And an interesting goldfinch strategy for combating brood parasitism of the Brown-headed Cowbird.
1/6400, f/6.3, ISO 800, Canon 7D Mark II, Canon EF 500mm f/4L IS II USM + EF 1.4 III Extender, not baited, set up or called in
A little over a week ago I found this male American Goldfinch feeding on thistles in the mountains. I’ve always liked the color combinations in my photos when goldfinches in breeding plumage are foraging on the red-purple thistle flowers and in this case I think the flower cluster is particularly interesting and attractive. A different choice of aperture would have helped to get the tail sharper but I chose not to take the time to make the adjustment.
American Goldfinches are among the latest songbird breeders in North America, often waiting to nest until early July. Flowering thistles are an important food plant for them so it’s thought that they delay nest building until that food source will be available at the best time for feeding chicks. A single musk thistle plant can produce as many as 120,000 seeds so thistle is a source of abundant food for them.
American Goldfinches are almost exclusively seedeaters but unlike most other granivorous songbirds they don’t temporarily switch over to an insect diet while feeding nestlings, suggesting that they’re well adapted to fulfilling the high protein requirements of their growing chicks from a diet of seeds. This may be an adaptation meant to combat some of the negative effects of brood parasites, especially the Brown-headed Cowbirds that lay their eggs in the nests of other species.
Cowbird eggs laid in goldfinch nests hatch successfully but nestling growth is retarded (likely because of insufficient protein from a seed diet) and they nearly always die before they fledge.
Ron
Thanks. For the next 2-3 weeks my blood numbers will be very low and I’ll tire easily, but as before, these will bounce back. In 5-6 weeks I will have another bone marrow biopsy and my doctors believe that both mutations that caused the leukemia will be completely gone. The very best news we had hoped to hear. I’ll still be monitored for awhile in case of relapse, but there is a strong chance it is now gone for good.
That’s simply wonderful news, Dan! I couldn’t be happier for both you and Barbara. It’s been a difficult time for you both.
Sure hope it gets the job done Dan…..not fun for sure……. 🙁
Dan, keeping fingers crossed for you. Really hope the chemo did the trick. BMBs are no fun — hopefully, they do yours with Versed. Gentle hugs.
Beautiful and fascinating.
I am constantly in awe at the ‘small’ adaptations which allow a species to survive and thrive. And at the length of time those adaptations take. Presumably if other birds had stayed with the ‘whole seeds’ thing the cowbirds would have had to adapt.
I am so grateful to be a part of this classroom over the air, and to all the teachers I have found here.
Thanks very much, EC.
Fascinating info (now I will be able to impress my friends with “granivorous”).
Interesting that this Goldfinch has a black tip on its upper bill. They are numerous at my feeders here in western WA and none have that. Regional variation? Do bills change as plumage does? Genetic anomaly? Is the tip just in shadow?
Good eye to spot that black bill tip, Lyle. I don’t think it’s shadow or an anomaly. This from BNA Online about this species:
“In nestlings, gape flanges cream color, mouth lining geranium pink. Bill color changes concurrently with plumages. Change under hormonal control and indicative of breeding condition (Mundinger 1972). In Juvenile and throughout first winter, bill dark grayish brown. During spring, bill gradually changes color, from base of bill outwards, to orange yellow (extreme spectrum orange); dark tip persists. See Alternate Plumage for discussion of beak color variation among individuals. During breeding season, the bill is more intensely colored in males than females. In fall, the bill color reverts to dark grayish brown concurrent with Definitive Prebasic Molt.”
Thanks. I will look for bill color changes next spring.
You really nailed this shot, Ron! Loving the vibrant colors, the tilt of the thistle and the acrobatics of the Goldfinch! I can even see his little tongue. 😛 Wondering if his cheek is looking a little scruffy because he’s been shoving seeds into gaping maws all day. 😉
Had no idea about the whole seeds-only and cowbird thing. Once again, you’ve combined eye candy and the teachable moment! You can take the teacher out of the classroom… 😉
Thank you, Marty. You mention the “tilt” of the thistle. Not only is the stem tilted but the flower head eventually does too. I find it interesting that one of the most commonly used common names for this plant is “nodding thistle” because as the flowers mature and the seeds develop the flower head leans over. I like common names that help with ID.
