Episode 17: Shownotes & Transcript

Welcome to The STEM Sessions Podcast.  I am your host, Jarl Cody.

Mid-June of 2021, noticed a bird building nest in my trumpet flower plant

• Identified as a Northern Mockingbird
• Carrying sticks and grass into the trumpet flower, then fly out and repeat
• I could watch nest increase in size over time by looking from below

Heard northern mockingbirds in my neighborhood for years

• Sing all day and all night
• I’ll wake up at 3A and hear them if my window is open
• Knew nothing about the species or its life cycle

Beginning of July, noticed the mockingbirds were carrying insects instead of grass

• Around the fourth, started hearing the sounds of babies screaming for food when parents stopped by

Few days later, two babies were hopping around the canopy of the trumpet flower plant, and one was hopping around the yard

• Parents kept watch, and kept feeding them
• Watched the babies get bigger, lose their baby feathers
• Explored more and more of my backyard
• Actually started flying and not just hopping around
• Eventually, they all left our yard

Researched a lot about northern mockingbirds to make sure I wouldn’t cause them to abandon the chicks

• Figured I’d share the research now

And like the last episode, I’m reading from an outline instead of a script. 

This is The STEM Sessions Podcast Episode 17 – The Northern Mockingbird

The Northern Mockingbird. 

• Scientific name Mimus polyglottos, meaning the “many-tongued mimic” 
• Sometimes called the American Nightingale
• State bird of Arkansas, Florida, Mississippi, Tennessee, and Texas. 
• All night serenader. 
• Devoted parent. 
• Aggressive defender of its territory.

Medium sized songbird

• Slender body, small head, long legs, long tail feathers;
• Long thin bill with a very slight downward curve at the tip
• Wings are short and broad

Overall coloration is gray-brown

• Paler colors, sometimes white, on breast and underside
• Pale eyes

Colors become flashy in flight

• When wings extended, black underside with large white patch
• Outer tail feathers also flash white when flying
• When running on open ground, it often stopes every few feet and partly spread its wings to flash its white patches; may be territorial or stirring up insects

Exhibits limited sexual dimorphism

• Male is slight larger than female; with body lengths of 8.5 to 10 inches (21.5 to 24.5 cm) for the male, and 8 to 9 inches (20 to 23 cm) for the female
• Male about 10% heavier at 51 g (0.11 lb) compared to 47 g (0.10 lb) on average
• Coloration the same, except for dark tail feathers on female

Populations are currently stable or increasing

• Traditionally associated with the U.S. Southeast, including Texas
• Today, crowd sourced sightings map on ebird.org shows them all over North America
• Hotspots in Texas, the south eastern US, Cuba, Puerto Rico, etc
• But frequently seen in Mexico, the US West, and new England
• Less frequently in norther states and Canada

Range has fluctuated over the centuries

• Late 1700s to early 1900s, pet trade decreased wild population in the northern ranges
• Pet trade was stopped, population rebounded
• Recent decades expanded north, especially into New England, perhaps result of widespread planting of multiflora rose, a source of favorite berries and good nest sites.
• mainly a permanent resident, northernmost populations may move south during harsh winters

Three recognized subspecies of the northern mockingbird

• M p polyglottos: Found in the southern and eastern United States
• M p leucopterus: Also called the western mockingbird; found in western NA from the plains to the pacific ocean, and in Mexico
• M p orpheus: found in Cuba, Dominican Republic, Puerto Rico, and Caribbean Islands

Subspecies appear very similar to each other, primarily differing in average size

• Mockingbird on the islands (M p orpheus) tends to be smaller than the southern and eastern mainland bird (M p polyglottos)
• Western mockingbird (M p leucopterus) is largest of the subspecies but has shorter tail

Famous for its songs

• Often repeats a phrase 5-7 times before switching to the next piece of music
• One study recorded at least 39 songs, and 50 distinct calls
• As its name “many tongued mimic” implies, it can parrot nearly any sound in their immediate environment
• Calls include other birds, car alarms, cell phone ringers, musical instruments, dogs barking

Male sings all day and all night to attract a mate and establish his territory

• I can personally attest to “all day and night” not being an exaggeration
• If bedroom window is open, commonly hear him singing all night; sometimes annoying, sometimes pleasant
• At first, I woke up several times confused as to what I was hearing, because I couldn’t understand how could something make that many unrelated sounds

Males and females both reach sexual maturity at approximately one year old

• Breeding occurs in spring and early summer depending on the climate
• Male sings to attract nearby females
• Courtship involves the male and female chasing each other through the male’s territory
• Male tries to dazzle the female by leaping and stretching his wings to show the aforementioned white patches
• Highly aggressive males are preferred

After finding his mate, male begins building nest

• Tree or shrub, typically no higher than ten feet above ground
• My mockingbirds built nest about six feet off the ground
• Male uses twigs to builds foundation, and weeds, grass, leaves to build the cup
• Female lines cup with softer materials like animal hair, moss, small roots

Female lays two to six eggs in a clutch

• Greenish to bluish gray, blotches for camouflage
• Approximately an inch in size
• Only the female incubates the eggs
• Hatch after 11-14 days
• Both parents actively feed and protect the hatchlings

