Seasons of the Hummingbird



Some sahuaros fell victim to record cold in 2011.

The Sonoran Desert does have seasons.   Some visitors think that there are only two:  spring and Hell.  We do have a winter, but it's a short one.  One of the reasons we live here is to escape cold weather.  Winter usually begins around mid-December and ends mid-February.  Temperatures are normally in the 50's and 60's, but there are a few days when the daytime temps plunge to 18 degrees F.  Weather that cold takes a toll on Sonoran Desert vegetation, which on average can bear maybe the low 20's.  Last year, we had record cold temperatures over a period of four days.  This punishing cold killed a number of cactus and desert trees.  Even some of our age-old symbols of the soutwest, the sahuaro, succumbed. 

On hard freeze nights (and days), I hang Christmas lights on my hummingbird feeders to keep the nectar from turning to ice.  The year-round hummers, the Anna's and Costa's, must have food within four hours of coming out of their nightly torpor.  Torpor is similar to hibernation, but unlike hibernation--which may last months--torpor lasts days or hours depending upon the animal's needs.  Hummingbirds go into torpor mostly at night when they need to conserve energy that would otherwise be used to keep them warm.  Their metabolism slows to a point that barely sustains life.  In this state, they appear to be deeply sleep, which is, in part, true.   Torpor enables these flying jewels to use about 50% less energy.

Keith took this shot of a female Rufous on her nest
at the Arizona-Sonoran Desert Museum's hummingbird aviary.

Another Desert Museum photo, this one of a Violet-crowned hummer.

It takes the hummingbird about 20 minutes to come out of torpor and fire up its metabolism for the day.  Once all vitals are back to normal, the bird must feed.  I have carried out fresh nectar on particularly cold days and been surrounded by distressed birds frantic for nourishment.  One female Anna's was so anxious she perched on my hand to feed.  That was a moment I will forever cherish.

When our second season, Spring, rolls around migrating hummers return north, heading as far as Alaska.  They make rest stops at gardens and nectar feeders along the way, fueling their amazing journey.  At this time, we look forward to seeing the orange-beaked Broad-billed, the slender but noisy Black-chinned, and our two flying copper pennies--the Rufous and Allen's.  Our year-rounders begin to nest as early as January.  They build tiny, two inch diameter nests made from bits of plant material, hair, and even insect skeletons.  The inner nest cup is lined with soft bits of fur, down and feathers.  The most important component is an unusual one--filaments of spider- and cobwebs which bind together the nest materials and attach it to the nest host.  In the Sonoran Desert, the host is often a cholla.  The spider webs allow the nest to stretch and contract, keeping mother bird and chicks snug and warm.   On a recent visit to the hummingbird aviary at the Arizona Sonoran Desert Museum, a docent told us that the museum stocks the aviary with spiders to ensure an adequate supply of these important nest binders.

By Summer, the hummingbird chicks have fledged and headed to new territory.  Our hummer population drops dramatically, and so does our grocery bill for sugar.  In the Fall, which begins in  August for many migrating hummers, our feeders are mobbed with hungry birds.  Again, we see the Rufous, Black-chinned, Broad-billed, and Allen's.  Many juvenilles jostle for positions on the feeding ports.   By late October, the migrants are gone, leaving us with our colorful Anna's and Costa's. 

The hummingbird cycle of life has come full circle, and the four seasons have contributed their part in the Sonoran Desert.



A Broad-billed poses for Keith at the Desert Museum's aviary.