Interested in observing Peregrine Falcons? Then the following is a MUST READ!
Observing Breeding Behavior
by Janet Linthicum University of California, Santa Cruz
photos © Will James Sooter
It is important that suspected nesting areas be adequately checked,especially early in the breeding season. In areas where reproductive success is being monitored, all territories should be checked at least twice during the nesting season. More frequent visits may be necessary to determine exact timing or outcomes if precise information is needed, for example in manipulation efforts. Visits are usually most productive if they occur at dawn or dusk, because behaviors such as food and nest exchanges are highly likely to occur at these times. During other parts of the day, more time may be required at a site to get the same information. All sites should be documented in such a way that a later researcher can easily find them. Directions to the site, photographs, and sketches are all extremely helpful, and should be put on file (confidentially) in case the current researcher is not available for future survey work.
Incubation. Mid-March (April or later in northern areas or high elevations). Determine whether the territory is occupied by one or two falcons. Record presence of falcons, age, courtship, incubation behavior, nest location, band status, etc. If no falcons are seen, the site should be visited again, and possible alternate sites checked, as Peregrines can be very hard to detect during incubation. First-time layers often lay eggs later than expected for their region. Incubation lasts approximately 33 days.
Nestlings. Late April to June in temperate latitudes. Determine whether adults are still attending the nest where eggs were laid, and whether young have hatched. If there is nest failure, the pair may have relocated and laid another clutch on a different ledge. If it is possible to see into the nest from the observation point, record the number of young.
Fledging. Late May to mid-August. Depending on previous nest chronology, young should be ready to fly near this time, roughly 40 days after hatching. Recycling after egg failure can cause nest departure to be delayed from the ìexpectedî date by a month or more. Record number and sex of fledged or near-fledged young. At sites where the observer cannot see into the nest, young must be counted after fledging. The resulting number should be considered a minimum, as some young could go undetected or have died or dispersed before the visit
Peregrine fledging Juvenile Peregrine perched Peregrine fledging
This information is intended to help in determining reproductive status at eyries where the observer cannot see into the nest, and so must ascertain status based on behavior. It is written primarily for those watching nests intensively, for example if manipulation is planned, but may also be useful for individuals with limited experience. It is helpful if observers use this information to describe vocalizations and behaviors in a standardized way. For example, reports of Peregrines ìpeepingî or calling do not convey useful information to the reader. Detailed descriptions of behavior can be found in Cramp and Simmons (1980), Sherrod (1983), and Ratcliffe (1993).
BOWING. A general display used in many situations, especially as part of courtship.
MALE OR FEMALE LEDGE DISPLAY. The falcon stands over the nest depression (scrape), leaning forward (bowing) and ee-chupping. The male often stares at the female during a male ledge display. Ledge displays are often accompanied by;
SCRAPING. Either bird can do this. The falcon runs its breast through the substrate or nest depression, pushing out with its legs behind. The bird is forming the nest cup (scrape), but this is also part of courtship. Scrapes may be made at several potential ledges before one is finally chosen for laying.
MUTUAL LEDGE DISPLAY. Often this is precipitated by a male or female ledge display. The other bird joins the first on the ledge and both bow and ee-chup over the scrape, sometimes touching bills. This can also happen outside the eyrie.
FOOD TRANSFER. The male offers food to the female by approaching her or standing near, with food in talons or beak, ee-chupping. The female takes the food from the male, usually ee-chupping or wailing. This can happen in the air or
perched. The male often signals the female that he has food by wailing as he approaches the cliff.
LANDING DISPLAY AND HITCH-WING POSTURE. (male). A pre-copulatory display in which ìshouldersî are held high, as if in a shrug, and male often prances as if on tip-toe.
COPULATION. The female leans forward and moves her tail to one side. The male rests on his tarsi on her back, flapping his wings, and presses his tail underneath the femaleís. Copulations are usually accompanied by wailing on the females part, and chittering or ee-chupping by the male. When the male departs, the female usually ee-chups a few times, and often rouses (shakes her feathers).
Peregrine Falcons copulating
CACHING. Peregrines sometimes store uneaten food for later retrieval. They usually have several favorite cache spots on the cliff or elsewhere in the territory.
CASTING. The falcon hangs its head and wags it from side to side with mouth open. Eventually a pellet (casting) of non-digestible material is expelled.
EE-CHUP. A repetitious, staccato ee-chup ee-chup ee-chup sound. Males have a higher-pitched ìeechipî. Variations include a slower chip chip chip, usually during ledge displays and while feeding young. Ee-chup usually implies social recognition, but a very similar sound, louder and more staccato, is given as a response to vagrant raptors, usually Peregrines.
CACKING. Very loud cack cack cack -- A response to disturbance, either a raptor or other animal (including the observer) too near the eyrie.
Adult Female Peregrine "cacking" Immature Peregrine Falcon "wailing"
WAILING. A long, slow, ascending waaaaaa waaaaaa waaaaa. Sometimes connotes hunger, but also used in a variety of circumstances. Youngsters have a more insistent variation of this call, which is often referred to as hunger screaming.
