Notes from the Station

Species: Black-headed Grosbeak
Most recent capture date: 5/08/2022
Age: at least one year old
Sex: female

Species: Wilson’s Warbler
Most recent capture date: 5/08/2022
Earliest capture date: 4/27/2019
Age: four years old
Sex: male

Notes: Unlike the individual in the previous post, this bird is staying to breed at our Jasper Ridge site. He had a large cloacal protuberance, indicating that he is actively breeding now.

Species: Wilson’s Warbler
Most recent capture date: 5/08/2022
Age: one year old
Sex: female

Notes: This time of year at our Jasper Ridge site, we get two groups of Wilson’s Warblers: all are migratory, but for some this site is just a stop on their way north, while for others it is their destination for the breeding season. This bird is just passing through. Interestingly, our breeders tend to have more black in the crown, even on females; it would be unusual for an individual that looked like this to be breeding at our site.

Species: Common Yellowthroat
Most recent capture date: 5/08/2022
Earliest capture date: 5/31/2018
Age: at least six years old
Sex: female

Notes: The oldest documented Common Yellowthroat was 11 years, so she has a while to go if she wants to break the record, but six is still impressive! This venerable warbler had a full brood patch, indicating that she is either incubating eggs or brooding young chicks.

Species: Sharp-shinned Hawk
Most recent capture date: 4/17/2022
Age: about one year old
Sex: male

Species: Brown-headed Cowbird
Most recent capture date: 4/23/2022
Earliest capture date: 5/01/2019
Age: at least four years old
Sex: female

Notes: Instead of building a nest and raising her own chicks, a female Brown-headed Cowbird lays eggs in other bird’s nests for them to raise. This involves searching for other birds’ nests and monitoring them to know when to add her egg, sneaking in at the exact right moment to go unnoticed, and (because success rates are low) laying 20+ eggs per season. Whew! I think raising your own chicks might be easier… (It’s thought that cowbirds developed this strategy because they followed herds of bison as they roamed, eating bugs off of them, so the birds couldn’t stay in one place long enough to raise their own chicks.)

Species: California Quail
Most recent capture date: 4/17/2022
Age: more than one year old
Sex: male

Notes: A common bird in the area, but not a common one in our nets! Quail usually stay too low to the ground to be captured. The colors and patterns on this bird were amazing to see up close.

Species: Bewick’s Wren
Most recent capture date: 4/03/2022
Age: 7-9 days old

​Notes: We have a few nestboxes at the banding station, and this year a pair of Bewick’s Wrens took advantage of one. We disturbed them just long enough to put a band on this chick and their one sibling (there were also three unhatched eggs in the nest, an unusually high proportion of failed eggs), then popped them back in the nestbox to continue to be cared for by their parents. We hope we’ll see them again in the nets one day! (Don’t miss this chick’s big fuzzy eyebrow tufts, a classic feature of baby songbirds.)

Species: Common Yellowthroat
Most recent capture date: 4/02/2022
Earliest capture date: 4/09/2021
Age: more than one year old
Sex: male

Species: Mallard
Most recent capture date: 4/02/2022
Age: more than one year old
Sex: female

​Notes: This was quite the surprise! Ducks do like to hang out at the banding station, but they are usually too big to end up in our nets. In fact, we believe this is the first time a Mallard has been caught in one of our nets! We can’t band ducks – the permits for banding game birds are different from those for other birds – so we just took some data on her plumage and sent her on her indignant way. The size of the iridescent blue patch on her wing told us that she was hatched earlier than 2021.