In a post last October, I talked about the Brown-headed Cowbird brood parasitism. I talked about dreading the day I witnessed this parasitism on camera — tortured by what, if anything, I would do about it. Well … that day came on March 21. The House Finch nest I was so excited about was the scene. (As a quick recap, Cowbirds do not raise their own young. They lay their eggs in other bird’s nests … typically one egg per nest …. then leave the host parents to raise the nestling.)
Decisions Decisions
Although it is against the law to remove a Cowbird egg, I was ready to do whatever it took to protect the Finch and her brood. After some research, however, I was quickly educated in the Law of Unintended Consequences (LUC). A study was done, legally, in which the Cowbird’s egg was removed from some nests and left in others. It turns out, the Cowbird may retaliate if her egg is removed — destroying the host’s own eggs. In the study, the nests in which the Cowbird egg was removed faired worse than the untouched nests. Great.
I then came up with what I thought was a brilliant plan — take the Cowbird egg out at dusk — and freeze it. Then, return the no-longer-viable egg to the nest at dawn. The LUC hung over my head — that and I vowed to do no harm. I reminded myself that these birds are not of my creation. I got myself back in the box. Decision made.
The Scene
On March 20, I noticed that the Finch nest no longer had two eggs — just one remained. I played back the video — and there was the Cowbird removing an egg in preparation for placing her own egg in the nest. Early the next morning, the Cowbird reappeared. She was ready to lay her egg — except — the mother Finch was on the nest and was not having it! Although only half the size of the Cowbird, the Finch held off the Cowbird for 9 minutes. The Finch was ultimately pushed aside, but stayed with her nest. Unlike the labor video of the Eastern Bluebird, the Cowbird literally shot her egg into the nest and took off — the whole laying process taking just 10 seconds. I love the fact that the Finch lunged forward and gave the departing Cowbird one more peck!
Today the nest contains 4 eggs — 3 Finch eggs and 1 Cowbird. In many cases, since the Cowbird picks on smaller birds, only the Cowbird nestling survives. In this case, however, there may be a different outcome. Cowbird nestlings in Finch nests don’t fare well. Cowbird nestlings rely on a protein diet, while Finch nestlings are fed plant matter. Either way, I do not like it.
But — I do like witnessing the valor of motherhood as the Finch protects her nest. At the end of the day, that is the uplifting takeaway from this whole experience.
