Ok. I admit that's bit dramatic and over the top but, honestly, there is something up with goldfinches and bushtit nests this year. Let me explain:
Goldfinches don't build quite the elaborate nests that bushtits do. Goldfinch nests are basically a cup fashioned with sticks and grass stitched together with.... spider web. Unfortunately bushtit nests are a handy source of spider web since it (along with lichen) is the primary building block of the bushtit nest, allowing it to be stretchy and strong at the same time. Every year I do get goldfinches attempting to pilfer material from bushtit nests. Often the bushtits fend them off. But sometimes they just can't. Usually this interest by goldfinches is short-lived and peaks around the time bushtits are building their first nests so they can repair the damage. After that, goldfinches have usually lost interest and are minding their own business. Usually.
I already knew that goldfinches can have quite a dramatic and negative effect on a bushtit nest. Once, in Arizona, I found a bushtit nest (after a laborious and exhausting search of several hours) in the building stage that was being constructed by a happy little pair. The next day I came back to find a goldfinch ripping off material faster than the poor bushtits could bring it in. And they didn't even seem to notice. By the following day nothing remained of the nest and the pair had disappeared -- presumably to find a safer neighborhood.
Here in Portland I have seen goldfinches removing nest material from bushtit nests, but it rarely seems to effect the integrity of the nest. Sometimes the nest looks a bit "fluffy" afterwards, but it survives.
Not so this year. This year the goldfinches have gone mad. I don't know if the unseasonably cold and rainy May has forced them to be more aggressive about stealing spider web from bushtits or what. Perhaps they are rebuilding lost nests in record numbers? Regardless, they have caused devastating consequences to some of the nests I've been following.
One nest fledged a first brood successfully and was incubating a second when the goldfinches removed enough of the neck of the nest to cause it to be abandoned and then fall to the ground. Another nest with only 10 day old nestlings (they fledge at 18 days) is just hanging by thread and a hole has been torn into the neck such that the poor nestlings are essentially in a hanging cup nest -- open to the elements. I expect it to fall and the nestlings to disappear any day now.
Still another nest was close to fledging their first brood and the goldfinches removed enough material to cause it to fall, leaving the nestlings on the ground and easy pickings for the predators that doubtless devoured them that night. Finally, I have far more bushtit nest starts that get to the "hanging sack" stage and then are abandoned as threadbare and forlorn wisps. They have been stripped of their material by.....goldfinches.
I thought nest predators were the bushtits' worst enemy. Who would have guessed that this year it would be goldfinches?
I replied to an earlier post a few months ago, describing a bushtit nest in Seattle's Central District that looked like it had been remodeled from the previous year. I've been watching it from my kitchen window every day. So active in the last few weeks! It has really been a bright spot in an otherwise awful time. This morning, the nest was gone. I found it in a bush below the tree. The bottom had a big hole in it, but there were still two unhatched eggs inside. No sign of the adults. One of the unhatched eggs looks like it has a tiny beak mark in it, from the outside. I am so heartbroken. I'd include photos, but it doesn't look like I can attach them to a comment, and I don't have an email address for you. If you'd like to see the photos, let me know how to send them. Jill (jill.freidberg@gmail.com)
ReplyDeleteHi Jill, I'm so sorry you lost your nest :-( Sadly, that is a common outcome and may have been any number of predators: crows, jays, squirrels, raccoons, etc. The puzzling thing is the eggs that were left. That would suggest a non-predator, like goldfinches. But you would have noticed the goldfinches and a gradual decline in nest quality if that was the case. So.....a. bushtit mystery. the good news is they often renest nearby, so you may have a new nest in your yard next year. This year it's a bit late. thank you for your offer of a picture, but I have seen many. Sadly. Best,
ReplyDeleteSarah