I am seeing more House Wrens using my nesting boxes this year– of course, this is a native cavity-nesting bird and protected by federal laws. One thing I’ve noticed about this egg clutch is the nest cup lined with a larger amount of another species’ feathers. I see a feather or two, tiny ones, in a house wren nest usually — but not this much. Note the feather colors…could this be under-feathers from a dead bluebird which the wren found on the ground? Your thoughts are welcomed always. Another thought I have is it is from a dead bluebird, looks like a possible cat attack on the bluebird perhaps.