Caterpillar-craving Chickadees

Dr. James J. S. Johnson

Lay not up for yourselves treasures upon earth, where moth and rust doth corrupt, and where thieves break through and steal; but lay up for yourselves treasures in heaven, where neither moth nor rust doth corrupt, and where thieves do not break through nor steal.

(Matthew 6:19-20)

Although moths are famous as pests, to humans (since Biblical times, as the above quote shows), moth caterpillars are desired and delectable food for hungry chickadees—and chickadees need lots of food energy for fuel, to live out their brave and busy lives.

Chickadees are brave little birds, resilient enough to tough out winter weather, while less resilient birds migrate south for milder climes. 

The resilience of these petite yet robust little passerines was recently appreciated by Alonso Abugattas (a/k/a “Capital Naturalist”*), in the May (A.D.2023) issue of CHESAPEAKE BAY JOURNAL. (*This is the same Alonso Abugattas, longtime natural resources manager for Arlington in Virginia, who was recognized as a “Regional Environmental Champion” by the Washington metro area’s Audubon Naturalist Society.)

One of my favorite birds is the chickadee.  The Carolina chickadee (Poecile carolinensis) is the one we usually see around the Washington, D.C. area.  The nearly identical black-capped chickadee (Poecile atricapillus) usually lives farther north, though the species overlap a bit in central and south Pennsylvania.  The black caps are known to venture farther south during irruption years, when there is severe cold weather or food shortage.  The energy and resourcefulness of chickadees, along with biological adaptations, allow them to live in our yards year-round.  In winter, when most other insect-eating birds migrate [south], they augment their diet with seeds.  People who feed birds are likely to find chickadees, which are particularly fond of black oil sunflower seeds, to be among their best customers. …

Chickadees have several ways of conserving energy [i.e., body heat when it is cold outside]. They fluff their feathers and grow up to 30% more feathers in winter to trap body-warmed air. They can also enter torpor [i.e., overnight semi-hibernation metabolic slowdown], reducing their body temperatures by as much as 20 degrees on winter nights to conserve fat reserves.

[Quoting Alonso Abugattas, “Meet the Carolina Chickadee, Resourceful ‘Bringer of News’”, CHESAPEAKE BAY JOURNAL, 33(3):39 (May 2023).]

In Texas the Carolina Chickadee is a year-round resident in the north (even as far as the northeast corner of the Panhandle), east, and central (including much of the Edwards Plateau) parts. [See Roger Tory Peterson, A FIELD GUIDE TO THE BIRDS OF TEXAS AND ADJACENT STATES (Boston: Houghton Mifflin, 1988), a/k/a BIRDS OF TEXAS, at pages 141, plate 38, & 172.]

Chickadees are easy to identify: “Chickadees are the only small birds with the combination of black cap, black bib, white cheeks. … [noticeably] smaller than sparrows.” [Quoting Peterson’s BIRDS OF TEXAS, cited above, at page 172.]

However, distinguishing between Carolina Chickadees and Black-capped Chickadees is not so easy.  In fact, these chickadees belong to the same created (on Day 5 of Creation Week) created “kind” of bird, because they successfully interbreed. (In fact, other chickadee hybrids are known, such as hybrids of Mountain Chickadees with Black-capped Chickadees.)

Unsurprisingly, hybridization occurs where Black-capped Chickadees share ranges with Carolina Chickadees, such as in Colorado. [See Kelsey Simpkins, “The Chickadee You See Sitting on a Tree? It Might Be a Hybrid”, CU BOULDER TODAY (Oct. 22, 2022), posted by University of Colorado Boulder, at http://www.colorado.edu/today/2022/10/28/chickadee-you-see-sitting-tree-it-might-be-hybrid .] In fact, hybridization also occurs with the Black-capped Chickadee and its range-sharing cousin, the white eye-browed (but otherwise similar-looking) Mountain Chickadee.

