Found an Egg? We'll Tell You What Laid It

How egg ID actually works

Bird eggs are surprisingly distinctive when you get past the obvious “white and oval” description. Length and width together get you most of the way to a species ID — a 17 mm egg is almost certainly a budgie, a finch, or a Java sparrow; a 47 mm egg with a faint cream tint is almost certainly a macaw, a chicken, or a duck. Shell color and surface texture (smooth vs matte vs speckled) eliminate most of the rest.

This tool uses Euclidean distance in (length, width) space against a database of typical mean dimensions for 25 species. Top three matches are returned with confidence weights calculated by inverse distance — closer matches get exponentially more weight. When you specify shell color, candidates that don't match get a hard penalty and drop in the ranking. The result is a fast, transparent guess that admits uncertainty.

Real-world variation is the biggest caveat. A given hen lays eggs that vary 10-15% across her own clutches; first-time layers and calcium-deficient hens produce eggs outside the typical range; older hens lay larger eggs less often. The number you get with a digital caliper is accurate to a tenth of a mm — but the "typical" figure for any species is itself a population mean with a wide tail. Use the tool as a shortlist, not a verdict.

One thing the tool can't do: identify wild eggs you find outdoors. In the US (and most of Europe and the UK) it's illegal to disturb, photograph closely, or possess any wild bird's egg without permits. If you genuinely found a wild egg out of a nest, photograph it from a distance and call your local wildlife rehabilitator — don't bring it home, and don't try to incubate it.