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Adult Description
- Medium-sized waterbird.
- Black back and head, white underside.
- Stout, deep, round-tipped bill.
- Throat white in nonbreeding plumage, with some white on face.
Immature Description
Similar to nonbreeding adult, but with shorter, shallower bill without white lines or grooves.Relative Size

crow-sizedMeasurements
- Both Sexes
- Length: 16.9 in (43 cm)
- Weight: 17.8-31.4 oz (505-890 g)
- Wingspan: 24.8-26.8 in (63-68 cm)