Angazi and dot

Its been a full year since my last blog. In that time the project has progressed in leaps and bounds.  Anyone following the facebook page will have been aware that we are flat out monitoring over 40 active nests - from a database of 65 known sites - this year.  In October I was awarded my MSc with a cum laude pass and have upgraded the research to a PhD.  As such there is a lot to look forward to with another couple of seasons of research.

The last blog posts was regarding the GPS transmitter that was attached to Don, the young eagle hatched from the Victoria Country Club nest in the 2012 season.  Unfortunately that transmitter failed after 6 weeks of tracking, but provided some interesting juvenile movement data.  I am waiting for the technology to improve before proceeding further with juvenile dispersal and survival tracking and hopefully we will have funding and resources to commit 10 trackers to juveniles early in the 2015 year.

In the meantime this blog is being resurrected in response to the Victoria Country Club nest once again.  After a year’s rest and relaxation for Victoria and Albert they have once again built a nest on the artificial platform and have diligently hatched a new brood!

On Wednesday the 5th of November, after confirming the little chick was at least 5 days old.  I climbed to install a new monitoring camera for this chick who is currently holding the temporary name Angazi (after we initially named the 2012 chick Donna – which inevitably turned out to be a male and he had to suffer a name change to ‘Don’).

Climbing 17 meters up this massive Blue Gum, upon reaching the lip of the nest I discovered Angazi was not a solo child.  Indeed at a very critical time the second chick was midway through ‘pipping’ – sawing its little way out of the shell.  I hurried the installation as quickly as I could and hopefully the second will survive that period of disturbance.  Five days on the strong chick Angazi is still obviously thriving, but what of the second chick?

Going up - the foam filled backpack and riot helmet with false eyes are protection against possible attack!

taking strain at about the 12 meter mark

at 17 meters up a 35 meter Blue Gum, one peers over the lip of the nest

getting into position to install the camera

and making a few minor pruning maneuvers to improve visibility

the camera is now installed and safely mounted inside a solid steel security box to protect from possible eagle attacks

checking all is well and descending on the other side of the tree

Only one chick ever survives from natural Crowned Eagle nests.  This is termed 'obligate fratricide'.  As difficult as it can be to witness - it is not easy to justify removing and hand raising the younger chick (sometimes termed Cain-and-Abel rescue) as there can be many complications with imprinting, preparing suitable release areas, and justifying so much of human and financial resources for minimal local conservation benefit.   In this instance we will let nature take its course, as it does across dozens of Crowned Eagle nests in the study area every year.  And hopefully we will record the sibling interactions and the eventual death of the second chick - a very interesting and noteworthy piece of information to publish - on the monitoring camera which is set on a timelapse setting.  Due to technology and power constraints there is no live stream footage from this camera and I will look forward to future blog posts reporting the outcome of these interactions – and the subsequent development of Angazi.

Thank you to Leon Heyes for documenting the successful camera installation!  All photos except these last two are credited to Leon.

the nest site - with Angazi, Dot, and plenty of fresh food: a Hadeda Ibis nestling, and a young Rock Hyrax

Angazi at around 5-7 days old and young Dot having cut its way a third around the shell

Sharing a table

Egyptian Goose below the Crowned Eagle nest

I knew very early on in the season that Egyptian Geese had an interest in the Zimbali crowned eagle nest.  On the 25th of September, even while the eagles were incubating, I observed a pair of geese flying up to branches on the underside of the nest, at first I thought they were trying to steal nesting material, but they were probably trying to steal the entire nest.  Fortunately the female eagle sat strong and steady and the geese backed off. I have no record of the geese interactions during the incubation period and the first 20 days of chick rearing, I only suppose that the eagles were very forceful or the geese wisely cautious.  And during the months after the camera was installed, while the young eagle was flightless and sedentary on the nest, there were no incidents observed. On the 18th of December the eagle chick was ringed with a yellow N2 band, she was measured as a large female and returned to the nest. N2 fledged at about 115 days of age around the 26th of January.

After fledging, young crowned eagles are still completely reliant on the adults for delivering food, and unlike many other raptors which will chase and steal prey from the incoming adults crowned eagle fledglings wait courteously on the nest for the food to be served.  This can go on for five months post-fledging and so my diet studies using the cameras continue for months after.

I timed my next camera service once the young eagle had made its first flight, and didn't notice anything unusual - unknown to me at the time was that the first few eggs of the clutch were deceptively hidden, covered by the detritus of nesting material .  On the next camera maintenance visit three weeks later the goose nest was obvious, lined with goose down, and again the eggs were deceptively covered.  I got a hell of a fright when one of the geese swooped past me and landed on the nest hissing with fury  -  I thought it was one of the eagles!  I laughed as the adrenaline rush of fear gave way to amused chagrin at the silly goose.

Silly goose on the left !

