Tree Swallow

Tachycineta bicolor

The tree swallow is a migratory bird of the family Hirundinidae. Found in the Americas, the tree swallow was first described in 1807 by French ornithologist Louis Vieillot as Hirundo bicolor. It has since been moved to its current genus, Tachycineta, within which its phylogenetic placement is debated. The tree swallow has glossy blue-green upperparts, with the exception of the blackish wings and tail, and white underparts. The bill is black, the eyes dark brown, and the legs and feet pale brown. The female is generally duller than the male, and the first-year female has mostly brown upperparts, with some blue feathers. Juveniles have brown upperparts, and gray-brown-washed breasts. The tree swallow breeds in the US and Canada. It winters along southern US coasts south, along the Gulf Coast, to Panama and the northwestern coast of South America, and in the West Indies. Source

Where it is now

In the last 8 weeks this bird was recorded 15,001 times across 54 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 13°C (typically 8 to 19°C, from 50 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 45°N in April to 54°N in June, about 1,000 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.