Understory: a bird guide for the places where your phone gives up

Aniruddha Sarkar — Sun, 11 Oct 2026 18:24:58 +0000

This is a submission for the Hacktoberfest Open-Source AI Challenge Week 1: Touch Grass

What I Built

Understory is a bird guide for the places where your phone gives up.

You point a microphone at a singing bird. It tells you what you are listening to using a model that runs on the machine, then writes a short field note: where the bird lives, and what it is probably doing right now. Then it gets out of the way.

The whole interaction is one press and one card. The note is appended to a plain markdown file, so the reading happens back at the car, not while the bird is still in front of you. The screen is the shortest part of the walk.

It is built for someone with an old laptop, no data signal, and no intention of uploading every recording of their local patch to somebody's cloud.

Understory  15:13  [offline guard: on]
  Heard: European Robin (99%)
         also Eurasian Blue Tit (60%)

  It is likely foraging for insects in a woodland area. It is probably
  searching for a mate or nesting material.

  (AI field note — a hint to look, not a tick on a list.)

  logged -> ~/.understory/fieldnotes/2026-10-11.md

Demo

No deployed link, on purpose: there is nothing to deploy. A tool whose whole point is that it needs no server is best shown the way you would actually use it, so the demo below is a real run with the offline guard switched on.

$ understory.py id robin.mp3 --lat 52.52 --lon 13.40 --offline
Understory  15:13  [offline guard: on]
  Heard: European Robin (99%)
         also Eurasian Blue Tit (60%)

  It is likely foraging for insects in a woodland area. It is probably
  searching for a mate or nesting material.

  (AI field note — a hint to look, not a tick on a list.)

  logged -> ~/.understory/fieldnotes/2026-10-11.md

$ understory.py id greattit.ogg --lat 52.52 --lon 13.40 --no-narrate --offline
Understory  15:10  [offline guard: on]
  Heard: Great Tit (100%)

  logged -> ~/.understory/fieldnotes/2026-10-11.md

$ understory.py id quiet-room.wav --no-narrate --offline
Understory  15:11  [offline guard: on]
  Nothing bird-shaped in that clip. Try again quieter, or closer.

Identification alone is ~6 seconds on a 4-core CPU. The written note adds 30–45 seconds, which is exactly why the phone goes in the pocket: you watch the bird while it writes, and read the card when you are done.

Code

Aniruddha120 / understory

Offline bird field guide: BirdNET identifies on the CPU, local Gemma 3 writes the field note. No signal, no cloud, audio never leaves the machine.

Understory

Point it at a bird. Keep your phone in your pocket.

Understory listens to a bird, works out what it is with BirdNET (open model runs on the CPU), and has Gemma 3 (open weights, served locally by Ollama) write you a short field note: where to look and what the bird is probably doing.

Everything runs on your machine. No API key, no account, and no internet — it keeps working in a valley with no bars, and the audio never leaves the device. A --offline flag hard-blocks every non-loopback socket so you can watch it refuse to phone home.

What the small model is and isn't allowed to say

Asked for plumage, a 1B model invents colours. Asked for a song, it invents calls (both happened during development). So its job is scoped to the two things it gets right reliably: where the bird lives and what…

View on GitHub

MIT licensed. 285 lines of Python, 61 lines of tests, no framework, no cloud SDK. ./setup.sh fetches both open models once; after that it runs with the wifi off.

How I Built It

Two open models, chained, both local:

Job	Model	Where it runs
Identification	BirdNET GLOBAL 6K v2.4 (6,522 species)	TensorFlow Lite, CPU, 1–4 s/clip
Field note	Gemma 3 1B (Q4_K_M)	Ollama, CPU, ~3 tok/s

The pipeline is deliberately boring, because the interesting part is what it doesn't do:

mic ──► 48 kHz mono WAV ──► BirdNET ──► top species ──► Gemma 3 ──► card + markdown log
                                                             │
                                                  no network, ever

BirdNET reports one hit per 3-second window, so collapse() keeps the best hit per species and counts the rest. A bird that sings four times across a minute is more convincing than one that appears once.

