Tuesday, 27 January 2015

Night watch

An adult female Tawny Frogmouth perched beside her two chicks

Now that the last summer moon is waxing to almost a quarter, it is possible to go out at night and watch the local wildlife without the aid of torchlight. I don't use spotlamps to watch animals as they ruin our night vision, and probably wreck their eyesight too. All we can see is whatever is within the light-zone, outwith that, all is black, darker than if not using a light at all. It is much better to go out at dusk and gradually let your eyes become accustomed to the dark. Anything more than a quarter moon is enough to see under and when there is a full or nearly-full moon I even use binoculars as there is enough light.

The adult delivers a grasshopper to one of the chicks

So, over the past few evenings I have been out watching a family of Tawny Frogmouths with two recently fledged chicks. These youngsters will still be dependent on their parents for about a month after leaving the nest. Frogmouth families typically all roost together during the day, then at dusk the fledglings flit to an open branch, and the adults soon begin bringing food to them. The birds leave their roost about half an hour before full darkness and it is in that first half-hour they are most active. These two adults delivered about ten items per hour for the first hour, mostly within the first half-hour. In the following hour there were no feeds and the two chicks went quiet, snuggled up together and seemed to go to sleep. Not too surprising as the prey items were mostly large grasshoppers which would have probably been more than enough to satisfy the chicks' appetites.

I last saw the adults fly off, presumably to find food for themselves before they would come back and gave the chicks more food. I have used camera traps before to monitor their food delivery times throughout the night and the pattern seems to be; they will bring occasional items during the rest of the night then a few in quick succession as dawn approaches. As with most nocturnal animals, they are more active around dusk and dawn, so those are the best times to watch for them.

At night, Tawny Frogmouths seem to become different birds from the shy ones we see by day. They are so confident under darkness and they do not seem to fear humans. Not only do they allow close approach, but I have had birds fly down to catch insects at my feet (probably stirred up by me) then carry them off to their chicks sitting on a branch a few metres away. Those are the special wildlife moments which we keep in our minds forever.

The two fledglings snuggled up together, head to tail.

Thursday, 22 January 2015

Last chicks fledged

A family of Tawny Frogmouths sitting quietly in a tree. As they are nocturnal, they roost by day, relying on their cryptic plumage and minimal movement for concealment from potential predators such as Brown Goshawks. 

The last broods of Tawny Frogmouth Podargus strigoides chicks have finally fledged almost three months after the first broods to do so on 25th October 2014. These final broods fledged on the 16th and 17th January; a brood of one and the other of two, both were from relaid clutches after the adults had lost their first clutches. The pair who finally reared the single chick lost two previous clutches in separate nests to predators unknown (likely Brush-tailed Possum Trichosurus vulpecula). They built a new nest in another tree after each time the eggs were taken, while the pair who reared the twins lost their first brood of chicks after they had left the nest too early. That was possibly after the nesting birds were attacked by a predator, but as these birds are not under constant monitoring, and there was no evidence, we'll never know. They re-used the same nest for their second clutch.

The adult female is on the far left (she has reddish markings on her wings), then the male and two still partially fluffy chicks. Frogmouths usually adopt a 'stick pose' if a potential predator approaches such as a human, but these birds have seen me so often, they know me and here have only partially adopted that pose.

Now that the final results are in I have calculated the breeding success of the sample of Tawny Frogmouth pairs that I study here in Canberra, Australia. I monitored 48 territories this year, similar to most recent years, and most successful pairs (23) reared two chicks, 7 reared three, 8 reared one, another 8 reared none and there were 2 single birds; one male and one female - pity they never met up.

This chick, like so many young fledgling frogmouths, has yet to learn to adopt a protective pose like its parent, in this case mum. Her plumage colouring and posture conceal her well, but I have seen better (see some older posts).

The figure of 17% of pairs not rearing any chicks might seem a high failure rate, but I have recorded almost twice that one year. Overall the breeding success of the population (and that is what matters as all animals must eat to live, including predators) was above average with 1.6 chicks fledged per pair (avg. 1.4), or 1.9 per successful pair (avg. 1.8).

The adults close their eyes and watch one's approach through narrow slitted eyelids. That conceals their bright yellow irides which would betray their camouflage. This chick however, just cannot resist peeping around the branch to watch me with partially open eyes. It will soon learn how to behave safely.
So that ends my study season of Tawny Frogmouths for 2014. It seems a long time since the birds first began building their nests in late July, and it won't be long before July comes around again. For further details of the frogmouths over the season and in previous years click on the links to the right of the page.

What wonderful days and nights I have had with them - great birds.

The male was perched in an adjacent tree, unobtrusive and inconspicuous.

Wednesday, 21 January 2015

Lesser Wanderer

A Lesser Wanderer basks in the sun while perched on a low twig. 

I was out at The Charcoal Tank Nature Reserve beside West Wyalong, New South Wales, over the weekend (on a bird-banding trip) and there were several of these Lesser Wanderer Danaus chrysippus butterflies flitting about. They all flew low over the ground, landing on the tips of sedges and shrubs in open glades to bask in the sun.

