Falcon Nests: Where and How Falcons Raise Their Young

Falcons do not build nests in the way that many other bird species do. Instead of constructing a woven structure from twigs and grass, falcons lay their eggs directly on a scrape, which is a shallow depression in a substrate such as rock ledges, cliff faces, tree hollows, abandoned nests of other birds, or human-made structures. The peregrine falcon (Falco peregrinus) is the most widely studied species for nesting behavior, and its adaptability to urban environments has made it a model for understanding how falcons select nest sites, lay eggs, and rear chicks. This article provides a practical guide to falcon nesting behavior for students, researchers, life-science professionals, and informed general readers, with a focus on peregrine falcons and their urban adaptation. The content covers nest site selection, egg laying, incubation, chick rearing, and the conservation challenges that affect nesting success, including disease and environmental contaminants.

At a Glance: Falcon Nesting Behavior Overview

The table below summarizes the key nesting characteristics of falcons, with a focus on peregrine falcons and comparisons to other falcon species where evidence is available.

The table reflects general patterns from the approved evidence. Specific clutch sizes and incubation behaviors vary by species, region, and individual pair.

Nest Site Selection in Falcons

Falcons select nest sites that provide safety from predators, proximity to hunting grounds, and structural stability. The peregrine falcon historically nested on cliff ledges and rocky outcrops, but it has shown a remarkable ability to adopt urban structures that mimic these natural features. Tall buildings, bridges, and industrial towers offer vertical relief, hard surfaces, and limited ground access for predators, which makes them attractive alternatives to natural cliffs.

Natural Nest Sites

Natural falcon nest sites include cliff ledges, rock crevices, and occasionally tree hollows. Peregrine falcons in Central Europe have been documented using tree nests, and reintroduction programs have specifically worked to restore tree-nesting behavior in populations that lost this habit. The reintroduction of tree-nesting peregrines in Central Europe demonstrates that falcons can return to historical nesting substrates when suitable trees are available and disturbance is managed. A related Scopus record for the same reintroduction effort confirms that this approach was applied in the early 2000s.

Cliff nests are typically located on ledges with a slight overhang, which provides protection from rain and direct sun. The scrape is often positioned near a vertical wall that offers shelter from wind. Falcons do not add substantial nesting material, although they may use existing depressions or the remnants of nests built by other raptors.

Urban Nest Sites

Urban peregrine falcons select nest sites on tall structures that resemble cliffs. Buildings with ledges, window sills, and rooftop parapets provide suitable surfaces. Bridges offer protected ledges under the deck, and communication towers have platforms that mimic natural outcrops. The diet of urban peregrine falcons has been studied in Maribor, Slovenia, where researchers documented the prey composition of falcons nesting in an urban environment. The Scopus record for the Maribor diet study provides bibliographic confirmation that urban peregrine populations rely on available bird prey within city landscapes.

Urban nest sites present both advantages and risks. The vertical surfaces deter ground predators, and the abundance of feral pigeons and other urban birds provides a consistent food supply. However, urban nests are exposed to human disturbance, including maintenance work, window cleaning, and noise. Nesting falcons may also face higher exposure to environmental contaminants in urban areas. A study of peregrine falcon eggs in West England found that perfluorooctane sulfonic acid (PFOS) and perfluorohexanesulfonic acid (PFHxS) residues were significantly higher in eggs from Devon, an area around urban settlements, than in Cornwall. The PFAS and heavy metals egg study also reported that perfluorooctanoic acid (PFOA) residues were significantly higher in Lancashire, an inland study area, than in Devon. These findings indicate that urban and inland nesting habitats can expose falcons to different contaminant profiles.

Habitat Type and Movement

The habitat surrounding a nest site influences how falcons move and forage during the breeding season. A study of prairie falcons in the Morley Nelson Snake River Birds of Prey National Conservation Area in southwest Idaho used GPS telemetry to track adult falcons during the 2021 and 2022 breeding seasons. The prairie falcon movement study categorized flight movements into two behavioral states: canted movement, which is relatively slow and tortuous and likely associated with foraging, and strafing movement, which is relatively fast and directional and likely associated with commuting to foraging areas. The study tracked 17 falcons moving through four habitat types, including sagebrush, non-sagebrush shrub, annual herbaceous, and perennial herbaceous areas. This research shows that the habitat matrix around a nest site directly affects how falcons allocate time to hunting versus traveling, which in turn influences their ability to provision chicks.