The offline guard is the part I care about. "It works offline" is a claim; I wanted it to be a test. --offline swaps out socket.connect and socket.connect_ex for the duration of the run and refuses anything that is not loopback:

@contextmanager
def offline_guard():
    real_connect = socket.socket.connect

    def guard(sock, addr):
        if addr[0] not in ("127.0.0.1", "::1", "localhost"):
            raise OSError(f"Understory is offline: blocked connection to {addr!r}")
        return real_connect(sock, addr)

    socket.socket.connect = guard
    try:
        yield
    finally:
        socket.socket.connect = real_connect

Loopback stays open because Gemma is served on 127.0.0.1. Everything else — a telemetry ping, a model download, an accidental analytics import — dies with a visible error instead of quietly succeeding. The test suite asserts both halves: a real loopback connection succeeds, and a connection to 1.1.1.1:443 raises.

Two things bit me on the way, and both are arguments for open tooling in miniature:

Ollama refused to pull Gemma. My installed version was too old and the registry answered 412 … requires a newer version of Ollama. The "upgrade" was a 1.4 GB download. The lazy fix was to skip the registry: fetch the GGUF from Hugging Face and ollama create it from a Modelfile. Ollama autodetected the gemma3-instruct template and it just worked. The model is a file. Nothing got to tell me no.
tflite-runtime blew up under NumPy 2. AttributeError: _ARRAY_API not found, because the runtime is compiled against NumPy 1.x. Pinning numpy<2 fixed it — two lines in requirements.txt and one confused afternoon.

Why Does Open Innovation Matter?

Four things here were only possible because every piece is open.

It runs where the birds are. No signal is the premise, not a limitation. A cloud API is not slow in a valley — it is absent. BirdNET on the CPU turns a dead zone into a working tool. This is the whole reason the app is shaped the way it is: the screen disappears because nothing about the interaction needs a network round-trip.

Nothing leaves the machine. Bird recordings are location data. What you recorded, and where, reveals your patch, your routine, and the hours your house is empty. With a local model I am not promising to delete your audio later; it was never sent. That is a structurally different guarantee from a privacy policy, and it is the one a birder would actually want.

It costs nothing to run, forever. No tokens, no quota, no per-request billing. I can leave it listening for an hour, or run it every morning for a year, and the cost is identical: the electricity. Metered APIs quietly teach you not to use your own tool — you start rationing the thing that was supposed to be fun. This one costs the same when you use it badly as when you use it well.

Every layer is swappable. BirdNET is one .tflite file. Gemma is one .gguf file. That is not a slogan; it is the reason the section below exists. When the small model got the field notes wrong, I did not file a ticket and wait for a release note. I changed the prompt, re-ran it, and then changed the model — in the same afternoon.

# same app, a different local Gemma, no code change:
understory.py listen --seconds 12 --model understory-gemma-4b

Where the Open Model Was Wrong

I asked Gemma 3 1B to describe a Great Tit's markings. It wrote:

"a small, dark greyish-brown plumage with a distinctive white stripe across the chest … a short, repetitive 'cheep-cheep' song."

That is wrong on both counts. A Great Tit has a black head, white cheeks, and a yellow breast split by a black stripe, and its song is a ringing two-note phrase, not a cheep. A 1-billion-parameter model on a laptop CPU is a fluent writer and a poor ornithologist. I had asked it for recalled facts, which is the one thing it cannot do reliably.

The fix was not a bigger model. It was to stop asking.

I checked that claim rather than trusting it. I swapped the 1B for Gemma 3 4B — one GGUF file, one command, no code change — and the prose really did get better:

"European Robins typically favour woodland edges and gardens with dense shrubbery. The bird is likely searching for invertebrates amongst the foliage."

That is a better sentence, and it is still only habitat and activity, so the scoping holds as the model grows. But it took four minutes and twenty seconds to write one note on this CPU, against about forty seconds for the 1B. A four-minute wait at the trailhead is not a field tool. The bigger model fixed the prose and broke the walk, which is the whole lesson: on a laptop in a hedgerow, a bigger model is a slower model before it is a smarter one. Money spent on parameters buys words, not time.

