Forest Little Eagles

A juvenile Little Eagle swings low over a dense forest canopy in the Namadgi National Park, ACT.

This was a recently fledged bird from a nest hidden deep in the forest. The Little Eagle Research Group have watched the adult birds over the breeding season, however viewing is limited due to the topography of deep undulating hills cloaked in forest, with few lookout positions for watching their movements. Then this week, the nest was found.

The group have observed birds hunting over woodland and dense forest canopies in other parts of the ACT, and they have data from GPS-tagged birds which support this. One tagged bird in another site spent much of his time over the dense forest of the Brindabella range, including the higher ridges at approximately 1300m, then in the non-breeding season he moved to the coastal forests of NSW. That bird seemed to specialise in hunting camopy birds.

Birds have been seen to dive into the canopy to snatch birds from the branches. They have been seen to catch Crimson Rosella, Yellow-faced Honeyeater and what was either a Striated Pardalote or a Weebill. Both of these latter species were in a mixed flock and as the eagle wrapped its talons around the whole bird, it couldn't be determined which species was caught. The prey remains found below this nest were of Crimson Rosella, King Parrot, Red Wattle bird, White-eared Honeyeater and Black-faced Cuckoo-shrike. The latter have been abundant in the ACT this year and other eagles have also been eating them.

The juvenile, a male by its smaller size, spent its time perched in the canopy watching for its parents bringing food, or taking short turnaround flights in about a 200m radius of the nest. This open perch on a dead branch was less typical than the more favoured branches below the top of the canopy. Much of the forest was burnt in 2003 and there are still dead trees standing amongst the re-established canopy.

The nest was set in a clump of mistletoe on a lateral branch in the lower part of the canopy. And there were remains of an older nest underneath the current one. So, the birds had likely nested there in previous years when they had been seen in the same area.

It was such a delight to see a true wild nest in wild habitat. So many nest sites from our and other studies are in human-manipulated habitat, such as woodland partially cleared for farmland. 

This is the nest area seen from outside the canopy. There is no sign of the nest. The birds were generally quiet, the fledgling seldom called and the birds were difficult to see when perched, even from imediately beneath. They sat quietly watching us when we stood beneath them. Only glimpses of birds in flight gave hints of the nest location.

Little Eagles in the ACT have been described as rarely seen in the the more heavily forested parts of the ACT (Taylor and Canberra Ornithologists Group 1992). And  they have been described as avoiding dense forests and not breeding above approximately1000m (Debus 2017). Yet this nest was in dense forest at 1265m. These birds could have been easily overlooked, and other Little eagles would likely be just as difficult to find in such habitat. How many more Little Eagles are breeding in such extensive areas of dense forest, not only in the ACT but elsewhere in the country. Do some eagles specialise in hunting canopy birds and other eagles specialise in hunting terrestrial prey in more open habitats. Or are individuals birds adaptable to either.

The more we study the more questions we open...

References:

Debus, S. (2017). Australasian Eagles and Eagle-like Birds. CSIRO, Australia.

Taylor, McComas. & Canberra Ornithologists Group (1992). Birds of the ACT - An Atlas, Canberra Ornithologists Group and Australian Capital Planning Authority, Canberra. 

A chat with the ABC on LIttle Eagles in the ACT

This is the female Little Eagle who is mentioned in the talk. She is here incubating her egg/eggs, the second clutch she laid this year after the first clutch and part of the nest were blown out of the tree in a storm. At least one chick has since hatched.

This a brief post to connect readers to a recording of Stuart Rae of the Little Eagle Research Group chatting to Georgia Stynes of ABC Canberba Radio Afternoons show. You can have a listen here.

The host, Georgia, and the producer Sarah Grieb were very professional and efficient, which made the talk easy. It is a light introduction to the work being done by the project team, and so much more could have been said, but we managed to cover a lot of ground in ten minutes.

Always good to share.

A sad end

After thousands of kilometres flown on migration flights over four years, one of the GPS-tagged Little Eagles, Y2, has been found dead. This was her flying in february 2021, two years after being fitted with a tag.

This was how Y2 was found in september this year. The exact cause of death cannot be proved, however the evidence points to her having been at least partially eaten by a feral cat if not killed by a cat. Her colour band number Y2 can be clearly read, and her GPS-tag was still attached and signalling. That was how her location was known and indicated that something was wrong as she had not been moving.

