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  • Writer's pictureAllan Sander

Costanera Sur Ecological Reserve - December

Updated: Feb 7


“Lily Trotter!” Until you witness this colorful bird’s oversized feet will you then understand why it was given such a title. Imagine your toes, when splayed, covering a third of your body! This adaptation distributes the jacana’s (Jacana jacana) weight over a greater surface area allowing it to walk across floating vegetation without sinking. This is just one of an impressive list of water birds to be seen at the Reserva Ecologica Costanera Sur in downtown Buenos Aires, Argentina.

Many a large metropolis host a park or gardens that symbolizes its heritage. Those with a lengthy existence I enjoy most, flora having persevered and now stands majestic and tall. The Reserva Ecologica Costanera Sur is a recent addition to the Buenos Aires landscape. Ironically, it became an official public park and protected area for wildlife on Earth Day, June 05 in 1983. It was to be a landfill for future development, the concrete debris coming from the destruction of properties in 1977 for urban reform. Politics started and ended the process allowing nature to reclaim and repopulate these 860 acres for the citizens to enjoy.

My first trip was more of a cultural, historical venture back in July of 1994; however, natural history is what intrigues me the most so a stop at the park was essential. We zigzagged our way through the eastern part of the city before crossing onto the boulevard fronting the Laguna de los coipos (Coypu Pond). The waterway seemed more like a sprawling moat, with mats of Water Lettuce (Pistia stratiotes) along its edges. Established back in the early 1900’s, this became the public swimming area or Balneario Municipal. No longer will you find the local *Porteños frolicking in these waters, instead, this sea of green and yellow has become a waterbirds’ Shangri-La.

It is now December, but eighteen years later, I cross Avenida Dr. Tristan Achaval Rodriguez and find myself gazing out over Laguna de los Coipos once again. Subzero temperatures and layers of snow are typical conditions for the Northern Hemisphere, but here it is sunny, hot, and humid. There is a lot of activity out on the lagoon below. And up here from where I stand you have strolling couples, families, vendors on bikes, music, I overhear political banter between friends and running the length of the esplanade, an assemblage of parrilla trailers. Yes, plenty of entertainment on top but my interest is on the other side of the wall.

As with many ‘wildlife’ parks within a rural setting, the fauna becomes habituated to human traffic. Inadvertent table scraps or crumbs that rain down from feeding patrons are quickly consumed by awaiting finches, cowbirds, or pigeons. When chunks of bread are tossed over the edge into the water, a feeding frenzy of coots and pochards ensues.


Right now, a small raft of coots in the distant open water is heading in my direction and is about to enter this luxiourous mat of vegetation.

The lead bird acts like an icebreaker plowing its way through so others can follow. The water lettuce can be so tightly matted that it still becomes a struggle.


Much of the waterfowl is attracted to the patches of open water where food is plentiful and more accessible. This gave me the opportunity to observe the four species of coot’s unique field marks. First off, rather than having completely webbed feet like many other waterfowl, they have lobed feet (...as do the grebes). Also, this genus can be identified to species by the differences in the ‘frontal shield’ – basically an extension of the upper mandible over the forehead that resembles a shield.

Coots and gallinules are part of the Rallidae family of birds, along with the rails and crakes. I am including the Common Gallinule (Gallinula galeata) in this ‘coot’ I.D. class as it is an active participant among today’s subjects. This fellow is more slender-bodied, not as chunky as the coot. It also is not all one color, having an olive-brown lower back and rump, a blackish head and neck with bluish gray upper parts. It stands out among the others by having a large, broken white line along its flanks. The tip of the bill is yellow, its base and frontal plate are bright red.

The coots have a black head and neck with slate-gray upperparts. The Red-gartered Coot (Fulica armillata) has a pale-yellow round frontal plate and a brighter yellow bill, where they are separated by a very distinctive merlot red band. The bird possesses a red garter at the base of each tibia, as does the gallinule.

Fulica leucoptera, the White-winged Coot, has the same body color scheme. The frontal shield is smaller, more rounded and is always a deeper yellow than its pale-yellow bill. It has a trailing white edge to its wings seen during flight.

Finally, the Red-fronted Coot (Fulica rufifrons), has a brown lower back, similar to the gallinule, and evident white-tail edges. It has a bright yellow bill with a base that seems to have been smeared with dark red lipstick. The maroon-red shield is narrow, terminating in a point.

“Herons, ducks and swans, Oh my!” Growing up in North America, it seems every continent has its version of the Great Blue Heron. Here in South America, it is represented by the slightly larger Cocoi Heron (Ardea cocoi).


Another wading bird genus unique to the tropics, with three species, is the Tiger-herons. Only the Rufescent (Tigrisoma lineatum) will be found here, but it is a real showstopper, especially when it shows off those rufous-cinnamon head and neck feathers.


And wandering all about the lagoon in their robes of white are the numerous Snowy (Egretta thula)...


...and Great egrets (Ardea alba).


Waterfowl can be found all over this urban oasis. Rosy-billed Pochards (Netta peposaca) are abundant.


The males rosy-red bill intensifies with color at its base where it swells up much like the forehead plate of a coot. The face and neck have a deep purple sheen melding to black on its backside.


Another beautifully plumaged bird is the Silver Teal (Spatula versicolor); it proudly plies the water wearing a black cap, with cream-colored cheeks, a warm brown body smudged in black that merges to flanks thinly barred in black and white. All highlighted by a pale blue bill, a large yellow patch at its base, and divided down the center by a thick, black stripe.


There are also Speckled Teals (Anas flavirostris),


I find a mated pair of Lake Ducks (Oxyura vittata),



Pied-billed Grebe (Podilymbus Podiceps)


and White-tufted grebe (Rollandia rolland),


plus two species of whistling ducks: White-faced (Dendrocygna viduata) and Fulvous (Dendrocygna bicolor).