Egg Laying and Clutch Characteristics

Falcons lay eggs directly on the scrape without constructing a nest. The female typically lays one egg every 24 to 48 hours until the clutch is complete. Clutch size varies by species and is influenced by food availability, female condition, and environmental conditions.

Incubation Behavior

The female performs the majority of incubation. A study of laughing falcons (Herpetotheres cachinnans) in southwestern Ecuador and northwestern Peru observed that the female spent 90.1 percent of the day on the nest during incubation, leaving only to feed on prey delivered by the male. The laughing falcon breeding behavior study documented an incubation period of approximately 40 days at one nest and found that the female showed a tendency to take breaks between 08:00 and 09:00. The same study recorded that the nestling was fed an average of 1.3 times per day, with food brought entirely by the male.

Peregrine falcons follow a similar pattern. The female incubates the eggs for most of the day and night, while the male hunts and delivers prey to the nest area. The male may briefly take over incubation while the female eats, but the female remains the primary incubator. This division of labor ensures that eggs are kept at a stable temperature and protected from predators.

Eggshell Quality and Contaminants

Eggshell quality is a critical indicator of nesting health. The PFAS and heavy metals study in West England measured eggshell index values in peregrine falcon eggs and found no significant relationship between eggshell index and PFAS residues. The egg contaminant study reported that long-chain perfluoroalkyl acids were predominantly detected in the eggs, with PFOS, PFHxS, and PFOA residues differing significantly among counties. The absence of a relationship between eggshell index and PFAS residues suggests that these contaminants may not directly impair eggshell thickness, but the study authors noted that further research is needed to determine the impact of PFAS on peregrine populations.

Chick Rearing and Parental Care

Once the eggs hatch, the parents shift from incubation to provisioning. The female broods the chicks for the first several days, while the male delivers prey to the nest. As the chicks grow, the female also begins to hunt, and both parents contribute to feeding.

Feeding Rates and Prey Delivery

Feeding rates vary by species, chick age, and prey availability. A study of saker falcons breeding in Bulgaria observed that adults fed nestlings at intervals of 31.5 to 55.3 minutes, depending on chick age. The saker falcon behavior study also documented that feeding duration was shorter in the morning hours, averaging 11.35 minutes between 07:00 and 12:00, compared to 18.81 minutes in the afternoon between 12:00 and 17:00. This study also recorded a notable case where a male saker falcon alone fed and cared for three nestlings for 19 days after the female disappeared. The male stopped feeding the nestlings after finding another female, and all three nestlings were subsequently found dead. This observation underscores the critical role of both parents in chick survival.

Sex Differences in Prey Provisioning

Sex-related differences in prey provisioning have been documented in other raptor species and may apply to falcons. A study of the black-and-chestnut eagle (Spizaetus isidori) in Ecuador found that males provided more prey to nestlings than females, with 227 prey items delivered by males versus 99 by females. The eagle nestling diet study also reported that females hunted heavier prey than males, averaging 1.19 kilograms versus 0.95 kilograms. While this study concerns an eagle species instead of a falcon, it illustrates the broader pattern of parental role differentiation in raptors, where males often take on the primary provisioning role during early chick rearing.

Diet Composition During Chick Rearing

Falcon diets shift seasonally and by breeding phase. The Eleonora's falcon (Falco eleonorae) provides a clear example of this pattern. A systematic review of Eleonora's falcon trophic interactions found that insects dominate the non-breeding and pre-laying periods, while birds become the main prey during chick rearing. The Eleonora's falcon diet review recorded 120 insect species and morphospecies from 47 families as prey, with Coleoptera, Hymenoptera, and Hemiptera being the most frequent insect orders. This seasonal shift in diet reflects the energetic demands of chick rearing, when parents need to deliver high-calorie prey to growing nestlings.

