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 summary of four years study

The study group have recently completed a four-year report of the findings so far from the Little Eagle study. Here is a summary of the report submitted to Ginninderry Joint Venture and the whole can be read on their website at: https://ginninderry.com/wp-content/uploads/2021/07/LE-report-2017-2020-Ginninderry70.pdf .

The Little Eagle Hieraaetus morphnoides is listed as Vulnerable in the ACT and NSW and has nested in the Ginninderry area. Ginninderry Joint Venture joined and has partly funded a cooperative study of the Little Eagle in the ACT and nearby NSW since its inception in 2017. The project aims to gain insight into the bird’s population in the ACT, its breeding ecology and movements, how the birds use the proposed Ginninderry development area, and provide information to guide conservation of the species.

Main points

A minimum of 15 Little Eagle territories were identified in the ACT. There were minima of 9 pairs in 2017, 2018 and 2020 and 10 in 2019. The whole of the ACT was not surveyed and it is likely that there were more, undetected, breeding pairs. Six territories were identified in nearby NSW and there were minima of two pairs in 2017, five in 2018, four in 2019 and five in 2020.

The annual mean number of chicks that fledged per pair with a nest in the ACT was 0.40, range 0.30-0.55, and 15 chicks were reared over the four years. In NSW, the mean fledging success was 0.67, range 0.50-0.80.

397 prey remains and 810 pellets were collected. The main prey were European Rabbit (39.9% of prey remains, 43.2% of remains in pellets), birds (43.5% of prey remains, 37.4% remains in pellets) and reptiles, all of which were lizard species, (6.9% of prey remains, 16% of remains in pellets). Carrion was seldom taken.

The mean nearest-neighbour distance between nest sites in the ACT was 5.59 km, range 0.9-10.5 km, which was closer and more uniformly spaced than random.

16 birds were fitted with GPS-transmitter tags to investigate their movements. All six territorial males mostly stayed within 3 km of their nest site during the breeding season, mean 80.7% of records, range 66.3-92.9%. And 90.5% of records from one female were within 3 km.

Birds were recorded in most of the northern part of the ACT, ranging over grassland, woodland, the forested Brindabella hill range, pine forest and undeveloped ground in or near urban and industrial areas.

All five adult males and one of two adult females tagged in the ACT left in dispersive migration post breeding, and four tagged juveniles dispersed similar distances and directions: mean distance 1543 km, mean direction NNW, 331 degrees.

Six birds flew to savannah in the Northern Territory and far north Queensland, one wintered in the cane field district of south-east Queensland, one went to the coastal forests of south-east New South Wales, two flew as far west as grasslands in south-eats South Australia, and one wintered in the heavily industrial parts of inner Melbourne. One adult female remained in the ACT, 20 km from her nest site. 

The report finds that the Little Eagle is widespread in the ACT, and one pair that nest 1.5 km outside the Ginninderry development area use parts of that area for hunting. Following three dry years, more birds laid eggs and hatched young in the fourth, wet, year. The main prey, rabbits, were abundant following the rain. This might have been the reason more eagles bred that year. Although this is a descriptive study, and long-term data are required to achieve significant data analysis to identify the main factors in the ecology and movements of the Little Eagle, the information gained so far has already aided management decisions for conservation of the species in the ACT.

A Little Eagle fitted with a GPS-transmitter soars past a hillside.

A short note on an analysis of Little Eagle pellets 

An adult female Little Eagle eating a rosella provided to her by her mate.

A short article has been recently published in Canberra Bird Notes, describing a sample of food items in Little Eagle pellets in the ACT area. The main prey items were rabbit and small-medium sized birds and smaller number of lizards.

Rae, S., Davies, M., Mulvaney, M., Fletcher, D., Kiggins, R., Stol, J., Roberts, D., and Olsen, P. (2021). Prey items identified from Little Eagle pellets collected in and around the Australian Capital Territory. Canberra Bird Notes 46: 64-69.

