New butterfly for Australia!

April 9, 2012 — April 11, 2012

Within 15 minutes of the heart of Darwin city, we discovered a new butterfly for Australia!

 New butterfly for Australia!

This theory lasted until mid-morning, when we checked out several more sites in the area. Every site we stopped had at least a few Tawny Costers. In the end we recorded around twenty individuals from three completely separate sites, evidence of a thriving population. I have no doubt had we spent more time looking, we would have continued to find many more Tawny Costers in the area.

The Tawny Coster is found from India and Sri Lanka all the way to Sumatra in Indonesia. I tried to find information on the butterflies of Timor, to see if the species was known from there, and it turns out there was a recent record from the island. The butterflies are the classic shape of an Acraea butterfly, with elongated upper wings and short round lower wings. The outer surface of the wings has complex orange, black and white patterns, most notably with strong white and black scalloping on the bottom border of the lower wing. The inner wings are a solid orange with black spots, and have an almost waxy sheen in strong light, as can be seen in some of the photos in this trip report. Male butterflies are much brighter than the females in this species.

Behavior-wise, the butterfly has a slow flight, almost erratic in pattern, but with very fast wingbeats. They flew an unpredictable pattern, mostly low to the ground over short grassy areas, but occasionally higher into the low canopy of nearby trees. Every few minutes they would settle, usually on a flower for feeding. While at rest they would open and close their wings almost constantly, though they never settled in one place for long. The flowers that were being fed on were mostly forb species in the grass, however on one occasion the butterfly fed on the flowers of a nearby Acacia tree. On a few occasions butterflies were seen to rest on bare stony ground, where they kept their wings folded tight together, and flushed readily if approached.

I have been helping butterfly expert Dr Michael Braby learn more about these butterflies, and we have an article in the latest edition of Myrmecia, the journal of the Australian Entomological Society.

So there you have it. I am amazed to have been lucky enough to stumble across a special butterfly like this, and even moreso to be the first person to realise they were something new, particularly so close to one of Australia's major centres. It was a wonderful moment that I'll never forget.

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Addendum

It has now been just over five years since I first found a colony of Tawny Coster butterflies on the Cox's Peninsula near Darwin. Things have moved on, and the butterfly has rapidly naturalised across most of the top end of Australia. By November 2015 they had been recorded in Broome, WA, and just this month, April 2017, they have officially been recorded in Cairns and I have heard from Michael Braby that the species has been recorded in both Longreach and Charter's Towers.

It really has been a privilege to bear witness to the self-introduction of a species to Australia, one which has clearly naturalised and added itself to the native fauna of our country. It is a process we knew occurred, but to watch it happening before our eyes has been truly amazing!

 

With that in mind, clearly this butterfly has further to travel. Keep an eye out and let us know if you see this species further south. Perhaps one day soon they will reach me here in Brisbane!

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 East Point

With only a morning to spend before leaving Darwin, we decided to try for Rainbow Pitta at East Point.  This site is good for the species through summer, but April turned out to be a bit to late for the species.  We did hear one call, once, but not close enough to help us find it.  We were compensated for our efforts with some other great sightings though.  Bird highlights included great views of Northern Fantail, Green-backed Gerygone, Broad-billed Flycatcher and Red-headed Honeyeater.  We also were fortunate enough to come across some great reptiles, with a beautiful red-morph Australian Bockadam being the best, but a beautiful Ctenotus essingtoni skink was also a nice way to end the trip.

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 Good luck at Leanyer

No trip to Darwin would be complete without a visit to the sewage plant.  Access is a little more restricted than it used to be - everyone needs to do an induction now to get in, not just the drivers of the vehicles.  But this was easy enough to complete, and PowerWater were great about getting us through the process from afar.  Once inside the treatment plant, birds started coming thick and fast.  Despite the heat (it was around 35 degrees C), we started with great views of Crimson Finch and Chestnut-breasted Mannikin.  White-winged Black Terns were there in abundance, many in full or nearly full breeding colours.  The usual party of Pied Herons was sitting on piping near the entrance, which always makes for a good photo. Nosing our way around the ponds we found Rufous-banded Honeyeaters in abundance in the mangroves outside the fence, and a small party of Yellow White-eyes made a brief appearance.

As we pushed around the back of the ponds, the stars of the day started appearing.  First we had a flock of martins buzzing around us, which is sometimes a herald for an unusual swallow or two making an appearance.  True to form, an immature Barn Swallow joined them and flew around us.  Young Barn Swallows can be difficult to separate from Welcome Swallow, though the latter would be far more unusual in Darwin.  Thanks to some photographs we took we were able to make out a darker band around the breast (red, not blue, but still darker), and a generally more white tone to the breast.