In any case – the camera was kept operating to see what would happen at this peculiar situation, and Zimbali has been a thrilling data-set to analyse both because of an exceptional diversity of prey remains, and this peculiar interaction between geese and eagles.

One would think that the eagles would simple dominate here, overpowering, even killing the geese right there on the nest site.  Recent Black Sparrowhawk research revealed that geese overpowered and usurped sparrowhawks, but the interaction between this particular eagle and goose duo has been somewhat of an example of commensalism.  In ecology, commensalism is a class of relationship between two organisms where one organism benefits without affecting the other- derived from the latin commensalis, meaning 'sharing a table'.

A summary of the situation – which I hope to describe in more detail on a journal note (so take heed of the copyright and intellectual property statement at the footer to the blog), is:

On the 28th of January, just a few days after the young N2 fledged, the goose first visits the nest and digs a goose-sized divot in the rotting nest lining. The first egg is laid on the 2nd of Feb and is subsequently kicked out - a full clutch of 7 eggs is laid by the 8th.

During the early stages of incubation the eggs are left covered and concealed for long periods while the eagles continued to deliver food, and the juvenile continued to eat casually on the nest. I am utterly shocked at how long these eggs can go without being brooded – and during data analysis held little hope for the success of this clutch of geese. Even up until the 10th of Feb N2 slept the night on the nest.  For the next few weeks the nest is shared between eagle feeding and geese brooding.

By the latter weeks in February the antagonism becomes clearer, maybe the geese eggs require far more attentiveness in order to ensure the survival of the duck embryos. So while the adult eagles still drop prey at the nest, it appears that the geese throw them out.  Zimbali visitors have had wonderful experiences with the trusting N2 while she had to eat her meals on the forest floor.

Floor food, a Blue Duiker leg. Photo by Benine Du Toit

The clutch of eggs were last seen on the evening 12th of March, and even on this day N2 had a nice feast of cane rat on the nest. By the morning of the 13th, the brooding behavior of the goose had noticeably changed – she now held her wings dropped – the eggs had probably hatched during the night, and the first glimpse of ducklings are seen shortly before 10am.  She keeps a very close watch over her brood and only leaves the nest once, very briefly, that evening.  The next morning, just 24 hours after hatching, its time to scarper before the little ducklings become eagle snacks.  At 6.42am the mother goose guides her little brood off the nest.  They jump and parachute 25 meters to the ground!

N2 received another meal from her parents at midday, and after eating her fill, she curiously crushed the hollow half-shells left in the nest.  Another month of camera monitoring until the 8th of April revealed no further trace of a goosey interest. N2 continued to receive meals, and consume them in peace on the nest.  The most recent photos were taken of a happy and healthy 'Miss Zimbali' on the 26th of May, and so it seems, life goes on!

Miss Zimbali as she is affectionately known by Adele Kieser (photographer)

Photo by Adele Kieser

VCCE Treadmill

All five nests that are being monitored by camera traps are all still successfully tending their growing chicks.  With 250,000 photos now gathered, there is an almost overwhelming bulk of data to use for prey identification.  Skimming through some of this data suggests I will be able to obtain a good proportion of positive identification of prey.  Some unusual results are already appearing including one Golden Mole at the Zimbali Coastal Estate nest.  All cameras have now been set to a reduced schedule for better battery endurance - after ringing of the nestling there needs to be about a month of complete undisturbed peace at the nest to ensure the first flight is a natural and unforced development.

The Victoria County Club nest has thrived on their artificial platform this year.  This next installment of the Victoria Country Club family has been quite a careful selection.  Donna has been exercising more and more as the new flight feather grow and unfurl from their pins.  The exercises are getting more and more frequent, and bolder and higher in the jumps and intensity of wingbeats.  Before she gets too confident, I scaled the nest to ring *him* on the 26th of December.

Donna’s father has recently been named Albert, only natural considering mom has been christened Victoria for some time.  This regal pair has been doing their bit for the local community who sometime take issue with the cheek of furry hands invading kitchen pantries.  In December quite a number of monkeys have succumbed to Alberts hunting prowess.  Here are a few photos from Christmas day, where Albert gave Donna a couple of meaty presents.

The Empress' New Clothes

This sequence documents the development of the first pennate body feathers of Donna as her growth advances from 48 to 62 days of age.  Shown here with one photo around 5pm each day.

The first body feathers to develop are those of the scapulars and wing coverts.  These provide a level of waterproofing on the top surface that allows her to now sit alone on the nest through all weather.  Victoria is still doing all the feeding and regularly brings sprigs of gum leaves to keep the insects at bay, but now spends most of her time off the nest perched in nearby trees.  She is able to guard over her chick while also keeping an eye out for easy hunting opportunities.

Life in the clouds

The second installment of Victoria and her little Donaa (?or Donald).  Daily photos except for a few days where there are just too many superb photos to avoid uploading

Eleven days of fickle weather experienced by these birds is demonstrated by soggy eagles and misty backgrounds.