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  • Writer's pictureAllan Sander

Chasing the Chauna

Updated: Feb 19

 “Spring is in the air!”  Well, it is actually the aves that are, literally.  And one could not ask for a more suitable representative than with the graceful curves of the Fork-tailed Flycatcher (Tyrannus savana). 

Buds of the Tipu trees (Tipuana tipu) have recently shed their winter coat, attracting insects and the birds that feed on them like the Yellow-browed Tyrant (Satrapa icterophrys).

House wren, Brown-chested martins, and Tropical kingbird.  It was a great way to start the day for us, especially for a couple of first-time birders.  A quick, “About face!” and a totally different habitat comes into view, Laguna Coypu.

Granted, I have been here before at the Reserva Ecologica Costanera Sur, but it is always fun to see some familiar faces.  My target, however, is to have the group find the Southern Screamer (Chauna torquata), locally referred as Chauna.  Still there are plenty of other highlights; one can tally four species of coot, plus a gallinule, with just one stop! 

Red-fronted Coot (Fulica rufifrons)

“Which one is that? It is so pretty!”  No doubt there once you see a male Rosy-billed Pochard (Netta peposaca).

The same can be said for the distinguishing field marks of the Silver

and Yellow-billed Teals.

The bright cinnamon bodies of Wattled Jacanas (Jacana jacana) cannot be ignored, especially when racing across this seemingly endless convergence of vegetation. 

A continual flow of Brown-chested Martins (Progne tapera)

and White-rumped Swallows zip in and out.  The occasional Blue-and-white swallow is thrown into the mix.  In flight the top view of the White-rumped Swallow (Tachycineta leucorrhoa) shows the obvious white-rump field mark. 

Topside, the black mask of the White-rumped Swallow has a thin, white facial “V” emanating from the base of the bill, just stopping short of the eyes.

“Kis-ka-dee!”  (Pitangus sulphuratus) Probably is the most prevalent and easily recognizable call for this large flycatcher; it seems to be everywhere! 

There is constant activity and always birdsong to keep you alert.  The social Monk (Myiopsitta monachus) and Nanday Parakeets just cannot shut up, it is just not in their nature.

Throngs of House Sparrows and Rock Doves race between the feet of today’s crowd.  Not to be spread short are starlings and the occasional Shiny Cowbird (Molothrus bonariensis).

A cruising Chimango Caracara (Phalcoboenus chimango) drops in for hopes of an easy morsel. 

The brazen Limpkin (Aramus guaruana) belts out its bugle-like call as it settles nearby. 

The black bodies of Neotropical Cormorants (Phalacrocorax brasilianus) are like ink spots splashed across the canvas.  Many dot the tiny islands, some grooming, others with wings spread capturing the heat to dry their feathers.

Looking ahead towards the south entrance to the reserve, I am a bit concerned.  I do not see any activity, “Is the gate closed?”  It is a bit disheartening having traveled this far with hopes of introducing our group to the area’s bird life and then this…  We can only hope it will be open mañana.  Still, from our vantage point there is constant movement on both sides to keep us entertained.  Tucked in at the far edge of the pond Jim comes up with a Green Kingfisher (Chloroceryle americana). 

We continue up to the gate area as there are many large Tipu trees that might host some more sightings.  Eared Doves (Zenaida auriculata)...

...and Picazuro Pigeons (Patagioenas picazuro) feed on the ground between the exposed roots. 

Rufous-collared sparrows sing in the distance, but the bickering Rufous Horneros drown out any effort to pick up any other songs. 

Turning around, heading north, we begin our walk up the length of Laguna de los Coipos.  A Yellow-billed Teal (Anas flavirostris) swims towards us.  Basically gray overall it has a darker brownish-gray head that is flecked in black with a dark yellow bill which is split in half with a thick band that continues to the tip; flaring out slightly to each side. 

