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Team Concludes 40th Season of Falcon Monitoring at Pinnacles National Park

By Wildlife Biologist Gavin Emmons and Science Communication Specialist Jessica Weinberg McClosky, San Francisco Bay Area Inventory & Monitoring Network

Brown and white falcon with her beak open and her feathers puffed out, making her appear larger. She's perched on a rock at the entrance to a triangular cliff cavity, which has a white bundle of nestlings inside.

Adult female prairie falcon calling and perching defensively at her cliff cavity nest, with young nestlings huddled together just behind her to the right. NPS / Gavin Emmons

July 2025 - The falcon monitoring team recently finished up its 40th year of breeding season observations around Pinnacles National Park’s iconic rock formations. With 21 young prairie and peregrine falcons all fledged from their cliff cavity nests, the park lifted its raptor advisories in early July, reopening climbing areas to visitors for the rest of the year. All told, we saw mixed nest success and a bit of inter-species drama. Other raptor species nesting in the park also treated us to some exciting observations.

The breeding season started off wonderfully normal, with nine prairie falcon pairs and four peregrine pairs occupying nesting territories. One of the prairie falcon pairs did not end up nesting, and then the other 12 falcon pairs had very mixed nesting success.

Three small, fluffy white nestlings with some blueish skin around their eyes. Two are looking towards the one on the right, which is vocalizing in the direction of the camera.

Peregrine falcon nestlings inside their cliff cavity nest. These young are less than a week old. Note the yellow-white knob on the tip of their beaks. This is an "egg tooth" that the young use to help tap at the inside of an egg to assist them with hatching. The "egg tooth" disappears after the first week of nestling development. NPS / Gavin Emmons

Three fluffy white nestlings with bluish faces vocalizing inside a rocky cliff cavity.

Peregrine falcon nestlings in their cliff cavity nest - these are the same young pictured in the previous photo, but now around 21-23 days old. Peregrine and prairie falcon young usually fly from the nest for the first time at around 42 days old. NPS / Gavin Emmons

Four prairie falcon pairs raised 14 fledglings and three peregrine pairs raised seven. Meanwhile, four prairie falcon nests and one peregrine nest failed during egg incubation or nestling-rearing. Although 21 fledglings is below the 1984-2024 average of nearly 28, it is similar to last year’s count. It’s also within the normal range of variation that we expect to see based on our many years of data collection.

Line graph of falcon fledgling counts since 1984 showing lots of variability year to year. The last three years are low compared to the two years before that. In the last two years, the total counts are just above the lower standard deviation line.

Although 21 total fledglings (solid gray line) is below the 1984-2024 average of 27.7 (dark gray dashed line), it is similar to the 20 fledglings we saw in 2024. It’s also within the normal range of variation indicated by the dashed gray standard deviation lines. Compared to last year, the prairie falcon fledgling count (orange line) is slightly down and the peregrine count (blue line) is slightly up. NPS / Jessica Weinberg McClosky & Gavin Emmons

We suspect that some of the nest failures may have been due to predation by great horned owls or other nest predators. And at least two prairie falcon pairs included young birds likely nesting for the first time. In these cases, parental inexperience could have been a factor. Another prairie falcon nest failure may have a rather different explanation.

Side view of a peregrine falcon with her beak open and the backs of her wings and tail angled towards the camera. A pair of feathers on each wing have more of a blue-gray hue compared to the other more reddish-brown feathers.

Adult female peregrine falcon scold-calling in flight near her active nest site. Note that this female is brownish overall, with newer blue-gray flight feathers showing in molt on both wings. This is likely a young female adult nesting for the first time this year. NPS / Gavin Emmons

Peregrine falcon flying and calling, with the top side of her wings and tail facing the camera. Most of her wing feathers are reddish brown patterned with some white, but a couple have a more gray-brown hue.

Another female peregrine with evidence of some different feather ages. NPS / Gavin Emmons

As peregrine recovery continues at Pinnacles, it's interesting to see how they interact and compete with prairie falcons. Both species rely on limited cliff cavity nest sites for breeding. Midway through this season, a peregrine pair that has been nesting at South Chalone Peak for the last several years decided to nest at North Chalone Peak instead. They pushed out a prairie falcon pair that had nested at North Chalone Peak for many years. The displaced prairie falcon pair attempted to nest at rock formations just to the north but ultimately failed, possibly due to the late attempt at beginning egg incubation.

In addition to falcons, we confirmed many other raptor species breeding in the park this year. These include American kestrels, red-tailed, red-shouldered, and Cooper’s hawks, great horned and long-eared owls, golden eagles, and white-tailed kites.

Owl with a big round facial disc and ear tufts, on a moss-draped branch, looking over its shoulder at the camera.

Adult long-eared owl perched in its nesting territory. NPS / Gavin Emmons

Beatufilly patterned gray, rusty, and white kestrel with black accents leaning its head down and picking apart the head of a small gray rodent with its beak.

Adult male American kestrel eating a shrew. Biologist and photographer Gavin Emmons had never seen a kestrel eating a shrew before, so this was a nice highlight! NPS / Gavin Emmons

Bird with a light, rusty breast and gray wings clumsily balancing on a cluster of leafy branches with its wings out above its head and its beak open, mid-vocalization.

White-tailed kite fledgling, hopping and flapping on branches near a nest site, still figuring out how to make use of its wings! NPS / Gavin Emmons

Striking white bird with red eyes and a rodent in one of its talons, about to land on some bare branches. We see the underside of the wings and tail fully spread out as the bird slows down.

Adult white-tailed kite with California vole prey. NPS / Gavin Emmons

Long-eared owls are a California Bird Species of Special Concern, and it's always a treat to see them nesting successfully. Two pairs fledged young in the park this year. The nesting pair of white-tailed kites was also a big highlight this season. White-tailed kites are specialist hunters, and in our region, they primarily eat California voles. California vole populations fluctuate a lot, and in recent years, the lack of voles has meant a lack of kites nesting at Pinnacles. However, this year we’ve noticed California voles all over the place. This vole population spike is likely the reason the white-tailed kites returned to nest at the park this year. The kite pair successfully reared four fledglings.

The Pinnacles falcon story will continue to unfold once again next January—stay tuned!

For more information

Pinnacles Raptor Advisories and Raptors webpages

San Francisco Bay Area Network Falcon Monitoring webpage

Falcon monitoring data, 1984-2024

Pacific Coast Science & Learning Center Prairie & Peregrine Falcons webpage

Prairie & Peregrine Falcons Blog

Contact Wildlife Biologist Gavin Emmons

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