In Our Backyard

We see quite a few hummingbirds in our yard.  They are among my favorite things to watch - they are pretty fearless, and will come right up to us.  I expect because they want us to get out of their territory.  They haven't learned much about sharing yet.

Hummingbirds are among the smallest of birds, most species measuring in the 3–5 inch range. They can hover in mid-air by rapidly flapping their wings 12–80 times per second (depending on the species). To conserve energy while they sleep or when food is scarce, they have the ability to go into a hibernation-like state (torpor) where their metabolic rate is slowed to 1/15th of its normal rate.  They are also the only group of birds able to fly backwards.  They can fly at speeds exceeding 34 mph!

Hummingbirds drink nectar, a sweet liquid inside certain flowers. Like bees, they are able to assess the amount of sugar in the nectar they eat; they reject flower types that produce nectar that is less than 10% sugar and prefer those whose sugar content is stronger. Nectar is a poor source of nutrients, so hummingbirds meet their needs for protein, amino acids, vitamins, minerals, etc. by preying on insects and spiders.

Hummingbirds drink by using protrusible grooved or trough-like tongues. Hummingbirds do not spend all day flying, as the energy cost would be prohibitive; the majority of their activity consists simply of sitting or perching. Hummingbirds feed in many small meals, consuming many small invertebrates and up to twelve times their own body weight in nectar each day. They spend an average of 10–15% of their time feeding and 75–80% sitting and digesting.

With the exception of insects, hummingbirds while in flight have the highest metabolism of all animals, a necessity in order to support the rapid beating of their wings. Their heart rate can reach as high as 1,260 beats per minute!  They also consume more than their own weight in nectar each day, and to do so they must visit hundreds of flowers daily. Hummingbirds are continuously hours away from starving to death, and are able to store just enough energy to survive overnight.

Hummingbirds are for the most part unsociable. In fact, the adjectives pugnacious and feisty are often appropriate. When more than one hummingbird is around, it is often a scene of repeated high-speed chases. In fact, male and female hummingbirds do not form a pair-bond after mating and the female is left to care for eggs and chicks alone.

Hummingbirds do not need the help of other hummingbirds, either to locate food or fend off predators. Other hummingbirds are competitors for the flower nectar upon which they thrive. The help that a male might provide a female does not outweigh the burden of having a male around competing for food.

What is all this fighting about? Plants take time to secrete nectar into their flowers. In an ideal world, hummingbirds should time their visits to flowers to take advantage of a full load. But they wait to feed at a flower at the risk of other hummingbirds beating them to the punch. It is therefore worth the effort for hummingbirds to chase away competitors so they have access and control of their favorite flowers.

In many cases, hummingbirds defend small territories around a favorite flower patch, and do so even during brief stop-overs for refueling during migration. Where many species live together, the large species attempt to dominate flowers and get the biggest drinks of nectar and smaller species try to sneak in for a few sips.


Do you attract hummingbirds to your yard?

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Venus Transits the Sun

We've had quite an interesting couple of weeks, astronomically speaking.  First the solar eclipse at the end of last month, and just Tuesday, Venus transited the sun!

When Venus passes directly between earth and the sun, we see the distant planet as a small dot gliding slowly across the face of the sun. Historically, this rare alignment is how we measured the size of our solar system.
Transits of Venus have a strange pattern of frequency. A transit will not have happened for about 121 ½ years (prior to 2004, the last one was 1882). Then there will be one transit (such as the one in 2004) followed by another transit of Venus eight years later (in the year 2012). Then there will be a span of about 105 ½ years before the next pair of transits occur, again separated by eight years. Then the pattern repeats (121 ½ , 8, 105 ½ , 8).

If Venus and the earth orbited the sun in the same plane as the sun, transits would happen frequently. However, the orbit of Venus is inclined to the orbit of earth, so when Venus passes between the sun and the earth every 1.6 years, Venus usually is a little bit above or a little bit below the sun, invisible in the sun’s glare.

We watched it using a similar method as we used to watch the eclipse - a pinhole projector.  We used binoculars to enhance the image of the sun projected on the paper though.  And it worked!

You can see it as a little black dot on the white spot of the sun.

Enlarged and enhanced, you can see it slightly larger.

Did you miss this one?  Are you looking forward to the next transit? Mark your calendars - you will be able to see it in 2017, in about 38536 days.

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