Yes, you understand that teacher thing…
What I find especially interesting is that of the three goldfinch species (American, Lesser, and Lawrence’s) the American Goldfinch is the most parasitized by Brown-headed Cowbird, but chicks rarely survive for the reasons you give. Because of nest timing, Cowbirds rarely parasitize American Goldfinch in the north (it’s too late for cowbirds), but southern populations are hit and may cause some nest abandonment. Lesser and Lawerence’s Goldfinches nest much earlier and cowbirds are nesting at that time as well. A cowbird chick would have the same poor survival in their nests, however. Yet, there are only a couple of records even known of a Brown-headed Cowbird laying eggs in a Lesser Goldfinch nest. I’m not sure why since nest timing overlaps but I suspect that the nests are rarely unattended by the goldfinches giving cowbirds only a small chance to slip into a nest. American Goldfinches leave the nest a bit more frequently (but not often) while the first couple of eggs are in the nest, then they stay very close and give cowbirds only a small chance to enter.
Very interesting background info, Dan. Thanks for providing it.
Big congrats on getting through your last day of chemo yesterday! I hope you feel well enough to enjoy the accomplishment.
Beautiful photo or the gold finch and musk thistle… 🙂 Knew they nested late and thistle was a preferred food source – we certainly have an abundance of Canada Thistle – like you aren’t familiar with those 😉 – and have more Bull Thistle around this year as well as all the other varieties. All late this year due to weird weather. The fact that they really don’t eat insects and the lower protein is a stratgy against the Cow Bird are new to me! Always something to learn! Tomatoes – HA! I’ll be lucky to get a couple with cold/hail then too much heat to set fruit.. 🙁
Yup, I had a lot of experience with Canada Thistle when we were farming. Nasty stuff when it gets started in a field.
Folks in Cut Bank try to raise tomatoes every year and generally get poor results. Cold and a short growing season put the kibosh on them but if you live in northern MT an optimistic attitude is almost a must…
Some years the tomatoes do well – years like this…….. 🙁 They are getting newer varieties out for short season and cooler weather. Doesn’t do us a lot of good with the yo-yo weather we have………
Thanks Ron. Love Lesser Goldfinches and they are very common here, but I knew none of the information you have provided this morning. Thank you. I have often thought that Lesser Goldfinches provide some of the best and most colorful bird photos I have taken.
Everett, I have far fewer opportunities with Lesser Goldfinches. I used to see them more often than I do now.
Can’t help but feel a little sorry for the poor cowbird chicks – talk about paying for the sins of the fathers (or, in this case, the mothers)! Thanks for the lesson and the lovely picture.
I have some of the same empathy for them, Robyn. They’re part of the grand scheme of things too and after all, they’re a native species.
I knew none of this. Thanks, professor. And what a handsome fellow!
He sure is. Thanks, Arwen.
Always thought Goldfinches were smart. I knew about their reason for later families and the need for thistle but didn’t make the connection for cowbirds. Now I know they are smart! 🤔 We don’t have musk thistle (at least I have not come across it) here but there is an endless supply of other varieties. That certainly is a beautiful flower on top. I’m going to have to see if that does indeed grow in this area. On a side note…reading your post yesterday about Shannon loving fresh tomatoes, I’ve been harvesting mine for about a week now…nothing beats that warm fresh tomato. It is worth the long wait! Something like Goldfinches waiting for thistle seed! 😊
“Something like Goldfinches waiting for thistle seed”
Thanks for the chuckle, Kathy.
My tomatoes were late because of our cold spring and being nipped by frost one morning. I was almost going out of my mind waiting for BLT’s this year since I absolutely refuse to buy those poor excuses for tomatoes you find in grocery stores.
Checking into the Musk Thistle…apparently we do have it in Wisconsin but confined to the southern part of the state. As with all invasive species it is creeping further north into new territory. Adaptation is the name of the game!
Great post! Knew about goldfinches and that they nested late, etc., however, didn’t know about them not feeding insects to chicks and that is why cowbird chicks don’t survive. Many thanks professor for that tid-bit of information, much appreciated.
Thanks, Dick. As you know adaptations for survvival are endlessly fascinating.