CHITTERING. Like ee-chupping but quicker and less defined. Usually used by birds in proximity, often when one bird is being made uncomfortable by some aspect of the interaction, or during play by fledglings.
Both birds are visible for extended periods outside the nest. This can happen when there is a partial clutch.
PAIR FLYING. Both birds engage in high speed acrobatic displays, with no apparent hunting or territoriality involved. This indicates that the female is probably not lethargic with eggs yet. Sometimes males engage in spectacular flight displays while the female watches.
TANDEM HUNTING. Self-explanatory. Again, the female is probably not laying eggs yet.
LEDGE DISPLAYS. See above. NOTE: Sometimes the falcons concentrate courtship in one spot, then suddenly lay eggs in a different, often more cryptic location. If both birds are suddenly no longer seen together, or activity at the expected nest subsides, suspect that the birds have moved and that they might have eggs.
FOOD TRANSFERS. These occur, male to female, in the air or at a perch throughout the nesting season. As incubation approaches, concentrate on the male after the transfer. He is often the key to incubation as described later.
COPULATION. Before and during egg laying, Peregrines copulate frequently. When the clutch is complete they rarely copulate.
LETHARGY. Just before and during the period of egg laying (approximately eight days for four eggs) the female becomes lethargic. She can look dumpy, including fluffed-up feathers while perched, hanging her vent feathers (the feathers in front of the cloaca, underneath the tail) to an unusual degree, leaning slightly forward while perched, waddling when walking, dozing with one or both eyes closed for long periods, and generally remaining near the nest and being inactive. She might also spend considerable amounts of time in the nest by herself. After laying an egg, she may have periods of being more active, but lethargy is a general demeanor to note. Those without much previous experience with Peregrines should be aware it is comparative and subjective.
PARTIAL CLUTCH. The falcons usually begin incubating after the second or third egg, even if a fourth is to be laid. Before incubation starts, they often guard the eggs, standing in the nest or within sight of the eggs. This is an indication that at least something is in there. Again, the male is the key. After a food transfer or nest exchange, watch the male. If he enters the nest for a while (even a long while) then comes out and perches out of the nest while the female also remains outside, you are fairly safe in assuming that full incubation has not started.
During the normal course of incubation, one of the adults is nearly always on the nest. Exceptions are during disturbance, for short periods on particularly warm days, or for a few minutes during food exchanges. The female does the majority of incubation. The male brings food to her several times daily, or sometimes simply relieves her and takes a turn on the eggs while the female eats, preens, and relaxes. When she returns to the nest to relieve the male, he usually appears on the ledge when she disappears; an unaware observer may think only one bird was involved in a brief visit to the ledge. A common mistake is failure to realize that the bird leaving a spot is not the same bird that just arrived there (i.e., nest exchange as opposed to just perching briefly). This is why it is important to be able to distinguish sexes.
The Tiercel (male) performs a food exchange with his falcon (female) partner
During food exchanges the male arrives with food, often wailing or ee-chupping and passing in front of the eyrie where the female can see him. She then exits the eyrie and takes the food, either at a perch or in the air. This exchange gives a good opportunity for locating the nest. The best way to determine that incubation is occurring is to train your attention intently on the eyrie and be certain that the attending falcon remains in the nest until relieved by the other adult. This can be very tedious, but is worth the trouble because otherwise it is possible to see a lot of behavior, and yet not determine what is happening. Observation of several sequences in which an adult attends until a nest exchange occurs indicates that incubation is underway. If the observer is unable to see the eyrie opening, other behaviors may be helpful. For example, VOLUMINOUS EXCRETION has been used to determine incubation in coastal California, where the observer sometimes cannot see the cliff face that the eyrie is on. When a nest exchange is occurring (e.g., the male brings in food and disappears toward the nest, and soon thereafter the female appears coming from that area) watch the female. After she perches, she soon slowly leans forward and emits a large quantity of excreta. This can also occur while flying. This behavior indicates that the falcon has been unable to defecate for a prolonged time (i.e., has been incubating). Also watch for rousing (shaking of all feathers in a relaxing manner), stretching, and preening intensively. All of these are normal behaviors, but tend to be exaggerated after a stint of incubation.
Some pairs lose their eggs to breakage, weather, or other factors. If this occurs while laying is still underway, they may relocate to a different ledge and attempt to complete the clutch there. If the clutch has been completed and incubation is underway, and the eggs are then lost, the first egg of the second clutch is usually laid approximately fourteen days later if recycling occurs. Sometimes, falcons exhibit the ìlost lookî after failure, returning to the scrape repeatedly but not staying, and wailing frequently. The falcons usually change ledges after failure, sometimes quite a distance away (possibly an alternate cliff), so do not assume they have given up if they are not in the usual places. Re-nesting may occasionally occur after loss of a young brood, or even after a second set of eggs is lost.
