BOOBOOK

Australasian Raptor Association

( Archived Extracts )

Issue 17 (1) & (2) of the magazine included the following articles :

Table of Contents :
(Composite)

	Establishing Priorities For Searching Coupes For Nests of Wedge-Tailed Eagles.
	Conserving Australia's Threatened Birds.
	A Comparison of Two Methods for Studying the Diet of Peregrine Falcons.
	More on HAART'S Eagle.
	Even Man was fair Game for Raptors some 2.5 Million Years Ago.
	An Electrocution Survival Success Story.
	A Talk With Mark Holdsworth, President of the A.R.A.
	Seal Beats Sea-Eagle to Penguin.
	Attempted Capture of Honeyeaters And Lorikeets by Little Eagle.
	Nesting Marsh Harriers.
	Competition Between Wedge-Tailed Eagles and White-Bellied Sea-Eagles For Nests.
	Should the U.K's Raptors be Culled?
	Recent Technological Advances in Raptor Research.
	Socio-Economic Aspects of Raptor Conservation.
	Good News For Owls and Jobs.
	Forest Owl Project (FOP).
Book Reviews :
	"Birds of Prey." Ian Newton.
	"Birds of Prey." Floyd Scholtz
	"Mitigating Bird Collisions with Power lines : The State of the art in 1994."

"Establishing Priorities for searching coupes for Nests of Wedge-Tailed Eagles"

ASSESSING COUPES

A common questions asked of foresters and planners in Tasmania is "Of these coupes, which ones might have eagle nests?"

While a thorough search of every coupe would seem preferable it is not necessary. In any case, the resources for such usually don't exist. Therefore, it is necessary to prioritise the coupes for searching.

The following notes describe the steps I recommend for this process. Three main characters of the coup need to be assessed.

Ranks are assigned to each of these characters and an average rank (the assessment rank) for the coup is calculated using all three ranks or at least the first two if information about nearby nests is unavailable. This average forms the basis for setting priorities for searching.

1. Area of potential nesting habitat in the coupe.

Basic breeding biology of the species must be known. We need to measure the area of relatively undisturbed (by people), old growth eucalypt that occurs on sheltered parts of slopes with similar aspects to those of the nearest nests. Although active nests rarely occur within 250m of regular, heavy human disturbance, disused nests may be there (ie, they were there first). Even these nests are valuable. Disturbance and animals' reaction to such is dynamic and these nests may become viable. In any case, their presence advertises to eagles that the place is good for eagles.

Simply put, small areas have a lesser chance of holding a nest than large areas. If there is no potential habitat the assessment need go no further.

2. Proximity of active nests

Since active nests (nests where breeding has been attempted in the past 5 years) are evenly spaced we can use the 'nearest-neighbour distance' (nnd, the average distance between nearest active nests) to predict where other nests might be. Remember that nesting densities (and thus nnds) vary between districts. That's why information from nearby or at least similar habitats is most useful. If the potential habitat in a coupe is 1 nnd away from the closest active nest then the likelihood of a nest being there is obviously high but if half a nnd away the chances of a nest are remote. Since most eagle territories contain several nests close by, potential habitat very close to an active nest also has a very high chance of containing a nest.

Since the nnd is an average of a range of values, errors compound and accuracy of prediction diminishes as we go beyond 1 nnd. Thus, ranks assigned should be moderated, when the coupe is 1-2 nnds away from the nearest active nest I suggest by a rank of 1 and when 2-3 nnds away by 2. This means beyond 1 nnd this factor is not very usefull in predictions and I recommend not extending predictions beyond 1 nnd and making every effort to get information on nearer active nests.

3. Number of suitable nearby nest sites.

If there are other suitable nest sites (10 ha or more of potential nesting habitat) nearby then the chances of the potential habitat in question having a nest are obviously less than if it was the only suitable nest site for some distance.

With rare exceptions a territory's alternate nests are within an area of radius of about 0.2 of a nnd. Thus, we can rank a coupe's potential nesting habitat in regard to its uniqueness as a nest site.

Example Coupe DG118B has an area of 77 ha. It is wrapped around one end of a large, gullied hill. All of the coupe is old-growth eucalypt. Active Wedge-tailed Eagle nests in the district average about 11km apart, generally have south-easterly aspects and on large hills the nests are usually on mid to lower slopes. There is a nest regularly used for breeding 9 km away. What is the potential for a nest?

The mean rank (the assessment rank ) = 3

SETTING PRIORITIES

This assessment rank of 3 for the coupe does not give any absolute measure of the probability of a nest being there. However, when compared to assessment ranks for other coupes in the district it allows priorities for searching to be set.

