Species: Tree Swallow
Most recent capture date: 4/26/2023
Age: at least 11 months old
Sex: female
Notes: This female is incubating eggs in one of our nestboxes. When I first checked the box, I wasn’t sure anyone was inside: she had filled it with so many scavenged duck feathers that I couldn’t see anything else. Her chicks will hatch into a very comfortable world. When her chicks are big enough, we will band them too.
Species: Black-throated Gray Warbler
Most recent capture date: 4/16/2023
Age: around ten months old
Sex: Female
Notes: A migration rarity for us, and more common in the fall than spring; we get an average of one of this species per year. We know this individual is a female from her lack of the eponymous black throat.
I have perhaps been watching too many fashion reality shows lately, because this bird makes me think that someone looked at the Black-and-white Warbler and thought: “Almost right, but it needs a pop of color!”
Species: Common Yellowthroat
Most recent capture date: 4/16/2023
Age: around ten months old
Sex: Male
Notes: This time of year we have several types of Common Yellowthroats at CCFS. Some are locals who breed here, while others are just passing through on their way to breeding grounds elsewhere. A good clue to identify which is which is how fat they are: a very fat bird is probably migrating, not staying here. (Birds don’t generally bother to put on a lot of fat unless they are migrating.) This fellow was the fattest bird I have ever seen, so he is almost certainly just passing through.
(You might say “Well I’ve seen fatter birds than that!” but this isn’t the kind of visible-from-afar volume that results from the bird fluffing up their feathers; this is physical fat stores, which you can only see by looking beneath the feathers at the bird’s skin.)
Species: Dusky Flycatcher
Most recent capture date: 4/9/2023
Age: At least 9 months old
Notes: The last time we caught a Dusky Flycatcher at CCFS was spring 2014 – and the last time before that was spring 2004! It looks like they’re on a once-a-decade schedule. We are within their breeding range, but they’re much less common here than in the mountains to the east.
Species: Golden-crowned Sparrow
Most recent capture date: 3/26/2023
Age: At least nine months old
Notes: Like the last posted bird, this fellow is molting from his winter plumage into his fancier summer duds. He won’t bother replacing his flight feathers, but he will spruce up his crown, swapping the brown for black-and-yellow stripes.
Species: American Goldfinch
Most recent capture date: 3/18/2023
Age: almost one year old
Sex: Male
Notes: I was excited about one American Goldfinch back in November – on this March date, we caught six! After our post about American Goldfinches, some folks suggested that their local decline could be due to the ongoing drought and their preference for more humid environments. An anecdote is not data and all that, but it is interesting that after being more-or-less-constantly flooded for four months, CCFS has a flock of American Goldfinches again…
(And if you’re wondering why this fellow looks so patchy: he’s molting from his brown winter [“definitive”] plumage into his bright yellow breeding [“alternate”] plumage.)
Species: Yellow-rumped Warbler, Audubon’s subspecies
Most recent capture date: 3/5/2023
Earliest capture date: 12/24/2017
Age: at least 5 years old
Sex: Male
Notes: Another venerable old warbler! Like another recently-posted yellow-rump, this guy has been getting his face sticky while foraging and pulling his feathers out. He’s working on growing them back (those little spikes under his chin will be feathers), but in the meantime he appears to have a yellow “beard”. Appropriate for his old age!
Species: Northern Flicker, red-shafted subspecies
Most recent capture date: 3/18/2023
Sex: Male
Notes: We’re collaborating with a Stanford researcher on a genetic study of flicker hybridization, so we collect a genetic sample from every flicker before we release them. This individual doesn’t appear to be a hybrid, but sometimes birds turn out to have small genetic traces of hybridization – for example, if his great-great-grandmother was a yellow-shafted flicker, that might not show up in his plumage, but we’ll see it in his genes.
