Hardy Hummingbirds Survive the Polar Vortex Plunge

On January 13, I accompanied Mark Armstrong to another hummingbird banding in Knoxville, Tennessee, just six days after local temperatures plunged to a record low of 2° F during the Polar Vortex.

Photo credit:  Mark Armstrong

A wintering hummingbird was discovered at the home of Christal Pettit early in October.  Soon after she had taken her feeders down thinking all the migrating Ruby-throats had left, her husband noticed a hummingbird hovering in an area where a feeder once hung.  Krystal quickly made nectar and hung a feeder out and her wintering hummingbird has been steadily present since.

Christal (left) and her daughter, Evan, watch as Mark Armstrong, Master Bander of hummingbirds bands the hummingbird and measures its wing, tail, and beak.  Each of these measurements give the bander information about the gender and species of the hummingbird, in this case, a mature female Rufous.

Mature females look alike in the three Selasphorus species which include the Broad-tailed, Rufous and Allen's hummingbirds. They each have green feathered backs and, usually, a cluster of reddish-orange gorget feathers on their throats.  The Rufous species is by far the most commonly found wintering hummingbird in Tennessee and in the eastern United States.

Mark uses a straw and blows the feathers away from the belly to assess the amount of fat the hummingbird has stored.  This hummingbird's fat was rated a "one" with zero indicating no fat deposits, and she weighed 3.9 grams, a healthy weight for this species.  This means she is receiving enough nutrition to not only nourish herself, but to store fat reserves for later use.  

Additionally, this mature female was molting feathers--losing worn feathers and growing new ones to replace them.  In the image above, you can see the three brownish old feathers with frayed ends on the left compared to her new grayish feathers with smooth edges.  She was also showing new feather growth on her body and head. Molting, in general, is a sign of good health and nutrition and Mark commented that this bird was molting more heavily than he had seen in other hummers he's captured this season.

Photo credit:  Mark Armstrong

Above you can see the Rufous female tail feathers compared to the male's tail feathers shown in my previous post.  Females have white tips on their three outer tail feathers on each side.  The white tips lack pigment, which adds strength to feathers, and are worn more easily during the process of nest building and feeding young during the breeding season.

Above, Mark and Christal give the hummingbird a drink before she is released.

It is a joy to meet the people who host these wintering hummers and to share in their excitement about their visitors.  To date, Mark has banded nine Rufous hummingbirds in east Tennessee and recaptured four--three that he previously banded, and one bird that was banded in Tallahassee, FL last year as a juvenile. Recapturing a bird after it is banded enables researchers to learn more about the age, health and migration patterns of the hummingbirds that are migrating east for the winter.

Photo credit:  Billie Cantwell

Other reports on area hummingbirds varied after the severe weather front moved through. Billie Cantwell and Colin Leonard's male hummingbird, that first began wintering at their home in 2011, continues to frequent their feeder.  The above image, taken several days after the severe weather, shows the light arrangement that Billie and Colin hung over the feeder to keep the nectar from freezing.  The light is a 150 watt flood light or spot light that is non-LED and gives off heat.  When temperatures were in the single digit range, Billie moved the feeder closer to the lamp; when the temperature moves up to 17 F or higher, the feeder is hung farther away.

Photo credit:  Jon Dempersmier

Above, another female hummingbird continues to winter in Seymour, Tennessee, and was photographed at the feeder by Jon Dempersmier January 8th, the day after the record cold.  Though Mark has not recaptured this bird, yet, she wears a band and is likely the Rufous female that he banded at Jon's home last season.

Photo credit:  Katheryn Noblet

The adult female Rufous, above, that made a fall migration stop-over at Katherine Noblet's home in Johnson City, departed prior to the severe weather and was last seen on December 4th.

Photo credit:  Marnie Mitchell

The mature male Rufous pictured above has been wintering in Smithville, TN, at the home of Tommy and Virginia Curtis, and was seen frequenting the feeders following the severe front.  He departed on January 9th, likely, to resume migration.

Photo credit:  Wally Manspeaker

The image above was taken on January 6th, in Russellville, TN, as the artic air was approaching with high winds that rocked the feeder and brought windchills of -14 degrees F in east Tennessee.  Wally's female Rufous was among the several that were not seen on January 7th, the morning of the lowest temperature drop.  Included in this group were Sherry Ladd's mature male Rufous, Candy Casey's adult female Rufous, and Jim Turnblazer's juvenile female Rufous.  

Candy Casey wrote a letter to Bob Sargent on January 7, asking about the disappearance of her bird, fearing that the female Rufous had perished in the cold as the front moved in.  His response was interesting and reassuring.

"Twenty-five years of banding records tell me that most ADULT Rufous, male or female, tend to leave their primary winter site(s)...between December 15 and January 15.  If they leave earlier than that, it is...in my opinion, because their easy supply of tiny bugs and spiders has been diminished.  This occurs often when winter deepens.... I would bet the farm that your little cold-hardy female Rufous has gone south and then will turn westward toward her nesting grounds in Washington, Oregon, British Columbia or maybe even SE Alaska.  Don't take your feeder down just in case she's hanging out somewhere close,  In my opinion she is not likely to be dead but merely moved on to the south or southwest."

Many of us will be watching for the return of these birds next fall and looking forward to re-capture reports that will affirm their survival and successful migration.  It is clear that this hardy strain of eastern-migrating Rufous hummingbirds is challenging our notion of hummingbird frailty and raising many questions about their winter survival strategies.

In east Tennessee, report winter hummingbird sightings to Mark Armstrong at Woodthrush@bellsouth.net or 865-748-2224. For a list of contact information for other eastern areas, visit winter reporting on the Hummer Study Group website or report sightings to Bob and Martha Sargent, Rubythroat@aol.com or 205-681-2888.

Links and Resources:

What is a Polar Vortex?
Climate Change and the Polar Vortex

Western Hummingbirds Wintering in Tennessee
Allen's Hummingbird in Tennessee
Rufous Hummer in Knoxville 
Other blog posts on Wintering hummingbirds in Tennessee
In recent years, fourteen species of hummingbirds have been documented in the east during fall and winter months.  Visit Bob Sargent's information on wintering hummingbirds
Bob Sargent describes the Rufous Hummingbird as very cold-hardy.
Sargent on wintering Calliopes and the Allen's Hummingbird
Hummingbird banding
Hummingbirds in watercolor
Hummingbird art on Vickie's Sketchbook blog
Cornell's All About Birds:  Rufous Hummingbirds
Bird Banding Laboratory
Birds of North America--I highly recommend subscribing to the online version for detailed descriptions of all North American bird species.