Report on the 2020 nesting of the White-bellied Sea-Eagles
Introduction:
There has been a Sea-Eagle nest in the Newington Nature Reserve at Sydney Olympic Park by the Parramatta River for many years, with a succession of eagle pairs renovating a nest in the breeding season. There are few early records of successful breeding however and several eagles were found dead. Following the death of a pair of breeding eagles in 2004, necropsy and chemical analysis of tissues was undertaken in order to determine the cause of death. Further study was recommended. Their success or failure appears to be closely linked with environmental conditions, particularly the accumulated Persistent Organic Pesticides in Homebush Bay and the Parramatta River. Nesting failure has been caused by infertile eggs, sibling rivalry, Beak and Feather Disease, injury and Trichomoniasis (see previous reports for more detail).
As in previous years since 2009, the breeding relationships, behaviour and diet of the White-bellied Sea-Eagles were studied using video CCTV cameras and by limited physical observation during daylight hours, from the time of nest renovation to fledging and beyond where possible. In early 2020 a new Research Proposal was submitted and all approvals gained.
The Sea-Eagle is listed in NSW as Vulnerable under the Biodiversity Conservation Act 2016 and nationally as Marine and Migratory under the Environment Protection and Biodiversity Conservation Act 1999.
Summary :
The breeding pair of eagles renovated the nest used the previous year. The first egg SE-25 was laid on 18th June 2020, followed by the second, SE-26 on 21st June 2020. The eggs were laid 82 hours apart. Delayed incubation reduced the gap to 40 hours at hatch.
Both eagles fed the nestlings, though the male brought most of the prey. There was no significant sibling rivalry. The second hatched SE-26 was seen to have an injury or deformity of its right leg; intervention was not permitted.
The first hatched SE-25 branched on 10th October 2020 and fledged the following day at 75 days from hatch. It left the nest area after a week. There was a reported sighting of SE-25 on 5th November 2020 at Putney Point. No further sightings recorded.
SE-26 fledged on 30th October 2020 at 92 days from hatch and remained in the nest area for some weeks. It was found unable to fly from a high balcony and was rescued. After assessment and care it was euthanised as it was determined to be unable to survive in the wild and would be in pain.
Although two nestlings fledged, SE-26 was euthanised and the survival of SE-25 is not confirmed.
Nest Renovation:
Renovation of the previous nest began in mid April. Both eagles brought sticks to the nest, manipulating sticks to build up the sides of the nest again. Both brought leaves to line the nest and form a bowl for the eggs.
From April 19 to the laying of the first egg, the eagles made 462 trips to the nest with sticks or leaves. The male brought 270 sticks and the female 192.
Egg lay:
The first egg (SE-25) was laid at 09:35 (9:35am) on 18th June 2020. As in past years, delayed incubation was observed and the egg was left uncovered over 11 hours on the first night. (details below)
The second egg (SE-26) was laid at 19:25 (7:25pm) in the evening on 21st June 2020, some 82 hours after the first egg. Full incubation of both eggs then began, with the female on night duty.
Delayed Incubation:
As in previous years, the White-bellied Sea-Eagles showed delayed incubation between the laying of the two eggs. The eggs were laid some 82 hours apart and hatched just over 45 hours apart. Once the second egg was laid, full incubation began.
The first egg was left uncovered almost all the first night, after lay in the morning. It was very cold being a June night. Egg 1 was uncovered over 21 hours total at night and nearly 10 hours by day before egg 2 was laid. Both the male and the female incubated the first egg. Only the female incubated at night.
Graph 1:
Number of hours the first egg was uncovered during incubation before lay of the second egg.
Egg 1 was uncovered over 21 hours total at night and nearly 10 hours by day before egg 2 was laid.
Eggs laid 82 hours apart.
Graph 2:
Number of Hours both eagles incubated before lay of egg 2The female alone incubated at night for around 14.5 hours total.
The female incubated by day for around 16 hours and the male for around 19 hours.
As the lay of the second egg approached, incubation time increased.
Incubation:
After the second egg was laid, full incubation continued , with both adults covering the eggs during the day. The female incubated almost all night, with only brief breaks to roll the eggs or stretch. The male incubated at night only once, on July 3, when the female did not return to the nest all night. At other times the male slept on a nearby branch or out of sight. Several times the eagles were disturbed on the nest by the Boobook.
During the day, the eggs were only uncovered for a total of around 14.5 hours, averaging a daily total of 24 minutes – with frequent short breaks for rolling the eggs, stretching or changeovers.
Graph 3:
Total hours incubation by day between lay of egg 2 and hatch of egg 1Female incubated for nearly 219 hours
Male incubated for over 156 hours.
Prey Provisioning:
Prey brought to the nest during incubation period
Almost all of the prey was brought to the nest by the male – though the female probably caught prey herself when off the nest. Most prey brought in this period was fish.
| Fish | Bird | Eel | Unknown |
|---|---|---|---|
| 23 | 1 | 0 | 3 |
Nestling Stage:
The first chick SE-25 hatched on 28th July 2020, after 40 days of incubation. The second SE-26 hatched on 30th July 2020 after 39 days. SE-26 hatched just over 45 hours after SE-25, with the delayed initial incubation of 82 hours. This has been seen in previous years.
Both male and female brooded the young nestlings, gradually spending less time brooding as the chicks developed. In the first 3 weeks, the female brooded for longer than the male. The chicks were uncovered during the day for gradually longer periods as they grew stronger and began to develop their feathers.
