Saturday, 27 August 2016

Thick Bush and Clear Roads

An adult male Flame Robin Petroica phoenicia

Winter is almost over in Canberra and the first of the Spring migrants are moving in, as I have seen on a few recent August days up in the nearby Brindabella Ranges, in the Namadgi National Park. The White-eared Honeyeaters were the most vocal with their chopping calls, there were a few Flame and Scarlet Robins, back from their winter quarters in the lowland paddocks and woodland, but most of the birds had yet to return. 

The forest was rather quiet overall. At this time of year the characteristic sound is that of singing lyrebirds. These birds reside there all year and lay their eggs in mid-winter when snow is on the ground. Their incubation takes several weeks and the single chicks take several more weeks to fledge. So, perhaps they need to lay early to give the young time to grow over their first year. 

A small part of the heavily forested Brindabella range

I first counted lyrebirds in the area in 2001 and 2002, before the catastrophic bush fire which burnt out most of their habitat in January 2003 - over a hundred thousand hectares. As I had those counts, I have been counting them in the years post-fire to measure how their numbers have compared over the years since.

They came back slowly from single birds singing along transect lines, to similar numbers as pre-fire after several years. Now however, their numbers are dropping and on one transect there have been no birds for two years. The reason? One might be because the fire destroyed so many trees and most of the ground cover including the leaf litter, that the regrowth has come up thickly with grasses, shrubs, ferns, and saplings all competing for space. That has created a dense mass of vegetation at ground level. Lyrebirds need leaf and bark litter to forage in for invertebrates, their main food, and leaf litter needs space to collect on open ground.

A Superb Lyrebird Menura novaehollandiae forages on an open part of forest floor

It  is good to see the forest recovering, but it will take many more years for the full structure of the mature forest to re-establish. The lyrebirds will survive, and once the saplings grow tall and shade out the lower plants, the ground cover will open up and leaf litter will build up, then the lyrebirds will have more foraging habitat. 

Thick regrowth smothers the forest floor - no room for leaf litter to collect and lyrebirds to forage

The open ground is also an important habitat feature for other birds such as the robins. The Flame and Scarlet Robins both hunt by perching on a low branch, then swooping down to catch invertebrates they see on open ground. As there is now so little of that under the close ground covering vegetation, they are largely restricted to hunt in what open spaces there are. The main ones being those along the forest roads.

The artificial open ground of a forest road - but leaf litter only collects along the edges 

There were robins hunting along most of the roads, which made bird-watching of them easy. I wondered how many there were hunting in the thick vegetation. However, the bush where I tried to walk in for a look was impenetrable, wandering off the track was not an option. There are some open spaces, and there will be lyrebirds and other ground-foraging birds there. And there will be more in future as the forest grows into shape.

A male Scarlet Robin Petroica boodang hunts from a perch above the forest road

The open roads are also good for insects as they allow sunshine to reach the ground. It is cold up in the ranges and insects benefit from the extra sunshine through the gaps. What amazed me was how the robins were mostly catching small insects that I could not even see. Butterflies were easier to spot as they spend much time basking in the sun. Such as the Australian Painted Lady butterflies that were out sunning themselves last week.

An Australian Painted Lady Vanessa kershawi basks in the sun on a forest road
 (note the specific blue centres to three ocelli on the hindwings)

The Australian Painted Lady is a migrant butterfly and these were probably some of the first to arrive in the area. Soon the forest will be busy, and noisy once the large numbers of migrant birds return. 

Flame Robins are rather smart-looking birds

Tuesday, 2 August 2016

Varied Sittellas

A Varied Sittella Daphoenositta chrysoptera walks down a branch

I have been out doing the rounds of the Tawny Frogmouths over the past week, and will be doing so for the next few months as the breeding season runs on from now. Although it is still winter in Canberra, the birds are beginning to nest and the frogmouths are in pairs beside their prospective nest sites. Some have even began to build, adding a few sprigs to forks in the branches.

Meanwhile, many of the passerines are still in mixed winter flocks, flitting through the woodland canopy. And while I was out, I was passed by a flock of Varied Sittellas as they worked their way through a wood. There were twelve of them in the party, it took me several attempts to count them as they shifted position so often and quickly.