Black-capped chickadee is by far the most common of the two i.e., of Black-capped Chickadees and Carolina Chickadees] and has a much wider range spanning pretty much the entirety of the USA and southern Canada, though they’re also found in Alaska.  Conversely, the Carolina chickadee is relatively confined to the southeastern USA.  The two birds converge [i.e., overlap in ranges] along a wide strip spanning from New Jersey to Kansas.  In terms of looks, the Black-capped chickadee is slightly larger than the Carolina chickadee [which is an advantage for preserving body heat in cold winters].  The Black-capped chickadee also has more strongly contrasting plumage, including a paler breast and underside of the body.  To confuse these birds further, they often hybridize (frequently!) across the strip where they meet, particularly when the Black-capped chickadees push further south during [winter] than they would usually do.  Hybrid Black-capped and Carolina chickadees are pretty much impossible to identify [apart from DNA studies].  . . .

However, where Black-capped and Carolina chickadees meet, they can learn each other’s songs which renders this form of identification quite useless! For example, most Carolina chickadees sing Black-capped songs in Pennsylvania, and about 60% sing both Black-capped and Carolina songs. This intermixing of songs causes chickadees to sing strange mixes of each other’s songs, leading to increased hybridization.

[Quoting “Do Carolina and Black-capped Chickadees Hybridize?” in “Carolina Chickadee vs Black-capped Chickadee: What Are the Differences?”, BIRDFACT (April 11, 2022), posted at https://birdfact.com/articles/carolina-chickadee-vs-black-capped-chickadee#:~:text=Carolina%20and%20Black-capped%20chickadees%20are%20not%20particularly%20related%2C,when%20they%20come%20into%20contact%20with%20Carolina%20chickadees .]

The observed behaviors of chickadees are a study in themselves—they have special habits of communication (including vocalized “talking” and visual display “body language”), courting, breeding and nest life (including nest-building, egg laying, incubation, nurturing hatchlings, etc.), territory defense, and more. 

One such behavior is territory defense, a behavioral habit that is unusual among North American passerine songbirds. In particular this has been observed of Black-capped Chickadees, though there is not reason to suspect this habit is absent among its southern Carolina cousins.

Black-capped Chickadees are unusual in terms of territory [stewardship]. Like some other birds, they hold both breeding and nonbreeding territories, but unlike any of our other common birds, their nonbreeding territory is occupied and defended by a flock and not by an individual bird or mated pair.  These flocks are highly structured [i.e., organized] and have predictable patterns of movement.  …

In late summer after the young [fledglings] have dispersed, Chickadees gather into small flocks that remain together until the start of the next breeding season.  … A flock usually forms around a dominant pair that has just finished a successful brood.   The flock contain six to ten birds, some juveniles, some paired adults, and some single adults.  It establishes a feeding territory which it defends against other neighboring flocks. …

Once the breeding phase starts [in spring], winter flocks break up and you will have fewer Chickadees at your feeder.  If one or two pairs remain in the area to breed, you may see the female do Wing-quiver [visual display] as she is fed by the male in courtship, and later you may see the young [hatchlings] do Wing-quiver as they are fed by the parents.

[Quoting Donald W. Stokes, A GUIDE TO BIRD BEHAVIOR, VOLUME I (Little, Brown, 1979), at pages 166, 171, 173]

Chickadees are also famous for another habit:  gobbling up caterpillars!

So, if you dislike swarms of insects (such as flies) during summertime, or if you fear moths marring your beautiful clothing (see Matthew 6:19-20), you should appreciate the moth-munching insectivorous diets of chickadees:

Chickadee parents feed their young almost exclusively on insects. Caterpillars [i.e., crawling insect larvae of butterflies and moths] are their favorite. It takes about 9,000 caterpillars to raise one brood. Studies have shown that when insects aren’t available, the young [chickadee hatchlings] can die if fed only seed. This is why chickadees prefer to nest near native trees (and, in turn, native insects) as opposed to yards with nonnative plants [that are less “hospitable” to the insect populations that chickadees prefer to eat]. Their reproductive success is at stake.

[Quoting Alonso Abugattas, “Meet the Carolina Chickadee, Resourceful ‘Bringer of News’”, CHESAPEAKE BAY JOURNAL, 33(3):39 (May 2023).]

Caterpillars provide more metabolic value than just nutritious protein; because caterpillars contain carotenoids, eating caterpillars helps chickadee feathers to be colorful, bright, and shiny.

So, as moths (including their caterpillar larvae) remind us to store up incorruptible treasures in Heaven (Matthew 6:21), we can also appreciate how God has purposed many of those lepidopteran caterpillars to fuel the brave and busy lifestyles of chickadees.