This was a male - the lower wing spots are large and main one has a white centre.
The upper wing spots are also large (previous image).

The species is common and widespread over most of Australia, but not so common in the south-east, so these were just about on the edge of their main range. As they are migratory, perhaps these specimens were pushing south in the height of summer. Or they could have been the offspring of butterflies that had flown south earlier in the year, as the females can lay several sets of eggs per annum.

The head and thorax have a marvelous chequered pattern

As I stalked ever closer and closer to them I gradually realised how boldly the head and  thorax are marked. The black and white pattern is stunning, and out of our usual human scale of perception..

There was a light wind, so the butterflies had to constantly flip their wings wide open,
over-extending them to compensate for the tricky sun-basking conditions

Thursday, 8 January 2015

Red Jungle Fowl and descendant breeds

A handsome Red Jungle Fowl in his true colours

Other shots I took while at Taronga zoo in Sydney included these of Red Jungle Fowl Gallus gallus, the wild ancestors of the familiar farmyard chickens. The roosters are spectacular birds with rich golden napes and large red wattles. They are quickly recognisable as related to the farmyard birds.

A hen Red Jungle Fowl with chicks - like domestic hens, she scratches up leaf litter for the chicks to snatch food for themselves, she does not feed them.

The hens are less like their farmyard relatives however, with dull sleek plumage and stiff upright tails. These are perfect adaptations for life in thick forest - their natural habitat in Asia. I reflected on the colours and shape of chicken breeds currently reared in captivity. So, below, I have a dded some examples for comparison and study of how far some have departed from the original wild type. These were all photographed in my own backyard.

A hen Red Jungle fowl crosses a road with her brood - showing off her stiff upright tail. Note how the chicks are all of the same colour, with a broad dark stripe down their backs for camouflage on the forest floor. Domestic chicks usually have a wide variety of colouring, based on this wild type, but very diverse.

A Golden Wyandotte pullet - she has a similar shape as her ancestors,
 with a stiff upright tail and bolder contrasting black and brown feathering

A grey Plymouth Rock hen - similar to the wild type but with grey rather than brown plumage (there are brown varieties of this breed) and a smaller tail

A Light Sussex pullet - she has a heavier build and less flamboyant tail than a wild hen,
and her colour has been selected out to mostly white

A black Pekin bantam - she has an exaggerated tail, much broader than a wild hen,
and her colour has been selectively bred to a dark type.

A white Silkie hen - the colour of the wild type has been lost, her feathers are all fluffy rather than lying tight over her body, and her wings and tail feathers are much reduced

Friday, 2 January 2015

Cryptically coloured eyes

 When we see a tiger's face close up, unnaturally close - we focus on the pupils but not the irides

During a recent rip to Taronga Zoo in Sydney I was attracted to the eyes of the female Sumatran Tiger Panthera tigris Sumatrae and started thinking why they were that colour. But it is obvious that they are adapted as part of the overall colouring of the animal. As a predator, it would be less successful if, as it crept up on prey slowly easing through the grasses and bushes, there were two bright or bold block-coloured irides staring out from the cover. The prey could detect such eyes more quickly and escape. Eyes sometimes need to be camouflaged as much if not more than the rest of an animal's body.    

When seen from a distance, more naturally - a tiger's eyes blend in with the rest of the animal's cryptic colouring

When I watched the large Saltwater Crocodile Crocodylus prosus in its enclosure, I immediately saw the similar adaptation. In this case the crocodile's eyes are coloured like the greens, yellows and greys reflected on the water surface. What prey species ever saw a floating log with big yellow eyes.

A Saltwater Crocodile swimming with its eyes above the waterline - its irides are coloured like the water

Their first glimpse of a crocodile's eyes would be their last.

Even when seen close up, the eyes are cryptically concealed by their colouring
 - but if you do manage to see a wild one this close, you are too late, it also has big teeth and strong jaws

It's not only predators which have cryptically coloured eyes, some potential prey species have also adapted the strategy, and while still in the zoo I was prompted onto the topic of the obvious arms race between predators and prey. If its works for one, the other can use it too.

It's not only predators that have cryptically coloured eyes,
potential prey species have them too - like this Bush Stone-curlew

The best example I found of a prey species with such an adaptation was the Bush Stone-curlew Burhinus magnirostris. These birds live in open woodland with plenty of leaf and bark litter on the ground. They are largely nocturnal birds, so they lie up on the forest floor during the day - literally so. Their defense strategy is to lie out flat on the litter where their camouflage blends with the dappled greys and browns of the substrate. But they need to keep an eye on any potential predator, so when they open their eyes to watch, their mottled irides do not betray their position.

The Bush Stone-curlew is cryptically coloured all over,
 to match the shadowed leaf-litter habitat it lives in

Zoos might not be everyone's favourite method of saving animals, but in the current world they are necessary. They are educational, as shown here, and they help conserve animals. Taronga Zoo runs various conservation programmes, so if you like tigers and can help financially please click here to help conserve tigers.