Although their colouring blends well with that of the dead limbs they climb on,
their quick jerking movements and constant twittering betray their presence.

Sittellas fill a similar niche as European nuthatches, searching for invertebrates in dead wood, mostly by climbing down the branches rather than up like treecreepers. They are also known as barkpeckers, which is very apt, as they chip away at the dead bark, opening up cracks with their seemingly delicate, but obviously strong little bills. The bottom mandible is curved, allowing them to probe deep into holes.

They are comfortable in all postures

Sittellas are cooperative breeders, the whole group helps to build one nest and feed the chicks when they hatch, but that will be a few weeks yet. For now, they will work together as a team, searching for food in the dead branches. This is one of those species that would be lost if all the standing dead timber were felled. Tidying up dead wood is not good for nature.

They even perch on top of branches like other birds

One bird which likely has eggs now is the Wedge-tailed Eagle, and a single male bird glided over the canopy while I was with the Sittellas. A sign that his partner was probably on the nest incubating eggs.

A Wedge-tailed Eagle slipped overhead

The sittellas were noisy, constantly chittering as they had to be to keep in contact with one another. The eagle was silent as it soared alone. And the frogmouths sat quietly in the winter sunshine, patiently waiting for Spring.

Meanwhile, the Tawny Frogmouths sat quietly in their sunny winter roost

Monday, 25 July 2016

Clifftop lepidoptera

A pair of Six-spot Burnet Moths Zygaena filipendulae on the stem a red-campion flower
with the empty cocoon of the female below
I went out to the sea cliffs on one of those warm days last week, when it really felt like full summer with blue skies and sunshine. And the lepidoptera thought so too.

My initial reason for the trip was to spend a while watching the seabirds, so I headed out to some of the best viewpoints I know to see the kittiwake chicks which were quite large and would soon be fledging. Most of the guillemot chicks had left their ledges, but there were still some about as well as razorbills, shags and herring gulls. The fulmars were not long hatched so they will be on their nest ledges for months yet.

However, it was while walking between viewpoints that I noticed the flutter of activity along the cliff-top. There were butterflies and moths flitting all across the grassland and heath. The cliff-tops around the coast of Britain hold some of the least disturbed habitats in the country, for they are seldom grazed, and wild flowers thrive there. I shifted my attention.

The female on the left - her wings are still not fully unfolded after emerging

The most abundant species were Six-spotted Burnet Moths. The adult males had already emerged and were patrolling over the grasses and herbs for females. These were only just emerging that day, probably under the influence of the hot sunshine. The males detect them by scent and there were clusters of males in some places, swarming over single females as they emerged from their cocoons. Once one male had coupled with a female, the others seemed to accept they had lost their chance to mate with her and went away to seek another. One female had been found by a male before she had fully emerged and the two moths lay attached as she slowly pulled out of her cocoon and extended her wings.

A frenzy of males swarm over the source of a female's scent 

There was plenty bird's-foot trefoil about, so once their eggs were fertilised, the females would lay their eggs on the leaves of this favourite food plant of the caterpillars.

A male couples with a female before she has fully emerged from her cocoon

While the Burnet moths were colonial, the butterflies were mostly single, with males chasing away any intruders of their species, or even those of other species. While at the same time trying to attract and mate with any females that came through their territory.

The herb-rich clifftop grasslands

Meadow Brown butterflies were the most common in the grasses, because the caterpillars feed on various grasses. However, although there were lots of them about, whenever I tried to follow any to photograph, they would wander over a large area then dip into the sward, fold their wings and disappear in the strong shadows. It was easier to stay still, wait til they landed beside me and then take a photograph.

A male Meadow Brown Maniola jurtina  

The females were especially elusive, skulking in the tallest vegetation, safe from predators. Although there were few passerines about that would have taken them; mostly meadow and rock pipits and they prefer to hunt on short sward and generally eat small insects.

A female Meadow Brown

The male Common Blues were the most defensive of their territories and quickly chased off the large Browns as soon as they appeared on their patch.