The female brooded at night, spending less time as the chicks grew and just sleeping on the nest or nearby from about 30 days from hatch as the nestlings grew feathers and were able to thermoregulate.
Graph 4:
Total Number of hours Daytime brooding during the first 3 weeks from hatch
Graph 5:
Number of hours chicks uncovered for first 3 weeks from hatch during daytimeNote day 9 power was off
On days 11 and 14 the weather was very wet and the chicks were covered by the female.
Prey and feeding during the nestling stage:
During the nestling stage, the female fed the nestlings most of the time, with the male contributing many fewer feeds. The female fed the nestlings a total of 337 times, compared with the male 35 times. There was some sibling rivalry initially, but both nestlings received sufficient food.
As the nestlings grew stronger and developed skills, they began to feed themselves more often, rather than being fed by either parent.
Graph 6:
Total number of daily feeds from hatch of SE-25 to 3rd November 2020 after fledge of SE-26
Prey:
The male brought most prey to the nest during the nestling stage. Initially the male brought prey, while the female fed the nestlings. As the chicks grew, the female brought prey in as well. Feeding sessions lessened in time as the chicks began to self-feed.
From an early stage, it appeared that the younger chick, SE26, had an injury or deformity of its right leg. Although this limited its movement and ability to grasp prey, it was able to self-feed. However, in grasping prey and maintaining balance, observers noticed raw wounds on the other foot. As the Research Approval for this Project does not permit intervention at the nest, the team just continued to monitor and observe the progress of both nestlings.
Prey brought to the nest from hatch of SE-25 to 4th November 2020
| Prey | Female | Male |
|---|---|---|
| Fish | 38 | 117 |
| Bird | 49 | 83 |
| Eel | 4 | 1 |
| Fox | 1 | 0 |
| Leftover | 2 | 0 |
| Unknown | 1 | 7 |
| Squid | 0 | 1 |
| Turtle | 0 | 1 |
| Total | 95 | 210 |
During this Nestling stage an unusual number of Silver Gull nestlings were brought as prey – gulls were nesting in Homebush Bay nearby as well as on the Ryde Bridge.
The female brought a fox kit in as prey – again unusual. Foxes often have a den in the Nature Reserve forest and are often heard on camera. This kit may have been road kill or even taken by the female.
Fledging:
The first hatched SE-25 branched on October 10 and fledged the following day at 75 days from hatch. It left the nest area after a week. SE-25 was then not seen in the area and its survival is not confirmed.
SE-26, in spite of its weak legs, was also flapping and strengthening its wings and lifting a little from the nest.
SE-26 fledged on October 30 at 92 days from hatch and remained in the nest area for some weeks. She returned to the nest to receive food and was seen flying strongly in the nest area. There was still concern with her ability to be able to catch prey or survive in the wild. Around two weeks after fledge on November 14, SE-26 flew into a semi-enclosed balcony on the 22nd floor of a local unit block. Due to the enclosed nature of the balcony and furniture SE-26 could not take off again. The resident contacted WIRES for assistance. WIRES volunteers removed the Eagle from the balcony and it was assessed by a local emergency the Animal Referral Hospital and then taken to Taronga Zoo Wildlife Hospital. After examination, it was found that SE-26 had a poorly healed fracture of the right leg. There were also extensive injuries to the left leg, likely caused by overcompensating to support the right leg. NPW&S stated that on welfare grounds the decision for euthanasia was recommended. The full statement is included below.
SE-26 was determined a female and was euthanised on 26th November 2020. Permission for taxidermy was received and SE-26 is on display in the Birdlife Discovery Centre.
Acknowledgements:
The EagleCAM research project team acknowledges the assistance of National Parks & Wildlife Service and Sydney Olympic Park Authority in approving this research and facilitating access to the Nature Reserve and other facilities.
We acknowledge the essential assistance from the EagleCAM team:
Camera installation, electrics, cabling and maintenance: Judy Harrington, Geoff Hutchinson, Bob Oomen and Chris Bruce
Daily Operations & Socials: Shirley McGregor
Minnit Chat: Helen Stibbs
Research Notetakers: Dasha, Cathy, Kathryn, Pat and Helen
Camera Operations: Dasha, Cathy and Helen
Additionally, we also have a wonderful team of volunteers including Facebook admins, chat moderators, ground observers and more (too many to mention here). Above all, thank you to our Supporters, for funding this project.
Statement from National Parks & Wildlife Service:
"This breeding season has brought mixed news. SE-25 successfully fledged and left the nest however SE-26 was noted to have a malformed right leg during its’ development. This didn’t hinder SE-26s’ growth or ongoing development, successfully fledging and leaving the nest, only returning at times to be fed by the parents.
On Saturday 14th November SE-26 flew into a semi-enclosed balcony on the 22nd floor of a local unit block. Due to the enclosed nature of the balcony and furniture SE-26 could not take off again. The resident contacted WIRES for assistance. WIRES volunteers removed the bird from the balcony and it has now been assessed by a local emergency and Taronga Zoo vets.
Examinations over the last few days found SE-26 has a poorly healed fracture of the right leg. There are also extensive injuries to the left leg, likely caused by overcompensating to support the right leg. SE-26 is in pain from its’ injuries. Unfortunately surgery is not possible and amputation is not an option either since Sea Eagles require both legs to support themselves on the ground and to hunt.
On welfare grounds the hard decision to euthanise SE-26 has been reached. SE-26 would not survive in the wild or do well in captivity. Further complications are likely to develop even in the short term.”
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