Falcons are raptors that belong to the genus Falco. There are around 40 species of falcon found worldwide, exhibiting a range of sizes and behaviors. Falcons are powerful predators that specialize in hunting other birds in flight using their sharp talons and curved beaks to catch and kill prey.
One of the most distinguishable features of falcons is their remarkable nesting behaviors. Falcons utilize a variety of nesting strategies and put tremendous effort into building nests and raising their young. Here, we will explore the fascinating details of falcon nesting biology and behavior.
When is nesting season for falcons?
The timing of nesting season varies for the different species of falcon, and is primarily determined by the local climate and availability of prey. In general, nesting season corresponds with the warmer months that are optimal for rearing chicks.
For example, peregrine falcons in North America breed between February and August, with activity peaking in March through June. Other species like the merlin initiate nesting earlier, with egg laying starting as early as late March. Tropical species like the bat falcon can breed year-round, taking advantage of consistent prey availability.
The duration of nesting season can extend 4-5 months for larger falcons to allow sufficient time for multiple broods. Smaller species like kestrels may only nest for 2-3 months. Geographical location also plays a role; more northern falcon populations generally exhibit shorter, more synchronized breeding seasons.
Where do falcons build their nests?
Falcons utilize a variety of natural and man-made structures to build nests that provide shelter and seclusion:
– cliffs: Many falcons, including peregrine falcons, gyrfalcons, and prairie falcons build scrape nests on ledges or crevices of high vertical cliff faces. Cliff nests provide height for easy flight access and protection from land predators.
– trees: Some forest and woodland falcons like the American kestrel nest in tree hollows and cavities. Merlins and aplomado falcons may build stick nests in trees at moderate heights.
– buildings: Peregrine falcons readily adopt man-made structures in urban areas, building nests on tall buildings, bridges, and power towers that mimic natural cliffs.
– ground: Open country falcons may nest directly on the ground, such as prairie falcons that scrape out dirt bowls lined with debris in areas of short vegetation. The nest bowl provides some concealment from predators.
– burrows: The aplomado falcon and common kestrel sometimes use abandoned burrows in banks, termite mounds, or agave plants to host their nests. Underground burrows offer insulation and seclusion.
– scrapes: Many falcons do not construct elaborate nest structures. They simply scrape out a shallow depression or ledge on a surface using their talons and beak, then line it with debris. Scrapes may be located on cliffs, buildings, trees, or the ground.
Ideal nesting sites
Regardless of nest type, falcons select nest sites that provide:
– Elevation for easy take-off and landing
– Protection from extreme weather conditions
– Seclusion from predators and threats
– Nearby open hunting ground with ample prey
What materials do falcons use in their nests?
The nest materials used by falcons vary somewhat based on habitat and nest location. However, most falcon nests are relatively crude structures, consisting of collected twigs, grass, and debris scraped into a depression to form a shallow bowl or platform. Common materials include:
– Sticks and twigs – Provide infrastructure for nests in trees and on ledges
– Grass, moss, leaves – Softer lining materials
– Feathers, fur – Provides insulation, often plucked from prey remains
– Dirt, gravel – Materials raptors dig out and scrape when making ground nest bowls
– Old nest lining – Some falcons will reuse lining from previous years’ nests
– Garbage – Peregrine falcons in urban areas may incorporate man-made debris like paper, plastic, and cigarette butts
– Food scraps – Leftover prey items help cement nest materials
The quantity and complexity of nest materials varies greatly. Forest falcons build more elaborate stick nests while cliff-nesters may have only minimal debris defining a scrape. Kestrels usually have the most rudimentary nests of all the falcon species.
Who builds the nest?
In most falcon species, the female takes the lead in selecting the nest site while the male gathers most of the nest materials. The female then arranges the gathered sticks, grass, and feathers into a suitable nest bowl or platform.
However, the male may contribute more substantially to nest construction in a few species like the peregrine falcon. In merlins, both sexes are reported to equally share in nest building duties prior to egg laying.
Partnerships are crucial, as a complete nest must be built before egg laying can commence. Falcons may take anywhere from a few days to over a month to fully construct a nest each breeding season.
How are falcon nests constructed?
Falcon nest building proceeds in a number of stages:
Site selection
The female falcon chooses an appropriate nesting site that provides elevation, seclusion and protection as described above. Some pairs may use the same nesting site across different years.
Material gathering
The male falcon flies out to collect sticks, grass, moss, feathers or other relevant materials, often snapping branches directly from trees. He may need to make hundreds of trips back and forth over days or weeks.
Nest shaping
The female shapes the material brought by the male into a nest bowl by scraping, pushing, and trampling. She continually refines the nest structure up until egg laying.
