During the course of my studies of our mundane bestiaries, I have noticed the omission of the swift.
While my own estimates would put it at at least size -8, I would request that any of you familiar with such details please provision me for my endeavours. A compatriot of mine has expressed that she has encountered such a creature, magical in nature, but that she is uncertain of it's might.
(To translate, one of my fellow players has expressed an interest in the story flaw Magical Animal Companion, and has expressed that she would like said Animal to be a swift. en.wikipedia.org/wiki/Swift )
Remind that player that RoP:M p34 establishes typical familiars at MM10 unless another player wants to play it. It might not be a hard rule, but I strongly suggest you don't let anyone get a MM25 extension to their powers for free.
Please re-read the core rulebook flaw "Magical Animal Companion." where that specifies that said animal companion (not a familiar) is Magic Might 10 - Size. Thus a negative size increases the magic might. This is not a familiar, it is a story flaw.
The thrush is listed at Size -8, and weighs about 83g. Since the common swift averages at 44g, it would be Size -9 (one point of Size roughly doubles the weight). You have a great opportunity to study breakthroughs into the Limit of the Lunar Sphere --- at least some authorities state that swifts overwinter on the moon. Others believe that they bury themselves in the mud at the bottom of ponds.
Yes, I believe it was written as +1 but that it's actually +2 and that's been fixed in the errata. So if you check the mass/weight to find the Size, add 2 to that Size to get a bird's Size for its mass/weight.
Apologies for the confusion. The tables in HoH:MC include the +2 adjustment mentioned. I simply reduced the size by 1 because swifts are half the weight of thrushes. However, upon actually checking, the thrush is listed at Size -6; therefore a swift should be size -7. A non-bird with the same weight as a swift would be Size -9 (a frog, for example)