Her body was found underneath bracken, below trees where she had been roosting frequently after her return migration flight to her summer home range. 

Her tail was lying a few metres from her body, the cut off ends to the bases of the feathers indicate that they had been bitten off by a predator or scavanger, possibly a fox or a cat. A bird would not cut off the feathers, they pluck them. The head and a leg were missing, and the body had been chewed rather than crunched like a fox would do. And the body had been eaten from the back and rear, another feature of a cat kill.

Her wing feathers had also been bitten off, rather than plucked.

Y2 was fitted with her tag in November 2019 and she died in September 2023, only 470m from where she was tagged. Meanwhile, in between, she had made four migratory flights to Cape York, to the exact same area, and back to the same summer home range area in the ACT. See more details of her movements in a previous post on this webpage on 13 May 2022. She would leave in March/April each year and return in late August/September. Yet, she was an adult bird when tagged, so how many trips and kilometres did she fly in her whole life. 

A bird to remember.

Wildfire smoke reduces Little Eagle flight activity

D2, one of the featured birds, is seen here upon his release after being fitted with a GPS-transmitter.

A new paper from the Little Eagle Research Group has been published online in Emu - Austral Ornithology - 

Wildfire smoke reduces Little Eagle (Hieraaetus morphnoides) flight activity.

Stuart Rae, Renee Brawata, Claire Wimpenny, Micah Davies and Jaimie Hopkins 

see the article here 

Abstract

There have been few empirical studies of the sensitivity of birds to the effect of air pollutants. In late 2019 and early 2020 the Australian Capital Territory (ACT) and much of south-eastern Australia were affected by extreme wildfire events and smoke extended to surrounding areas. Prior to this event, GPS transmitters had been fitted to a sample of Little Eagles Hieraaetus morphnoides in the ACT as part of a study of their movement behaviour. Three of these birds carried transmitters in the breeding season during the fires and in the previous breeding season. This offered opportunistic analysis of data from both periods to test for effects of smoke on the birds’ flight behaviour. The effects of particulate matter in the air of ≤2.5 microns in diameter (PM2.5) and covariates on flight status were investigated with a binomial generalised linear model with logistic link. The birds were more likely to fly when there were low levels of PM2.5 and the odds of flying decreased as density of PM2.5 increased at a rate of 0.202% per ug/m3. None of the sample birds died during or after smoke exposure, although their respiratory system might have been affected.

Z5, one of the other subject birds, prior to release after being fitted with a transmitter.

 On their way home

The Little Eagles that breed in the Australian Capital Territory and nearby New South Wales are heading back to their nesting areas. At least two females are back at their previous nest sites and the males are on their way too. Several birds are fitted with GPS-trackers and the project team have been following their movements. 

Y4 (above), a male Little Eagle who has bred in the Canberra area in recent years is on his return from the Northern Territory where he spent the non-breeding season. He spent his time in the area at the northern end of the line in the figure below. He seemed to begin his journey on the 23rd July, then went back north. There was a period of heavy rain then and this might have caused him to go back for a few days. He left again on the 30th July and kept going south.

He overwintered in the same area last year and left on the same date, the 23rd July, taking a very similar route each year. Compare the two routes in the figures. He immediately headed south-east, crossed into northern Queensland, then tracked south over western Queensland. He clipped the north-eastern border of South Australia this year but kept just ouside last year. Then he crossed the border into New South Wales east of Tibooburra and from there headed for Canberra.

It seems that he took a determined direct route home, with no lengthy stops. His northward journeys were less direct and with stoppages. Perhaps he is in more of a hurry when returning to his nest site and partner.

By the time you read this article Y4 will likely be back at his nest site. His partner from previous years is already there waiting for him.

 Little Eagle Migration News

On this World Migratory Bird Day we would like to share an insight gained from the tracking study of Little Eagles that breed in the Australian Capital Territory area.

