On the Fourth of July this year a young Osprey died. A week later a young Peregrine Falcon died. The two incidents took place just a few miles from each other. Both birds were less than two months old, and had taken their first flights under watchful eyes of humans. Local Audubon Society had two cameras on the osprey nest, and volunteers were posted by the tower where the peregrine was hatched.
I had a brief encounter with Lux (the juvenile falcon that died later) on the evening of July 5, the day before she took her first leap into the air. She was on Campanile, the clock tower at the center of UC Berkeley campus. The tower rose 307 feet against the blue sky, showed its usual serene façade, and revealed nothing about a raptor's nest until the insistent high-pitched scratchy calls near the top broke through the summer lull. Even with one ear plugged up due to a cold, I could hear her loud and clear.
It saddened me to learn that Lux died bumping into a window in the building next to the tower. It is not just because I had witnessed her poking her head out of the balustrade on Campanile and that made me feel personally invested in her well-being; it is also because the team of Falcon Fledge Watch volunteers had spent so much time protecting the falcons yet could not prevent the ultimate death of one fledgling, and I really felt for the volunteers.
The two deaths prompted me to ask the question: How likely does a juvenile raptor live safely to reach its first birthday? In the case of peregrine falcon, the average first-year survival ranges from 40% to 50% after fledging (source). This doesn’t seem to differ much from the average fledgling mortality rate for passerines (42%) in the first couple of weeks (source). But for a small bird like Dark-eyed Junco it takes about 12 days of incubation plus about another 12 days to grow before it fledges; while for a peregrine falcon, the hatching and nestling periods add up to 64-74 days. It seems to be a much heavier investment on the next generation if you were a raptor parent.
I knew that DDT was the culprit to peregrine’s decimation, but was surprised to find that egg collection and hunting were rampant in the early days, and peregrines had not been that common even before DDT was widely used. More than 100 years ago, when Charles Keeler wrote about birds in California, he did not mention peregrine falcon in the main text, but gave an account of it in the appendix: “Irregularly distributed in California, occurring upon the islands of the southern coast and at various points in the interior.” (Bird Notes Afield, second edition, 1907.)
In 1946, Richard Bond wrote, west of Rockies, the bird was common (meaning more than 1 pair on average was observed in 2,000 square miles) on the coast, but rare inland. At the time, no western peregrines were known to nest on buildings, but they were already reported to nest on a barrel top in a marsh, an abandoned oil derrick, and a platform of a power pole; apparently they had no qualms about using artificial objects.
In my experience, peregrine falcons are not seen as often as ospreys along the east shore of the San Francisco Bay. But when shorebirds and ducks suddenly take off en masse, a falcon is likely to be hunting. This past January, in the two hours we were at Miller/Knox Regional Shoreline, twice did a peregrine falcon descend on the land-locked lagoon, and scared up not just ducks, pigeons and gulls, but two Canada Geese!
Seeing the fleeing of those birds of relatively large size, I can appreciate the formidable predator’s former common name, Duck Hawk, which was used by Keeler, but discouraged by the scientific-minded Bond because it hunts many other bird species than ducks.
Story of Lux and her home on Campanile.
Death of Lux.
Death of the osprey.
More photos of peregrines on Campanile taken by Minder Cheng.
I had a brief encounter with Lux (the juvenile falcon that died later) on the evening of July 5, the day before she took her first leap into the air. She was on Campanile, the clock tower at the center of UC Berkeley campus. The tower rose 307 feet against the blue sky, showed its usual serene façade, and revealed nothing about a raptor's nest until the insistent high-pitched scratchy calls near the top broke through the summer lull. Even with one ear plugged up due to a cold, I could hear her loud and clear.
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| In all three photos above, the female adult Peregrine Falcon stands at the right corner of a ledge below the top balcony. |
It saddened me to learn that Lux died bumping into a window in the building next to the tower. It is not just because I had witnessed her poking her head out of the balustrade on Campanile and that made me feel personally invested in her well-being; it is also because the team of Falcon Fledge Watch volunteers had spent so much time protecting the falcons yet could not prevent the ultimate death of one fledgling, and I really felt for the volunteers.
 |
| Juvenile Peregrine Falcon, Lux, looks out from the gap of the decorated parapet. |
The two deaths prompted me to ask the question: How likely does a juvenile raptor live safely to reach its first birthday? In the case of peregrine falcon, the average first-year survival ranges from 40% to 50% after fledging (source). This doesn’t seem to differ much from the average fledgling mortality rate for passerines (42%) in the first couple of weeks (source). But for a small bird like Dark-eyed Junco it takes about 12 days of incubation plus about another 12 days to grow before it fledges; while for a peregrine falcon, the hatching and nestling periods add up to 64-74 days. It seems to be a much heavier investment on the next generation if you were a raptor parent.
I knew that DDT was the culprit to peregrine’s decimation, but was surprised to find that egg collection and hunting were rampant in the early days, and peregrines had not been that common even before DDT was widely used. More than 100 years ago, when Charles Keeler wrote about birds in California, he did not mention peregrine falcon in the main text, but gave an account of it in the appendix: “Irregularly distributed in California, occurring upon the islands of the southern coast and at various points in the interior.” (Bird Notes Afield, second edition, 1907.)
In 1946, Richard Bond wrote, west of Rockies, the bird was common (meaning more than 1 pair on average was observed in 2,000 square miles) on the coast, but rare inland. At the time, no western peregrines were known to nest on buildings, but they were already reported to nest on a barrel top in a marsh, an abandoned oil derrick, and a platform of a power pole; apparently they had no qualms about using artificial objects.
In my experience, peregrine falcons are not seen as often as ospreys along the east shore of the San Francisco Bay. But when shorebirds and ducks suddenly take off en masse, a falcon is likely to be hunting. This past January, in the two hours we were at Miller/Knox Regional Shoreline, twice did a peregrine falcon descend on the land-locked lagoon, and scared up not just ducks, pigeons and gulls, but two Canada Geese!
Seeing the fleeing of those birds of relatively large size, I can appreciate the formidable predator’s former common name, Duck Hawk, which was used by Keeler, but discouraged by the scientific-minded Bond because it hunts many other bird species than ducks.
Story of Lux and her home on Campanile.
Death of Lux.
Death of the osprey.
More photos of peregrines on Campanile taken by Minder Cheng.
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