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The A4 categories apply to those species that are vulnerable as a consequence of their congregatory behavior at regularly used sites, either at breeding colonies or during the non-breeding season, including at foraging, roosting and migratory stopover sites. Such stopover sites may not hold spectacular numbers at any one time, but nevertheless, do so over a relatively short period due to the rapid turnover of birds on passage. For the purpose of the US IBA Program, we define a “relatively short period” as one season – spring, summer, fall, or winter – the dates of which should be determined based on the biology of the species in question.

Applying A4iii Criterion

Waterbirds include the following groups or families: Gaviiformes (loons), Podicipediformes (grebes), Anseriformes (geese, swans, ducks), Pelicaniformes (pelicans, cormorants, anhingas), Ciconiiformes (bitterns, herons, egrets, ibis, spoonbills, storks), Gruiformes (rails, gallinules, moorhen, coots, limpkins, cranes), Charadriiformes (all ‘shorebirds,’ gulls, terns, skimmers).

Seabirds include the following groups or families: Procellariiformes (all ‘tubenoses’), Pelicaniformes (tropicbirds, boobies, gannets, frigatebirds), Charadriiformes (skuas, jaegers, alcids) and they must recorded as breeding pairs.

• Mixed species aggregations that exceed these thresholds can be used to apply this criterion.
• Criterion A4iii is intended to be used primarily in two cases:
  (1) where sufficient population data are not available to estimate 1% thresholds with any degree of accuracy
  (2) to identify wetlands of international importance under Ramsar criterion 5 (citation).

NOTE: The relevance of criterion A4iii is very limited in the U.S. Therefore, the U.S. IBA Committee, following BirdLife Europe’s example, has agreed that it will not currently apply criterion A4iii, and only revisit it at a later date if sufficient justification can be made for its use.

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