Urban Falcon Nesting and Human Interaction

Urban peregrine falcons have adapted to nesting on human-made structures, and this adaptation has created both opportunities and challenges for conservation. City buildings and bridges provide nesting surfaces that are often safer from predators than natural cliffs, but they also expose falcons to human activity, environmental contaminants, and disease.

Nest Platforms and Artificial Structures

Conservation programs have installed nest platforms on buildings, towers, and bridges to encourage falcons to nest in safe locations. These platforms are typically shallow trays filled with gravel or similar substrate, which allows falcons to create a scrape. The success of these platforms depends on placement, height, and protection from disturbance. Platforms should be positioned away from high-traffic areas, sheltered from prevailing winds, and accessible for monitoring.

Monitoring Urban Nests

Monitoring urban falcon nests requires a combination of direct observation and remote technology. Nest cameras provide continuous footage of incubation, hatching, and chick rearing without disturbing the birds. Banding programs allow researchers to track individual birds and assess survival and recruitment. The peregrine falcon avian influenza study monitored individually marked adults and breeding territories in the mid-Atlantic region of North America, demonstrating the value of long-term banding and territory monitoring for understanding population dynamics.

Human Disturbance Risks

Human disturbance is a significant risk for urban falcon nests. Maintenance work on buildings and bridges can cause falcons to abandon nests or leave eggs and chicks exposed. Noise, lighting, and physical proximity can also disrupt incubation and feeding. Property managers and conservation agencies should coordinate maintenance schedules to avoid the breeding season, which typically runs from early spring through summer in temperate regions. If disturbance is unavoidable, a qualified wildlife biologist should assess the nest and recommend protective measures.

Conservation Challenges Affecting Nesting Success

Falcon nesting success is threatened by disease, environmental contaminants, habitat change, and prey availability. Recent research has documented significant population impacts from highly pathogenic avian influenza (HPAI) and per- and polyfluoroalkyl substances (PFAS).

Highly Pathogenic Avian Influenza

The current outbreak of HPAI is the largest panzootic ever recorded, impacting millions of wild and domestic birds worldwide. Peregrine falcons are obligate bird consumers and are considered susceptible to HPAI virus. A study of breeding peregrine falcons in the mid-Atlantic region of North America compared inland and coastal subpopulations and found that adult survival fell from 0.82 to 0.25 in coastal areas in the two years following the arrival of HPAI. The mid-Atlantic peregrine HPAI study also documented that territory occupancy declined by more than 50 percent in coastal areas following the arrival of the virus. Juvenile recruitment increased from 3.5 percent to 21.0 percent following the arrival of HPAI, suggesting that the recruitment pool may be diminished by the demand generated by increased adult turnover.

A separate study in the Netherlands found that significant mortalities of peregrine falcons occurred in 2016 to 2017 and 2020 to 2023, years of major HPAI H5 virus outbreaks. The Netherlands peregrine HPAI study reported that in 2023, over 80 percent of tested birds were positive for HPAI H5 virus. No HPAI H5 virus was present in unhatched eggs, which suggests that the virus is not transmitted through the egg. The study concluded that HPAI represents a serious threat to the peregrine falcon population in the Netherlands and, in combination with anthropogenic factors, may contribute to the decline of this species.

Environmental Contaminants

PFAS and heavy metals accumulate in falcon eggs and tissues, and exposure varies by region and habitat. The West England egg study found that PFOS and PFHxS residues were significantly higher in eggs from Devon, an area around urban settlements, than in Cornwall. The PFAS egg study also reported that several perfluoroalkyl carboxylic acid residues showed significant and negative correlations with carbon isotope ratios in eggs, suggesting that the sources of these PFAS may come from terrestrial habitats. The study authors noted that it remains challenging to determine the impact of PFAS on the Cornwall peregrine population given the variation in exposure among areas.

Habitat Change and Prey Availability

Changes in nesting habitat can influence falcon diet and population viability. A study of saker falcons in Slovakia from 1976 to 2016 examined how changes in nesting habitat influenced diet composition and potentially threatened the population. The Slovakia saker falcon habitat study provides bibliographic evidence that habitat change is a long-term factor affecting falcon nesting success. Similarly, the prairie falcon movement study in Idaho showed that habitat type affects foraging behavior, which in turn affects the ability of breeding falcons to provision chicks. The prairie falcon habitat study emphasizes that relying solely on population-level estimates obscures individual variation and can result in ineffective management strategies.

