This is not a test (as the old saying goes): This time around, I would really appreciate your help with the following immature/juvenile bird photos. As you can see in the photos below, one of these birds had a relatively thin, black bill and the other’s is yellowish and a bit bigger (in the field, I thought they were the same bird, oddly enough). You can obtain a larger photo by clicking on the images below.
I am guessing that the first is a warbler, maybe a Yellow-rumped Warbler and that the other is some sort of finch or sparrow (maybe a Pine Siskin?). Are there any experts in immature passerines who can help me out? Neither of these birds are lifers for me, of course, but I would love to clear up the mystery. BTW, they were taken a few days ago in Stanley Park in Vancouver, BC.