Caspian Tern

Hydroprogne caspia

The Caspian tern is the world's largest species of tern, with a subcosmopolitan but scattered distribution. Despite its extensive range, it is monotypic of its genus, and has no accepted subspecies. The genus name is from Ancient Greek hudro-, "water-", and Latin progne, "swallow". The specific caspia is from Latin and, like the English name, refers to the Caspian Sea. Source

Where it is now

In the last 8 weeks this bird was recorded 80,604 times across 137 areas (each area is a 5 degree square).

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Movement and weather

Each season it is first heard regularly where daytime highs are around 20°C (typically 15 to 29°C, from 36 areas). That range is wide, so temperature alone does not explain when it turns up.

Over the weeks it was present in the past year, its centre in North America ranged from 16°N in March to 47°N in July, about 3,400 km apart.

Arrival dates

The week it was first heard regularly in each region, after at least six weeks away. Dates differ from south to north, so a region has a range.

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Figures are effort corrected and come from automatic sound identification, which makes mistakes. How this is measured and how it compares with human observers.