Upper mandible definitions

Upper Mandible

upper part of beak.
Found on http://www.sialis.org/glossary.htm

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Upper mandible

upper half of the bill. The bill is a bony outgrowth from the skull covered with horny sheaths of keratin.
Found on https://www.britishbirdlovers.co.uk/identifying-birds/glossary-of-bird-part

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