Part of the Little Eagle Research Group’s aims is to study the birds’ movement ecology. This has been done by fitting a sample of birds with GPS-tracking devices. The study is not yet complete, all the data have not yet been retrieved as there are still birds carrying them. However, preliminary data show that several of the Little Eagles have returned to the same overwintering areas they went to on migration in previous years. Here we give one example, that of a female, Y2, whose migration was featured on this website on 20 September 2020.

This is Y2, the adult female Little Eagle who has repeatedly travelled to the same part of Cape York on migration. She is seen here hunting from a perch in a tree on the edge of the southern suburbs of the ACT. This photograph was taken between her journeys

The previous report showed a map of her route north to and south back from Cape York over the winter of 2020. 

A copy of Y2’s route migration in 2020 as previously shown.

In winter 2021, Y2 followed a very similar route north, and took more or less the same route south. In 2020, she flew farther to the east on the return journey. She took 14 days for her flight on the 2020 southerly flight and 15 days in 2021, travelling at an average of 130 km per day and roosting at night.

Y2’s return flight south in 2021.

The area in Cape York where Y2 has overwintered. The south-eastern edge of the Gulf of Carpentaria is in the top left of the image.

The zone in the above map that is marked in orange is where Y2 spent winter in 2020, 6388 km². The zone marked in purple was where she spent her time in winter 2021, 5366 km². The blue area is 82% of the 2021 area that was within the 2020 area, 4388 km².

In the ACT, the main foods eaten by Little Eagles are rabbits and birds, with a smaller proportion of lizards. There are no rabbits in Cape York. The habitat in the wintering area is savannah where they probably mostly hunt for birds, or lizards and small mammals.

The latest news as of this week: Y2 has flown north again to the same area for a third winter.

The route followed by by Y2 this year was similar to those in the previous two years. 

In 2020 she left the ACT on 14 March and took 10 days to reach her overwintering area, in 2021 she left on 26 March and took 9 days. In 2022 she left on 16 April, and took longer, 18 days. It is possible that weather might influence the timing or the birds' migration and further analysis of this is ongoing.

World Migratory Bird Day is an annual awareness-raising campaign highlighting the need for the conservation of migratory birds and their habitats. It is a global outreach and is an effective tool to help raise global awareness of the threats faced by migratory birds, their ecological importance, and the need for international cooperation to conserve them. This is a  United Nations Environment Programme.

 Feeding a fledgling

The Little Eagle fledglings are becoming a bit more independent now. Today, this one was calling to its parents whenever it saw them, begging for food. However, food delivery is slowing. While passing the time, this bird was seen to dive at potential prey on the forest floor, small  birds mostly from what I could see through the foliage. The eagle was quite happy to sit quietly up on a high branch while people walked past below, then it would stoop straight off its perch and try for a kill. Like so many kills I have seen, the points of impact, or possible impact, was just out of view. The last attack was actually towards me as I sat quietly below, and the eagle missed a Crimson Rosella on the edge of the path fifty metres from me.

The young bird was well aware of my presence, and it was relaxed enough to hunt while I sat about 100 m away. It is so used to people walking past and below its nest and surrounding trees - bush-walking is a very popular pastime in Canberra. This is probably the darkest young Little Eagle I have seen. There is barely a hint of juvenile red plumage, a touch on its legs, and even the red on the head is dark. 

The fledgling was still being fed though. The adult female brought in this juvenile Crimson Rosella and the two eagles began calling repeatedly to one another, the fledgling being particularly excited at the prospect of breakfast.  

The adult began plucking the rosella and I was waiting for her to carry it over to the fledgling. But, not so quick. She started to eat the rosella, from the head down, and did not show any intention of giving it to her youngster.

 

About forty minutes later, she did fly over to the fledgling with the lower half of the rosella. Yet, still she did not hand it over. She sat on a branch next to the young bird's branch and ate a little bit more, while the fledgling jumped to and fro between the branches, as if wanting to snatch the food, but wary. There was a pecking order, and the young bird was only given the food once the parent had eaten her share. 

 Storm Damage 

It is almost the end of the year and the young Little Eagles are fledging. The one above left her nest about two weeks ago, in early-mid December. She is a dark-phase bird and this shows up two flecks of her chick down on her dark breast. Otherwise she looks like a full-size Little Eagle. The red feathers on her nape are the most readily seen indicator that she is a young bird of the year. And note the large bulge in her throat, that is her crop, which is full. So her parents have been able to find ample food for her.

