From the publisher's website:
The Genius Guide to Races of Wind and Wing added three new playable races to the Pathfinder Roleplaying Game rules: the aellar, kestrel, and silfide. Because of space limitations, time restrictions, and playtesting needs, that PDF did not include alternative racial powers or alternative favored class options, such as are presented for the core races in the Advanced Player’s Guide. In an effort to ensure our new races have the same support as the core races of the game, this short, free supplement expands the rules of Wind and Wing to include new racial options. At each level, a member of each race can take one of the listed options when taking a level of a specific class as a favored class, as opposed to the normal bonus of +1 hit point or +1 skill point.
Since many of our readers like to use material from a variety of sources, along with options drawn from the Pathfinder Roleplaying Game Core Rulebook, the alternative favored class options presented here include base classes that have been published in the Advanced Player’s Guide and the Genius Guide line of products. For your convenience, we have noted the source of options that are not in the core rulebook.