Peregrine Falcon FAQ
Q. Do Peregrine falcons have any predators?
A. In non-urban settings great horned owls, golden eagles, and large mammals may prey on young falcons in the nest or at fledging. However, in urban areas Peregrines have relatively few predators. They will battle with any intruding peregrines.
Q. What do Peregrine falcons eat? How do they obtain food?
A. Peregrines primarily eat birds they catch in the air. A peregrine will typically fly above its prey, then fold its wings and dive or "stoop" at the other bird and grab it or strike it in the air, then retrieving the stunned or dead bird in mid-air. Urban peregrines tend to eat a lot of pigeons, and this pair is no exception, but they eat a variety of the species available.
Q. How much food does a peregrine eat in a day?
A. A peregrine eats the equivalent of one quail-sized bird per day or more. We have documented the remains of more than 200 different species of prey in peregrine falcon nests in California. On a given day a peregrine falcon might eat most of a pigeon, or part of a duck, or two or more sparrow sized birds to meet its nutritional needs. The chicks eat considerably more than this daily as they quickly grow.
Q. Where do peregrines get their water?
A. Peregrines get all the water they need for survival directly from the food they eat. However, they do like to drink water and bathe in it if it's available in a safe and secure location.
Q. Do Peregrine falcons mate for life?
A. Peregrines generally do keep the same mate from year to year. However, if a member of the pair dies or disappears, the surviving falcon will accept a replacement mate.
Q. How many young do Peregrines have?
A. A female peregrine usually lays 3 or 4 eggs, occasionally 5. The eggs are slightly smaller than a chicken egg, and are mottled with a dark, reddish-brown pigment. The female falcon will do most of the incubating, which averages about 33 days. The male will incubate the eggs while the female flies off to eat food he brings her, or just spells her. Not all eggs hatch, some are infertile and some die during incubation.
Q. The parents have left the nest, and the eggs are just sitting there! How long can the parents not incubate the eggs without damage to the developing embryos?
A. With two eggs in the nest, and probably at least one if not two more to come, the parents will do what we call "partial incubation", meaning they don't sit constantly, and not much is going on inside the egg. This helps the chicks hatch close together, since there are 48-72 hours between laying eggs, if they started "hard incubating" the first egg, the last could be up to a week+ younger than the oldest. Even when "hard incubation" has started, eggs can stand considerable chilling.
Q. What does the term “eyas” mean?
A. An eyas is a nestling hawk or falcon Plural is eyasses. If, near fledging, young leave the actual nest flying, it would be referred to as a "branching". An adult peregrine is sometimes referred to as a "haggard", a bird still in partial or full immature plumage is sometimes called a "passage" falcon. Males may be referred to as "tiercels", females as "falcons".
Q. I’ve seen the chick lying on its side or stomach, moving just a little every now and then, is this normal?
A. It's likely due to warm weather that's making the chick not interested in being brooded. The chicks, when they get warm, often push one or both legs out to the side to allow heat to dissipate from the skin of their legs. This is normal behavior.
Q. Will the youngest chick(s) get enough to eat?
A. Yes. Peregrines regularly raise three, four, or even five chicks. The adults make sure that each chick is fed enough. The chicks can communicate hunger through vocalizations and the adults will respond to them.
Q. But during the last feeding, one slept through it and didn't get fed. Is it sick, or weak?
A. No, most likely it still has food in its system from the last feeding and is "sleeping it off". It takes several hours to digest a large meal. The chicks get an abundance of food and don't need to be fed at every feeding. When that chick is ready to eat again it will join with the rest.
Q. Will the bigger/older chicks push the younger out of the nest or kill them?
A. No. Some (few) raptors such as eagles do this, especially if food is scarce, but peregrines do not. The chicks get along fine. We wouldn't have put the camera up and invited the public to watch if that were going to happen.