Practical Assessment of Falcon Nesting Sites

Assessing a falcon nesting site requires systematic observation and record keeping. The following steps provide a practical framework for evaluating nest site quality, monitoring breeding activity, and identifying potential problems.

Step 1: Confirm Nest Occupancy

Confirm that the nest site is actively used by falcons before beginning detailed monitoring. Observe the site during the early breeding season for signs of occupancy, including scrape formation, territorial defense, and courtship behavior. Falcons may use the same nest site across multiple years, so historical records can help identify active sites.

Step 2: Document Nest Site Characteristics

Record the following characteristics for each nest site:

• Substrate type, such as rock ledge, building ledge, bridge girder, or artificial platform
• Height above ground or water
• Aspect and exposure to wind, rain, and sun
• Distance to hunting habitat
• Proximity to human activity and disturbance sources
• Evidence of previous nesting, including old scrapes or prey remains

Step 3: Monitor Incubation and Hatching

Monitor incubation behavior to confirm that eggs are being incubated consistently. The female should spend the majority of the day on the nest, leaving only for brief periods to feed. Note the timing of incubation breaks, as consistent patterns can indicate normal behavior. Record the date of hatching when chicks are first observed.

Step 4: Track Chick Development and Feeding

Track chick development by recording feeding events, prey deliveries, and chick behavior. Note the species and size of prey items delivered to the nest. Document any changes in feeding rates as chicks grow. The saker falcon study in Bulgaria provides reference intervals for feeding frequency, with adults feeding nestlings every 31.5 to 55.3 minutes depending on chick age. The saker falcon feeding study also documented that feeding duration varies by time of day, with shorter feeding bouts in the morning and longer bouts in the afternoon.

Step 5: Record Fledging Success

Record the number of chicks that reach fledging age and the date of fledging. Compare fledging success across years and sites to identify trends. A decline in fledging success may indicate problems with prey availability, disease, or disturbance.

Records and Measurements for Falcon Nest Monitoring

Maintaining consistent records is essential for detecting changes in falcon nesting behavior and population health. The following measurements should be recorded for each nest site and breeding season.

The mid-Atlantic peregrine study used individually marked adults and breeding territories to estimate spatial and temporal patterns of adult survival, recruitment age, and territory occupancy from 2016 to 2025. The peregrine population monitoring study provides a model for long-term monitoring that can detect the impacts of disease and environmental change on falcon populations.

Common Failure Patterns in Falcon Nesting

Falcon nesting attempts can fail for a variety of reasons. Recognizing common failure patterns helps researchers and conservation managers identify problems and take corrective action.

Nest Abandonment

Nest abandonment occurs when falcons leave the nest site before eggs hatch or chicks fledge. Common causes include human disturbance, predation, and the loss of a parent. The saker falcon study in Bulgaria documented a case where a male alone fed and cared for three nestlings for 19 days after the female disappeared. The saker falcon parental care study reported that the male stopped feeding the nestlings after finding another female, and all three nestlings were found dead. This case illustrates that the loss of one parent can lead to complete nesting failure, even when the remaining parent attempts to compensate.

Egg Infertility and Embryo Mortality

Egg infertility and embryo mortality reduce hatching success. Contaminant exposure, poor nutrition, and genetic factors can contribute to these failures. The West England egg study measured PFAS burdens in peregrine eggs and compared them with eggshell index values. The PFAS egg study found no significant relationship between eggshell index and PFAS residues, but the study authors noted that further research is needed to determine the impact of PFAS on peregrine populations.

Chick Starvation

Chick starvation occurs when parents cannot deliver enough prey to meet the energetic demands of growing chicks. This can result from low prey availability, poor hunting conditions, or the loss of a parent. Feeding rates documented in the saker falcon study provide reference values for normal provisioning, with adults feeding nestlings at intervals of 31.5 to 55.3 minutes. The saker falcon feeding study also recorded that feeding duration was shorter in the morning than in the afternoon, which may reflect diurnal patterns in prey activity.