Another colorful waterbird has a black head and neck, its cheeks covered with a white-tufted fan that emanates from blood red eyes.  Top it off with a cinnamon body cloaked in black and you have Rollandia rolland, the White-tufted Grebe.  “Oh, how cute!”  One cannot argue our novice birder’s response when observing these birds. 


It is difficult to pull our eyes away from this little beauty, but I acknowledge a Southern Crested Caracara (Caracara plancus) cruising overhead.

We had not traveled much further along the causeway to find an interesting circus act. 

That is, a Cocoi Heron (Ardea cocoi) attempting to swallow a ‘large’ Cichlid.  You know the saying, “Not to bite off more than you can chew?” (In this case, swallow).  The fish length is one thing, it is the width that concerns me.  I look at the bird’s long neck and see this fat fish with its flaring dorsal fin and think, “No way!” 

Patiently I watch the heron leisurely adjusts its meal this way and that.  I feel like I am going to gag,

finding myself swallowing in an effort to help the bird along. 

It still seems doubtful...

...even when the dark mass is slowly engulfed and the bird’s throat expands like the gular sac of a pelican.  Wow, that fish probably weighed half as much as the bird itself!

Another close relative, the Great Egret, flies in our direction across the open water.

Eventually the water lettuce dominates, allowing a Common Gallinule (Gallinula galeata) to set the pace atop this expanse of vegetation. 

So, I too casually turn to scan the branches behind me and track the acrobatic maneuvers of Swallow-tailed flycatchers. 

At times it appears the elegant tail feathers might hinder their efforts in pursuit of prey.

Tracing the flight path of some Brown-chested Martins over the canopy redirects my attention to the sea of lettuce where another battle of predator vs. prey is underway. 

In the distance a cormorant has captured what we thought was a snake; wriggling every which way to free itself! 

I remove my pack and lie it atop the wall to support my camera.  One quick shot, and a look at my screen reveals an eel?  Later research concluded it to be a

Marbled Swamp Eel (Synbranchus marmoratus).

The tormented fish battled for ten minutes, at times wrapping around the bird’s bill, seemingly to have escaped to only be recaptured, partially swallowed, spat out to only be dragged through the routine another time.  Finally, the cormorant points its bill skyward, the neck is extended to its limit, and down it goes.  You could see the snake-like mass contorting from within. “That has to be painful!”

Normally, late afternoon is graced with a regular appearance of the Chauna.  We continue to scan but so far, nada!  “O.K., time for a break!”  A nice assortment of empanadas.  And as we eat, today’s entertainment features, “El pajaro de dedos grande,” “The long-toed one.”  This trait is evident as these delicate birds splay out those toes to distribute their body weight over a larger surface area.  This allows them to walk across floating vegetation without sinking. 

On close inspection, it looks as if the jacana’s bright yellow bill was glued on with its pink frontal plate.  It is such a bold contrast to the black head and neck and intense chestnut wings, and when they are opened, it is further enhanced with brilliant yellow flight feathers tipped in black. The coup de grace -- armed at the bend of each wing is an orange carpal spur used for defense. 

Perhaps the jacana is not as delicate as you think!

One does not have to be a birder to revel when viewing a Rufescent Tiger-heron (Tigrisoma lineatum). “It’s beautiful!”  Yes, It is truly one of nature’s beautifully adorned creatures.  The name, ‘tiger-heron,’ refers to the heavily barred, black-and-brown appearance of the immature’s plumage.  This adult Rufescent fluffs up its neck feathers, appearing more lion-like with a deep, rufescent mane trailing over its brown and white chest! 

Closer to us are a pair of Southern Lapwings, it seems they have staked claim to a slightly elevated patch of land.

“Oh, that looks like a cardinal. Out there in the pond.”

Sure enough, it is the Yellow-billed Cardinal

(Paroaria capita).

"Nice Find!"

And not much further we find another Paroaria species, the Red-crested Cardinal (P. coronata).

