191015 11h52 Female Crowned Eagle
delivering fresh leaves to nest with two,
1 day old eaglets.
190726 14h14 Courtship feeding, Male
Crowned Eagle delivering prey to female Crowned Eagle . Prey unidentified.
190826 10h09 Female Crowned Eagle
inspecting newly laid egg.
191008 10h50 Female Crowned eagle
collecting head of Red Duiker from male Eagle. The image was lightened to show
the head of the duiker.
20130911 An immature Crowned Eagle flying fledged
from the Municipal Nature Reserve nest flying over Shandon Estate.
192029 06h51 Crowned Eagle female with 15
day old chick
For the past twelve years the Crowned Eagles
around Nelspruit/Mbombela have been studied. The focus of the study has been on
determining the population density and whether the population is a source or a
sink. In other words, is their population a stable one producing a surplus of
chicks or is the population shrinking. To date the information obtained from
monitoring the nests tends to indicate that the population is healthy,
producing a surplus of chicks. The known
nests are used regularly, usually every alternative year, or annually if they
have a breeding failure.
The pair of Crowned Eagles that now nest on
Shandon Estate used a nest in the municipal nature reserve for a number of
years. Their nest was first discovered in 2007 and was already a massive
structure so had obviously been used for
many years previously. This nest was abandoned
in 2011 and they moved onto the Shandon Estate in 2012. This pair of eagles is
unique in that it is the only pair being monitored that has attempted to breed
every year since their nest was discovered. Most pairs breed every second
year. The reason for breeding annually is not known as they have had chicks annually and at least
two have successfully fledged. The
presence of a fledged chick is thought
to inhibit the urge to breed during the year after fledging as it still needs
to be fed for as much as ten months after fledging. This is similar to the
Martial Eagle which also breeds every alternative year. A possible reason why
this pair breeds every year is that the chick is not surviving. This was confirmed during the 2018 breeding season when in December, the three quarter grown chick was
suspected to have been killed by a Baboon on the nest. Quilled feathers from the chick's wings were
found below the nest. A male Baboon had been observed sitting near to the nest just
two days earlier. It is possible that
baboons have also been responsible for other chicks not surviving and this
being the reason why this pair of eagles breed every year.
In order to test this theory, a proposal
was put to the Shandon Estate management to install a remote recording camera
at the nest. With the guidance of Peter
Retief, a local computer specialist, a sophisticated remote miniature computer
called a Raspberry Pi and attached small camera, has been placed near the nest to try to record the
breeding activities of the eagles on a continual basis for an entire breeding
season. The camera and its accessories
were funded by the owners of Shandon Estate.
The camera was installed in March, long before the commencement of any
nesting activities, so not to disturb
the eagles. The camera was placed in the tree over twenty metres up by John Davies from the Endangered Wildlife
Trust. It has already taken some amazing
images of the pair of Crowned Eagles on their nest. The advantage of this
camera is that it can be programmed to take images as programmed by the
computer from Peter's desk! He can also observe the images being taken from his
office without disturbing the eagles. This is the first time this technology has
been used in South Africa to document bird nesting behaviour.
Discussion
The Raspberry Pi camera has been recording
images daily now for seven months without a hitch. A number of very interesting
images have been recorded during this period documenting behaviour patterns not previously recorded such as pair bonding and also the breeding behaviour
of the eagles on the nest. The camera
allowed us to determine when the eggs were laid even though we could not
actually see them. It also allowed us to determine the exact day of hatching
from recording the behaviour of the eagles. The eggs took 51 days to hatch. The "Cain
and Abel" battle where one chick
succumbs to the pecking by its sibling, was unfortunately not documented
clearly due to the depth of the cup in the nest. The surviving chick is now two
weeks old. Where possible, prey items are being identified. So far greater bushbabies, red duiker, rusty spotted genet and dwarf mongoose have been brought to the nest. If all goes well, the chick will start leaving
the nest in about 90 days time!
Acknowledgements
Peter Retief for developing and programming
the Raspberry Pi computer and camera and
his endless enthusiasm of the project, Petri Viljoen for initiating the
project, Jaco Badenhorst, the General Manager of the Shandon Estates for his
continued enthusiasm for the project and all property owners who have
contributed towards this unique project in various ways.
Garth Batchelor
