Peter Repetti

Does solar irradiation drive community assembly of vulture plumage microbiotas? - Animal Microbiome Background Stereotyped sunning behaviour in birds has been hypothesized to inhibit keratin-degrading bacteria but there is little evidence that solar irradiation affects community assembly and abundan...

Graves et al. (2020) found vulture plumage is dominated by Deinococcus, a bacterium famous for surviving extreme radiation. Dark, melanized feathers had the most. Feather-degrading microbes were nearly absent. Sun exposure doesn't just clean; it curates!

Turkey Vulture perched atop a broken tree snag with wings fully spread in the horaltic pose, backlit by warm morning light. Dark brown-black plumage with lighter brown feather edges visible across the wings and tail. Small red featherless head in profile, including sharp hooked beak. Dark, blurred foliage behind. September 9, 2025 @ 8:37 AM. Durham, North Carolina.

This isn't just a power pose. Turkey Vultures drop body temp overnight to save energy, then spread their wings in the AM to reboot: solar-heating flight muscles, UV-killing feather bacteria, baking off parasites. This "horaltic" pose is maintenance and power. #TUVU #PowerPose #BirdOfTheDay

Biophysical optimality of the golden angle in phyllotaxis - Scientific Reports Scientific Reports - Biophysical optimality of the golden angle in phyllotaxis

Why 137.5°? The golden angle ensures each new leaf or primordium is maximally displaced from all previous ones — optimal packing, minimal self-shading. Sunflower heads show it most dramatically: 34 spirals one way, 55 the other. Both Fibonacci numbers. This geometry is everywhere in plants.

Fig. 6: 3D model. 3 rules explain the spiral: (1) divide along the shortest wall, (2) new wall must pass through the outer face, (3) displace the division point away from the oldest neighbor walls. Rules 1+3 are sufficient. The model tolerates substantial noise and works across starting shapes.

Fig. 1: Time-lapse confocal imaging of the moss apical cell dividing over 48 hours. Each division produces a new daughter cell (future phyllid) and a new apical cell. The divisions rotate in a spiral; average divergence angle 126.9°, close to the golden angle. All from one tetrahedral cell.

Vascular plants and mosses both produce Fibonacci-like spiral phyllotaxis, but diverged 450MYA. One uses auxin transport across a multicellular meristem to get the shape, the other does so via a single cell dividing such that new walls avoid oldest neighbors. Convergent evolution or deep homology?

Female Northern Cardinal perched on a bare branch in falling snow, facing the camera. Plumage puffed for warmth, showing warm buff-orange body, red-tinged crest dusted with snow, red-orange bill, and dark face mask. Snowflakes fill a soft gray background. February 19, 2025. Durham, NC.

She's not migrating. Cardinals don't use torpor; they depress nighttime body temp ~1.3°C, saving an estimated 10-16% on energy. In winter, diet shifts from insects to seeds. Fat reserves hit 3x summer levels. Puffed plumage traps warm air. Brrrrr.
#NOCA #WinterSurvivors #BirdOfTheDay

My shorebird/duck knowledge is severely lacking. I've heard of the BBWD, but never seen one in person! I'm making up for my deficit thought this morning at Barnegat Light State Park in NJ. It's been amazing. Many lifer birds!

The first time I saw ducks sitting a tree: 🤯

10 Fun Facts About the Barred Owl Maniacal laughter. Pink wings. Tree climbing. This bird has a lot going on.

See #5!

Barred Owl perched in a lichen-covered tree, facing the camera with dark eyes and a pale facial disc. Its breast and belly feathers are visibly soaked and disheveled from hunting crayfish, with one wing draped loosely around a branch. Talons visible. Overcast sky behind. September 7, 2025. Sandy Creek Park, Durham, NC.

This Barred Owl is still drying off after a successful crayfish hunt. Some apparently eat so many that their underwing feathers can turn pink (!) from the carotenoids, like a flamingo. The most opportunistic owl in North America; 85+ prey taxa documented. #BAOW #portrait #birdOfTheDay

What a talented beast!!

Amazing capture!

Two male Hooded Mergansers on still water, facing each other with crests fully raised, displaying the striking fan-shaped white patch bordered by black. Both birds show golden-brown flanks, black backs with white striping, and bright yellow eyes. Their reflections ripple in the water below. January 26, 2025. Durham, NC

Hooded Mergansers can change the refractive properties of their eyes to hunt underwater by sight. Built-in goggles via their transparent nictitating membrane. These two males are sizing each other up topside, but the real action is below the surface. #HOME #DivingForFood #BirdOfTheDay

My #BirdOfTheDay offering is this male bluebird feeding his mate, a mating ritual seen regularly in the spring in middle Tennessee.

