Sunday, September 14, 2008

Ruby-throated Hummingbirds


I’ve kept the hummingbird feeder hanging outside my kitchen window full of fresh, sugar water since noticing the first hummingbird zooming around my flower garden in March. Since then, there have been at least a few visiting “hummers” each week. They are always a welcomed sight while preparing breakfast in the morning or washing dishes after dinner in the evening as I’m fascinated by their incredibly fast wing beats and helicopter-like ability to hover in place and fly backward. In the last couple of weeks, the 2 or 3 regulars at our feeder have turned into flocks of ruby-throated hummingbirds (Archilochus colubris) resembling swarms of mosquitoes. To my amazement, these birds are consuming more than 4 cups of sugar water every day!

From March to May, ruby-throated hummingbirds migrate from Mexico and Central America to and through Texas. They store up fat reserves and increase their body weight by as much as 50% before migrating across the Gulf of Mexico in as few as 18 hours. They can show up in our yards, literally, overnight. Some will follow the bloom of spring flowers and insect hatches northward to their breeding grounds in the northeastern U.S. and southern Canada. They leave their northern breeding grounds as early as July and as late as December in Texas. Males lead both the northern and southern migration.

Similar to most bird species, the females bear the responsibility of building nests, laying eggs, and caring for the young. They build a walnut-sized nest of spider silk, lichens, and plant down. These well-built nests can even be reused the following year. This nest holds two pea-sized eggs which the female will incubate for 12-16 days. Young are fed regurgitated nectar, spiders, and insects for about 10 days. Multiple broods may be raised each year, and hummingbirds can live as long as 12 years.

Adult male ruby-throats have an emerald green back, iridescent ruby red throat that may appear black under some lighting conditions, and a forked tail without white tips. Adult females are larger than males with an emerald green back, white breast and throat, and a rounded tail with white tips. Young of both sexes look like the adult female. These amazing birds weigh only 1/8th to 1/7th of an ounce. They can fly backwards, sideways, up, down, and even upside down for short distances. Their normal heart rate of 650 beats per minute (bpm) increases to 1,250bpm during flight. While hovering, their wings beat up to 80 times per second. The energy needed to maintain this high level of activity is provided by nectar, small insects, and spiders which they feed on 50-60 times per day. Nectar is lapped (not sucked) from plants and artificial feeders using their tubular tongue which extends well past the tip of their bill.

These fascinating little birds can provide excellent wildlife viewing as males try to defend the feeder from intruding hummers, multiple birds at a time will hover around the feeder, waiting for an opportunity to swoop in for a drink of the sugar water, they chirp and chatter as if scolding each other for taking too long, and chasing each other around the yard like young children playing tag. Even more intriguing to me than watching their behavior around the feeder, is watching them feed on their natural food sources of althea, honeysuckle, salvia, zinnia, and lantana. Recently, I even had one make several charges out of the elm tree I was dove hunting under as if to run me away from its territory.

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