Shearwaters: 10% of the world population

TL;DR

On its page for the LIFE Arċipelagu Garnija project, BirdLife Malta writes that the Yelkouan shearwater (Garnija) “Malta’s population is estimated to be around 1,600 – 1,800 pairs, constituting approximately 10% of the global population.” We compared both numbers with the regulator’s estimate and the published global estimates.

1. Malta’s count is plausible but older than the regulator’s. The Environment and Resources Authority’s Species Action Plan 2022–2030 gives 1,795–2,635 breeding pairs, overlapping and above BirdLife Malta’s 1,600–1,800. The BirdLife page is undated; its project ran 2016–2020.
2. The global population is poorly known. A peer-reviewed review (Bourgeois & Vidal 2008, Oryx) put it at 11,355–54,524 pairs, adding that most censuses are probably overestimates. The figure most often quoted today is 21,000–36,000 pairs (CIESM guide ◆).
3. “About 10%” is at the top of the range. With BirdLife Malta’s own count and 21,000–36,000 global pairs, Malta’s share is 4.4–8.6% (central 6%). With the regulator’s count it is 5.0–12.5% (central 7.8%). The regulator also says “around 10%”.
4. Verdict: largely supported (moderate confidence). Malta holds an internationally important share of a vulnerable seabird, which is the point of the sentence. The precise share cannot be pinned down, and the central estimates are closer to 6–8% than 10%.

1. Supported
2. Largely supported
3. Not substantiated
4. Misleading
5. Contradicted

IN THIS REPORT

1 The claim and what we could verify

The sentence is on BirdLife Malta’s page for LIFE Arċipelagu Garnija (LIFE14 NAT/MT/000991, 2016–2020) [1], read on 5 October 2026; the page carries no date. The same text appears on the LIFE PanPuffinus project’s species page. The European Commission’s LIFE project page [2] describes the project’s aims (to increase breeding pairs by about 10% and reproductive output by 25%) but gives no population total.

2 Method

Question. Is Malta’s population about 1,600–1,800 pairs, and is that about 10% of the world’s?

Evidence. We searched the peer-reviewed literature (OpenAlex, Crossref) and official sources for Maltese and global estimates, recorded them in data/cc-106/population_estimates.csv, and computed Malta’s share for each combination (tools/cc-106-report/calc.py): the lowest Maltese estimate over the highest global one, the reverse, and the ratio of midpoints. The IUCN Red List and BirdLife International data pages refused automated access, and we could not query the EU Birds Directive (Article 12) reports directly, so the current official global estimate is known to us only through the CIESM guide.

Grades. Bourgeois & Vidal (2008): C (review). ERA plan: C (official). CIESM guide: C, second-hand. Verdicts follow the five-point scale in Appendix A.

3 What the evidence shows

With the counts BirdLife Malta states, Malta’s share cannot exceed 8.6% unless the global population is below about 21,000 pairs. With the regulator’s newer count, 10% falls inside the range. The 2008 review’s range is so wide that it supports anything from 3% to 23%. A study of the largest colony, Tavolara in Sardinia, estimates it holds more than half of the world population (Pezzo et al. 2021) [6].

4 Where the evidence points different ways

5 Testing the claim

6 Verdict and requests for evidence

Why. Both numbers are of the right order and consistent with official and scientific sources, but the share is at the upper end of what the estimates allow and the global total is poorly known. Confidence is moderate because we could not read the current IUCN and Article 12 figures directly. What this verdict does not say. It does not question the species’ conservation need or BirdLife Malta’s conservation work; it tests a population share.

Evidence we are asking for

• From BirdLife Malta: the year and source of the 1,600–1,800 pairs, and the global figure behind “10%”.
• From ERA: the method behind 1,795–2,635 pairs and Malta’s latest Article 12 report figures.

7 Limitations

• The IUCN Red List and BirdLife International datazone refused automated access; the 21,000–36,000 figure is from the CIESM guide, which gives no source (◆).
• Seabird colonies in cliffs and caves are hard to census; all estimates are ranges with wide uncertainty.
• The ERA plan page was read from an Internet Archive copy; the plan document itself was not read.

References

1. [1] BirdLife Malta (undated). LIFE Arċipelagu Garnija. Read 5 Oct 2026. https://birdlifemalta.org/arcipelagugarnija/
2. [2] European Commission, CINEA. LIFE14 NAT/MT/000991 LIFE Arċipelagu Garnija, project page. https://webgate.ec.europa.eu/life/publicWebsite/project/LIFE14-NAT-MT-000991/life-arcipelagu-garnija---securing-the-maltese-islands-for-the-yelkouan-shearwater-puffinus-yelkouan
3. [3] Environment and Resources Authority. Malta Yelkouan Shearwater Species Action Plan 2022–2030 (page). Internet Archive copy of 8 Aug 2025. https://era.org.mt/malta-yelkouan-shearwater-species-ap-2022-2030/
4. [4] Bourgeois K. & Vidal E. (2008). The endemic Mediterranean yelkouan shearwater Puffinus yelkouan: distribution, threats and a plea for more data. Oryx 42(2):187–194. doi:10.1017/S0030605308006467. https://doi.org/10.1017/S0030605308006467
5. [5] CIESM. Mediterranean seabird guide: Yelkouan shearwater. ◆ https://ciesm.org/seabird-guide/yelkouan-shearwater/
6. [6] Pezzo F. et al. (2021). Productivity changes in the Mediterranean Sea drive foraging movements of yelkouan shearwater Puffinus yelkouan. Marine Ecology 42:e12668. doi:10.1111/maec.12668. (Abstract read.) https://doi.org/10.1111/maec.12668
7. [7] MiŻien. Estimates and calculation: data/cc-106/; tools/cc-106-report/calc.py.

Appendix A: series standards and verdict scale

Every investigation in this series follows the same rules so that verdicts are comparable and challengeable.

Confidence

High: multiple independent lines of evidence agree. Moderate: evidence is relevant but incomplete or indirect. Low: evidence is thin, second-hand or conflicting.

Evidence grades

A experiment · B observational study with a control or gradient · C review, guidance or official statistics · D assertion or anecdote. ◆ marks a source known only second-hand.

Standards

• Quote the speaker, not the headline, with outlet and date, and link the original where possible.
• Separate the claim from the evidence offered for it, and say who made which statement.
• Grade the evidence and show differing views side by side where the evidence is unsettled.
• State what we could not access or verify, and what would change the verdict either way.
• Ask for the missing evidence in specific, answerable requests.
• Offer a right of reply where a check finds a claim Not substantiated, Misleading or Contradicted (or a pledge Not measurable, Off track or Missed), before wider circulation, and append responses.
• Correct errors openly with a version number and change log.
• Whistle-blow only on evidence: a verdict of Misleading or Contradicted requires documents or data that can be shown, not inference.
• Check every side. Government, opposition, NGOs and developers are held to the same standard.

Appendix B: revision log