Perching or adapted for perching: insessorial claws.
[From New Latin Īnsessōrēs, the perchers (former order name), from Latin īnsessus, past participle of īnsidēre, to sit upon; see insidious.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
1. (Zoology) (of feet or claws) adapted for perching
2. (Zoology) (of birds) having insessorial feet
[C19: from New Latin Insessōrēs birds that perch, from Latin: perchers, from insidēre to sit upon, from sedēre to sit]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014