Of interest, we've had a 'pale' Pine Siskin coming to the feeder on Feb 5th & 6th. It's rather distinctive with subtle streaking, especially above and a rather 'pallid' cast to the plumage. Closer inspection shows the bird to have a yellowish wash on the breast, belly and undertail coverts somewhat resembling a weak version of the 'Yellow' adult male illustrated in Sibley (p. 534).
Pine Siskin - same bird, fairly pale with variable yellowish wash on breast, belly and (shown here) undertail coverts.
Pine Siskin - same bird, rather subtle treaking above and below. I'll post some shots of more typcially streaked birds in a day or so in addition to the bird shown below.