Welcome to the News section of the iNSiGHT Ornithology website (
www.simoncherriman.com). This blog contains updates about various things I've been up to, interesting environmental issues and observations I make regularly while going about my day. It is designed to be fun AND educational, and inspire you about our wonderful natural world. Happy reading!

Monday, 27 October 2014

Wedge-tailed Eagle Nesting Failures



Smashed eggs! Never a nice thing to find on any bird's nest that you have been monitoring with the hope it will soon house an eagle chick. However, such findings are to be expected and teach us a great deal about both the bird and its environment.

Above you can see a clutch of Wedge-tailed Eagle eggs that have been pecked apart by crows (judging by the beak size and shape, shown in detail below). This is not an example of predation - crows are unlikely to be game enough to 'eat from the lion's den', given how regularly they appear as eagle food. It is instead an indicator that the eggs were probably left exposed, which points to a desertion by the incubating female after she was forced off the nest in search of food. Clearly her mate was not hunting regularly enough, and perhaps there was not much to hunt.


A Wedge-tailed Eagle egg after crows have finished with it. Everything in nature is recycled.
 
It is easy for us humans to imagine that when birds breed, they incubate their eggs and produce young successfully with each attempt. However, the truth is that life in the wild is never easy, and it is naive to think that every bird succeeds at every breeding effort. A range of factors influence breeding success - food supply, weather, time of year, age and experience of the bird, predation, human disturbance, to name a few - and one or more of these can come into play for any pair of birds at any time. Successful breeding is indeed a miracle!

Being relatively long-lived, large raptors such as eagles do not need to breed every year, and in many cases they will not even attempt to do so unless conditions are perfect. Our research at Matuwa (Lorna Glen) over the past few years has shown that only about one third of the 35 or so eagle pairs will lay eggs each year. These pairs are in territories where local conditions suit reproduction. Other pairs remain present as long as their is enough food to support themselves, and only breed in good seasons (as published by Michaels Ridpath and Brooker in the 1980s, and Graeme Robertson, in 1987).


Carrion like this dead Red Kangaroo is important for keeping adult eagles alive in drought years.
 
Laying eggs is only the first step. Assuming both eggs are fertile (often one isn't), an incubating female must be provided with enough food to sit for 6 weeks before the eggs hatch. Then if they do, there is high demand from a growing eaglet for a constant supply of 'portable' prey for the next 3 months. In an arid environment like central West Australia, there is a minimum prey threshold required for eagle breeding. It is only after good seasons (sometimes one or two years after rainfall events) that this threshold is met, and it must be maintained from the onset of laying (May/June) right up to after fledging (around November).

In the last three years we've found that in most cases, arid eagles do not even hatch their eggs. The nest is deserted before hatching, leaving the eggs exposed, and scavengers like crows eventually break inside and consume the contents. In past years I've checked nests in November or December, by which time any evidence of eggs has gone (if they were abandoned in July or August. The state of the nest platform, and its lining, can tell us whether or not the eagles have bred in any given year, but that's another story!). However, this nest was inspected in late September, and the broken eggshells were still there to tell us their story.



**In case you are wondering about 'researcher-induced failure', here is some more information. When I mentioned 'monitoring a nest' at the top of this post, you might think 'are nests climbed during incubation and could this be a reason for the eggs' desertion?' In some cases, nests are climbed during incubation if we are unsure of their contents, but mostly climbing is avoided until chicks have hatched. However, failures that have been recorded at climbed nests have occurred in the same season as unclimbed nests, and there is no evidence in our studies which attribute failure to climbing. If flushed, an incubating female is often observed returning to her nest to sit again. And we have found broken eggs or shell fragments on many nests that were not even visited (let alone climbed) during the incubation period, but checked later in the year. The above photos show a nest that was visited and climbed for the first time in 2014 in August. The last time it was climbed was in October 2013 in a year when it had also failed. In 2012 this nest had 2 chicks in August, and when inspected in December that year, contained a dead nestling aged ~7 weeks, whose death we attributed to heat after a prolonged period of daily maxima above 46˚C. Prey abundance is clearly low in this territory although the resident eagles are regularly observed within it.

Monday, 20 October 2014

Kambarang Kites


KAMBARANG! This Noongar (Aboriginal) word is the name of the current season we are experiencing in south-west WA, also known as Spring. It is a time of plenty, when creatures of the bush are capitalising on abundant resources to raise their young. This is especially applicable to our fabulous birds of prey. If you've read my other posts before on Square-tailed Kites, you might have realised that I have quite an affiliation for this species! Being involved in the rescue of a chick in 2012 was all I needed to make this bird of prey soar up to become one of my favourite animals in Australia. Today I was again privileged to visit the same kite family for the third year in a row, and photograph their behaviour at a nest. It was so exciting to see the female brooding 3 small chicks!! (Last year their single egg failed, and the previous year they raised 2 chicks).