For Example coupe assessment rank searching priority DG118B 3 2 CF23C 2.5 3 SD113K 1.5 4 DF119A 3.3 1 DG118A 3 2 DS74B 1 6 FG68J 1.3 5

If resources are short a pre determined cut-off assessment rank (say of 2) can be used for those "To search or not to search?" decisions. Searches should not be done too far in time ahead of logging (say, no more than 3 years) since there is the chance of a nest being built after a search.

Nick Mooney (TAS)

MORE ON HAARST'S EAGLE

.....Many species of now extinct flightless birds, large and small, lived in the New Zealand forests about 1000 years ago. Their lives, despite their inability to fly, were relatively secure; the only predators were birds of prey. Of these only the giant eagle, Harpagornis moorei, could possibly have posed any threat to the adults of the moa species and Harpagornis was certainly a giant.

The largest females (which were bigger than the males) had a wing span approaching three metres and may have weighed up to thirteen kilograms. It possessed enormous talons and its head, equipped with a wickedly hooked, flesh-tearing beak, was proportionately larger than those of most eagles. Its skull was, in many ways, more like that of a vulture than an eagle (although it was probably feathered rather than naked) and its size undoubtedly reflects the size of the prey upon which it mainly fed.

However, despite any threat which might have been posed by this monstrous raptor, all the flightless birds survived successfully here for thousands - and some for millions - of years. But when the first Europeans settled in this country some two hundred years ago, all of them had gone - and gone so completely that no-one was aware of their previous existence in New Zealand, not even the Maori people.....

B. McCULLOCH
(excerpt from Moas - Lost Giants of New Zealand, Harper/Collins, New Zealand)

"A Talk with Mark Holdsworth, President of the ARA & Observations on Birds of Prey in Tasmania"

After many years of waiting and procrastinating, my wife and I finally got round to fulfilling our promise to visit our Tasmanian friends. Via Frankfurt, Bangkok, Singapore, Sydney, and Melbourne we reached the island of Tasmania and arrived in its capital Hobart.

In our drives and bush walks which criss-crossed the state we observed so many birds of prey that we were unanimous that here, the world was in its natural order. Unfortunately this was not so, as Mark Holdsworth later told us. I gave Mark an overview of the German birds of prey situation as far as my knowledge extended. He pointed out to me that in Australia (including Tasmania) the taking of birds of prey for falconry purposes is illegal, and that a reversal of this is unthinkable.

It is difficult for Australian raptor proponents to reach and teach all people to tolerate raptors. Eagles have been protected for 10 years in every state, but not so long ago it was still possible to get a licence in Western Australia to shoot an eagle. The reported number of eagles shot to the present day of 2 million is shocking. It is also difficult to explain to farmers that the Wedge-tailed Eagle Aquila audax is not a sheep or a lamb killer. Many lambs die of weakness after birth and then become the target of the introduced fox or feral dogs. In Tasmania, there are no foxes, and eagles seen feeding on dead lambs have been in most cases scavenging. A study has shown that lambs are less than one percent of an eagles' prey. A further study points out that a breeding pair takes 800 rabbits in a year. We know that one pair of rabbits can potentially produce the enormous number of 500000 offspring in 5 years. One can imagine how much grass the rabbits get through and how much help the eagles are to farmers in maintaining their pastures. The rabbit, imported from England in 1859, gives the Australian farmer a yearly damage bill of well over 100 million dollars. The population of Wedge-tailed Eagles in Tasmania is estimated to be about 200 pairs with about half breeding. I asked Mark how raptors in Tasmania are affected by electrical cables. He explained that each year many birds of prey come to grief on powerlines, resulting in injury or death. Raptor enthusiasts in cooperation with the Hydro Electric Commission have an objective to modify 20 000 electrical poles in such a way that birds cannot be electrocuted.

Injured raptors that cannot be rehabilitated go to Wildlife Parks (small private zoos which are well controlled, part of Mark's work). At some parks' entrances one can read that some wildlife, including raptors, held there cannot be rehabilitated. Mark spoke with regret of the small number of people currently involved in raptor rehabilitation in Tasmania and the small number of ARA members given the size of Australia (about 400 in 16,000,000).

The status of many raptors in Tasmania is better than on the Australian mainland because there the introduced Red Fox provides much competition. The fox can achieve large numbers and when rabbit numbers reduce due to the myxomatosis virus, foxes can prey-switch and have a devastating effect on native wildlife. Such is an example of what we gleaned from Mark, who is a mine of interesting information on the birds of prey situation in that other end of the world and with whom I hope to maintain and intensify contact.