The prompt now asks only for where the bird lives and what it is probably doing — and explicitly forbids colour, markings, and song, because the birder can see and hear the bird, and markings belong in a field guide. I also added a confidence gate: below 50% the tool shows the hit but writes no note, so a coin-flip never gets dressed up in confident prose.

The notes got shorter, blander, and true. That is the right trade for a tool you are holding up at a bird: a bland true hint tells you where to look, and a confident false one sends you looking for a bird that is not there.

Taking It Outside

The first real use was my balcony. A sparrow came through, and the ID was right. The screen was on for about two minutes, then the phone went back in my pocket.

That is the whole report: one bird, correctly named, no drama. Which is the standard I would want a field tool judged by — the test is whether it is right when you are actually outside, not whether it is clever on a desk.

My Agent Session

Built with OpenCode. The session is saved here:

Understory: offline bird ID with BirdNET + local Gemma

You

Build an entry for the Hacktoberfest Open-Source AI Challenge Week 1 (Touch Grass). Theme: open-weight / open-source AI that gets people off the screen. Submission template is in the folder. Use DevRelay.

Agent

▸ get_challenge_details {"id": 79}

Input

{
  "id": 79
}

Output

Week 1 'Touch Grass', ends 2026-10-12T06:59Z. $2,450 / 17 winners. New project built in-window, one entry, tag #hf26challenge. Judging: Writing Quality (heaviest), Relevance, Creativity, Technical Execution, optional partner tech. Idea sparks: bird call ID with no signal, garden planner, run-club foliage routes.

Environment: Python 3.13, Node 22, Docker, ffmpeg, Ollama installed, 4 cores / 15 GB, NVIDIA 940MX (too weak - CPU inference). ~23h to the deadline. Asked the user to pick a direction.

You

Offline bird call ID. Aim at Best Use of Gemma.

Agent

▸ ollama pull gemma3:1b {"model":"gemma3:1b"}

Input

{
  "model": "gemma3:1b"
}

Output

Error: pull model manifest: 412: The model you are attempting to pull requires a newer version of Ollama. (installed 0.16.2, registry now wants 0.40.3)

The registry upgrade was a 1.4 GB tarball. Lazier: keep the installed Ollama and import a Gemma GGUF by hand, bypassing the registry entirely.

▸ http HEAD huggingface.co/ggml-org/gemma-3-1b-it-GGUF {"method":"HEAD"}

Input

{
  "method": "HEAD"
}

Output

200, content-length 806058240, not gated

▸ bash curl -L -o models/gemma-3-1b-it-Q4_K_M.gguf <hf-url> && ollama create underst...

Input

$ curl -L -o models/gemma-3-1b-it-Q4_K_M.gguf <hf-url> && ollama create understory-gemma -f Modelfile

Output

success - 'using autodetected template gemma3-instruct', model 806 MB

▸ curl /api/generate {"model":"understory-gemma","prompt":"what does a European Robin sound like?"}

Input

{
  "model": "understory-gemma",
  "prompt": "what does a European Robin sound like?"
}

Output

generated a sensible one-sentence answer, ~22s on CPU (~3 tok/s)

Agent

▸ bash uv pip install birdnetlib tflite-runtime librosa soundfile resampy

Input

$ uv pip install birdnetlib tflite-runtime librosa soundfile resampy

Output

birdnetlib 0.18.1 + the BirdNET 6,522-species TFLite model bundled inside the wheel (50 MB FP32 + 15 MB meta). tflite-runtime 2.14.0.

▸ python Analyzer().load_model()

Input

Analyzer().load_model()

Output

AttributeError: _ARRAY_API not found / numpy.core.multiarray failed to import - tflite-runtime 2.14 is built against NumPy 1.x but numpy 2.4.6 was installed

▸ bash uv pip install "numpy<2"

Input

$ uv pip install "numpy<2"

Output

numpy 1.26.4 - model loads, XNNPACK delegate on CPU

▸ python Recording(analyzer, 'robin.mp3', lat=52.52, lon=13.40).analyze()

Input

Recording(analyzer, 'robin.mp3', lat=52.52, lon=13.40).analyze()

Output

robin.mp3 -> European Robin 0.987; greattit.ogg -> Great Tit 1.000; silence -> no detections. Inference 1-4 s/clip on CPU.