Not all the chicks in the Canberra study area have or will fledge this year though. These quills were found below one nest, where a chick had fallen and its body scavenged, perhaps by a fox. 

The tips of the opening feathers indicate that the chick had been about four weeks age when it fell from the nest. That is a particularly vulnerable age for these chicks as they are large but still very downy. Down is easily soaked by persistent rain like the many heavy and prolonged downpours that fell during the eagles' nesting period this year. The adult eagles possibly also struggle to completely cover large chicks from rain. And they do need to go and hunt for themselves and their chicks, which exposes the chicks to rain and chilling. Or the adults might be all right to fast during the rain, but the chicks are less resilient and might die of hunger.

At least two chicks from separate nests have died during such storms this year. The chick in the above photograph however, has a well-sheltered nest, and it is almost ready to fledge. It is also very difficult to see. The bird in standing quietly on the edge of the nest, in the shade. Those same shady branches would have sheltered the chick from heavy rain. The two nests where chicks are known to have died were set high in the topmost branches of trees with little cover above them. 

The exact nest site selected by adult birds can be critical to their breeding success. 

A new season on the way

Welcome home. The first Little Eagles have returned to their nests in the Australian Capital Territory and surrounding parts of New South Wales. Although it is still officially late winter there have been some bright sunny spring-type days and after some decent rainfall in autumn and winter the land is green, so different from the dry dust and smoke of last summer.

A pale morph male Little Eagle glides over his dark morph mate as she sits atop their nest tree. The tree is alive, only the top branches are dead.

The nest which has new sticks added, is concealed in the foliage.  

The pair were calling excitedly to one another, 

the male diving past her as she lifted her wings.

Then upon some signal between them, he jumped from the next branch and they copulated. Note how her tail is fully turned and tilted to one side, and his tail is firmly pressed over her cloaca. His talons are held forward and loosely closed as he balanced on his heels.

After a minute or so, he gently launched up off her back.

He landed next to her and both birds began preening and staightening their plumage.

Several minutes later, the male took off and went away hunting, soaring low over the nearby treetops. 

When the female took off about half an hour later later, she flew a different line, past her neighbours. And she quickly turned in alarm.

Her neighbours are Australian Magpies and one swooped very very close to her. The magpies have their nest three trees away and they will attack any animal they consider to be a threat to their nest, eggs or young, including humans. The eagle is more than capable of protecting herself, better than humans, and she casually drifted away to hunt over a nearby creek line.

The third annual report on the study of Little Eagles breeding in the ACT area - 2020

A recently fledged Little Eagle, showing her uplifted crest.

THE BREEDING SUCCESS AND DIET OF LITTLE EAGLES IN THE ACT AND NEARBY NSW IN A DRY YEAR, 2019

Rae, S., Mulvaney, M., Fletcher, D., Wimpenny, C., Brawata, R., Kiggins, R., Stol, J., Davies, M.,  Roberts, D., and Olsen, P. (2020). The breeding success and diet of Little Eagles in the ACT and nearby NSW in a dry year, 2019. Canberra Bird Notes 44: 145-151. Open pdf

Abstract. Fourteen Little Eagle (Hieraaetus morphnoides) territories have been identified in the ACT in three years of study, although not all have been occupied in all years. In the ACT in 2019, spring rainfall was well below average and maximum temperatures above average. A minimum of ten pairs of Little Eagles were located in the ACT during the 2019–2020 breeding season. Nine pairs had nests and at least six laid eggs. A minimum of three pairs successfully fledged a chick each. Of four pairs that were monitored in nearby NSW, single chicks were successfully reared by three pairs and one nesting attempt was disrupted during incubation by a pair of Wedge-tailed Eagles (Aquila audax). Overall breeding success was lower than for 2018 but similar to 2017. The main prey types were: mammals (50%) of which rabbit was the main species; small/medium-sized birds (43%); and reptiles (7%). Similar proportions of mammals, birds and reptiles were eaten in 2019 and 2018, and a

higher proportion of mammals than in 2017.

Proportions of food types in the remains of Little Eagle prey collected during the breeding season in the ACT and nearby NSW in 2017 (n = 109), 2018 (n = 131) and 2019 (n = 96).

