As one of the world’s largest predatory birds, Golden Eagles (Aquila chrysaetos) are an imposing sight, soaring above open grassland and steppe landscapes. Nest spots are chosen on rocky ledges and prominent spots on cliffs, or in the uppermost branches of tall trees, with a wide view over their hunting grounds. Remote, isolated areas are preferred where there is minimal chance of disturbance from humans.
A remote, undisturbed location is vital for Golden Eagle pairs when selecting a nesting site, with a spot that offers a clear view of the surrounding area a key factor. It’s not clear whether the male or female is responsible for the final choice of site, and nests – called eyries – that have been successfully used in previous seasons are regularly used again in subsequent years.
Several alternative nests may be built within the same territory and are maintained throughout the breeding season by both males and females.
Clifftops and rocky ledges are Golden Eagle’s favored nest locations in treeless landscapes. Where tall trees are available, the upper branches will readily be used as nest sites, and where no trees or cliffs are present, eyries may be built on the ground. Artificial nest platforms, designed to boost the chances of successful nesting, have also been used with positive results. Occasionally communication towers, electricity pylons and other manmade structures are used.
Location is key, with inaccessible clifftop sites offering protection from any predators brave enough to try and attempt a raid of these fearsome raptors’ nests. In order to keep up with the intense demands of feeding hungry, rapidly growing chicks, a nest in close proximity to feeding grounds is also a top priority.
Another important factor that affects an eagle’s choice of nest location is the accessibility for taking off and catching hold of good updraft for hunting, so a relatively open landscape with no obstructions or dense swathes of forest is preferred.
Clifftops and rocky ledges are Golden Eagle’s favored nest locations in treeless landscapes
Golden Eagles remain together all year round, and breeding activity begins from January to March onwards across the northern hemisphere.
The earliest eggs are laid from late January to February along the Pacific coast of the US, and slightly later, into February and March further east. In Canada and Alaska, it’s not unusual for breeding to be delayed until late March to early May or June at the latest.
In Europe, March is the peak laying month, with the entire breeding season taking around four months, and the latest clutches are complete by August. Further south, across northern Africa, laying occurs from October to January.
Around a month ahead of the first eggs being laid, nest preparations begin, with as many as four alternate nests constructed within a Golden Eagle’s territory.
A stick base is constructed by the male and female together, collecting suitable large sticks from the ground or snapping off old branches that catch their eye. Both live and dead branches are used and carried to the nest site using beaks and feet. Bones, antlers, and manmade materials including litter, metals and even paper money may also be incorporated into the structure as it takes shape.
Males and females work together to add fresh green leaves and other foliage to the inside of the nest structure, forming a loose internal cup. Lichens, moss and grasses are the most common materials used for the inner lining.
The final structure is rounded, bulky and unruly, but tightly bound together. A first-year nest is usually around a meter across, but as nests are constantly upgraded and reused year after year, they can grow to quite dramatic proportions, with a Scottish nest recorded as 5.2 m high.
A Golden Eagle collecting nest building materials
Golden Eagle pairs form strong bonds and mate for life. However, if one mate dies, then a replacement will be found fairly quickly.
In areas where Golden Eagles are resident all year round, pairs can form at any point during the year, and mates remain strongly bonded beyond the duration of a single breeding season. Less is known about pair bonds of migratory Golden Eagles, although it’s believed that pair bonds may not always survive during the winter period, particularly if they return to a territory that has since been claimed by another pair.
Courtship rituals include mutual flight displays, chases with soaring and gliding and pairs perching huddled close together. During courtship flights, males repeatedly pick up rocks and drop them, before swooping to catch them again mid-air in an attempt to impress a prospective mate. Females then complete a similar display, with sticks or earth, and the partnership is sealed for life, rather than repeated annually as in some bird species.
Copulation between golden eagle pairs can occur throughout the year, not just during the breeding season, although it most commonly takes place between 40 and 46 days before eggs are laid.
A pair of Iberian Golden Eagles - Golden Eagle form strong bonds and mate for life
Around the same size as a large hen’s egg, golden eagles’ eggs measure on average 6.8 cm to 8.6 cm (2.7 in to 3.4 in) in length and 4.9 cm to 6.4 cm (1.9 in to 2.5 in) in width and weigh around 140 g (0.3 lb).
Golden Eagles’ eggs are creamy white in color and are heavily marked with darker blotches, which range from yellow-brown to darker gray. The texture of the eggshell is similar to that of a chicken’s egg.
A typical clutch consists of between 1 and 3 eggs, with 2 being the most common. On rare occasions, nests containing four eggs are observed and one example of a five-egg nest was recorded in 1928. Eggs are laid every other day until the clutch is complete, with incubation beginning as soon as the first egg has been laid.
Golden Eagle pairs will raise a single brood each year. If the nest fails, re-nesting attempts are rare, but not unheard of.
Female Golden Eagle at the nest with two week old chick - Golden Eagle pairs will raise a single brood each year
Both male and female Golden Eagles develop incubation patches, although in females these are more prominent. Females undertake the larger share of incubation duties and all overnight brooding. Males incubate for between 10 and 14 percent of the time, but bring food to their mate on the nest.