A male common Blue Polyommatus icarus

The adult Blues were feeding on bird's-foot trefoil and clover, both of which are also food plants for their caterpillars. So all in all, the rich flora on the cliff-top with the abundant grasses, trefoil and clover was clearly a good habitat for the moths and butterflies.

Sea-cliffs are always great to visit for wildlife, but on that warm sunny day it was especially worth exploring. The seabirds were still on the cliffs, busy as ever, and the lepidoptera were busy on the tops. Let's hope these little sanctuaries never get destroyed,

A female Common Blue

Tuesday, 19 July 2016

Honeysuckle Eyrie

The Golden Eagle breeding season is almost over, with most of the chicks fledging soon or having already left their nest. This one was jumping about and exploring its surroundings, taking very short flights between the nest and an adjacent ledge. It hadn't yet taken its first full flight a few days ago, but it might have done so by now as I write this.

This bird has been reared in one of my favourite eagle eyries, set below a deep overhang with a lush growth of honeysuckle which was in full bloom. How did the honeysuckle get there? Perhaps the eagles brought in sprigs to add to the eyrie and seeds came with them. The plant is certainly vigorous, probably a result of fertilisation from the droppings and prey remains in the eyrie.

This the first time I have seen a chick fledge from that nest since I first knew it in 1982. The birds have alternative nests on nearby cliffs and last year they raised a chick in one of those, which is very high and rather inaccessible. In the past, the birds' breeding efforts usually failed if they tried to nest on this relatively low and accessible crag. Disturbance was the most likely cause for their failure as they were usually successful if they nested on the big cliff. This territory is on ground once used for sheep rearing, and now that sheep numbers have been greatly reduced in that area and in the Highlands in general, there seems to be less disturbance.

There was a heavy mist when I checked the eyrie, some would call it rain, but the chick was well sheltered by the overhang. I was soaked through. The chick had a lovely big nest to play about in, and the view from the cliff is quite dramatic. What a wonderful eyrie to grow up in.

Monday, 18 July 2016

Lots of insects - and birds

A Yellow Wagtail Motacilla flava eyes off a crane fly Tipulidae

As a final post on my recent trip to Norway, I would like to mention the insects, the profusion of insects which make it possible for so many migrant birds to breed in the tundra and birch forests. The most noticeable insects are the mosquitoes, of which there are thousands, millions, and all the females are intent on sucking blood. This is probably the most deterring factor for me to visit the arctic, but for the birds it is perhaps the most alluring factor. And many other insect species also thrive in high numbers, all adding up to form the rich feeding grounds for birds to rear their chicks. Of course, on balance, it is worth the discomfort to study the birds.

Mosquitoes torment a Short-eared Owl Asio flammeus chick

However, not all birds eat insects. The owls eat voles and have to endure the mosquitoes like we humans.

Male Red-spotted  Bluethroats Luscinia svecica are one of the more conspicuous birds in the birch forests
they often perch on on high perches when hunting for insects

The most obvious and abundant passerines feeding on the insects are the Yellow Wagtails, Red-spotted Bluethroats and Willow Warblers Phylloscopus trochilus. However, in some years the weather can be cold and insects scarce. Then the passerines are scarce too, as so often happens with bonanzas, it can be a case of boom or bust. The migrant birds clearly take a risk in flying so far north to breed, but the risk must be worth taking or else evolution would have selected against such behaviour.     

Female Red-spotted Bluethroats are one of the less conspicuous birds in the birch forest
when they hide on their nests 

The waders also rely on the insects. The adults eat them, often probing for the larvae, and the chicks eat them, often as adults, picking emerging mosquitoes as they lie on the water surface. If only they could eat a few more mosquitoes before they eat me. But now that I am back south and away from the mosquitoes, birch flies and horse flies, I have cast them out of my thoughts. I can now concentrate on the good memories; the wealth of flora and fauna in arctic Norway. That was a great trip.

Wood Sandpipers are very conspicuous when they have young.
They often stand on high perches overlooking the mires where their chicks are feeding
- even in the rain