Brown-headed Cowbird

Molothrus ater

The brown-headed cowbird is a small, obligate brood parasitic icterid native to temperate and subtropical North America. It is a permanent resident in the southern parts of its range; northern birds migrate to the southern United States and Mexico in winter, returning to their summer habitat around March or April. Source

Where it is now

In the last 8 weeks this bird was recorded 171,071 times across 43 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 6 to 17°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 32°N in February to 48°N in May, about 1,700 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.