Chicks leave nest after 10 to 12 days

• Fledglings can’t fly well; short awkward flights like domestic chickens
• Run along ground more than fly
• Still have baby feathers, but adult flight feathers quickly grow in
• Hide in bushes and taller grass
• Male becomes primary care giver, and is responsible for feeding, protecting, and teaching the fledglings to find food, but female is also involved

Fledglings independent after 10-15 days

• Flying is still a bit awkward, but they can get high in tree for protection and find their own food

During fledging process, parents begin building a new nest for their next brood

• Up to four broods in a year depending on weather and available resources
• New nest each brood
• Generally monogamous for the length of the breeding season, and sometimes for life
• Female may choose a new mate between broods if male does not provide enough feeding or protection

My observations more or less tracks with this timeline and description

• Started building nest around June 13
• First heard chicks on July 3; so likely hatched around June 29 or June 30
• First chick left nest on July 8; second and third on July 9
• By July 15, fledglings could fly well enough to leave the ground for higher tree branches and the roof; though wing and tail feathers had not fully grown in
• On July 18, and still heard the occasional baby cheep from high in my cypress trees, and still see parents, but not feeding anymore
• By July 22, everyone had moved on

Both parents are very protective of their territory, nest, eggs, and chicks

• Attack and yell at animals they deem to be threats
• I saw them dive bomb squirrels, other birds, and feral cats
• Recognize returning threats, calling and attacking earlier each time they see it
• Study showed as the same human approached and threatened a nest, alarm calls and attack flights increased each day
• When a new human approached, alarm calls and attack flights immediately decreased
• We gave the parents, nest, and babies plenty of space
• Parents in my backyard never attacked or yelled at us; maybe they understood we weren’t a threat

Diet of northern mockingbird mostly insects and berries and fruit

• Depending on location, could be a 50/50 split between insects and plants with insects in spring summer and fruit in fall winter
• Personally saw the parents bring back grasshoppers, beetles, and worms
• Caterpillars, ants, wasps, spiders, snails also on the menu
• Discovered the parents using my compost bin as a buffet, pulling out worms, other insects, and pieces of fruit
• Fledglings also hung around compost pile for easy food and warmth

Abundance of food can influence the sex ratio of offspring

• Male chicks require more food (larger body size)
• Bias for raising male chicks at beginning of season when food is more abundant
• Food was plentiful in my yard and neighborhood, but no idea what the sexes of my three chicks were

Although they are smaller birds, the northern mockingbird’s aggressive behavior makes them less appealing targets of predation is subject to predation

• But owls and hawks may still hunt adults if no other food is available
• Fledglings are vulnerable to raptors and domestic and feral cats because they often run along open ground
• Eggs and nestlings also vulnerable to raptors, cats, sometimes snakes so well built, hidden, and defendable nest is vital
• Weather patterns such as cold winters, mild winters, drought also impact population numbers

Watching a pair of northern mockingbirds raise three chicks was stressful

• Couldn’t use our backyard as we normally do
• If too close to the nest when parent stopped by with food, had to back off
• Had to take care watering when fledglings were running around
• Couldn’t trim bushes or trees
• Babies made noise from sunrise to sunset
• Humans interpret their squeaking calls as frantic or being in danger, which triggers us to want to help, but the parents obviously knew what they were doing

Along with the stress, experience was educational and rewarding

• First had to identify and research the type of bird to make sure I didn’t do anything to make the situation more difficult
• I wouldn’t have learned any of the information in this episode had they not selected my trumpet plant
• Even bought a good monocular so I could observe from a far

It’s been over a month since the babies successfully fledged

• I see and hear the occasional mockingbird, and I’m sure the parents have moved to a new nesting site
• I always want to encourage wildlife, so I took it as a big compliment they chose our yard for a nesting site
• And I very much look forward to the next experience

Thank you for listening to The STEM Sessions Podcast. 

This episode was researched, written, and produced by Jarl Cody.

Here at The STEM Sessions, we strive to share accurate and complete information, but we also encourage you to do your own research on the topic we discussed to confirm the accuracy of what we’ve presented.  Corrections are always welcome.

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Finally, please remember STEM is not a tool exclusive to experts, policy makers, and talking heads.  Every presenter is susceptible to unconscious and, sometimes, deliberate bias, so always verify what you read and what you’re told. 

Until the next one, stay curious.

REFERENCES

“Northern Mockingbird”
https://www.audubon.org/field-guide/bird/northern-mockingbird

“Northern Mockingbird”
https://ebird.org/species/normoc

“Northern Mockingbird”
https://abcbirds.org/bird/northern-mockingbird/

“Mimus polyglottos – Northern Mockingbird”
https://animaldiversity.org/accounts/Mimus_polyglottos/

“Urban mockingbirds quickly learn to identify individual humans”
Douglas J. Levey, Gustavo A. Londoño, Judit Ungvari-Martin, Monique R. Hiersoux, Jill E. Jankowski, John R. Poulsen, Christine M. Stracey, and Scott K. Robinson
https://www.pnas.org/content/106/22/8959

“Nestling Sex Ratios in Two Populations of Northern Mockingbirds”
Brett E. Schrand, Christopher C. Stobart, Dorothy B. Engle, Rebecca B. Desjardins and George L. Farnsworth
https://sci-hub.se/https://doi.org/10.1656/058.010.0215