Christmas Bird Count: the longest-running tally
On Christmas Day 1900, ornithologist Frank M. Chapman proposed counting birds instead of shooting them. Twenty-seven observers ran 25 counts. The count, run by the National Audubon Society, now covers thousands of circles across the Americas and beyond.
The unit is fixed: a circle 15 miles in diameter, counted within a single calendar day in a window from 14 December to 5 January. Teams walk or drive set sectors and tally every bird by species. Verdict: a crude method made powerful by sheer duration — more than a century of comparable winters.
Breeding Bird Surveys: tallies on a timer
The North American Breeding Bird Survey began in 1966 under Chandler Robbins, now coordinated by the US Geological Survey and the Canadian Wildlife Service. Each roadside route is 24.5 miles long with 50 stops about half a mile apart. At each stop the observer records every bird seen or heard in exactly three minutes.
The UK equivalent, run by the British Trust for Ornithology with partners since 1994, uses randomly selected one-kilometre squares walked along two transects. Different design, same principle: fixed effort per unit, so this year's tally compares with last year's.
Counting what will not stand still
Large flocks break simple tallying. The standard workaround is block estimation: count a block of 10, 50 or 100 birds, judge how many such blocks fill the flock, multiply. Experienced counters re-estimate with a different block size and compare. When numbers matter, two observers count independently and reconcile.
- Block estimation: fast, biased low for dense flocks.
- Photo counts: accurate, done later from images.
- Double observer: slower, gives a measurable error rate.
Traffic counts
Automatic sensors handle most road data, but manual classified counts remain common for turning movements at junctions and for vehicle types that sensors confuse. Counters sit at the kerb with a tally sheet or a multi-key counter board, one key per vehicle class and direction, and record in 15-minute periods. The 15-minute block is the field version of writing a subtotal every row.
The hand tally counter
The mechanical clicker — a thumb lever driving a four-digit wheel register — traces back to the counting mechanisms that Curtis Veeder developed after founding his company in 1895; Veeder-Root became a byword for mechanical counters. Today's versions are near-identical and cheap.
| Survey | Started | Unit | Effort | Tally method |
|---|---|---|---|---|
| Christmas Bird Count | 1900 | 15-mile circle | One day | Species tally by sector |
| N. American BBS | 1966 | 24.5-mile route | 50 × 3-minute stops | Point counts |
| UK BBS | 1994 | 1 km square | Two visits per season | Transect counts |
| Manual traffic count | — | Junction | 15-minute periods | Sheet or key board |
Error control in four rules
- Reset and zero-check the clicker before every period.
- Write the reading down at each interval; do not trust memory.
- Use one counter per category, never one for two.
- Reconcile with a second observer on a sample of periods.