Q. The chick has a huge swelling on its neck, is this normal?
A. Birds of prey have something called a "crop", a storage area for food located just under and to one side of their neck. This allows them to eat more at a time than their stomach can handle, and slowly process it over several hours as it passes from crop to stomach. So, in the non-breeding season an adult might eat a pigeon in the morning, and "turn over its crop" over several hours, eating only once that day. You can't often see this on the adults because they're feathered, although a practiced eye can pick out a noticeable bulge after they've had a large meal. On the chicks, however, it is quite obvious. As the chick is fed, the first few bites pass fairly directly to the stomach, and then the crop begins to fill. Depending on the size of the meal, as the chick gets larger and eats more at a time, the crop may appear huge. This will induce a bout of heavy snoozing while the chick's body assimilates all this food and turns it into ever more chick. Interestingly, this digestive process causes the chicks to generate considerable heat themselves, so you may notice at this stage that the chick doesn't want to be brooded for a few hours after a large meal, then when it is "empty" it returns to "brooding mode".
Q. That chick just vomited! Is it sick?
A. If a small chick gets too much food at once, it may spit the food back out. Also, it may have been casting. Peregrines will cough up pellets of undigested material, such as feathers and small pieces of bone, at least as early as 2 weeks of age.
Q. What will keep the chick from hopping out to the ledge and falling off prematurely?
A. Most baby peregrines, and many other falcon species, are raised on ledges, with no nest structure, on precipitous cliff faces. All of them could potentially fall. Some youngsters do fall from ledges, but it is very very rare. Even before they can see, the chicks do not like the feeling of nothing below their feet. They can't see much until they're about five days old, but they also don't move around much until they're older.
Q. Why do some eggs not hatch? Is this because of DDT, or a clumsy parent, or temperature related?
A. Not all eggs are necessarily fertile, and some fertile eggs just don't hatch, much as some human pregnancies aren't carried to term. If any eggs remain intact when we band chicks, we'll collect them for pesticide analysis, and we'll be able to tell if they were fertile. "Urban" peregrines tend to be relatively "clean" of pesticides compared to those in "wilder" environments. This is probably because they eat more pigeons and starlings, which are lower on the food chain, so accumulate fewer pesticides than, say, wading birds that eat invertebrates in a marsh.
Q. If some of the eggs won’t hatch, why do the adults continue to incubate them?
A. Eventually, they do stop incubating. When we used to remove thin-shelled eggs from wild nests for captive incubation, and replace them with artificial eggs, we knew we had to replace the latter with chicks at or near the "due date", or the adults would have abandoned the nest and not accepted the fostered chicks.
Q. How do you know what sex the chick is when you band it?
A. By the time the chick is old enough to wear a band, we are able to sex the bird by the size of its feet and thickness of the tarsus. By the time they reach 3 weeks of age they have achieved adult weight at about 650 grams for males and 950 grams for females. As you can imagine the difference is quite obvious to the practiced eye. If there is any doubt we use the larger female band.
Q. Do the leg bands hurt the falcons or affect the way they hunt?
A. The bands placed on peregrine falcons are a comprised of a very lightweight aluminum and are specially sized to fit a falcon's leg. They do not hurt the bird in any way and are comparable to a human wearing a bracelet. The leg bands do not interfere with flight or grasping of prey.
Q. How do the parents react to the banding....do they try and attack the person banding the youngster?
A. The birds can respond in any number of ways as you might imagine, but for the most part they voice their objections to our intrusion by stooping (diving) past the nest ledge at high speed while vocalizing or "kacking" loudly. This is temporary, soon after the banders leave the peregrines' behavior returns to normal.
Q. What happens after fledging? How long does it take for a youngster to learn to hunt successfully? Do both parents stay around for that process?
A. It takes most young peregrines about six weeks to learn to hunt, and become independent. At first they are tentative, but within a few days, when a chick becomes more proficient at flying, the adults will begin passing food in the air, which will provide training in agility in addition to lunch. Normally there are siblings to "crab" with (play with in the air using talons and etc., honing flight skills), but if the nest only contained a single chick, it may turn most of its attention, as all young peregrines do, to easy targets such as dragonflies, or large birds to "tag", etc. Gradually they turn to more appropriate prey. The adults will continue to feed them as necessary until they have the skill to confidently feed themselves, at which point they will leave the territory and strike out on their own. There is no evidence suggesting that the adults "drive them away".