Hatching is a gradual process, with eagle chicks taking their time to fully make their long-awaited entrance into the world. They can be heard from inside the egg around 15 hours before the first cracks in the eggshell appear.
Once the shell is initially broken, no further activity follows for around 27 hours. By 35 hours, the shell is completely broken apart, and chicks are entirely free from the egg by 37 hours, covered in a fluffy white down and largely inactive for the first 10 days.
Eggs from the same clutch hatch several days apart, in order of when they were laid. The early nesting period is a dangerous time for younger eagle siblings, with one of nature’s most intense displays of sibling rivalry.
The older hatchling will habitually try and attack the younger, weaker nestmate, jabbing with its bill or even physically ejecting it from the nest. These attacks usually die down after the first 3 weeks, although even if targeted younger nestlings survive the vicious attacks, they may end up starving as they often stop begging their parents for food.
The brooding of young eagles by parents continues for up to 20 days, during which time the young are unable to regulate their own body temperatures.
Both male and female Golden Eagles develop incubation patches, although in females these are more prominent
Male Golden Eagles tend to be ready to leave the nest earlier than females, developing stronger wings and practice flapping and hopping for several weeks prior to attempting to fly.
The earliest recorded fledglings successfully left as early as 45 days, while the last to leave the nest have been recorded as finally taking the plunge at 81 days. On average, fledging is complete in around 64 days.
For the first few weeks after fledging, young eagles will remain within around 100 m of the nest and will continue to be supported by their parents with feeding.
After around 2 to 3 weeks, their confidence and stamina improve enough to attempt circling flight but are not strong enough to complete similar heights to adult birds until around two months after first leaving the nest. Association with parents begins to ease when they reach around four months, and they are largely independent by around 12 weeks.
The first three years of a golden eagle’s life are usually solitary, as they search for suitable territories and perfect their survival and hunting skills.
After young Golden Eagles hatch, both parents are observed to bring food to the nest, although only females are seen to regularly feed the young directly. Young eagles feed themselves by around 5 weeks and are able to tear prey into manageable chunks by 6 weeks.
Young hatchlings continue to be brooded on the nest for overnight warmth and protection by the female until they reach between 17 and 45 days, usually around 20 days. Females will continue to roost at night for up to 54 days after hatching and remain nearby, keeping a vigilant watch over young until they are fully independent.
Gradually, juvenile Golden Eagles begin to shun the attention of their parents and are ready to strike out on their own. Hunting attempts, initially under the watchful eye of both parents, gradually move further afield and independent foraging missions replace prey deliveries by between 120 and 160 days.
Male Golden Eagles tend to be ready to leave the nest earlier than females, developing stronger wings and practice flapping and hopping for several weeks prior to attempting to fly
Despite their size and reputation as formidable, powerful birds, nesting is a risky business for Golden Eagles and survival beyond the nesting stage is not guaranteed.
As apex predators at the top of their food chain, Golden Eagles have few predators themselves, although nests have been observed to have been destroyed by bears, wolverines and once by a raven.
Threats from humans are perhaps more pressing and potentially lethal, with hunting, habitat loss and pollution among major concerns. Hunting of other game, using lead ammunition has the knock-on effect of contaminating carcasses they feed on.
Pest control chemicals that target rodent populations are also hazardous to eagles that prey on small mammals that have ingested poisonous substances.
Globally Golden Eagles are considered a species of least concern and have legal protection in most parts of the world. Populations are generally stable in much of North America and show some slight increases in many parts of Europe.
Although nests may be regularly reused, it’s rare for a breeding pair to use the same nest for more than four years in a row.
Young Golden Eagles do not gain their full adult plumage until their fifth year, although breeding may be possible the year before this.
A prized tick on every bird enthusiast’s species list, nesting Golden Eagles are safest observed from a respectful distance. Causing as little disruption as possible will give these true giants of the natural world the best possible chance of successfully raising their young to reach the fledgling stage.
Webcam footage is a great way of making sure every step of a newly hatched golden eagle’s life is documented, with observation of their rapid early growth and rocky sibling relationships a fascinating real-time natural soap opera.
A prized tick on every bird enthusiast’s species list, nesting Golden Eagles are safest observed from a respectful distance
Golden Eagle eggs are incubated for between 43 and 45 days before hatching.
Survival until adulthood or even fledgling age is not guaranteed, with only two out of every four nestlings living long enough to fledge. Of those that do leave their nests, only around 25 percent will survive to reach maturity.
Golden Eagles build their nests in remote spots and are highly sensitive to disturbances around their nest sites, and may abandon a nest that they feel is under threat. For this reason, many conservation organizations have set up dedicated camera feeds that stream live footage allowing people to view nests and nestlings up close without the risk of causing any distress.
The chief way of helping to promote Golden Eagle conservation in the wild is by keeping a safe distance from nesting and roosting sites, and not causing any damage or degradation to their habitats.
Any traces of human activity in areas where Golden Eagles are nesting or roosting should be avoided, for example, the use of pesticides or chemicals on gardens or farmland, no litter or plastic pollution and lead-free practices in local hunting to prevent eagles from feeding on any contaminated prey.
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