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.