Winter may not officially be over, but the Snowy Owls seem to have gone into hiding already. I've checked two different servers and haven't found a single owl. It could be that I was just terribly unlucky and someone had just cleared out the zone of owls, but there have also been reports on the WarcraftPets forums of missing feathery friends in Winterspring.
There's been some speculation over just when these flying pets would disappear, since they originally did not follow the seasonal timing of the Winter Squid. At first this was believed to be a bug/effect of the expansion being released at an awkward time for the Snowy Owl, but it's getting really hard to tell.
On the official Pet Battles forum, a player reports that all the Snowy Owls stopped spawning midnight of February 28 (in other words, March 1st). Other users on WarcraftPets also noticed the lack of owls starting on the first of March. I'm hoping to get an official confirmation on the date of its last spawn.
At the moment, it would appear that the Snowy Owls spawn on November 1st and stick around until March 1st, while the Winter Squid spawns between September 23rd and March 20th. It's puzzling why they wouldn't share the same dates, as they both require "winter". On the other hand, one is fished up and the other is a flying critter, so there's no absolute reason they should follow the same pattern. In the end, they are both showing up during WoW's "winter", however short or long the duration.
Since the Snowy Owl appears to have gone into hibernation now, be sure to keep your eye out for the Qiraji Guardling! "Summer" is coming. :P