This tree-bordered edge indicates the northernmost boundary of the lagoon.  It always seems to host an array of aves.  A Baywing Blackbird (Agelaioides badius) lands nearby scaring off the cardinal. 

I hear the short up-and-down slurring song of a Rufous-and-black Warbling Finch (Poospiza nigrorufa).  “Guys, hang on, let me record this and play it back.  You will really like this bird!”  Sure enough, it pops, literally with color, into view. 

My last photo op of the day is with some cooperative Masked Gnatcatchers (Polioptila dumicola), clad in bluish-gray above and gray below, with a black tail tipped in white.  The male wears a jet-black mask. “How cute!”  Indeed.

Bright and early and off to the Vicente López Ecological Preserve, about 40 minutes from our hotel.  We are just outside the Buenos Aires metropolitan area, further up the coast on the Rio de la Plata.  Referred to as the La Plata River in English; it is actually an estuary, where the Uruguay and Paraná Rivers empty.  It flairs out as it continues to the Atlantic Ocean for 180 miles, to eventually attain a width of 137 miles – making it the widest estuary in the world!

We briefly take time to scan the reedbeds for any activity.  Mostly swallows and martins cruising overhead.  We are anxious to get to the entrance for possible rail sightings.  Our first trip bird of the day has a Spot-winged Dove (Patagioenas maculosa) cooing from a nearby tree. 

Passing a ball field, the grounds are alive with great numbers of Eared Doves. 

A line of trees borders our route hosting a

Chalk-browed Mockingbird (Mimus saturninus),

Brown-chested Martin (Progne tapera),

and a several horneros, walking about. 

Below a pair of lapwings go about their business, indifferent to our presence.


Through the gate and into the forest a House Wren (Troglodytes aedon) greets us from out of the shadows, warming itself in the light of the morning sun. 

The mouse-like squeaks of a Sooty-fronted Spinetail (Synallaxis frontalis) have us

stretching and turning for a view within the thick vegetation.  The bird periodically flies back and forth across the trail.  I took advantage of the lag time to photograph butterflies among a small exposed patch of flowers: Actinote melanisans and...

...Tegosa claudina, or Claudina Crescent.

Entering the now shaded trail, the occasional Creamy-bellied Thrush flashed from the understory.  Keeping to the right led to a pleasant boardwalk.

About halfway across allows a panoramic view to the lagoon.  It seems the regular flow of Picazuro Pigeons overhead was a constant – no matter where we traveled!  Minimal plant growth along the water’s edge did not bode well for rail sightings. 

All eyes rise on cue to the pleasant whistling song of a Bluish-gray Saltator (Saltator coerulescens)  A coot skims across the surface, carving an expanding “V” in its wake.

I fall behind with the intent to capture more of the experience.  Clusters of pink ‘cotton-candy’ eggs are strewn all about, future Apple Snails! (I have to ask a Limpkin if they are edible). 

A rapid twitter echoing across the pond has me raise my camera to capture a fleeting Tropical Kingbird (Tyrannus melancholicus). 

I detect a large mass higher up, “Chuana!”  I race down the remaining length of the bridge shouting, “Guys!  Guys! Look up!  There’s a…”  I find them already gazing towards the heavens, “Yes, a Screamer!”

Finally!  At first sighting, with its broad five and a half foot wingspan, I felt it might have been an eagle!  As if on cue, the main attraction turns around for another curtain call!

Back to terra firma. We are at the southern end of the preserve; it is completely fenced-in to protect the habitat.  Beyond is another playing field adjacent to a low-lying weedy, marsh.  At this junction there is a lot of activity, especially one leafless tree.  A vine-covered fence running perpendicular to the field has a continuous influx of House Sparrows.  A Tropical Kingbird sallies out to capture its winged prey.  Another saltator appears and drops out of sight into the weeds.  The same birds come and go in what has been declared the “Bird” Tree!  Next wave has a Variable Oriole, Solitary (Black) Cacique, a tiny flycatcher that captures my interest and a Sayaca Tanager (Tangara sayaca). 

