Wednesday, August 22, 2012

... to build a nest

This is the story of one eagle pair and their struggle to build a nest.  With a little help and intervention they are off to a fine start for this year.

The recent history follows:
It begins in 2010 – when a pair of Crowned eagles arrived to build a nest on the lower end of the Victoria Country Club Estate. The nest was being constructed about midway up a tall gum tree.  A large lateral snag leaned out providing a crux for the foundation.  The egg hatched on the 10th of November 2010, and the residents of VCCE followed intently the development of this eaglet.  People were watching every day, and Ron was there the moment this eagle, christened “Jeffrey”, took his first flight on the 13 of February 2011.

As typical of these young eagles, Jeffrey leeched off his parents for the rest of the year, and as the summer of 2011 moved in – wind and rain took its toll on the nest site.  The whole construction fell away. Nothing was left.  If these eagles, like others around, were going to breed every second year, they would need to prepare a new nest from scratch.

I first arrived on the scene in early May.  First contact was with Ron Perks, he was delighted to pass on all the details of Jeffreys growth to independence.  With Ron and Kelson Camp, we went down to the gum stand to show me where the nest used to be. I mentioned that the pair could well return to breed again this season – but where.  In June they were being seen around more and more often.

Despite his proclaiming me the fundi in eagle matters, Ron’s interpretation of eagle behavior seems to be spot on.  And during the next few months I was easily able to deduce what these birds where up to from his descriptions.  Despite the reluctance of biologists to anthropomorphize animal behavior, it doesn’t seem to do any harm – afterall, in more recent years the community has been served several helpings of humble pie when we discover, for example, chimpanzees have culture, dolphins have language, and elephants grieve for lost family members.  The eagles pair up and have a strong bond with each other, personalities shine through and it seems each pair has their unique relationship quirks.

A quote from Ron’s notes to the VCCE residents goes as such
18 June 2012
Bill Farrell phoned me from their stand at VCCE, to say the eagles were in last year’s nest tree and the male was flying in sticks to the top of the tree. He was doing his best to start a base so as to start building a nest. However it was an impossible place to make a nest as every branch or stick he flew in would fall out of the tree. He tried for a whole week to get the nest started where she wanted it and she just sat and watched. It made me think that with all the effort he was putting into building this nest, she must be a good catch!
27 June 2012
I phoned crowned eagle expert Shane Mcpherson [sic], who had visited the nesting site, and told him that the male was failing in his bid to win the female’s attention as he could not start the nest in the spot she wanted…

The location for the 2010 nest was no longer an option, the small snag was all that remained of their main bracing branch.  The tree rises and rises 40 meters up to a three-way fork just shy of the top of the crown.  This is where they decided to try and rebuild.  The fork was comprised of stems only the girth of my thigh, and whenever the wind picked up slightly, the top third of the tree would tilt and sway. It was totally inadequate.  This was no place to build a nest.  Oddly, despite there being many other possibly nesting sites in nearby gum trees, the eagle just HAD to have their nest in THIS tree.  So they tried and they tried.

For three weeks the male would fly to a nearby quinine tree, consider his options before selecting a branch.  Jumping onto it and tussling with the tree, sometimes comically, he would eventually succeed in breaking large branches and swooping across to the nest.  Every time the wind blew the gum tree would tilt and shake. Many hopeful VCCE residents would watch to see each branch tumble to the ground. The female too would be accompanying the male much of the time.  She was often very nearby – watching her mate toil away, and apparently with a critical eye.  Most of the time she did not assist.   Homemaking is the males charge apparently.

I had head of a few instances where artificial nest platforms have been successful.  Locally, Ben Hoffman of Raptor Rescue has on several occasions constructed a platform to replace a fallen nest in the midst of a breeding season.  Also, I had discussed some months prior with Garth Batchelor of the Crowned Eagle Working Group up in Mpumalanga about their development of a platform.  It sounded very similar to the situation we were facing here.  So it was worth trying.

After a treacherous track cutting effort through a thicket of carnivorous Mauritian Thorn, Kelson Camp and his team made it to the base of the tree – a request by me so that I could access and climb. I decided that we would try and put in a nice set of bracing beams adjacent to where the old nest used to be – to lure them down to a more accessible, as well as more solid and permanent, nest location.