Disease Mortality

Disease can cause mortality in adult falcons and chicks. HPAI has been documented as a significant cause of mortality in peregrine falcons in the Netherlands and the mid-Atlantic region of North America. The Netherlands peregrine HPAI study reported that over 80 percent of tested birds were positive for HPAI H5 virus in 2023. The mid-Atlantic peregrine HPAI study documented a decline in adult survival from 0.82 to 0.25 in coastal areas in the two years following the arrival of HPAI. These findings highlight the need for targeted HPAI surveillance and disease mitigation measures for falcon conservation.

Welfare and Safety Context for Falcon Nest Monitoring

Monitoring falcon nests requires attention to both bird welfare and human safety. Disturbance during incubation can cause falcons to abandon nests, so monitoring should be conducted from a distance whenever possible. Nest cameras and remote telemetry reduce the need for physical access to nest sites.

Minimizing Disturbance

Limit visits to nest sites to essential activities, such as banding chicks or assessing nest condition. Schedule visits during the early morning or late afternoon when temperatures are moderate and falcons are less likely to be stressed. Keep visits brief and avoid approaching the nest directly if the adults are present. If a falcon shows signs of distress, such as vocalizing, diving, or abandoning the nest, withdraw immediately and reassess the monitoring approach.

Human Safety

Falcons are protective of their nests and may attack intruders that approach too closely. Peregrine falcons are capable of high-speed stoops and can strike with considerable force. Anyone working near an active falcon nest should wear protective headgear and eye protection. Work at height on buildings, bridges, and towers requires appropriate fall protection and should be conducted by trained personnel.

Disease Precautions

HPAI can be transmitted to humans through close contact with infected birds or contaminated surfaces. Anyone handling falcons, eggs, or nest material should follow appropriate biosecurity protocols, including the use of gloves, masks, and disinfectants. Dead falcons should be reported to the relevant wildlife authority and tested for HPAI if the virus is suspected. The Netherlands peregrine HPAI study emphasizes that targeted HPAI surveillance and disease mitigation measures are necessary for the conservation of this species.

Professional Escalation Criteria

Certain observations warrant escalation to a qualified wildlife biologist, veterinarian, or conservation authority. The following criteria indicate situations that require professional assessment.

Dead or Sick Falcons

Report dead falcons or falcons showing signs of illness, such as lethargy, inability to fly, or neurological symptoms, to the relevant wildlife authority. If HPAI is suspected, do not handle the bird without appropriate protective equipment. The Netherlands peregrine HPAI study documented that significant mortalities of peregrine falcons occurred in years of major HPAI H5 virus outbreaks, and testing of dead birds is essential for detecting the virus.

Nest Abandonment

If a falcon nest is abandoned during incubation or chick rearing, assess the cause before intervening. Human disturbance, predation, and the loss of a parent are common causes. If the nest contains eggs or chicks, contact a qualified wildlife rehabilitator or falcon specialist to determine whether intervention is appropriate.

Contaminant Exposure

If falcon eggs or chicks show signs of contaminant exposure, such as poor hatching success, developmental abnormalities, or reduced fledging success, collect samples for laboratory analysis. The PFAS egg study provides a model for measuring PFAS burdens in peregrine eggs and comparing them with stable isotope and eggshell index values.

Population Declines

If territory occupancy or fledging success declines across multiple years, escalate the findings to a conservation authority. The mid-Atlantic peregrine HPAI study documented that territory occupancy declined by more than 50 percent in coastal areas following the arrival of HPAI, demonstrating the value of long-term monitoring for detecting population declines.

Frequently Asked Questions

Where do peregrine falcons build their nests?

Peregrine falcons do not build nests. They lay eggs directly on a scrape in a shallow depression on a cliff ledge, rock crevice, or human-made structure such as a building ledge, bridge girder, or tower platform. In Central Europe, reintroduction programs have worked to restore tree-nesting behavior in peregrine populations, as documented in the reintroduction of tree-nesting peregrines study.

How long do falcon eggs take to hatch?

Incubation periods vary by species. A study of laughing falcons in southwestern Ecuador and northwestern Peru documented an incubation period of approximately 40 days at one nest. The laughing falcon breeding study observed that the female spent 90.1 percent of the day on the nest during incubation, leaving only to feed on prey delivered by the male.

