White-tailed sae eagle (c) Dr. Allan Mee
Mated White-tailed Eagles can produce one to two eggs per year. The eggs are laid 2-5 days apart in March or April and are incubated for 38 days by both parents. The first chick to hatch is always the largest and strongest and would be the more dominant at feeding times, although chicks are quite tolerant of one another. The female does most of the brooding and direct feeding, with the male taking over now and then. In the case of the Mountshannon eagles it was observed that the male bird did equal share of incubation. Change-overs may be approximately every two hours, although incubating birds may sit for hours at a time while the off-duty partner forages. For the first 2-4 weeks after hatching, the female remains in close proximity of the nest and may be seen actively brooding, as the White-tailed Eagle hatchlings are unable to regulate their body temperature at this time and require to be sheltered in order to prevent excessive heat loss and potential mortality. The male provides all the food required at this time, with the female not usually commencing hunting until after the third week.
The young are able to feed themselves from 5-6 weeks and they fledge at 11-12 weeks. They remain in the vicinity of the nest as they are still dependent on their parents for a further 6-10 weeks.
The breeding cycle of many White-tailed Eagles commences in late Winter when courtship display and prospective nest site selection may take place. In most cases recorded in Europe the courtship hopefully ends successfully with chicks hatching in middle to late spring. In 2013, the first of our two chicks was born on the 28th April and the second perhaps four days later. White-tailed Eagles form life-long monogamous partnerships once they become sexually mature. This usually happens when birds are around five years of age although some individuals may be precocious and attempt to breed at an earlier age. White-tailed Eagles are remarkably faithful to their partners and to their chosen nest location. Normally, individuals will only form a fresh pair bond should an existing partner die.They seem to enjoy each others company spending considerable amounts of time together roosting, and gently and majestically riding the thermals above the Lough. The Mountshannon Eagles as of 2014 are six years old for the male and five years for the female.
In contrast to Golden Eagles, White-tailed Eagles can be very vocal especially during courtship and at the onset of the breeding season. This frequent loud calling often takes place in the vicinity of the eyrie and consists of a series of barks or yelping cries that increase in tempo and pitch. Should the adults become alarmed, a loud and far-carrying ‘klee-klee-klee (-klee)’ is uttered, often dramatically piercing the tranquillity of an otherwise quiet landscape. This will soon be known as the Lough Derg ballet!
At the dawn of every New Year White-tailed Eagle s ready themselves for the onset of yet another breeding season. Although monogamous, individual eagles will be keen to reaffirm their pair bonds with their existing partners and to show fidelity with their chosen breeding territory. This they do in a series of circling and soaring flights often high above the nest location. The courting pair spend much of their time together and are often perched side by side on their eyrie.
White-tailed Eagles have a characteristic aerial courtship display which culminates in the pair locking talons in mid-air and whirling earthwards at great speed in a series of spectacular cartwheels. This death-defying stunt may come to an end only a few feet above the ground or water before the birds soar upwards again. To catch even a glimpse of this is a thrilling, once-in-a-lifetime experience for many birdwatchers. Displays of this nature most often involve young or recently established pairs. The courtship appears to take on less significance as individual birds get older and pair bonds grow stronger. Their flight displays end abruptly once the eggs are laid.
Talon-grappling is not confined to courtship display and may be used by territorial birds as a way of discouraging intruders. Despite their fierce look and awesome power, White-tailed Eagles often have a pacifistic approach to confrontation only engaging in physical combat with other birds as a last resort. It is worth mentioning that in most recorded case they seem to be comfortable sharing the same range as the golden eagle which seems to have a slightly different diet.