Though I was chuffed at my handiwork, it at first did not look promising.  We left the eagles to their ways over the weekend – all the while the male continued to ignore my design and keep flying Quinine branches up to the top fork. Each falling away in turn.  So rather than leave it to the males dogged stubborn determination I took a chance at attempting to persuade the female to change her focus (and hopefully in turn the males).  I took the role of the male eagle for an hour one evening – and left a tempting fresh carcass on the platform, thereby mimicking a prey delivery that a male might do to court his girl.

The female was seen on the platform the next morning – and for many hours sat and relished her prize – at one point the male even snuck under her nose to steal a small morsel and flew to a nearby perch to finish it.  YES! From that point on we were on the right track. Nest building could begin in earnest.  I visiting a week later and James Walker relayed some weekend observations: on a Saturday, from 7am to midday, James counted 33 branches flown in and added to the construction.

Weeks later with several other nests around Durban well into incubation, the nest was being more beautifully built.  An uncountable number of matings were witnessed, they starting mock copulations even as early as June, and so suspense was growing and the possibility that this pair wouldn’t get down to business this year was starting to creep into my thoughts. On the 18th of August I stopped in on a whim to check things out. Just the previous evening Ron had seen the female on the edge of the nest – he mentioned that she was standing there looking very uncomfortable “her vent feathers were fluffed out – like she was wearing an oversized nappy”.   I thought it was a perfect description for an eggy bird!

We watched for an hour as the female sat low in the nest, and at intervals got up, strolled around the nest, fussed, looking intently into the nest bowl, and moving back into the bowl and wiggling her brood patch back over the hidden egg.  Of note during this time – I watched in amazement for a few minutes as she stood at the edge of the nest, plucking hair of some animals hide and flicking it haphazardly into her nest bowl – this egg needs plenty of warm insulation.

Jeffrey two years ago

the snag without a nest

the setting - the quinine tree on the right and nest tree to far left 

what eagle wouldnt be tempted to use this platform - 20 meters up

breaking a branch from his quinine tree

off to the nest

and back to the quinine tree

to fetch another branch

we suppose she was pleased with his nest building efforts

the nest midway through construction

and now complete with eagle laying flat on her egg(s)

I have so many thanks to give to Ron and the VCCE staff and residents for supporting the research

Monday, August 13, 2012

Winter Birding and Ringing

Another week of nest surveys to look forward to this week.  I wonder how many of the six active nests will have hatched, and which others will have now laid eggs and be incubating.

Just before I go – here is a quick update on birding and ringing.  On Saturday we had another Darvill session, and after ringing about twenty birds I’d picked up two new species ringed: Three-banded Plover, and Brimstone Canary.  This now takes the number of Natal species ringed to 46, with a total of 235 individuals.

Thick-billed Weaver  Amblyospiza albifrons

a family (male, female, juv) of Sombre Greenbul  Andropadus importunus

juvenile Olive Bush-shrike  Chlorophoneus olivaceus 

Black-collared Barbet  Lybius torquatus

juvenile Greater Joneyguide (very cool binomial) = Indicator indicator

Gurney's Sugarbird  Promerops gurneyi

a first ever ringed at Darvill.  Black-crowned Tchagra  Tchagra senegalus

Three-banded Plover  Charadrius tricollaris

Grey-headed Bushshrike  Malaconotus blanchoti

those bushshrikes pack a heafty hooked tip and strong bite!

I have been casually birding during my busy days in the field – not having time to go out and look for anything in particular.  Turns out that several of the eagle nests are in great reserves, and my study area encompasses a wide variety of habitats from the high country of the midlands, and through great city reserves such as Kloof Gorge, down along the coastal forests.  In particular Zimbali Country Estate is turning out to be a great place to pick up exciting species, first time was the special Spotted Ground Thrush, and more recently Wattle-eye.  Last week at Shongweni Dam I scared a Narina Trogon off its roadside perch.  The number of species seen during July was 147.  And Darvill on Saturday added Croacking and Lazy Cisticola, as well as Red-headed Quelea, to push my total South Africa list to 400 species.

Spotted Ground Thrush  Zoothera guttata

Friday, August 10, 2012

First Nest Camera

After a week-long trepidatious build-up to the first instalment of a nest camera, this afternoon I breathe a sigh of relief that I had a wonderful eagle to break the ice with. Since the 2nd of August, when I saw that the two eggs had hatched, I had a red mark on the calendar for this climb.  The eaglet is two weeks old (has killed the second hatched young – as is normal for these eagles), and can tolerate a fair bit of exposure while I fumble around the nest site.

