It wasn’t supposed to happen, the arrival of peregrine falcon chicks this season at UC Berkeley. The campus’s male falcon, Grinnell, was dead, and his longtime mate, Annie, was alone on the nest atop the Campanile, unable to both hunt and incubate eggs.
But starting last Thursday, two of the eggs that biologists predicted wouldn’t hatch have produced two fluffy, healthy chicks — a third egg wasn’t viable — thanks to the unusual and just-in-time arrival of Alden, Annie’s new partner, just hours after Grinnell was hit by a car in downtown Berkeley on March 31.
And after helping Annie incubate the eggs, Alden’s proving to be a dependable hunter, bringing in prey for the newborns and their mother while Annie broods them.
“This season has been extraordinary. We’ve really been bouncing between the highest highs and the lowest lows,” said Sean Peterson, an ornithologist with Cal Falcons. “It’s amazing to me that we have reached the point where the chicks have hatched and appear to be doing great, given all the events at the start of the year. The behaviors and events we’ve seen have been very surprising and have really shown how unpredictable nature can be.”
The third egg may have failed due to a genetic abnormality, or because it got too hot or too cold at some point, or it may not have been fertilized, Peterson said, adding that Annie “has never had her entire clutch of eggs hatch before.” This is Annie’s sixth Mother’s Day on the tower, where she and Grinnell made their home in late 2016, and she’s now produced 15 chicks. One, Lux, died while learning to fly in 2017.
Peterson said an average of three chicks a year learn to fly from successful peregrine falcon nests. “When you factor in that Annie has never had a nest fail, she is doing quite a bit better than average,” he said. Two of Annie and Grinnell’s offspring — Larry and Sequoia — have known territories.
Last Friday, Cal Falcons hosted for the public a Hatch Day 2022 event outside the Valley Life Sciences Building, with local experts available to answer questions about the campus’s falcons. About 100 people attended, some from as far away as Davis, Livermore and San Jose.
Mary Malec, one of the experts, said that the guests she spoke to “seem very accepting of Alden,” despite the widespread grief that ensued after Grinnell’s unexpected death. She added that “… most people have not only accepted Alden, but think he’s the best thing that has happened at this nest this season.”
While a falcon that lose its mate can require weeks to bond with a new one, said Malec, a study by scientist Grainger Hunt of “floaters,” or unattached adult peregrine falcons, notes that these birds “have seamlessly taken over eggs in the nest with no period of pair bonding, so it’s clear this has happened before. … It’s a survival system that has worked again in keeping this species going.
“Taking over when he might have no actual offspring this year will give Alden the opportunity to continue as the breeding male in future years.”
Alden had been around Annie and Grinnell’s territory for a month or more prior to Grinnell’s death, added Malec, “so Annie was familiar with him.”
The new chicks — one hatched on Thursday, May 5, the other on May 6, Hatch Day — will be in the “baby” phase for their first 10 days as hatchlings, said Peterson, and will be working on growing and developing internally. By Day 10, they will start growing their wing and tail feathers, can keep themselves warm and will be able to eat more complete meals.
About 3 1/2 weeks from now, their legs will be fully grown, and around the end of May, they will be banded and their sex can be determined. At that point, Annie and Alden will spend less and less time in the nest while the chicks start exploring on their own. The campus’s annual Fledge Watch, a period of time when the youngsters begin flying and volunteers position themselves near the tower to monitor their progress, is expected to begin in mid-June.
Recently, falcon chicks also hatched at UC Davis’ Medical Center and on San Jose’s city hall.
Malec said that Cal Falcons volunteers continue to be on campus regularly, to monitor the falcons’ activity, which turned dramatic last October when Grinnell was wounded by rival falcons and hospitalized. Annie didn’t accept Grinnell back immediately after he was released in November, also showing interest in the male rival who’d injured Grinnell. After Annie and Grinnell reunited on New Year’s Day, Annie mysteriously disappeared in late February for about a week, in the midst of preparing her nest, then returned only to lose Grinnell soon after her first eggs had been laid.
Now, new hatchlings are in the nest, the rival falcons have left, and Alden has arrived to help Annie and her young. Said Malec, “He’s making it work.”