Sibling chicks after the female was banded and put back in the nest. She had yellow electrical tape fastened to one of her bands. Her brother received blue on his, when it was his turn. Credit: Mary Malec

UC Berkeley’s baby falcons got a rare visit to their Campanile nest early Friday morning from humans who measured them, banded them, took feather samples and determined their health and sex — and did their best to avoid Annie and Alden’s talons. The peregrine falcon parents took turns swooping low to try and ward off the visitors, some of whom wore protective helmets.

This article was produced by UC Berkeley and first published on Berkeley News

“Alden was on patrol and came down and buzzed us; Grinnell never did that. He’d leave, and Annie would be the most defensive,” said Mary Malec, one of the visitors and a member of Cal Falcons who monitors local raptor nests for the East Bay Regional Park District. She pronounced Alden “a tough dude,” complimenting his dedication to fatherhood.

Turns out he’ll be helping Annie parent a male and a female chick this spring and summer — Annie’s 11th male and 4th female offspring since her arrival at the bell tower in 2016. Grinnell, Annie’s longtime mate, was the territorial male on the Campanile until his death on March 31. Alden took his place hours later and was welcomed by Annie.

Cal Falcons launched a contest Friday for the public to name the siblings via its social media channels — InstagramFacebook and TwitterKids can suggest names on their own special form. Name suggestions must be made by 6 p.m. on Monday, May 30 (Memorial Day). Cal Falcons will choose the finalists, which will be announced the following day, May 31, and the public can then vote for their favorite two names. The winning names will be announced on Friday, June 3.

A recap of Friday’s banding process and more information about Annie, Alden and the chicks can be found in a livestreamed YouTube Q&A hosted Friday at noon by environmental researcher Sean Peterson and biologist Lynn Schofield of Cal Falcons.

Measuring and banding

Dr. Zeka Glucs (left), assisted by Natalie Tan-Torres, band a chick while Annie, the mother falcon, patrols from above. The women are wearing helmets to protect them from Annie attacking them with her talons. Credit: Mary Malec

The chicks’ check-up and banding — calm, quick and ethical — was done as it is each year by Dr. Zeka Glucs, director of the Santa Cruz Predatory Bird Research Group. Her assistant was Natalie Tan-Torres, a volunteer community scientist with Golden Gate Raptor Observatory. During the process, the fluffy, white-feathered babies were cradled in a comfortable position by Tan-Torres and visually isolated, to relax them.

Each chick received two bands, which will stay in place for the rest of their lives. The first was issued by the national Bird Banding Laboratory and has a unique nine-digit number that differentiates the chick from all other birds banded in North America. That band number is associated with all the data collected for the bird at the time of banding. The numbers are small and difficult to see if you’re not in close contact with the bird.

The second band has only four characters in much larger type that can be seen through binoculars from afar. This four-character code is enough to differentiate the falcon from other falcons in the region.

Blue electrical tape was put onto the male chick’s Bird Banding Laboratory band and yellow tape on his sister’s band. When volunteers are monitoring the young birds as they start flying off the tower — fledging is expected to start on Tuesday, June 14 — the Cal colors on their legs will help distinguish them from each other, said Malec.

Glucs, a guest at the livestreamed Q&A, said that male falcons wear a size 6 band, females wear a 7. To compare the band size of falcons to those of other birds, she said tiny hummingbirds get a special band, warblers wear a zero, eagles are a size 9, and swans have neck rings as bands.

A falcon chick’s sex is determined by the width of its legs, right above its feet, since its leg bones are fully developed by this age. Males’ leg bones are thinner at that part of the leg than those of females. And a female falcon generally has a body size that is 30% larger than a male.

At the nest Friday, “the boy was noisy, the girl was very quiet” during their exams, which determined they are in good health and are learning to preen — they had no ectoparasites on their skin, said Malec. Pin feathers were clipped from each bird’s upper back for studies about the heavy metals present in birds of prey and also for genetic studies, which could reveal if either of the new chicks is the biological offspring of Alden.

Said Glucs, “I’m very curious about this nest, genetically.”

“In my narrative of this story,” she said, “Annie was doing some weird stuff, too, before this all happened, going off to odd places, … perhaps it’s possible she and Alden had been acquainted before he showed up as a new Campanile male. So, I’m not going to put anything past him at this point, and I’m hoping we’ll be able to glean some information on paternity from these chicks since we have … at least one year of genetic data where we know Grinnell was the male on territory. I’m hoping to have some answers for you guys … about this year’s dad for each chick.”

What’s next for the chicks

Annie the protective mother falcon dives toward the nest box as her chicks get banded. Credit: Bridget Ahern

Schofield said the chicks appear to be “developing wonderfully. Both are eating well and growing fast … and their flight feathers will be coming in soon.” They can regulate their body temperatures by now, and are too large to be kept warm underneath Annie; recently, they were shaded occasionally from the hot sun by their parents. They’re walking around awkwardly and will explore the tower’s balcony area more in the coming weeks.

Since one of the chicks is female, she added, “that means she is much larger than her sibling, and we might start seeing a different dynamic than we have in previous years when they fledge, since females begin flying later than males, and it is possible the two may spend less time together than (Annie and Grinnell’s) broods of all males have.”

As for Alden, he’s drawn laughs from Cal Falcons webcam viewers by bringing moths to the chicks a few times, but there are quite a few moths on top of the tower, “and for many falcons, if they see something they can easily grab, they’ll do it. … He also hunts somewhat smaller prey, which is normal, and he’s able to bring in several prey items per day; … he prefers water birds, such as sandpipers and terns,” said Schofield.

The fact that Alden is attempting to feed the chicks is remarkable, she said, since “it’s a role female falcons typically take on, solo. … Alden is a bit of an outlier. … This isn’t something Grinnell tried to initiate often.”

“He’s a champ,” Malec said of Alden, adding that his arrival to help make this year’s hatch a successful one “is so amazingly fantastic.”

News about Larry

Glucs shared some exciting news in the Q&A, telling viewers — about 1,100 people tuned in and a few hundred more have watched it since — that Lawrencium, or Larry, one of Annie and Grinnell’s female offspring, had raised chicks this spring that just began to fly. She and her mate, whose territory is on Alcatraz Island, “are parents of at least two fledges,” she said.

Those falcons can’t be banded because their nesting territory is just above that of a pair of aquatic birds called cormorants, which are very sensitive to nest disturbance, Glucs said, adding that raptor experts will try to use cameras and other tools to monitor the progress of these falcon fledglings, the grandchildren of Annie and Grinnell.