By Andrew Berry
Our research has confirmed that the pair of golden eagles Harper and Athena are a nesting pair and hatched an egg during 2019. This is a true story about our Bernheim golden eagle pair, gleaned from the GPS data collected from both Harper and Athena during nesting season 2019 in Canada.
Using GPS data and Google Earth, we can see where these golden eagles go, how long they stay there, and how this pair interacts, demonstrating an incredible amount of information about their lives. This GPS dataset is the basis for the nesting story and the foundation for most golden eagle stories we tell at Bernheim. I promise all parts to be true to the best of my interpretation of the data.
Let’s pick back up from the last post during spring in northern Manitoba.
April 22-24, 2019
Data suggests Athena laid eggs, likely two or three, during this time period.
April 28, 2019
Athena sat on the nest continually, while Harper continued to hunt. Harper began to provide Athena short breaks for flights, usually occurring between 2 – 3 p.m., but not every day. I would expect that the frequency of these breaks might depend on weather and other factors such as nearby presence of predators.
May 1, 2019
Temperatures were still very cold, with an average for the month of May just 30.1˚ F and average winds of 13.2 mph. The landscape still frozen, Harper and Athena divided their time between the two main tasks of food procurement and care of the eggs. Athena spent all of her time on the nest, while Harper foraged and made returns to the nest presumably to feed Athena.
May 4, 2019
After 6 days on the nest, Athena took a 1-hour flight while Harper sat on the nest, but she only traveled 1 mile out across the lake and could always see and hear Harper on the nest. She was showing to be extremely dedicated to the incubation process. With it being just 28˚ F on May 4, it seems that extreme weather conditions and likely snowfall would make the task of continual incubation difficult.
May 6, 2019
Harper again relieved Athena for a flight from 1:30 -3 p.m. That night, he stayed away at the south eyrie. Data showed that Harper stayed at the old nest site several nights during May. The reason is uncertain, but could include territorial defense of old nest or use of the site as preferred hunting location.
May 11,, 2019
Both eagles were briefly away from the nest, but Harper quickly headed back after encountering Athena several miles south of nest in what looks like communication between the pair. She returned later and all seemed well, and she may have squawked at him a bit. The communication between golden eagles, particularly distress calls as observed between Athena and Harper at Bernheim, are what you might imagine a pterodactyl to sound like.
May 14, 2019
Athena visited the old nest site in the morning and spent 2.5 hours away from 7:30-10 a.m. This is the earliest and longest she left the nest during the incubation period. As usual, Harper stayed on the nest while she was gone.
May 17, 2019
Athena was still on the nest and Harper was traveling and hunting. He made regular returns to the nest but continued to occasionally stay out all night, either at the old nest site or other locations. He moved around some during the night as the sunlight continues to lengthen. In northern Manitoba, there is very little darkness in summer, and occasional night movements by Harper may be explained by longer days for hunting or other activity.
No big changes occurred during the following few weeks, which was good. Finally . . .
BIG NEWS!!!!!
June 3, 2019
Athena stayed at the nest for the next 6 days. It appears from her staying at the nest during this long stretch that this is the period when the egg(s) successfully hatched. Incubation is presumed to last 42-45 days, and if these eggs were laid on April 22, they would hatch approximately 6 weeks later during the week of June 2.
Hatching is a special event, and while we don’t know how many eggs hatched, we can confirm from our data that the golden eagles produced at least one chick in 2019. They had been working hard for 7 weeks to repair and build two eyries, lay and incubate eggs, feed both adult eagles, and defend the nest from other golden eagles and possibly other predators. Hatching then began with chirps from the egg as much as 37 hours before fully emerging from the shell. During the first few days, eagle chicks have a dense covering of greyish down, then turning snow-white by 6 days.
June 9, 2019
Athena spent nearly all her time on the nest. This is the brooding period, which involves covering and sheltering the young. Brooding is a near constant necessity for the first 20 days. The mother eagle provides warmth from the cold and shelters the nestlings from the heat of direct sunlight. Heat is a serious threat to nestlings, and may have been an issue on June 18-19 when temperatures reached 81˚ F. The chicks must also be shielded from any rain, snow, or marauding predators that would dare raid a golden eagle’s nest. Athena made a short flight, 9:45-10:30 a.m. while Harper guarded the nest. This pattern continued throughout June.
Feeding is a two-eagle job. Harper spent nearly all his time hunting, increasing the quantities of presumed waterfowl for the mother and nestling(s). June’s warmer temperatures thaw the landscape, bringing astounding numbers of migratory waterfowl to nest on these shared Canadian lakes.
The mother eagle must tear up food for the chicks until they are almost a month old. The nest becomes a messy place with eaglets creating pellets, carcasses piling up, chicks defecating in the nest, and constant activity between chicks and parents. Greenery has been documented as being added to nests during this period to cover debris or possibly repel parasites.
July 1, 2019
Now approximately 25 days old, the chick(s) have primary, secondary, and tail feathers emerging. They are standing and feeding themselves, and we see that Athena’s behavior began to change. She took longer trips while Harper waited at the nest. This behavior is likely a signal that Athena was ready to get back to hunting and spending some time away from the nest.
Click here to view the complete timeline of Harper and Athena’s activities in Canada in summer 2019.
Stay tuned, as we finish out the timeline of the breeding season in our next post. There is still a long way to go before these chicks could fledge and leave the nest after ~70 days. Or get the complete story during Bernheim Eagle Week at the Golden Eagle Lecture, February 21 at noon at the Bernheim Visitor Center.