Readers’ wildlife photos

After a long hiatus, UC Santa Cruz biology professor Bruce Lyon is back with some amazing photos of his favorite bird, the peregrine falcon.peregrine falcon). Bruce’s narration and ID are indented, click on them to enlarge the photo.

The lyrics to the Beach Boys song “California Girls” are “I wish they could all be California girls.” For a pair of peregrine falcons (peregrine falcon) on the central coast of California, the sentiment was instead “I hope they’re all California gulls.” The female of the pair likes to prey on seagulls, but only California shearwaters (california gull).

This is a pair of falcons that I have been observing for nearly a decade and have reported on several times on WEIT (some sample posts are available here , here , and here ). The newly arrived couple often hunted at home. They perch on the cliffs near their cave nests and spend long hours gazing out to sea. Other local peregrine falcons do this in the spring to pursue migrating shorebirds like cormorants, but this female pair was hunting gulls and did so before nesting. Peregrine falcons can be skittish about prey, but this pair is surprisingly tame when it comes to food and can withstand some amazing natural history encounters.

Below: Two people gaze out to sea in search of birds. Female Peregrine Falcons (right) are typically much larger than male Peregrine Falcons (50-60% larger, depending on region), which affects the size of prey they capture.

Below: Sometimes hundreds of seagulls fly north toward the cliffs using updrafts deflected off the cliffs. Most of the passing gulls are western gulls (Western gull), a rather large seagull, weighing about 1000 grams (2.2 pounds). Compared to other native gulls, the Western Shearwater has a dark gray back and tops of wings, a thick, yellow bill, and a red spot near the tip of its bill.

Below: Whenever western gulls fly over the cliffs, the females ignore them.

California gulls also came, but in smaller numbers. They are much smaller than Western Gulls (600 grams, 1.3 pounds), have a thinner bill, a red and black spot on the tip, and a light gray color on the top of the wings and upper back. The yellow legs of breeding adult gulls differ from the pink legs of western gulls, a convenient way to identify dead gulls when falcons have removed other diagnostic features.

Below: Unlike Western gulls, female gulls show a strong interest in California gulls. She watches them closely as they fly by, often adopting a “prepare to pounce” stance before making her move. Interestingly, she did not immediately chase a flying seagull, but waited until it disappeared from sight around the corner of the cliff before taking action. My guess is that part of her strategy for catching seagulls is to strike out at close range and she waits until the target seagulls are unaware of her interest.

Below: Targeted California gulls take immediate action after a flyby. After leaving the cliff, she raced after the seagull at full speed.

The first few times the female went out chasing gulls, I was only sure of the outcome when she quickly came back without prey. When she didn’t return immediately, I initially thought she hadn’t made it, as the various peregrine falcons I’ve seen almost always bring their prey back to the nest. Instead, I think she missed the gulls but stayed out looking for other prey because she had left the roost.

Picture below: One day, she went out to chase a seagull but didn’t come back. I became suspicious and went to look for her. I found her feeding on gulls about 300 yards north of the nest, on a ledge above the waves at the corner of the cliff. The black spot on its bill and yellow feet confirmed it was a California gull. It turns out that eating the gull where it is killed rather than carrying it back to the nest is the norm for her. Seagulls are very heavy prey and I doubt it would take too much effort to carry something that big a long distance.

Below: Eventually, the male approaches the carcass along with the female, but initially keeps his distance and pecks at the entrails. Female peregrine falcons can be possessive of food, especially if there are chicks to feed, but this is in February before nesting. Males are usually very deferential, perhaps because females are much larger.

Below: Eventually he comes to the body with her. I have never seen such sharing of food with other peregrine falcons before.

the following. Another California gull killed. Again, when the female went out for a chase and didn’t come back, I continued looking. I found this pair sharing a California Gull on a very narrow ledge above the channel, very close to the early kill shown above.

Below: I was surprised to see a male feeding a female, as shown in this photo. Females are perfectly capable of feeding themselves, so perhaps this mating feeding is a form of bonding?

the following. Male seagull surrounded by gull wings. The wind was very strong, and the seagull’s wings kept flapping in the wind, flapping the male falcon’s head. A gust of wind finally blew the gull off the small ledge and landed on a rock shelf below near the waterway.

the following. The female walks up to the fallen carcass and begins feeding, but large waves threaten to overwhelm the continental shelf and the carcass is in danger of being washed out to sea.

the following. The female tried to pull the gull away from the danger area, but was unsuccessful. Eventually, a huge wave swept over the ledge, and the receding water dragged the gull out to sea. I watched for several minutes, but the falcon did not rescue the seagull from the water.

the following. Later, when the couple had chicks. They did bring the gulls to the nest and the female is pictured sitting with the gulls close to the nest. Parents often eat part of their prey before bringing it back to the nest, so gulls brought back to the nest may have been partially eaten and easier to carry in flight.

I have never seen this female actually capture a gull, as the capture always happens in a corner out of sight. However, some friends did see a female seagull chasing a seagull, catching up with it, swooping on its back and throwing it to the ground. They did see how the gulls were wiped out.

Below: I did see the female of an adjacent pair capture a California Gull. In my peripheral vision, I saw what I thought were two seagulls fighting in the distance in the sky before they slowly circled to the ground, hugging each other tightly. Something didn’t seem right for a gull fight, so I walked over to the scene and, to my surprise, flushed the female falcon off the ground with a freshly killed California gull. This “seagull war” is actually a peregrine falcon hunt.

Perhaps because I scared her and she was already flying with a heavy load in the air, the falcon did fly 500 meters back to her nest with the seagull. Her flight looked really hard.

Below: A second western gull was not amused by the situation and chased the female falcon back to the nest.

the following. “On wings and prayers”. When preying on small birds, falcons usually pluck all flight feathers from their wings, but they do not do this on larger prey like gulls. This allowed a complete pair of wings to be attached to the carcass, and falcons would sometimes fly around with these winged carcasses, as shown here. The expression on wings and prayers refers to undertaking an endeavor that has little chance of success. This would seem to be appropriate for falcons hunting gulls, as the chance of successfully killing a gull in a given chase appears to be much lower than with some prey species such as the Faralop. However, in terms of value for money, the Seagull is probably worth the effort, as the Seagull weighs about 20 times as much as the phalarope.