One interesting observation I recorded on film was the male kite (who is responsible for delivering most of the food) landing on the nest with an entire Silvereye nest, which contained one chick. Square-tails specialise in foraging close to the canopy and picking off nestling songbirds, which are usually extracted from their nest and carried off. But for 'small and tricky to handle' prey species like Silvereyes, there's nothing like delivering food inside a pre-made shopping basket!

The female kite 'checks the shopping basket' as she removes the Silvereye's nest from her own nest.

The male kite barely spent any time at the nest - he would deliver prey and then take off again on another hunting foray. The female fed her chicks with the delicate care that all mothers in the animal kingdom show, and after feeding she took care to brood them beneath her warm feathers. Here you can see the female feeding 2 of her chicks, an image which has been ingrained in my mind for most of the day. It is a scene that I will certainly never forget!



Saturday, 18 October 2014

Latest Eagle Research


Isn't he gorgeous (the eagle chick I mean!!)? This is a Wedge-tailed Eagle chick aged about 7 weeks. I've just returned from the middle of Western Australia where I've been carrying on the research on Wedge-tails which began back in 2011. You can read more about what the latest field trip has involved by visiting the latest blog post on the Wedge-tailed Eagle Tracking website here.

Monday, 6 October 2014

Brown Falcons



Isn't he stunning? Here you can see an up-close view of one of our most fabulous and well-known species of raptor, the Brown Falcon (Falco berigora). Did you know that its species name 'berigora' comes from an Aboriginal word for this bird, originating in NSW? Ecologically, 'brownies' are probably equivalent to the multi-talented Common Buzzard of Europe and Asia - they will hover like a kestrel and swoop like a goshawk, or even hunt on the ground to run after and catch frogs, lizards and snakes. This 'jack-of-all-trades' characteristic helps explain their wide distribution and success in many different habitats.


Brown Falcon chicks! Like all the falcons, browns do not build a nest of their own. This species uses an existing one built by another raptor, corvid, magpie or babbler, as with 3 of the 5 other Australian falcons (Peregrine Falcons and Australian Kestrels will also nest on cliff ledges). The clutch of 3 in this old Wedge-tailed Eagle 's nest atop a tall Gidgee tree has now hatched and the chicks are into their first week, with eyes open and alert. It will be a few weeks until fledging. Here is another brood of three which are much more advanced - the youngest is a bit squashed under his sibling!! (can you spot him!?).

These gorgeous young predators are about 3 weeks old, and huddle together in their nest while they wait for their parents to deliver prey. Currently there are many small songbirds in the Mulga shrubland surrounding this nest - Zebra Finches, woodswallows and honeyeaters - which provide a good source of prey for these falcons.
As part of a study of birds in the arid inland of Western Australia, we've been recording the breeding of all species of birds of prey. Brown Falcons are one of the most common raptors and we have currently recorded 6 nest sites. Nestlings are being fitted with metal rings/bands on their legs - these are a fixed size, are applied when the legs are big enough to hold the ring (the rings do not stretch/grow), and most importantly are harmless to the bird. The older brood pictured above was lowered down in a soft bag where the chicks are weighed, measured and ringed.
At about 3 weeks of age, this Brown Falcon nestling (known as an 'eyass') is the perfect age for ringing.

Ringing nestlings allows us to identify individuals and gain more information on their movements and survival. Such information is important for conservation - it provides land managers with the most up-to-date and accurate knowledge required to help the environment support maximum biodiversity! This research is conducted under the Australian Bird and Bat Banding Scheme and has been approved by an Animal Ethics Committee to ensure it follows the Animal Welfare Act.
A bird in the hand is definitely worth two in the bush! But it also allows us to view detail not otherwise visible in the field. One of the most noticeable features of the Brown Falcon chicks we handled was their almost blue legs! Here you can see the detail of the scaly toes, which currently have soft and delicate skin, but will soon develop the tough armour that helps the species handle reptilian prey such as snakes.


The most amazing part of these falcon experiences was the nature of the adult male falcon who is pictured at the top of this post. As I balanced myself with small branches in the dense canopy of the Gidgee tree in which his nest was situated, and took photos of his very cute offspring after I'd placed them back, he suddenly alighted on the leafy outer foliage, just over a metre in front of me. He was in no way aggressive, but calmly clung to the canopy, lifting his wings to balance himself against each gentle gust of wind. I photographed him for about 10 minutes, and all the while he gazed across at me with those big, brown eyes that I knew could detect the finest detail on my face.
 

The silence was suddenly shattered by the female falcon, who arrived overhead with a loud call, warning me that she did not respect my proximity to her chicks. You can see a picture of her below - she is a much darker bird than the male. I knew then it was time to get down, and leave this family in peace. It was exciting to have ringed them, and think about where in arid Australia they might turn up down the track.

As with all my photos, these ones in this blog aim to offer 'insight' into a common yet beautiful bird's life, and enhance appreciation of just one of our many wonderful animals! I hope you've enjoyed them :)