Hi Osprey: I am one of those " winter texans ", from B.C., in my case based out of Mission in the Lower Rio Grande River Valley. For the reasons stated above, I think you will enjoy the Corpus Christi area. By all means, take one of the Whooping Crane boat tours based out of Rockport; very informative, and a lot of fun. Also a good day trip is to take the free ferry over to Port Aransas. No one has mentioned it, but Sandwich Terns start to show up first here in this area of the Texas Coast around the time of year you will be there. Probably a good idea is to take one of the earlier ferries, as this is definitely a college spring break destination. W.G. Jones State Forest in Houston will yield Red cockaded Woodpecker, Brown crested Nuthatch, Pine Warbler, and Carolina Chickadee.
Last year the area around Galveston State Park hosted a couple of rare birds around that time of year; Fork-tailed Flycatcher, and Yellow faced Grassquit.
If you have time to drive down to the Rio Grande Valley, you will be rewarded with a lot of great birding destinations. This year, rare birds being seen are Golden crowned Warbler, ( Fronter Audubon in Weslaco ), Rose throated Becard, ( Estero Llande in Weslaco ), Crimson collared Grosbeak, ( Allen William's backyard in Pharr ), Brown Jay, ( Salineno ).
Have a great trip, Thor