Agent

Wrote the CLI: mic -> 48 kHz WAV -> BirdNET -> top species -> Gemma field note -> one card + a dated markdown log. Added --offline, which monkeypatches socket.connect to refuse every non-loopback address, so 'it works offline' is checkable rather than a claim.

▸ python tests/test_understory.py First run: TypeError: guard() takes 1 positional argument but 2 were given - ...

Input

First run: TypeError: guard() takes 1 positional argument but 2 were given - socket.socket.connect is assigned on the class, so the replacement is called as guard(sock, addr). Fixed the signature.

▸ python tests/test_understory.py ok test_card_reports_a_miss_clearly / ok test_collapse_keeps_best_hit_per_spe...

Input

ok test_card_reports_a_miss_clearly / ok test_collapse_keeps_best_hit_per_species / ok test_offline_guard_blocks_the_internet_but_allows_loopback - a real loopback connect succeeds, 1.1.1.1:443 raises OSError('Understory is offline')

Agent

▸ search_dev_to_semantic {"query":"offline bird sound identification TFLite"}

Input

{
  "query": "offline bird sound identification TFLite"
}

Output

Saturated: 'Trail Birder: Identify Birds by Sound, Offline, with BirdNET and Gemma', TrailEar, EchoTrail, Who's Singing?, 'I Put 6,522 Birds in My Backpack', fieldcard - 7+ near-identical Week 1 entries.

Told the user their idea is the most crowded in the challenge and offered to pivot or differentiate. They chose to keep it and win on the angle. Renamed TrailGuide -> Understory so it is not confused with TrailEar / Trail Birder.

Agent

▸ python understory.py id greattit.ogg --offline Card: 'Great Tit (100%)'. Gemma note: 'a small, dark greyish-brown plumage wi...

Input

Card: 'Great Tit (100%)'. Gemma note: 'a small, dark greyish-brown plumage with a distinctive white stripe across the chest ... a short, repetitive cheep-cheep song'.

The 1B model invented the plumage (real Great Tit: black head, white cheeks, yellow breast with a black stripe) and got the song wrong. A 1B cannot be trusted for recalled facts. Rewrote the prompt to ask only for where to look, likely behaviour, and a field mark ONLY if certain, so the model stops guessing. A/B tested: new prompt stopped inventing markings.

You

Keep the angle, save the session, leave the outdoor test and the push to me.

It includes the smaller fights too: the offline guard's first version crashing because socket.socket.connect is assigned on the class and therefore called with self; the NumPy ABI crash; and the moment a semantic search of the challenge feed showed me that "offline bird identifier" was already the most crowded idea of the week — which is why the project is called Understory and not Trail-something.

Prize Categories

Best Use of Gemma — Gemma 3 is the half of this project that turns a species label into something a person can act on, and it runs entirely offline through Ollama on CPU. The failure above is part of why I am entering it here: the interesting engineering with a small open model is not calling it, it is deciding what you can honestly ask it — and then refusing to ask it anything else.

Thanks

Sample recordings used while testing, credited under their Creative Commons licences:

European Robin, XC509375 — Marie-Lan Taÿ Pamart, CC BY-SA 4.0
Common Blackbird, XC1059970 — Diana Tudor, CC BY 4.0
Great Tit — Vladimir Yu. Arkhipov, CC BY-SA 3.0

BirdNET weights are CC BY-NC-SA 4.0 (non-commercial); Gemma 3 is used under the Gemma Terms of Use. The code is MIT.

DEV Community: Aniruddha Sarkar

Understory: a bird guide for the places where your phone gives up

What I Built

Demo

Code

Aniruddha120 / understory

Offline bird field guide: BirdNET identifies on the CPU, local Gemma 3 writes the field note. No signal, no cloud, audio never leaves the machine.

Understory

What the small model is and isn't allowed to say

How I Built It

Why Does Open Innovation Matter?

Where the Open Model Was Wrong

Taking It Outside

My Agent Session

Prize Categories

Thanks