The seventh annual report on the study of Little Eagle breeding in the ACT, 2023 

 A Little Eagle being mobbed by a magpie. Not snow, poplar down.

Rae, S., Hopkins., J, Brawata, R., Wimpenny, C., Davies, M., Stol, J, and Olsen, P.  (2024). The breeding success and diet of little eagles in the ACT and nearby NSW in 2023. Canberra Bird Notes 49(1):41-50. (pdf link)

Abstract: In 2023, there was an increase in the number of Little Eagle (Hieraaetus morphnoides) pairs on territories from the previous year, and the overall breeding success was higher than in all previous years, 0.63 chicks fledged per nesting pair. There was a minimum of five confirmed pairs of Little Eagles with nests in the Australian Capital Territory (ACT), two pairs unconfirmed to have nests, and a single female. Two of the ACT pairs raised a chick each. Three nesting pairs were monitored in nearby New South Wales and two of those reared chicks, one of which reared a brood of two. Known causes of failure were wind damage to nests and eggs and breeding adult mortality. Two adult females were possibly killed and eaten by Feral Cats (Felis catus) and one male died of unknown cause. Birds formed most of the prey remains (44%) and Crimson Rosella (Platycercus elegans) was the most frequently taken species. European Rabbits (Oryctolagus cuniculus) formed (44%) of the prey remains and the other prey (12%) were all Eastern Blue Tongue (Tiliqua scincoides scincoides).

The remains of an adult female Little Eagle in a nest wood. The feathers had been bitten off, the head was seperated and the breast bone had been neatly cleaned of all flesh.

The good news. Confirmation of a new breeding territory in extensive dense forest in Namadgi National Park indicates that Little Eagles do breed there and hunt over continuous canopy. Much of the ACT and nearby NSW is covered with forest, so this needs to be considered in our study of Little Eagle population and habitat use.

The bad news. Deaths of three breeding or potentially breeding adult birds in one breeding season is new to this study. Two of the losses of adult Little Eagles were possibly due to predation by cats, this raises cause for concern.

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.

A short note on a beetle infestation of a Little Eagle nest

A recently published paper on the possible effect of a beetle infestation of a Little Eagle nest and the eagles' behaviour.

Rae. S., Roberts, D. and Olsen, P. (2023). Abandonment by Little Eagles Hieraaetus morphnoides of a nest infested with beetles. Australian Field Ornithology 40: 17-19. (pdf copy)

Abstract. A pair of Little Eagles Hieraaetus morphnoides in the Australian Capital Territory was recorded (on closed-circuit camera) feeding and mating on a nest and had added a layer of green pine sprigs in preparation for egg-laying. Many beetles, likely a species of Dermestidae, were recorded in the nest during the time that the birds were there. The eagles abandoned the nest and moved to another 1.7 km away, where they laid a clutch. It is possible that the beetle infestation was the cause of abandonment.

To watch the video recording of the beetles emerging, follow the link embedded in the PDF copy of the article.

The male Little Eagle with food on the nest.

Scores of Dermestidae beetles were filmed emerging from the eagle nest, indicative that there had been as many larvae within the nest while the eagles were preparing the nest for laying eggs in the springtime. The eagles added a considerable amount of pine sprigs to the nest lining before abandoning the nest, to lay in another nest within their home range. Both these behaviour acts are typical of birds' responses to avoiding disturbance from beetle larvae. The paper is provided as a note to illustrate this behaviour, which is probably under-recorded. The evidence in this case was only recorded opportunistically as the nest was under constant surveyance with a nest camera.

The eagle pair mating on the nest prior to abandoning it.

The fifth annual report on the study of Little Eagle breeding in the ACT, 2021

A particularly dark fledgling Litte Eagle, the offspring of two dark phase parents.

THE BREEDING SUCCESS AND DIET OF LITTLE EAGLES IN THE ACT AND NEARBY NSW IN A WET YEAR, 2021

Rae., S., Brawata, R., Wimpenny C., Stol, J., Roberts, D., Mulvany, M., davies. M. and Olsen, P. (2022). The breeding success and diet of Little Eagles in hrte ACT and nearby NSW in a wet year, 2021. Canberra Bird Notes 47: 81-87. (pdf copy)

Abstract. Monitoring of Little Eagles (Hieraaetus morphnoides) breeding in the Australian Capital Territory in 2021 was impaired by COVID-19 restrictions. It was a wet year. September and November, when most eagles lay eggs and hatch young, were notably wet. Six Little Eagle territories were recorded in the ACT in 2021. There were at least five pairs with nests, and a lone male was recorded at a sixth nest. All pairs laid eggs and one failed during incubation. The chicks in three nests died during periods of prolonged heavy rainfall and one pair raised a chick to fledging. In NSW, three pairs raised a single chick each. A known nest was built up in another territory in NSW but no birds were observed at it. The overall number of chicks reared per pair was 0.50. The proportion of rabbits in the birds’ diet was low compared with the three previous years. How weather and diet might affect the breeding success of Little Eagles are discussed.

The remains of a fledgling Little Eagle that died when a severe hail storm passed over the nest area. The partly scavenged body lay directly below the nest.

The wet weather continued in 2021 with mixed effects on the Little Eagles. All known pairs laid eggs which is indicative of a good food supply. Although rabbits were abundant, fewer were eaten by the eagles, perhaps because they had less access to them due to the prolific growth of tall grass and weeds, particularly thistles. The tall sward of dried thistle stalks from the previous year were thickened by fresh growth in 2021, presenting a formidable barrier to an eagle trying to dive after any terrestrial prey. The diet was supported by a higher proportion of birds than in the three previous years, so food was not likely a cause for breeding failure. Rather, severe storms with strong winds and high rainfall were more likely the main cause of breeding failure. This was supported by the remains of two chicks found below their nests and another that disappeared, all after storms. The direct and indirect effects of high winds and rain will be monitored in future years. 

Over three years of movement data from one bird

This is V4, the Little Eagle who features on the masthead of the Little Eagle Research Group facebook page. The antenna of her gps-tag can just be seen in that photo, protruding behind her. She has now dropped her tag as can be seen here, as she sits in a tree above where the tag was found today.

The habitat was a bit overgrown after three rainy years, with tall thick shrubs, and tall grasses and forbs beneath.

The tag was tricky to see, lying amongst the grass and leaf litter.

The tag (made by GeoTrak Inc.) is about 6 cm long, with a 20 cm antenna, and painted eagle brown to blend in with bird's plumage.

Fortunately, the tag was still sending out its position via satellite, so we could read the coordinates of where it was lying and find it quite quickly depsite the terrain.

The tag was fitted with a teflon harness, like the straps of a backpack. A weak link of cotton thread joined all four straps at the breast, and this was designed to break after a period of time. 

The thread broke three years and five months after deployment, perfectly timed as the device was still running, but we do not expect it to last much longer. In that time, data from four breeding and three wintering seasons have been downloaded, a wealth of information. The bird spent all that time within the Australian Capital Territory, spending each non-breeding period in the same area about 20 km from where she was first caught and tagged, and about 10 km from her current nest site.

She has done well and we wish her all the best. 

Thank you for the data lovely bird.

 A short note on Little Eagles.

This article was recently published in Boobook, the newsletter of the Birdlife Australia Raptor Group. It gives a brief description of some movements by a few eagles between nest sites.

To enlarge the article to read the pages click on them on a mobile, or copy to desktop.

If you like this article or would like to keep up with other raptor research in Australia, why not consider joining the Birdlife Australia Raptor Group. Go to the Birdlife Australia webpage and follow the links.

 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.