This year's report shows that Little Eagle breeding success was lower in 2019 than in the previous two years, which were also low. It was dry in the study area in all three years, especially so in 2019, and potential prey species were likely low in abundance. Rabbit has been the most commonly taken prey item over the three years of study and it is likely that drought conditions have affected their numbers and those of the other main prey, small-medium sized birds. These results show how it is important to study such birds as raptors over several or more years as long-term data are more likely to reveal any causes for their breeding success than single or even three years' data.

The second annual report on the Little Eagle study - 2019

An adult Little Eagle flies low overhead

PRELIMINARY RESULTS FROM STUDY OF LITTLE EAGLES IN THE ACT AND NEARBY NSW IN 2018–2019

Rae, S., Wimpenny, C., Mulvaney, M., Davies, M., Fletcher, D., Roberts, D., and Olsen, P.

(2019). Preliminary results from study of little eagles in the ACT and nearby NSW in

2018-2019. Canberra Bird Notes 44: 145-151. Open pdf

Abstract. There was a minimum of nine nesting pairs of Little Eagles (Hieraaetus morphnoides) in the ACT in the 2018/19 breeding season. Seven pairs laid eggs and five pairs successfully fledged a chick each. Two pairs were seen attending nests but were not known to have laid eggs. Four additional breeding pairs were monitored in nearby NSW; single chicks were successfully reared by three of these and one nesting attempt failed. The main prey type was rabbits (61%), then small/medium-sized birds (32%) and lizards (7%). More rabbits and fewer birds and reptiles were eaten in 2018–19 than in 2017–18. Samples of birds’ movements were followed with GPS-satellite transmitters. Adult males ranged mostly within 2-5 km of their nest sites and they left their breeding areas in early March. By April one had flown 2000 km to northern Queensland, one 450 km to Melbourne and another had ranged between 50 km west of the ACT and 100 km to the east. Juvenile eagles stayed mostly within 2 km of their nest sites before they left the area in early March. By April, one juvenile had dispersed 2000 km to Northern Queensland and another 450 km to south-east Victoria, via Yorke Peninsula in South Australia. A juvenile reared in the ACT in 2017 flew to south-east Queensland in its first winter, then to south-east Victoria via South Australia in the following spring and summer.

Flight paths of Little Eagles that dispersed from the ACT post breeding season: 

three adult males (D2, X2 and Z5) and three young birds (B6, D4 and V2). 

The highlight of this year's report was the distribution of the birds out of the breeding season. The above map shows how both young and adult birds dispersed widely across eastern Australia. Click on the link above to read the full report.

Confirmation of Little Eagle Hieraaetus morphnoides migration by satellite telemetry

Publication of the results from a study of the movements of a Little Eagle out of the breeding season using data downloaded from a GPS satellite transmitter fitted to the bird.

Brawata. R., Rae. S., Gruber.B, Reid. S. & Roberts, D. (2019). Confirmation of little eagle (Hieraaetus morphnoides) migration by satellite telemetry. Australian Journal of Zoology, 66(4): 247-250.
https://www.publish.csiro.au/ZO/ZO18060 

Abstract. The post-breeding migration of an adult male little eagle (Hieraaetus morphnoides) was followed from south-eastern Australia to the Northern Territory using a GPS satellite transmitter. The bird bred in open woodland habitat on the edge of the city of Canberra, Australian Capital Territory (ACT), before it flew more than 3300 km in 18 days, to winter in an area of eucalypt savannah in the Northern Territory. It remained there for 59 days, within a range of ~30 km2 , after which the last signal was transmitted. The bird was subsequently resighted back in its ACT territory at the end of winter, thus completing a return migration. This is the first confirmation of post-breeding migration for the species.

Map showing the north western movement of the male Little Eagle from Canberra in the Australian Capital Territory, to Kalala Station, near Daly Waters in the Northern Territory.

The study group have fitted GPS tags to 13 Little Eagles to date and continue to monitor their movements. Other birds have so far been recorded as far west as the York Peninsula in South Australia around eastern parts of New South Wales and Queensland, then north as far as the Cape York Peninsula.

Acknowledgment to J Olsen who helped by catching and tagging the first bird followed in this study.