As hatching approaches, the adults often become more aggressive. During the early nestling stages the young require almost constant brooding, which can be hard to distinguish from incubation. The main difference is that after a food exchange, the female takes the prey into the nest rather than eating outside (she may pluck it before entering the eyrie). During the early nestling stage most females do the majority of feeding. Males provide food, and may brood young during the femaleís absence. After approximately two weeks, depending on ambient temperature and number of chicks, the young no longer need constant brooding. Therefore, both adults are often outside the nest for extended periods. This is easily mistaken for nest failure. Depending on size of prey and number of young, the nest may only be visited a few times a day by the adults. Clues to presence of young include continued territoriality by adults, absence of courtship behavior, frequent hunting attempts, sometimes hunger screams of young, and, of course, prey deliveries.
Adult tiercel (male) delivers prey to his offspring who are both larger than he is and growing rapidly and getting ready to fledge.
As the young age, they begin eating on their own, and sometimes a prey delivery is extremely brief. Also, late in the nestling stage the female hunts, and the male as well as the female feeds young. Some males are absent from the immediate nest area most of the day, either hunting or perched out of sight, except when delivering prey. Clues to failure include either adult eating full meals without delivering food to the eyrie, decreased territoriality and presence at the cliff or resumed courtship behavior if recycling is occurring, and frequent wailing.
Observers should find an observation site with optimal visibility, but where their presence does not interfere with normal falcon behavior. In some cases distant locations can provide a better overall view of the cliff and falcons coming and going. However, those with little observation experience with Peregrines may find them difficult to spot from a distance, and vocalizations can be very helpful. The falcons respond more to an observer above the nest than to one below or across from it. Cacking birds are disturbed enough that observers should retreat and find another location immediately. Signs of lower-level disturbance can include soaring above the cliff silently (watching the observer), perching where they can watch the observer rather than engaging in normal behavior, and sometimes displacement aggression such as assaulting a cormorant, gull, or other large bird in the cliff vicinity. Generally, if a falcon seems to be watching the observer(s), they should consider retreating to a more distant location. Even if the birds are not disturbed, they may be less inclined to engage in the behavior the observer is there to see if they are distracted. Before beginning observations, find a spot from which to observe for extended periods without becoming uncomfortable, distracted, or eager to depart.
Ideally, observers should learn to distinguish the male from the female, preferably while both are still visible simultaneously. The best indication of sex is size, females being larger than males. However, it can be extremely difficult to sex a single bird on this basis, and experienced observers often err. If there are identifying aspects of individual falcons, they can be very helpful once incubation has begun and the observer rarely sees both birds at once. In many pairs, the female looks darker overall on the breast and farther up toward the neck, and may have a darker, slightly brownish tinge to the back. The male looks more white on the breast from a distance, and silver on the back and especially in the rump area in flight. Some males are vividly orange around the cere (fleshy portion of beak) and feet (as opposed to bright yellow or yellowishorange). There is much variation among individuals, so get to know the pair if possible. Male voices are higher-pitched, and in flight their wings are more narrow with sharper ends. Peregrines molt their flight feathers during the breeding season, with females usually beginning to molt before males. Differences in the gaps in wings and tail can be helpful in distinguishing individuals during a given day's observation. Occasionally one of the pair is a yearling. Yearlings have bleached considerably during the year and may appear blond rather than brown, and could be confused with an adult at a distance. A good method of checking is to note whether the marks on the breast are vertical streaks or horizontal bars. Occasionally, one may encounter a yearling that has already molted partially by its first spring, or a two-year-old that molted incompletely its first year. These birds may breed successfully, although many do not.
Recently fledged young are brown with vertical streaks on the front, and may appear somewhat larger than adults of the same sex, because their flight feathers are slightly longer.
Recently fledged Peregrine Falcons. Note vertical streaks on the front of each bird as opposed to horizontal bars found on the front of adults.
Fledgling Peregrine Falcon exercising her wings . Two Fledgling Peregrines engage in mock combat.
Their wing tips in flight are more rounded than those of adults. They often flap their wings while perched (exercise), land clumsily, and engage in mock combat, tumbling and playing together in the air. When an adult is in view, they hunger-scream, and often chase the adults. In begging while flying, they sometimes appear to flap their wings quickly (flutter). Seen from above, powder down may cause young in flight to appear bluish, leading to confusion with adults; however young of the year have conspicuous light tips on the tail feathers.
For future reference, notes should contain a description of the adults, especially of bands (color and leg) and any unusual characteristics if possible. This can help future observers to determine longevity, continued occupancy, etc. Some Peregrines have alpha-numeric bands in addition to U. S. Fish and Wildlife Service (USFWS) bands.
These bands usually have two characters, numbers or letters or both, that are meant to be read at a distance. When one of these bands is read, it is necessary to draw the band as it appears on the leg for reporting purposes. This is because there are several combinations of the same characters in existence and how the characters are arranged on the band is important for identifying it. For example, characters can be horizontal and/or vertical, and may have a line between them. Some bands are more than one color.
Adult Peregrine Falcon hovering over her fledgling and watching it's first flight attempt.
Female Peregrine Falcon chasing down a Pelican to keep it away from her nesting area. She has her talons stretched out toward the Pelicans head!!! Forcing it down to the ocean below.