For minutes we observed Wedge-tailed Eagles in their marvellous flight. The sheep grazing underneath them were not at all disturbed. Only the ravens were fussed about the joint habitat occupancy. However, the eagles did not allow them to make an impression and continued their circling unabated. Before our eyes an eagle grabbed a rabbit and flew a kilometre away with its prey. We also observed a White-bellied Sea-Eagle Haliaeetus leucogaster over the sea. Twice we saw the Brown Goshawk Accipiter fasciatus, once catching prey. Another time we saw a collared sparrowhawk A. cirrhocephalus hassling a Swamp Harrier Circus approximans quite close to us. Twice we saw the fast flight of the Peregrine Falcon Falco peregrinus which is fairly common in Tasmania. Many times we observed the Australian Hobby F. Longipennis flash past, crying shrilly in the blue evening sky with its partner. But, by far the largest numbers observed were of the Brown Falcon F. berigora, twice seen catching prey in a field. Sensational for me was a sighting of the white variety of the Grey Goshawk A. novaehollandiae, glowing white and flying 50 metres above the wild forest canopy.

It was wonderful to be able to experience all these moments in the wild. Many moments we were able to capture with the video camera, but the actual meeting with the birds of prey in the wild will remain for us an unforgettable experience.

Our flight out became a real avian experience. We will not forget the sight of thousands of Black Swan Cygnus atratus which still occur in Tasmania in abundance, or the Laughing Kookaburra Dacelo novaeguineae (also called "laughing Hans"), the parrots and the many song birds of which I could only identify a few. But our main interest was obviously the raptors.

GERHARD KRUPKA (GERM) Orden Deutscher Falkoniere No.9, 1995

"Seal Beats Sea-Eagle to Penguin"

Further to the comments on raptors and oil spills in the last issue of ARA News we neglected to inform the editor of the following anecdote and beg it be published.

On Ninth Island, off Tasmania's north coast, while recording the behaviour of Little Penguins Eudaptor minor coping with oil spilled from BHP's IRON BARON in July 1995, we were watching an adult White-bellied Sea-Eagle Haliaeetus leucogaster obviously hunting said, sad penguins about 100m offshore. Suddenly the eagle did a 'U'-turn and swooped. Tapping away on our lap-tops we verily recorded the eagle had spied and attacked a penguin struggling shoreward. Just as the eagle, with gleaming talons, glistening beak and a glint in its eye dropped its legs for the pick-up the penguin erupted skyward in the hoary jaws of none other than an Australian Fur Seal Artocephalus pusillus (snatched from the claws of death by the jaws of death. What a life!). The eagle frantically back pedalled to avoid increasing the seal's ornithological intake and pulled up and away hungry but safe. On another occasion we saw a sea-eagle snatch a fish from a seal that was playing with it, so the competition can go either way.

NIGEL BROTHERS & SIMON GOLDSWORTHY (TAS)

"Nesting Marsh Harriers"

The following notes were made after a brood of three marsh Harriers aged 5-10 days was found at Christmas 1995 while cutting hay at Bagdad, Tasmania. A small area was left around the nest and further protection was added with cut hay.

	The mother roosted with the babies at night, while the father roosted close by.
	Both parents hunt, but in different directions. The mother hunts for 15 minutes, then returns to the area of the nest (but not to the nest) for about 15 minutes to half an hour. This appears to be a continuous routine throughout the day. Adult birds glide effortlessly through the air without flapping their wings and seem to be able to stay in the air just above the ground almost at a standstill while hunting.
	When they catch prey, the adults eat some themselves then drop it to their young and fly off again. Main food seems to be small birds and rabbits.
	When large birds - ravens, etc, - go near the nest, the adult harriers appear very rapidly and frighten them off.
	When people go near the nests of larger baby harriers, the adults fly above and call out, maybe trying to lead their young away from danger.
	These birds use various calls for different purposes. I have noticed 3 definite calls: one for hunting, one for calling out to their young, and another that is used when they are distressed.

On 13th January 1996 the harriers had started to fly. Even then they still tend to hide in the long grass and only fly if they have to as they are still being fed by their parents. They seem unbalanced on landing and take off but actually appear to fly quite well for 50 to 150 metres. At this point adult birds are much lighter in colour than their young.

TANYA MASON (TAS)

Peter 'Omar Tonelly is on to this problem of 'harvested harriers' and is developing a remote system for finding nests first. One problem that did not exist before is the high speed at which that many new harvesting machines operate. This means harriers are often killed before the operator can react. Jean-Marc Thiollay tells me that we are still better off than those trying to save harriers in France because they have to find the nests and keep then secret from the farmers who otherwise would kill them! There, our colleagues rescue chicks in secret at night and have developed a system where the chicks are moved 50-100m at a time, the adults usually attending. This seems amazing but on reflection is not unusual for ground-nesting birds. Perhaps the harrier chicks' penchant for leaving the nest and hiding nearby gives adults the behavioural flexability to cope with forced moves.

Ed