Notes from the Station

Species: Lesser Goldfinch
Most recent capture date: 8/31/2022
Age: at least 1 year old
Sex: female

Notes: The size of white patches on the wing and tail, and the amount of black on the crown, help us identify the age and sex of these little birds.

Species: Black-headed Grosbeak
Most recent capture date: 8/28/2022
Age: less than 6 months old

Notes: Yes, grosbeaks bite.

Species: Swainson’s Thrush
Most recent capture date: 8/21/2022
Age: less than 6 months old

Notes: What a difference a molt makes! Compare this slick-looking kid to the speckled Swainson’s Thrush from a few posts back: this bird has replaced their body feathers in the preformative molt and now looks all grown up.

Species: Anna’s Hummingbird
Most recent capture date: 8/20/2022
Age: over 1 year old
Sex: female

Notes: Did you know that hummingbirds are small? Hummingbirds are SMALL. This one has more pink in the gorget than we generally expect to see in a female; we can tell she is female by the pattern of white and black on her outer tail feather.

Species: Pacific-slope Flycatcher
Most recent capture date: 8/17/2022
Age: less than 5 months old

Notes: We call these Western Flycatchers, since it is difficult to distinguish Pacific-slope from Cordilleran Flycatchers in the hand, but detailed measurements of this bird and his location make it highly likely that he is a Pacific-slope. Western Flycatchers, or WEFLs (pronounced like “waffles” but with an E), are the defining species of our fall migration, showing up in great numbers just for this one brief period. Their big eyes, long “whiskers” (technically, rictal bristles), and flat boat-shaped bills give them lots of charisma.

Species: Song Sparrow
Most recent capture date: 8/07/2022
Earliest capture date: 6/15/2022
Age: less than 5 months old

Species: Brown Creeper
Most recent capture date: 7/26/2022
Age: less than 4 months old

Notes: One of my favorite birds to spot in a park or backyard – and the frequent, embarrassing cause of my audibly exclaiming “Oh, hi creeper!” in public areas – the creeper has excellent camouflage but can be readily distinguished from tree bark by the fact that it moves. These birds are tiny and quick, starting at the base of a tree and darting up and around it in search of insects in the bark crevices. They like to accompany flocks of other species such as juncos or chickadees.

Species: Swainson’s Thrush
Most recent capture date: 8/04/2022
Earliest capture date: 7/26/2022
Age: less than 4 months old

Notes: Another juvenile thrush, subtly different from the Hermit (see previous post): larger and with paler breast spots. Don’t let his apparent anxiety worry you; it’s just the combined effect of being a thrush – which always look worried – and having a baby’s downturned yellow gape.

Species: Hermit Thrush
Most recent capture date: 8/04/2022
Earliest capture date: 7/26/2022
Age: less than 4 months old

Notes: Hermit Thrushes’ juvenile plumage, with cute buffy teardrops on their shoulders, doesn’t last long – the birds quickly molt into plainer brown dress – so it’s fun to see while it lasts.

Species: Western Tanager
Most recent capture date: 7/24/2022
Age: about 15 months old
Sex: male

Notes: No, this isn’t a tropical bird that got lost – although they’re surprisingly easy to miss, these stunning tanagers breed and migrate in northern California. They’re not common at CCFS though: since 2005 we’ve averaged less than one Western Tanager per year, and that average would be even less if it weren’t for the six (!) young tanagers we caught during fall migration in 2021. Adult females and young birds are yellow and greenish-yellow: certainly pretty, but distinct from the conflagration of an adult male. The last time we caught an adult male at CCFS was 2004. We can tell that this fellow is in his second year because of the mix of black and brown plumage in his wing: an older adult would have only black.