Passeriformes observed within the Karen Mogensen Reserve. A Chiroxiphia linearis (Pipridae), a species typical of Central American tropical dry forests reaching its southernmost range border in the area B Campylorhynchus capistratus nicoyae (Troglodytidae), a subspecies endemic to NW Costa Rica, which reaches its southernmost breeding areas in the surveyed zone C Catharus aurantiirostris (Turdidae), species characterized by a local isolated breeding population D Hylocichla mustelina (Turdidae), regular winter visitor in the Karen Mogensen Reserve, but never recorded before from the Nicoya Peninsula. Photographs by: M. Dal Zotto (A, B, D) and G. Romeo (C).