Start by exporting the data from your Elasticsearch index to a JSON file. Use the Elasticsearch Scroll API for large datasets to efficiently extract records. You can execute the following curl command to retrieve data:
```
curl -X GET "http://localhost:9200/your_index/_search?scroll=1m" -H 'Content-Type: application/json' -d'
{
"size": 1000,
"query": {
"match_all": {}
}
}'
```
Continuously scroll through the data using the `_scroll_id` provided in the response until all data is exported.

Ensure that DuckDB is installed on your system. You can install it using pip:
```
pip install duckdb
```

Use Python to read the exported JSON file. You can use the `json` module to load the data into a Python dictionary or list structure. This can be done by reading the file line-by-line if the JSON is in a newline-delimited format:
```python
import json

with open('data.json') as f:
data = [json.loads(line) for line in f]
```

Transform the JSON data into a tabular format suitable for DuckDB. Flatten any nested structures into a more relational form, ensuring each document corresponds to a row with consistent columns.

Open a DuckDB connection and create a table schema that matches the structure of your transformed data. Ensure that the data types in DuckDB match those extracted from Elasticsearch:
```python
import duckdb

conn = duckdb.connect('your_database.duckdb')
conn.execute("""
CREATE TABLE your_table (
column1 TYPE,
column2 TYPE,
...
)
""")
```

Insert the transformed data into the DuckDB table. This can be done using the `executemany` method for efficiency:
```python
insert_query = "INSERT INTO your_table VALUES (?, ?, ...)"
conn.executemany(insert_query, transformed_data)
```

Finally, query the DuckDB table to verify that the data has been transferred correctly. You can run a simple SELECT statement to check a few rows:
```python
results = conn.execute("SELECT FROM your_table LIMIT 10").fetchall()
for row in results:
print(row)
```
This ensures that the data integrity is maintained and the data is accessible in DuckDB.

By following these steps, you can effectively move data from Elasticsearch to DuckDB without relying on third-party connectors or integrations.