Next in line was a flock of ducks.  Mostly Radjah Shelduck, they had been joined a few weeks back by a southerly cousin, the Australian Shelduck.  This lovely female was still there, though looking a bit ragged as she is moulting right now.  We felt quite fortunate to be one of what must be a small number of people to have seen both of Australia's shelduck species together in the wild.  With the ducks were a number of very well coloured up migratory shorebirds - Sharp-tailed Sandpiper, Common Sandpipper, Wood Sandpiper and Marsh Sandpiper.  A single Curlew Sandpiper was keeping them company, though it was lagging behind its companions in terms of breeding colours.

Our final highlight of the day was a single Eastern Yellow Wagtail that put on a great show for us, allowing an unusually close approach by the car for us to take some photos.  In all the time I worked in Broome I probably saw over 200 Yellow Wagtails, and none at any stage allowed us to reach anything close to the distance we were from this bird!  To add icing to that cake, it was in resplendant breeding colour too.

So at the end of the trip we had quite a swag of great birds, some nice photos, and an all round excellent time.

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Wildlife

Butterflies 5 species
Marsh Tiger (Danaus affinis) 1
Tawny Coster (Acraea terpsichore) 1
Spotted Rustic (Phalanta phalantha) 1
Lesser Wanderer (Danaus chrysippus) 1
Common Crow (Euploea core) 1
Land Birds 49 species
Rufous-banded Honeyeater (Conopophila albogularis) 2
Canary White-eye (Zosterops luteus) 2
Bush Stone-curlew (Burhinus grallarius) 1
White-gaped Honeyeater (Lichenostomus unicolor) 1
Zebra Dove (Geopelia striata) 1
Marsh Sandpiper (Tringa stagnatilis) 1
Tree Martin (Petrochelidon nigricans) 1
Varied Triller (Lalage leucomela) 1
Black Butcherbird (Cracticus quoyi) 1
Red-headed Myzomela (Myzomela erythrocephala) 1
Brush Cuckoo (Cacomantis variolosus) 1
Orange-footed Scrubfowl (Megapodius reinwardt) 1
Raja Shelduck (Tadorna radjah) 1
Plumed Whistling Duck (Dendrocygna eytoni) 1
Hardhead (Aythya australis) 1
Long-tailed Finch (Poephila acuticauda) 1
Mangrove Gerygone (Gerygone levigaster) 1
Rainbow Pitta (Pitta iris) 1
White-breasted Woodswallow (Artamus leucorynchus) 1
Sacred Kingfisher (Todiramphus sanctus) 1
Bar-shouldered Dove (Geopelia humeralis) 1
Wood Sandpiper (Tringa glareola) 1
Channel-billed Cuckoo (Scythrops novaehollandiae) 1
Green-backed Gerygone (Gerygone chloronota) 1
Shining Flycatcher (Myiagra alecto) 1
Wandering Whistling Duck (Dendrocygna arcuata) 1
Common Sandpiper (Actitis hypoleucos) 1
Curlew Sandpiper (Calidris ferruginea) 1
Collared Kingfisher (Todiramphus chloris) 1
Large-billed Gerygone (Gerygone magnirostris) 1
Rose-crowned Fruit Dove (Ptilinopus regina) 1
Grey Butcherbird (Cracticus torquatus) 1 Silver-backed variety
Barn Swallow (Hirundo rustica) 1 Immarture
Broad-billed Flycatcher (Myiagra ruficollis) 1
Australian Shelduck (Tadorna tadornoides) 1
Black-fronted Dotterel (Elseyornis melanops) 1
Green Oriole (Oriolus flavocinctus) 1
Grey Whistler (Pachycephala simplex) 1
Pacific Black Duck (Anas superciliosa) 1
Eastern Yellow Wagtail (Motacilla tschutschensis) 1
Crimson Finch (Neochmia phaeton) 1
Pied Heron (Egretta picata) 1
Double-barred Finch (Taeniopygia bichenovii) 1
Northern Fantail (Rhipidura rufiventris) 1
Lemon-bellied Flyrobin (Microeca flavigaster) 1
Brown Honeyeater (Lichmera indistincta) 1
Sharp-tailed Sandpiper (Calidris acuminata) 1
Masked Lapwing (Vanellus miles) 1 Sitting on eggs
Chestnut-breasted Mannikin (Lonchura castaneothorax) 1
Seabirds 2 species
White-winged Tern (Chlidonias leucopterus) 1
Whiskered Tern (Chlidonias hybrida) 1
Terrestrial Reptiles 2 species
Ctenotus essingtoni 1
Bockadam (Cerberus australis) 1

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