food sources also tend to be less efficient than a hummingbird).
It’s a version of the square-cube law. While everybody knows the square-cube law for supporting mass and why elephants have such thick legs (weight goes up as the volume, support goes up as the cross-sectional area of the legs), there’s a metabolism version of it too: heat generation goes up as the volume, but heat dissipation goes up as the skin area. The smaller any sort of heat-regulating animal is (and both birds and mammals qualify) the more they have to eat proportionate to their mass to keep everything running within its working range.