Not so common Common Terns

Common Terns (Sterna hirundo) are non-breeding summer migrants to Australia. Their distribution in Australia can be seen in the following Birdata screen shot. The number of sightings per month graph at the right in the screen shot shows that some birds, probably young non breeding birds, over-winter in Australia. The sub species longipennis is found in Australia and breeds in North and East Siberia. 

The Common Tern is common in the northern hemisphere, hence the name, however they are relatively uncommon in Australia. They can often be found roosting/resting with other tern species such as Little and Crested Terns where their presence may be overlooked so it is always worth a careful check through large flocks of terns to see if there are any other species present.

We mostly see the Common Tern in non-breeding condition with black bill, orange/red/black legs, white forehead and mottled dull black crown. The following photos were taken in Jones Bay on the Gippsland Lakes where a flood deposited dead tree provided a crowded resting site for mostly Common Terns with a few Little Terns and one Silver Gull also managing to find a spot to perch. 

Birds came and went and with each new arrival there were protests from the incumbent birds letting the newcomers know there was no room for them - this behaviour afforded a number of flight shots as incoming birds hovered looking for a spot to land.

In my waders, I managed to approach the birds by very slow and staged advances without them flushing. 

Please click on photos to enlarge.

 

Little Tern moulting out of breeding plumage - a few Little Terns shared the dead tree with the Common Terns.

After taking photos I slowly backed away leaving the birds undisturbed at their rest site.

Darter portraits

Darters in many ways are like cormorants however unlike cormorants they have a stiletto bill which they can use to spear fish. They are found in most aquatic habitats, both freshwater and saline, but not off shore in seas and oceans.

When in the water hunting they ride low with their body often submerged with only the head and long snake like neck visible. They are often seen perched with wings spread wide as they dry out. The male Darter in the following portraits was drying out with wings outstretched on the Richmond River at Ballina in northern NSW.

Please click on photos to enlarge.

I always find it a special pleasure to come across a Darter. This is partly because they are a little uncommon but I think it is more because they are unusual birds with a striking presence.

You can see some photos of a female Darter in this earlier post: http://avithera.blogspot.com/2017/07/darter-at-snowy-river-estuary.html

Eastern Reef Egret fishing

Eastern Reef Egrets are exclusively coastal and are relatively common on rocky shores around much of the Australian coast line and some off shore islands. In Victoria they are relatively rare and are most often found near Mallacoota with a few sightings to the west towards Cape Conran.  West of Conran there are very few records. There are grey and white morphs however whites are more common in the north and rare in Victoria where we see mainly greys.

I have been fortunate to observe Eastern Reef Egrets hunting fish on rocky shores on a number of occasions. They stalk with a crouched posture often with their wings partly spread, however their intense concentration and focus makes an especially strong impression on the observer. The long neck is usually contracted when hunting and is used for lightening fast lunges to catch fish with their long heavy bill which, while dagger like, is used like fine pointed tweezers to take hold of prey rather than as a spear to impale (1). While the overall posture shows the concentration I think it is the unblinking yellow eyes with the dark iris that give the greatest impression of concentrated focus.

The following selection of photos shows one bird hunting for tiny fish (I have seen them catch much larger fish that they can barely swallow) and while each fish may have been small, the good number it was catching and consuming more than made up for the small size (2). The bird was so engrossed in fishing that it tolerated my slow and careful close approach. I spent just over 15 minutes observing and photographing the bird and eventually left it still fishing.    

Please click on photos to enlarge.

I approached the Reef Egret slowly stopping frequently to allow it to adjust to my presence and using some rocks as partial cover.

The Egret was not too concerned by my presence and resumed hunting for fish.

Note in this photo and the one above the low crouched posture and partly spread wings. I assume the low position makes it harder for the fish to see the Egret.

The Egret made lightning fast lunges which were so fast it was hard to capture with the camera.

Most times this master hunter came up with a fish.

The fish were tiny but the Egret made up for this with quantity.

The small fish were quickly swallowed. Note the nictitating third eye lid is visible – this is an automatic reflex action to protect the eyes.

Note the forward facing eyes in this photo which are required to provide accurate vision for capture of small prey below the water’s surface. The surging water and moving fish make for difficult conditions however this fishing master made catching tiny fish look easy.

The bird had to keep an eye on the incoming waves to avoid being submerged and washed off the rocks.

Holding onto slippery rocks is helped by large feet with sharp claws and when required a wing was thrown out to help maintain balance.

Now and again the bird took a short break from the intense crouched hunting position.

This is an adult non breeding bird – there are no short nap plumes though there are some plumes on the back.

Note the long neck and white throat patch which is very small or absent in juveniles.

Shortly after this photo I slowly backed away – the bird continued fishing – no doubt the incoming tide and presence of fish presented an opportunity too good to leave.

(1) Note: While I have not seen fish speared by Reef Egrets it is likely they do this with larger fish. Darters are an example of a sharp billed fish hunter that spears fish.

(2) The photos were taken in August 2020 on a rocky headland on the north side of the Brunswick River entrance, NSW.

Sacred Kingfisher regurgitates a pellet

A broad range of bird species regurgitate pellets. The following extract from Wikipedia explains regurgitation of pellets:

A pellet, in ornithology, is the mass of undigested parts of a bird's food that some bird species occasionally regurgitate. The contents of a bird's pellet depend on its diet, but can include the exoskeletons of insects, indigestible plant matter, bones, fur, feathers, bills, claws, and teeth. In falconry, the pellet is called a casting.

The passing of pellets allows a bird to remove indigestible material from its proventriculus, or glandular stomach.

The sequence of photos below shows a Sacred Kingfisher with a small crab meal, but before it swallows the crab it regurgitates a pellet. Given the large number of crabs in this bird’s diet I imagine expelling the indigestible parts of the crabs, especially the exoskeleton, is more comfortable than passing them through the digestive tract and exiting the back end. (1)

Please click on photos to enlarge. 

Sacred Kingfisher with a small crab.

The bird seemed to be taking its time to swallow the crab. Its throat was enlarged.

And then, to my surprise, a brown mass appeared with the crab still held near the bill tip.

Previous photo cropped to reveal a closer look at the pellet which appears to contain small fragments of crab shell.

Then the pellet was dropped and in a flash the crab was swallowed.

The bird looks relaxed and satisfied with the pellet expelled and the crab consumed. 

Many birds regurgitate pellets. Raptors and owls readily come to mind. I have seen Woodswallows regurgitating the hard shells of insects. Wikipedia lists some other birds that produce pellets: 

Many other species produce pellets, including grebes, herons, cormorants, gulls, terns, kingfishers, crows, jays, dippers, shrikes, swallows, and most shorebirds.

There are three other reasons some birds regurgitate. One is to feed young. For example parrots and pigeons regurgitate pre-digested seed to feed their young. Many sea birds feed their young by regurgitating food gathered over long distances and time periods. For example pelicans, albatross and shearwaters. This is also a good way of avoiding or reducing theft of food for their young from pirate birds such a frigatebirds, skuas and gulls. 

The second reason birds may regurgitate is due to disease - sick birds may expel food from their stomachs. 

The third reason is in response to stress, perhaps to reduce weight to enhance their flight from attack or to vomit food onto an attacker in an effort to fend off the aggressor.

(1) Note the photos were taken on the Brunswick River in northern NSW. There were good numbers of Sacred Kingfishers in this area which contained river margins, tidal flats, mangroves and an ocean beach.  There were plenty of crabs which we saw the Sacred Kingfishers hunting on a number of occasions.