Abstract: We describe the prey items identified in 810 food pellets ejected by Little Eagles (Hieraaetus morphnoides) in the ACT and nearby NSW. European Rabbit (Oryctolagus cuniculus) was the most frequent prey species, found in 87% of pellets. The remains of birds were in 31% and reptile remains were in 13%. The most frequent birds eaten were Eastern and Crimson Rosellas (Platycercus eximius and P. elegans), and European Starling (Sturnus vulgaris). The reptiles were all lizards, and the most frequent remains were of Eastern Blue-tongue (Tiliqua scincoides scincoides), dragon sp. and skink sp. Miscellaneous items included, Black Rat (Rattus rattus), Red Fox (Vulpes vulpes), Eastern Grey Kangaroo (Macropus giganteus) and sheep (Ovis aries). Traces of insects eaten were scarce (in 1.8% of pellets) and all were either beetles (Coleoptera) or grasshoppers (Caelifera). The minimum numbers of the main prey types were: rabbit 141, bird 122 and reptile 52. Prey remains were collected at the same time as the pellets and on comparison, there were similar counts of rabbits (134) in the prey remains as in the pellets, more birds (159) and fewer reptiles (34). 

The pellets were collected from below roosting branches. The larger one shown here was more likely from a female eagle and the other two from a male. This is because the female birds are much larger than the males and are more likely to eject larger pellets, although this is not conclusive as there is considerable overlap in the pellet sizes, as that can be affected by the prey eaten and size of the meal.

The main contents of this pellet can be seen. It is mostly composed of rabbit fur and whiskers, and there are feathers, probably from either a Crimson or Eastern Rosella.

This pellet is also mostly composed of rabbit fur. The secondary item is a lizard as can be seen by the scales and claws in the lower end. Possibly a Cunningham's Skink.

A total of 810 pellets were collected over three years. Each pellet was individually bagged and labelled. And all pellets that were collected at the same place and time were bagged into batches. Then all pellets from each year were bagged together. They were all dried thoroughly prior to bagging to preserve the contents. Then they were all analysed one after the other. It is easier to do this all at once as familiarity of the various items speeds identification.

There is a lot more to fieldwork than fieldwork.

The fourth annual report on the study of Little Eagle breeding in the ACT area - 2020

A fledgling Little Eagle perches on a branch at the edge of its nest while the adult female looks on from a branch behind the nest.

BREEDING SUCCESS AND DIET OF LITTLE EAGLES IN THE ACT AND NEARBY NSW IN 2020

Rae, S., Mulvaney, M., Wimpenny, C., Brawata, R., Stol, J., Davies, M., Roberts, D. and Olsen P. (2021). Breeding success and diet of Little Eagles in the ACT and nearby NSW in 2020. Canberra Bird Notes 46: 56-73. 

Abstract. Twelve Little Eagle (Hieraaetus morphnoides) territories were occupied in the ACT in 2020. There were nine pairs, seven of which were confirmed to have nests, and it is not known if the other pairs had nests. There were single birds, a male and female, at two territories, and at one previously successful territory a female was seen with a lined nest but no male and no eggs were seen. Eggs were laid in at least six nests and young were hatched in all nests with eggs laid. At least three chicks died while still young, two in each of two nests with single chicks. Prolonged heavy rainfall was a possible cause of failure at these two nests and one nest was disturbed by Pied Currawongs (Strepera graculina) and Brown Goshawks (Accipiter fasciatus) probably causing chick death. A minimum of three pairs successfully fledged one chick each. In nearby NSW, four previously known nest sites in NSW were occupied and single young fledged from all. One chick died in one of these nests where two chicks had hatched. A fifth, new, pair with a nest were located but they apparently did not lay eggs. Despite higher loss of nestlings than in the previous three (drought) years, overall breeding success was slightly higher. The diet was composed of mammals (60.6%), of which European Rabbit (Oryctolagus cuniculus) was 52.4%, small/medium-sized birds (36.1%) and reptiles (3.3%). Rabbits made up a greater percentage of the diet than in the previous three breeding seasons.

Another fledgling Little Eagle, a dark phase one, flies over its nest area.

After three dry years, the wet winter and spring in 2020 began promising for the Little Eagles breeding in the ACT. The vegetation grew back after the rains and rabbits, a major food source for the eagles, were abundant. A higher proportion of eagle pairs laid eggs and hatched young than in the previous three years. However, the wet weather continued with some prolonged heavy rainfall when the chicks were still downy and vulnerable to hypothermia. This could have been the main cause of failure this year, or perhaps the adults could not find enough food during the rain periods and the chicks starved. What happened is uncertain, and it is only when we study birds closely that we detect such occurrences. One reason why this is a long-term study, is to collect data from enough years to assess how such factors as annual variations in weather can affect the birds breeding success.