I focus on capturing a photo of this tyrannulet to aid identification.  [It was a White-crested Tyrannulet, Serpophaga subcristata ].

Beyond this activity a Roadside Hawk (Rupornis magnirostris) soars across the open land.  It seems the Chuana was the spark we needed, our lucky talisman.

We are halfway round the park, it is quite small, as we cross another boardwalk.  A high, incessant trill has us stop, perched on an exposed limb we find a tiny Gilded Hummingbird (Hylocharis chrysura); it sounds more like a cricket than a bird. 

In the air more parakeets zip by, just another fixture of the city’s skies.  It was a pleasant stop, but I sure wish to have seen a rail or two.

Outside, back out in the open, we head back to the coastal reed beds. The wind has picked up a tad as swallows and martins slice through the air.  I find a Gray-breasted Martin (Progne chalybea) collecting mud for its nest.

The number of patrons has picked up, too; some have cast out a line into the water as they pass the time in idle chitchat or are simply relaxing and enjoying the sun. There is a continuous ‘ticking’ sound, like the tapping of two stones, from two different locations.  Generally, one would not give it a second thought, other than it might be an insect of some sort.  For us birders, it is a challenge to find the source of this song, a bird called the Wren-like Rushbird (Phleocryptes melanops).  “Just keep scanning the rushes.  It might pop up!”  I stand firm at my location.  There is a third bird calling off to the right.  Jim wanders over in that direction.  “I got it!  It’s over here!”  Here among the cement rubble, apparently remnants of a former boat ramp, water plants have reclaimed the open spaces.  At the base of some reeds, the bird’s boldly striped back and cryptic colors help conceal it among the shadows.

“Good find!” 

Striding back up to the grass lawn we discover a pair of Campo Flickers (Colaptes campestris) unearthing ants.  Driving that stout bill into the ground has impressive results.  I am amazed at the amount of soil it can move! 

Time for some sustenance – more empanadas, banana, and biscuits.  As I eat, I follow a Kiskadee when a smaller flycatcher erupts from a neighboring bush.  “Let’s have a look!” I am stumped for an I.D.  It seemed it might be a Bran-colored Flycatcher.  Still, I need to do more research.  [It turned out the bird was a female Bearded Tachuri, Polystictus pectoralis.]  Time to call a cab to get us back to Costanera Sur.

Under the Tipu trees we exit the cab and head into the reserve via the Ingreso Brasil (Brazil Entrance).  Caracaras ...

... and Fork-tailed Flycatchers circle about. 

Below two jacanas play a game of tag, zipping past a very contented Black-bellied Slider (Trachymes dorbigni) basking in the sun. 

Our first stop is behind the nature center, where a platform overlooks the Laguna de los Patos, Duck Pond.  With no visible water came very little activity.  So north we go onto the Tegu trail that separates the two ponds.  I find a young Harris’s Hawk (Parabuteo unicinctus) hidden in the trees.  I am anxious to reach the next viewing platform. 

Along the way a Masked Gnatcatcher and Saffron Finch (Sicalis flaveola) make a hasty entrance.

The open water at the far end hosts both

Silver and Speckled Teals, Red – gartered and fronted Coots, and a Tiger-heron

A Limpkin repetitively stabs through the floating vegetation for snails. 

On the flipside, there is a Coypu totally indifferent, just hangin’ out like a bump on a log.  I was hoping to see the graceful, Black-necked Swan - perhaps they prefer more open water.  

Still, standing proud like a king on top of his domain, is a Chauna.  Closer inspection, reveals a second bird hunkered down; they chose to nest atop this huge pile of logs stacked out in the lagoon.  “Cool!”

As we are leaving, a sharp “spit” rings out from the undergrowth.  ‘Pishing’ entices the bird’s curiosity to investigate and out pops a female Golden-billed Saltator (Saltator aurantiirostris).