#birds #canonbirdphotography #wildlife #BirdOfTheDay #bluebird

American Robin perched on a thick tree branch with its beak packed full of insects and invertebrates. The bird displays the species' characteristic dark gray-brown upperparts, brick-orange breast, and broken white eye ring. Soft green foliage fills the background, out of focus. The robin is in profile, facing left. April 23, 2025. Durham, NC

Beak crammed with every squishy invertebrate it could find. Maximizing prey per trip, minimizing flight time to the nest. The bill-loading strategy: efficiency over elegance. Parents of all sorts will recognize this energy math. #AMRO #Birds&Bugs #BirdOfTheDay

SLQ1 operates at ER–plasma membrane contact sites, running a pathway that opposes the LAZY auxin gradient. Wild-type gravitropism integrates both; their relative strengths set the growth angle! S149F breaks SLQ1 oligomerization, flipping the balance. Yoshihara & Spalding, PNAS 2025.

How do you find a gravity-sensing system nobody knew existed? First, knock out all 4 Arabidopsis LAZY genes so the plants can't stand up. Then, mutagenize thousands of those plants, and look for the one that pops back up! One aa change (S149F in SLQ1), and a whole new pathway emerges. #gravitropism

Please keep a list of obvious NZ omissions, especially if they were vocal enough to make you wish you had been able to recognize them. I'll refresh the NZ pack just as soon as I finish the 60-bird Europe pack I'm working on now.

Cleavage-independent activation of ancient eukaryotic gasdermins and structural mechanisms Gasdermins (GSDMs) are pore-forming proteins that execute pyroptosis for immune defense. GSDMs are two-domain proteins activated by proteolytic removal of the inhibitory domain. In this work, we repor...

In case you want more on gasdermin structures!

Recent cryo-EM structures reveal fungal gasdermins form heteromeric pores; unique for gasdermins. Signal transduction runs through amyloid scaffolds - same strategy as the mammalian necrosome - and fungal NLRs display 14+ distinct effector domain architectures. That's a lot of structural diversity.

Regulated cell death in fungi from a comparative immunology perspective - Cell Death & Differentiation Cell Death & Differentiation - Regulated cell death in fungi from a comparative immunology perspective

The fungal immune system runs on the same protein families as your innate immunity: NLR sensors, TIR signaling, gasdermin pore-formers. The pathways cluster in 2-3 gene operons, echoing bacterial defense islands. Billion-year-old toolkit, still in production.

Genetic Basis and Evolution of Structural Color Polymorphism in an Australian Songbird Abstract. Island organisms often evolve phenotypes divergent from their mainland counterparts, providing a useful system for studying adaptation under diff

The first candidate genes for structural blue in any bird were only ID'd in 2024, in Australian fairywrens. ASIP controls melanin; SCUBE2 may shape the feather nanostructure itself. Both are conserved across birds.

Male Eastern Bluebird facing directly toward the camera on a deck railing scattered with dried mealworms. There are several other bluebirds behind it, out of focus, creating a shallow depth-of-field effect. Vivid blue crown and wings, rusty-orange breast, dark eye staring straight ahead, directly at the camera. Durham, NC.

There is no blue pigment in this bird. The color comes from nanostructured keratin in the feather barbs, air channels that self-assemble and scatter light. We know the physics, but we are still working out the genetics that build the structures. #BirdOfTheDay #StareDown #EABL

The Osprey - Podcast Episode The Science of Birds - A deep dive into the life of Pandion haliaetus, a fierce, fish-loving raptor found across the globe.

This Science of Birds podcast was chock-full of interesting stuff. I'm gonna listen to it again now!

Founders Online: Home Founders Online: Correspondence and Other Writings of Seven Major Shapers of the United States (George Washington, Benjamin Franklin, John Adams, Thomas Jefferson, Alexander Hamilton, John Jay, James Madison)

Definitely wasn't expecting an osprey post to eventually lead me over to founders.archives.gov, but here we are.

Founders Online: Benjamin Franklin to Sarah Bache, 26 January 1784 Benjamin Franklin to Sarah Bache, 26 January 1784

Franklin was subtweeting G. Washington's org. in a private letter to his daughter. The Society of the Cincinnati still exists 242 years later as a "harmless historical society." (?) The eagle became one of the most recognizable national symbols on Earth. His critique didn't age great. #coolstorybro

Bald Eagles regularly steal fish from Osprey (kleptoparasitism). Why evolve plunge-diving when you can bully the specialist? Re: making the eagle our national bird, Ben Franklin criticized this behavior in a letter, calling it “a bird of bad moral character.” #nocomment

Bald Eagles catch fish too, but differently. Three toes forward, one back, massive curved talons, crushing grip. They snatch from the surface and rarely submerge. Full immersion is risky for a heavy bird. Osprey plunge feet-first, sometimes fully underwater. Specialist vs powerful generalist. #BAEA