This is a female or immature identified as such by its lack of rufous tones to its finely streaked undertail coverts and leggings.. Apparently it's not possible to distinguish juveniles from adult females in this species. The tail pattern suggests the widespread boreal race F. c. columbarius which is a migrant and winter visitor to this area. This individual was particularly confiding, allowing close approach along the trail. A bony "tubercle" can be seen inside its nostril, characteristic of falcons. Digiscoped with Panasonic DMC-LX5 | Nikon FieldScope III | 30XWA | hand-held (no adapter).
References:
Kesel, Antonia & Hoffmann, Florian & Baars, Albert & Danter, Leon. (2017). Do bony tubercle inside the falcon nostril effect breathing during high speed diving?.
Warkentin, I. G., N. S. Sodhi, R. H. M. Espie, A. F. Poole, L. W. Oliphant, and P. C. James (2005). Merlin (Falco columbarius), version 2.0. In The Birds of North America (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.44
White, C.M., Boesman, P., Kirwan, G.M. & Marks, J.S. (2018). Merlin (Falco columbarius). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/53231 on 8 December 2018).