I've witnessed several pathetic examples of this over the past few years; none are easy to watch.
Watched and photographed both Yellow Warblers feeding this immature Brown-headed Cowbird.
This Cottonwood tree was about ten feet from the Yampa River.
Best viewed in 'original' size.
Nikon D800
,AF-S VR Nikkor 70-200mm f2.8G with TC-2.0 E II 1/320s f/10.0 at 600.0mm iso500
UnCropped DX Image Reduced to 100 ppi for Internet Viewing
full exif