Nest lining
Closer to egg laying, the female focuses on lining the nest, weaving softer materials like grass, moss, and feathers into the base. She presses down with her body to create a snug, smooth depression.
Maintenance
Both adults keep repairing and bolstering the nest through incubation and chick rearing. More lining is added as eggs hatch to provide cushioning. Falcons may use the same nest for multiple years.
Reuse
In following years, some falcon pairs may patch up the old nest rather than building a completely new structure. Or, they may fully reconstruct the nest to renew materials. Other pairs may switch to alternative sites from year to year.
How big are falcon nests?
The size of falcon nests can vary from a tiny scrape of just a few inches across to large stick platforms up to 2-3 feet in diameter. Average dimensions include:
– Peregrine falcon – 1-2 feet wide, 2-6 inches deep
– Merlin – 8-13 inches wide
– American kestrel – 5-6 inches wide, 2-3 inches deep
– Gyrfalcon – Up to 5 feet wide for a large stick nest
Species that nest on cliffs and human structures tend to have the most minimal nest sizes, while forest-nesters build larger, more elaborate nests. The nest needs only be as large as required to securely hold eggs and chicks.
How many eggs do falcons lay?
Clutch sizes vary among the falcon species, ranging from 2-6 eggs. The most common clutch sizes are:
– Peregrine falcon – 3-4 eggs
– Gyrfalcon – 3-4 eggs
– Merlin – 4-5 eggs
– American kestrel – 4-5 eggs
– Aplomado falcon – 2-3 eggs
There is some regional variation as well. For instance, peregrine falcons at higher latitudes tend to lay fewer eggs per clutch. Higher food availability and smaller species size also correlate with larger clutches.
The female falcon lays eggs at approximately 2-day intervals until the full clutch is completed. The eggs are elliptical and heavily speckled or blotched for camouflage. The female begins incubating as soon as the first egg is laid.
How are duties divided between falcon parents?
Falcons exhibit well-defined parental roles and duties centered around the nest:
Female
– Selects nest site
– Arranges nest materials
– Lays and incubates eggs
– Broods newly hatched chicks
– Feeds chicks by tearing up prey items
– Defends nest vicinity
Male
– Provides most nest materials
– Delivers food to female during incubation
– Does majority of hunting once chicks hatch
– Feeds and defends chicks
– Guards nest site
There is substantial cooperation between mated pairs. For example, the female typically joins the male in hunting after chicks reach 2-3 weeks old and require more food.
For how long do falcons incubate eggs and brood chicks?
Incubation is the stage where the female falcon sits on the eggs to provide warmth until they hatch. Brooding refers to sheltering newly hatched chicks until they are old enough to thermoregulate. Incubation and brooding durations are:
– Incubation: 28-35 days
– Brooding: 10-20 days
The female falcon does about 90% of incubating and brooding duties. She turns the eggs periodically and may leave for short hunting breaks. The male brings food to the nest that the female can eat without fully standing.
Once chicks hatch, the female continues to shelter and guard them while the male ramps up hunting. After several weeks, chicks are able to maintain their own body heat, and brooding time decreases.
How long do falcon chicks stay in the nest?
Chicks remain in the nest for 4-8 weeks after hatching, with larger falcon species staying longer. Approximate fledging ages are:
– Gyrfalcon – 7-8 weeks
– Peregrine falcon – 6 weeks
– Merlin – 4-5 weeks
– American kestrel – 4 weeks
Young falcons develop quickly compared to many other bird species. They are ready to make initial flights soon after their flight feathers emerge, though parental care continues for some time after fledging.
The chicks stay near the nest site at first, perfecting flight skills and begging for food deliveries. Within a couple months they become more independent and disperse from the natal territory.
Do falcons reuse nests?
It depends. Some falcons like peregrine falcons exhibit high nest fidelity and reuse the same cliff ledges or building perches year after year. Other species, including merlins and American kestrels, more often switch to alternate sites between breeding seasons.
Reasons falcons may reuse nests include:
– Previous success – A productive nest in the past likely remains a favorable site.
– Limited availability – Particularly for cliff or tree cavity nesters.
– Familiarity – Returning to a known, safe location.
– Established territory – Ownership near the old nest may already be established.
Reasons for switching nests include:
– Site degradation – Erosion or collapse of old nest.
– Disturbance – Increased activity around the nest.
– Parasites – Buildup of bacteria, fleas, etc.
– Prey patterns – Better locations become available.
– Random dispersal – Especially in young or migratory falcons.