Do both parent falcons incubate the eggs?

The female performs the majority of incubation in most falcon species. The male delivers prey to the female during incubation and may briefly take over incubation while the female eats. The laughing falcon study found that the female spent 90.1 percent of the day on the nest, leaving only to feed on prey delivered by the male. The laughing falcon breeding study also documented that the nestling was fed an average of 1.3 times per day, with food brought entirely by the male.

What do falcons feed their chicks?

Falcons feed their chicks a diet of birds and, in some species, insects and small mammals. The diet shifts seasonally in some species. The Eleonora's falcon diet review found that insects dominate the non-breeding and pre-laying periods, while birds become the main prey during chick rearing. The Eleonora's falcon diet review recorded 120 insect species and morphospecies from 47 families as prey.

How often do falcon parents feed their chicks?

Feeding rates vary by species, chick age, and prey availability. A study of saker falcons in Bulgaria observed that adults fed nestlings at intervals of 31.5 to 55.3 minutes, depending on chick age. The saker falcon feeding study also documented that feeding duration was shorter in the morning, averaging 11.35 minutes, compared to 18.81 minutes in the afternoon.

Can falcons nest successfully in cities?

Yes, peregrine falcons have adapted successfully to urban environments. They nest on tall buildings, bridges, and towers that mimic natural cliff ledges. Urban falcons benefit from abundant prey such as feral pigeons, but they also face risks from human disturbance and environmental contaminants. The Maribor urban peregrine diet study provides bibliographic evidence of peregrine falcons nesting and hunting in an urban environment.

What threats affect falcon nesting success?

Falcon nesting success is threatened by highly pathogenic avian influenza, environmental contaminants such as PFAS, habitat change, prey availability, and human disturbance. The mid-Atlantic peregrine HPAI study documented declines in adult survival and territory occupancy in coastal areas following the arrival of HPAI

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References and Further Reading

• NCBI Literature Resources. National Center for Biotechnology Information.
• PubMed. National Library of Medicine.
• The influence of diet-mediated exposure of avian influenza on adult survival, recruitment and territory occupancy in peregrine falcons.. 2026.
• Per- and polyfluoroalkyl substances (PFAS) and heavy metals in the egg of peregrine falcon (Falco peregrinus) populations in West England, United Kingdom.. 2026.
• Highly Pathogenic Avian Influenza Contributes to the Population Decline of the Peregrine Falcon (&lt,i&gt,Falco peregrinus&lt,/i&gt,) in The Netherlands.. 2024.
• Eleonora's falcon trophic interactions with insects within its breeding range: A systematic review.. 2025.
• Sex affects the nestling diet of a large aerial predator of the Andes.. 2025.
• Breeding behavior of the Laughing Falcon (Herpetotheres cachinnans) in southwestern Ecuador and northwestern Perú. Ornitología Colombiana, 2021.
• Observations on the behavior of the saker falcon (Falco cherrug) breeding in Bulgaria. Travaux du Muséum National d'Histoire Naturelle "Grigore Antipa, 2024.
• Impacts of Habitat Type on Individual Prairie Falcon (Falco Mexicanus) Movement and Foraging Behavior During the Breeding Season
• Characteristics of the hunting behavior of the Red-footed Falcon ( Falco vespertinus ) in South-Eastern Bulgaria. 2018.
• Changes in nesting habitat of the saker falcon (Falco cherrug) influenced its diet composition and potentially threatened its population in Slovakia in the years 1976-2016. Raptor Journal, 2019.
• Reintroduction of tree-nesting Peregrines (Fako peregrinus) in Central Europe. European Journal of Wildlife Research, 2001.
• Reintroduction of tree-nesting Peregrines (Falco peregrinus) in central Europe. Zeitschrift Fur Jagdwissenschaft, 2001.
• Diet of Peregrine Falcons Falco peregrinus in the urban environment of Maribor (NE Slovenia). Acrocephalus, 2018.
• A remarkable new species of small falcon from the Quaternary of Cuba (Aves: Falconidae: Falco). Proceedings of the Biological Society of Washington, 2001.

This article is educational and does not replace institutional policy, professional advice, or applicable safety and regulatory requirements.