 Light and Dark

The Little Eagle juveniles in the Canberra area have all fledged and are now flying freely around their local patches. They are still dependent upon their parents to supply them for most of their food, although they are beginning to catch prey for themselves. Hence, it is a good time to catch and band them for later recognition. There are two colour morphs of the species, light and dark, and it is useful to hold these birds in the hand to see just how different they are from one another.  

              

The bird on the left above is a dark phase individual and the one on the right is a light phase. Although both these birds are juveniles and as such have typical red colouring, once they moult into adult plumage they will still retain the dark or light markings. In these examples, the dark bird is a male and the other a female, but the sexes can be either phase. And the female is actually larger than the male as is usually the case, but it is difficult to show this in photographs.

Both birds have individually numbered metal bands on their right leg and a unique coloured alpha-numeric metal band on their left, in these cases both are red. So if any readers see any Little Eagles, please check their legs for such bands and report their location to this study. The light bird has also been fitted with a GPS-satellite-tag on her back so that her movements can be followed.

The bands are red in the modern sense, the birds are red in the old sense, as in a red dog. A term that has been used since long before bright dyes have been used.

The dark birds have a smokey appearance which is created by the broad dark markings on the breast. The pale straw colouring of this bird's crown contrasts with his dark face.

The dark streaks on the pale bird's breast show as narrow lines and more red shows through. Her crown and nape have rich red colouring.

No matter whether light or dark phase, all Little Eagles have bright sharp eyes.

From egg to fledge

This female Little Eagle began incubating her egg about 16 September 2020. Her head can be made out on the top right of the nest. This post gives a pictorial description of the incubation and development of their chick. The photographs were taken by Sandra Lauer and her partner Jeremy, from a concealed watch point in a wood 200 m from the nest on an overlooking hillside. The birds never showed any alarm at their occasional distant presence. Little Eagles can nest closer than this to places frequently used by humans. Most people never notice them and the birds carry on with their business.

The male, a pale phase bird, would deliver food to the female either directly to the nest as in this case with a rabbit, or take it to an adjacent tree where she would slip off to eat it. The males usually cover the eggs while the females are off. Most of the incubation is done by the females and most of the hunting by the males who hunt for the females as well as themselves.

After about 36 days, the egg hatched, which would have been about 23 October. But the chicks are difficult to see when small and the females brood them tightly for the first week or so. This shot was taken on 1 November when the chick was just over a week old. It is still pure white and downy, although it can now hold its head up and move about the nest.

A week later, the female spent much of the time shading the chick from the direct sunshine by standing over the nest. This is typical behaviour. Once the chicks are two weeks old they can control their own body temperature more easily and require less brooding by their parents, but excessive direct heat from the sun can overheat chicks.

Once the chick was three weeks old, it was much stronger, shuffling about the nest and watching over its surroundings. The first of the chick's dark feathers are beginning to show, especially its flight feathers which will be the largest. The female still stayed close by, as here, standing on the edge of the nest. The males continue to supply most of the food for all the family.

By the fourth week, the chick is much stronger, standing high on its feet, rather than its heels when younger. The bird is losing more and more of its down by now and it has a pie-bald appearance. Its wings are noticeably dark. The female spent less time at the nest with it, but she would have been watching from nearby. 

Six weeks old and the female was still feeding the chick, although by now it could probably tear up small prey itself. Just as when the chick was tiny, the adult presents little pieces of food delicately to the chick. The female is a dark phase bird so the sexes could be easily recognised.

At six weeks, most of the body feathers have grown in and only flecks of down are left on its back and wings. The chick's face shows up white still. The feathers on its back and on the topside of its wings are dark, much darker than those of the parent birds. That is because their feathers are faded by years of exposure to sunlight 

Wing stretching is frequently practiced, more and more so as the chick nears fledging age. The chick also spent much time walking along and jumping between branches over the next two weeks. Although the wings look fully feathered they are not quite full length. And the tail is noticeably short. But it is beginning to look like an eagle.

This was the last time the chick was seen in the nest, when about 8 weeks old on 17 December, in a typical squinting view of the nest through a telescope. The adults had been tending egg or chick for three months. And they will still have to care for the chick for perhaps another three months before the family breaks up and they all disperse to their separate winter quarters.

p.s. The fledgling has been seen perched in the nearby wood in January, calling when the adults brought in food.