Typically, falcons show higher nest reuse when breeding habitat options are more limited. Pairs are more likely to move nests when alternative sites are abundant.
Do both male and female falcons defend the nest?
Yes, both the female and male falcon play a role in defending the nest site and chicks:
– Female – Primarily defends the immediate nest area. She swoops at intruders and predator birds. Also shields eggs and small chicks.
– Male – Guards the broader nest territory. He patrols the skies looking for threats and chasing off encroaching falcons.
– Both – May perform distraction displays to lure potential predators away. Work together driving off larger avian threats.
Female falcons tend to be more aggressive nest defenders earlier in the breeding season when incubating eggs. Males become more vigilant as chicks age and require greater food deliveries.
Nest defense is a risky necessity, as eggs and chicks are vulnerable to many predators. Defensive behaviors help ensure offspring survival, even at the potential cost of adult injury.
What are some common falcon nest predators?
Natural predators of falcon eggs, chicks and fledglings include:
– Raptors – Large owls, eagles, hawks, other falcons. Main threats are great horned owls and golden eagles.
– Mammals – Raccoons, foxes, ground squirrels, others that can access nests. Domestic cats threaten many ground nests.
– Reptiles – Certain snakes may take eggs or unfledged chicks.
– Ravens – Common ravens are important nest predators, especially for scrape nests on cliffs.
Manmade factors have enabled increased predator populations in many regions, presenting new challenges for nesting falcons. For instance, great horned owls benefit from urbanization.
In other cases like prairie and aplomado falcons, habitat loss has left nests more exposed due to diminished vegetation cover that historically concealed sites.
Do male falcons feed incubating females?
Yes, male falcons deliver food to the nest during the incubation period to provision their mates. Incubating female falcons have high energy demands, but are constrained to the nest and unable to hunt freely.
Therefore, males perform nearly all hunting duties in the early nesting stages. They tear apart prey items into small bits that the female can quickly eat before resuming egg warming. Males may deliver up to 8-10 prey items per day.
This behavior is crucial for allowing the female to remain on the nest for extended periods. Well-fed females are healthier and have greater reproductive success. Nest failure is more likely if males do not adequately provide for mates.
Some small items are left at the nest as supplemental food for the female. Larger prey remains and pellets are generally dropped far from the site to avoid attracting predators.
How do newly hatched falcon chicks get food?
Just hatched falcon chicks are altricial, meaning they are blind, mostly immobile, and helpless. They rely completely on their parents for warmth, protection, and provisioning.
To feed newly hatched chicks, the female falcon tears strips of meat from prey brought by the male. She pulls the food into smaller pieces and carefully passes morsels into the chicks’ mouths. Chicks stretch and crane their necks when begging for food.
At around 2 weeks old, chicks become more mobile and able to better handle larger chunks of food. The female starts leaving prey remains in the nest for self-feeding. By 3-4 weeks, chicks can tear at food themselves as adults deliver whole items.
The male’s hunting role becomes even more crucial after hatching, as he must provide enough food for the female and rapidly growing brood. Chicks may eat the equivalent of their own body weight daily.
What are some interesting falcon nesting behaviors?
Some fascinating aspects of falcon nesting biology include:
– Synchronized breeding – In areas like cliffs with dense falcon populations, nesting is highly synchronized between pairs to maximize resource availability.
– Egg turning – Female falcons methodically rotate eggs up to 5 times per hour during incubation using their beaks and feet to prevent embryo adhesion.
– Nest cleaning – Early in nesting, birds remove eggshell fragments and prey remains to maintain sanitation. Some species like prairie falcons line nests year-round.
– Scrape ceremonies – Specialized talon motions help shape optimal nest scrapes. Ceremonial digging motions may also help cement pair bonds.
– Feigning injury – Adults fake damaged wings or legs to lure potential predators away from nests, then fly off unharmed.
– Nest takeovers – Mature falcons may commandeer a nest already built by another pair and force them out in a type of nest piracy.
– Reuse by other species – Abandoned falcon nests are often adopted by other bird species in future years. Stick nests in particular may persist for a decade or more.
Conclusion
The nesting period comprises a critical phase of intense activity and energy expenditure for falcon pairs. Their navigating of mate provisioning, egg incubation, nest defense, and chick rearing underscores the adaptations that allow falcons to thrive as predators.
Understanding the insightful breeding ecology of these raptors provides a window into the natural histories of some of the most impressive birds across worldwide landscapes. Continued research helps elucidate the conservation needs of different falcon species during their peak season of vulnerability.
In broad terms, the nesting behaviors of falcons reflect finely tuned coordination between breeding pairs as they share duties and work together to successfully foster the next generation.