There are so many interesting surprises to experience.  Patrick points out a colony of honeybees.  They are in transition, having layered themselves around a Y-shaped branch before moving on to a permanent site – this location is much too exposed to the elements.  Irrelevant to the joggers and cyclists, a large Argentinian Tegu slinks its way across the road. Pausing, brazen and bold it stands thickly armored with beads of black and white.

Fleeting shadows and birdsong continually trigger the senses. A small mixed flock sweeps in with Baywing Blackbirds, Rufous-collared Sparrow (Zonotrichia capensis) and a pair of Saffron Finch. 

A few trees over hosts a vibrant group of Hooded Siskins (Spinus magellanicus). 

A Streaked flycatcher (Myiodynastes maculatus) lands on a contorted branch, the filtered light makes for a perfectly exposed image. 

We reach the junction with the Camino del medio or Middle Path where it opens up and there are less trees.  This raised path separates the Duck Pond from the Gull Pond, Laguna da las gaviotas and terminates at the Rio de la Plata.  Recent boardwalk construction is underway that will loop out into the grassland-marsh habitat of Gull Pond.  We continue along the Tegu trail and come across another one of its mascots.

I remind the group to keep an eye for movement among the dark understory.  This last stretch has less growth increasing one’s odds for spotting rails.  Our first sighting is of a Southern Yellowthroat (Geothlypis velata); an olive-colored warbler and this being the male, wears a black ‘bandit’ mask that separates the gray crown from the lemon-yellow underside.

“Hey guys!  I just saw, what looked like a chicken, run across the road!” “It probably was one of the Wood-rails.” [ Gray-cowled Wood-rail, Aramides cajaneus ] Collectively, all eyes gaze into the darkness with hopes of sighting our prey.  Often times these waterbirds are in pairs so I cross back to search the other side. 

Eventually we agree enough time has been spent and push on.  And wouldn’t you know it!  To the delight of everyone, the bird reappears like an apparition before vanishing into the shadows.

 Next, the chase is on to find a Chivi Vireo (Vireo chivi) serenading in the canopy.  The song is very similar to the Red-eyed Vireo and looking at the bird, it too can be confusing.  This bird has the same olive-green back and whitish belly, however, it is splashed with varied amounts of yellow on the underside.  And it does not posses that deep red-eye. 

Another North American knock-off, again in song and appearance is the Tropical Parula (Setophaga pitiayumi). Both songs have a rapid, ascending trill that peaks and terminates abruptly.  Females of both species are quite similar, except that the Tropical is completely yellow underneath, the Northern of both sexes have a white belly and partial white eye ring.

Nearing the end of Coypu Pond there are a several benches situated under a well shaded grove.  There is a lot of movement, especially in the center most tree. 

A small flycatcher eludes our identification, but I manage good enough images to research it later. (It was a Small-billed Elainea, E.parvorostris). 

A Sayaca Tanager shows up along with a Checkered Woodpecker (Dryobates mixtus

A response of “Oohs” and “Ahhs” can be heard when some Blue-and-yellow Tanagers (Rauenia bonariensis) make a guest appearance.  “We found another bird tree!”

Things calm down so an opportune snack break is in order.  I barely finish before the squeaky, mouse-like song of a Sooty-fronted Spinetail leads me into the brush, across the road, and back into the bush but I never quite get a decent chance for a picture.  Inadvertently I come across some blooming Lantanas that attracted a Glittering-bellied Emerald (Chlorostilbon lucidus); it took off before I could get close enough.  It was quite dark under the trees so I chose a respectable distance to use my flash in anticipation of where it might reappear, prefocusing on one of the flower heads.  It was not long before I heard its raspy call off to one side.  It zipped from flower to flower, pausing long enough for me to get off some shots. 

It was a great way to end the day.

Location: Costanera Sur Ecological Reserve and Vicente Lopez Ecological Preserve, Buenos Aires- Argentina

Date: October of 2023


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