Birdwatching Life List Progress Calculator

Introduction

A birding life list is a running total of the bird species you’ve observed. Some birders track a global life list; others keep separate lists for a country, state/province, county, park, or even a backyard “patch.” Whatever your scope, it’s motivating to quantify how close you are to a goal—especially when you’re planning trips, targeting missing families, or deciding whether to chase a seasonal specialty.

This calculator measures two simple outputs from your inputs:

• Progress (%): the share of the region’s species you’ve recorded.
• Remaining species: how many species are left (based on the total you chose).

Because bird taxonomy changes (splits/lumps) and different organizations maintain different checklists, the most important step is choosing a consistent total species count for your region (and sticking to it) so your progress trend is meaningful.

What numbers should you enter?

Species Observed

Enter the number of species you count as “on your list” for the region. Birders differ on rules (seen only vs. seen/heard, photographed, accepted by a review committee, etc.). The calculator works with any rule set—just be consistent.

Total Species in Region

This should come from a trusted checklist for the same region definition you’re using (e.g., “Texas,” “UK,” “Europe,” “Costa Rica,” “Cape May County,” etc.). Possible sources include BirdLife International, eBird/Clements, ABA, national atlases, and local ornithological societies. Totals can differ depending on:

• Taxonomic authority (Clements vs. IOC vs. regional committees)
• Whether introduced/escaped species are included
• Whether the list is “all-time recorded” vs. “regularly occurring”
• Checklist date/version

Formulas

The calculator uses two formulas:

• Progress percentage
• Remaining species

Math notation

Let:

• S = species observed
• T = total species in the region

Progress (%):

Remaining species:

Remaining = T − S

Interpreting your results

Progress percentage

Your percentage answers: “Of the species on the checklist I’m using for this region, what share have I already recorded?” A higher percentage usually indicates broader coverage across habitats and seasons. If your percentage plateaus, it may mean the remaining birds are uncommon, highly seasonal, nocturnal/secretive, offshore, or require travel to a specific sub-region.

Remaining species

The “remaining” number is a planning tool. You can use it to:

• Set short-term goals (e.g., “+25 species this year”)
• Estimate how much effort is left for a round number target (e.g., 500, 700, 1000)
• Decide whether to broaden your region (county → state) or narrow it (state → patch)

Worked example

Suppose you’ve recorded S = 350 species in a region whose checklist total is T = 1,100.

1. Compute progress: (350 ÷ 1100) × 100 = 31.818…%
2. Compute remaining: 1100 − 350 = 750

Result: You’ve seen about 31.82% of the region’s listed species, with 750 species remaining.

Approximate species totals by broad region (context only)

Totals vary by checklist authority and year. Treat the table below as a rough orientation—for an accurate progress value, use a checklist that matches your exact region and taxonomy.

Data note: For user trust, cite the specific checklist source and version date you’re using for your own totals (for example, “eBird/Clements v2024” or “BirdLife checklist 2025”).

Limitations & assumptions

• If observed > total: This usually means your total is from a different checklist/taxonomy, your region definition differs, or you included exotics/vagrants not counted in the total. Consider updating the total or aligning your list rules.
• Taxonomic changes: Splits can increase both your observed count (if you’ve seen multiple new split species) and the total; lumps can decrease both. Your percentage can change even if you don’t go birding.
• Checklist scope differences: “All-time recorded,” “regular/expected,” and “ABA countable” style lists produce different totals and therefore different progress values.
• Evidence standards: Whether you count heard-only birds, flyovers, or unsubmitted sightings is a personal rule. The calculator assumes your observed value reflects whatever standard you use.
• Not a database: This tool doesn’t store sightings, validate IDs, or deduplicate entries; it simply computes progress from the two numbers you provide.
• No seasonality weighting: The percentage doesn’t indicate difficulty. The last 5–10% is often disproportionately challenging due to rarity, pelagic species, nocturnal birds, or remote habitats.

FAQ

Which checklist should I use for “Total species”?

Use the checklist you already keep your life list under (e.g., eBird/Clements, IOC, ABA, national committee). The key is consistency: your observed count and total should come from the same authority and version.

Do migrants and vagrants count?

That depends on your checklist definition. Some totals include only regularly occurring species; others include vagrants and historical records. Match your total to your personal rules.

What if my region is a county/park rather than a continent?

Use a local checklist (eBird hotspot checklist, park checklist, county bird list) and enter that total. The calculator works the same way for any region size.

Why does my progress change when I don’t add new birds?

Taxonomic revisions can change the total species number (and sometimes your observed count if you update your list). Recalculate using the same checklist version if you want apples-to-apples comparisons over time.