I discovered the music of Messiaen in the mid-1970's and met both the composer and his wife twice: once in 1978 when Ms Loriod performed the complete "Vingt Regards sur l'enfant Jesus" (entirely from memory!) and again at the Cathedral of St. John the Divine (NYC) the following year when there was a celebration and performance over several days of his complete organ works (to date, obviously). While I can't perform his music, I spent many years studying/learning his entire oeuvre. While there are a number of works I couldn't recommend to anyone but a true die-hard (particularly works of his later years) I must say that getting to know all his solo piano music has been a wonderful experience.
While difficult on nearly every level, his "Catalogue d'oiseaux" (1956-58), a set of 13 virtuosic pieces bearing the names of specific birds and intended to use his transcription of those birds in their habitat, is a wonderful work to get to know, and perform if you have the chops. He also wrote an extended single movement solo piano work ("La fauvette des jardins") in 1970, running 30+ minutes, in the same genre as the Catalogue.
As andhow04 has pointed out "Petites esquisses d'oiseaux" are much shorter and less complex than the previous mentioned works, while still maintaining a lot of their style and essence. Because of this I highly recommend to anyone who might just be hearing this style of Messiaen's music (birdsong began to enter his music little by little beginning with "Vingt regards" and eventually became all-consuming by the mid-50's) for the first time to get to know these pieces and begin to acquire an intimate feeling of how deeply Messiaen was devoted to ornithology and love of birds in general before exploring the more extended works. It is completely unique music, and starting with the less demanding works could very well help the initiate come to love the music of the birds.
Finally, I want to offer andhow04 my praise for wonderful performances of "Petites esquisses d'oiseaux". Smaller they may be, but learning the very unique technique of this music is still demanding, and a fine performance these definitely are. Bravo! And thanks so much for posting them.
Lontano