On the 16th, 12 days after the discovery of the nest, a Brown-headed Cowbird hatched in the morning and an Abert’s Towhee later in the day.
On the 18th the second towhee hatched, 13 days after the egg was laid. The second small Bronzed Cowbird egg was pushed out of the nest.
Note how much larger the first hatched towhee chick is compared to the cowbird.
On the 23rd I discovered the second Abert’s Towhee chick had died and was removed by the parents later that day.
On the morning of the 27th I discovered the nest empty. There was absolutely no movement.
The towhee chick was perched just below the nest. I could not see the Brown-headed Cowbird.
I did not follow the juveniles after the last picture. Towhees continue to feed and support their young for an additional 4 to 5 weeks.
In the few years I have been birding, I have only seen towhees tending to juvenile Bronzed Cowbirds, never a Brown-headed. Here is a shot of a juvenile Bronzed Cowbird in my yard last year.
As you can see by this Bronzed Cowbird being fed by an Abert’s Towhee, the BRCO is a shorter yet heavier bird.
Brown-headed Cowbird — Chapter 2
Eggs in Parasitized Nest — Chapter 4