We had two days of terrible wet weather earlier this week, but as the weather cleared yesterday I checked in and found that all was well.  I noticed a piece of meat on the nest, and today discovered it to be the back half of a hyrax.  It was mostly concealed by fresh gum leaves - the only fresh leaves on the nest.  Obviously the eagles are making use of the insecticidal properties and keeping the food stores untainted.

a relief to see that the chick was alive and well after severe weather yesterday (9 Aug 2012)

the sole of a hyrax foot protrudes from concealing gum leaves

the best support team one could ask for

Most gratefully, there was an eager support team to help me out.  No eagles were to be seen on arrival and during the setup, but the female was perched concealed nearby and watching closely – she showed herself within seconds of me starting up the rope and called loudly.  Fortunately she remained in a nearby perch, and even apparently relaxed enough to preen and rouse while I was right at the nest.

There are many, many more climbs to do – this nest will need to be revisited in a three-weekly rotation to collect data and change batteries.  I am intrigued to see how these eagles respond with continued intrusion; do they habituate and calm down as months go by, or get more bold and aggressive as the young eaglet grows?  There should be nine other nests to include over the next two seasons, no doubt the individuals with respond differently.

a concerned eagle watches me closely

circa. 15 day old eaglet

camera installed - now anticipating the first data review in three weeks time

self portrait of concern

I consider there to be three spectacular monkey-eating eagles.  The Crowned Eagle of course; the largest of eagles, the Harpy, in tropical America; and probably the most striking, the Phillipine Eagle of that archipelago in Southeast Asia.  The Crowned is the smaller of these three, but has a reputation for being very powerful, and for defending its eaglet against all-comers. The worst thing would be to expect this every time, to relax and become complacent.

My nerves were already in a ruinous state before sitting back to watch a program on Harpy Eagles yesterday. The BBC filmmakers used stab-proof vests, riot helmets, and rawhide strapping to protect themselves against the Harpy attacks when installing and mending their nest camera.  The best I mustered was a foam stuffed backpack and motorbike helmet.  Investing in riot gear is a wise plan.

Enjoy watching this 6 part program on the Harpy in the Orinoco.

Tuesday, August 7, 2012

The Teacher Within

This semester I have taken on a lab demonstrating role for the second year Vertebrate Biology course.  There will be a three hour practical lab every week until November, most of which, as expected for a vertebrate biology course, are dissections.  I recall that during my undergraduate year this was the one paper that I aced, and received a letter from the lecturer for that course suggesting I pursue postgraduate research in this field.  Well well well…

Our second prac held last week was the one fieldtrip for the semester.  The group of 70-something students went down to the uShaka Oceanarium for the afternoon.  I was well impressed with the facility there and they had spectacular tropical reef tanks, as well as covering a variety of marine communities.

Though I’d never seen a dolphin show before and didn’t know what to expect – sadly I could only find its analogy as the aquatic version of a chimpanzee tea-party.  Admittedly I wish I knew more about the needs required, and those fulfilled, in this environment before making such a bold statement.

It is as one of the fortunate few who has had the opportunity to interact with dolphins at various times (swimming with spinner and bottlenose dolphins in Mauritius, having Common dolphins just a fingertip away riding in the bow wave of our family boat in the Bay of Plenty, and seeing large pods of Dusky dolphins frolicking off the Kaikoura coast), that this form of entertainment is compared against.
Sadly, one naturally has a weaker emotive response looking into the eyes of an enormous ragged-toothed shark in a similar sized aquarium.

My group investigating the open ocean fishes

Pineapplefish Cleidopus gloriamaris

In the same week, I threw myself into the deep end in an attempt to assist with a school camp.  The Padbury family run the Wilderness Training Programme; adventure activities for schools and other groups such as Africa Quest.  This was the first camp run for this particular Kloof school, and for many of the school kids it was their first night.  So it’s not too surprising that keeping 83! Grade 4’s (9-10 year olds) on task and out of trouble was going to be a challenge. 

Arriving at Southport on the South Coast at midday, they started out as a most unruly bunch.  Though we kept the activities running until 9pm on the first night - finishing with 'stalk the lantern', which on a full-moon night was quite impossible for the wee grommets.

The next day we had them worked out, and it was great to end the camp with a good couple of hours on the beach.  Not common in New Zealand, but widespread here as far as I can tell, are these concrete splash pools in the upper tidal zone.  The morning was made most memorable by the two pods of (maybe) bottlenose dolphin’s cruising the surf zone, and out on the horizon one or two humpback whales performing spectacular full breaches.