Whenever I came across any species of whistling duck, it was always in large numbers or at least a decent sized flock. Today, there have only been a few here and there. Still, a pleasure to see and hear; their vocalization is quite different than most ducks - **simply muse over the name. (…and check out the website xeno-canto.org for a listen).


Today, a new experience for me is the cute, little White-tufted grebe. It was fun to see the interaction of a family of about eight birds, feeding, bullying, preening, chasing one another.

One bird chose to search for food just below me among the aquatic plants. The slick-downed haircut of its white feathers against the black face really enhanced those blood-red eyes!


When the word “swan” comes up in conversation, it generally conjures up an image of a large waterbird with a long, sleek neck, wearing a vestment of porcelain white. However, there is a swan native to Australia that is completely black (Cygnus atratus)! Today, I am graced with a bird that has both color schemes, the

Black-necked Swan (Cygnus melancorhyphus). Its mate swims into view at the far end where the water is clear of vegetation. One bird pirouettes to face its partner, should their bills touch, and bodies meet, their necks would outline the shape of a heart.


Swans are heavy birds and consequently have oversized webbed feet. This allows them to run across the water to attain the momentum for generating lift under those huge wings. An all-white Coscoroba Swan (Coscoroba coscoroba) shows me how it is done. Wings flap hard (…revealing black wingtips), as the thick pink legs pick up the pace. The bird takes on the shape of a jetliner – the neck is extended forward, locked in and focused, the nose, its bright red bill, slowly rises, landing gear tucked tightly against the body until it is free of the water with only the air under its wings - take-off is complete!


“Oh, it is early!” I thought to myself. The streets were quiet with very little foot traffic. I did not have to worry about crossing the street, even at the stop lights. With so many buildings, I could not tell if the sun had broken the horizon - its penetrating rays would find it difficult to highlight the cobblestones of any back alley. As I near the water, Sol was making its debut above the tree line; its enchanting glow highlights the hyacinth across the water, traveling on up to the boulevard where under the spacious crowns of Tipu trees (Tipuana tipu),


the street is under silent slumber as it is showered gently with petals of gold.

Long shadows traverse across this gilded carpet in search of food. Their tips kiss its owner each time a morsel is found. These are the warm browns and yellows of Cattle Tyrant (Machetornis rixosa),


Rufous Hornero (Furnarias rufus)


and Eared Doves (Zenaida auriculata).


A pair of Shiny Cowbirds (Molothrusbonariensis) drop in, the male wears a very distinguished coat of glossy blue-black.



Off in the shadows a Rufous-collared Sparrow (Zonotrichia capensis) frolics among the discarded blooms.


The only means of access into the reserve is through a gated entrance on either end. I am closest to its northern border so, onward it is. I noticed a bit of a curiosity, a Grayish Baywing (Agelaioides badius) with a Tipu flower in its bill; its purpose I question. Nonetheless, it makes for a pleasant photo.


The same goes for a Limpkin (Aramus guaruana) looking out of place up in the tree.

I enjoyed a family of them earlier out along where the steps were fenced off, the formal entry for the Balneario Municipal as

I mentioned before. It has now become their own dining area, evident with the many discarded shells.

Unlike the other subspecies, this one only has white markings on its neck, not trailing across the back and wing coverts, where it is overall brown in color. Some sources feel it is a separate species and is referred to as “Guarana.”


This habitat harbors its favorite food, Apple Snails (Pomacea canaliculata) - their clutches of eggs looking like globs of melted cotton-candy, that can be found across any hard surface above the waterline.


It is still a bit early for much activity of the human sort, allowing me to hear a woodpecker chipping away from across the street. A long-standing cottonwood harbors a pair of Green-barred Woodpeckers (Colaptes melanochloros).


Scattered about is other avian activity; several Chalk-browed Mockingbirds (Mimus saturninus),


cowbirds and a loan Rufous-bellied Thrush (Turdus rufiventris) scamper about the lawn.


Circling overhead are two species of Caracara: The Crested (Caracara plancus) being the most prevalent,


and a Chimango (Daptrius chimango). I trace its flight until it perches in a nearby tree.


Picazuro Pigeons (Patagioenis picazuro) seem to be the most prolific bird on the wing.

I discovered a nesting bird due to the untidy pile of twigs tucked in a crotch of a tree.


I almost passed up a Spot-winged Pigeon (Patagioenis maculosa) feeding on the ground, thinking it was the former, but the extensive white spots on its wings required a second look.


Another pleasant distraction is the many Brown-chested Martins (Progne tapera) zipping about. They busily fly out over the water and come back to this stand of trees to rest.

I found one bird investigating a hornero’s domed mud-nest – a new tenant, perhaps?


Speaking of nests, a bit further down this tree-lined boulevard I came across some Monk Parakeets (Myiopsitta monachus).

In a large Monkey-puzzle tree (Araucaria Araucana), was this huge assemblage of sticks. These lodgings can weigh hundreds of pounds and house a dozen or more pairs of these bright green aves.


“About face!” Time to find that entrance, Ingreso Viamante. Before losing the view of the water there was a congregation of preening/relaxing birds including teal,

coots, and several Neotropical Cormorants (Nannopterum brasilianum); their wings spread wide to dry in the warming sun.



A pair of Limpkins wade along the weeded edge.


More scolding calls of the ever-present Great Kiskadee (Pitangus sulphuratus) eventually fade behind the wall of vegetation.


Among a stand of trees, a serenading Hooded Siskin (Spinus magellenicus) is first to greet me into the reserve.

Such a pleasant jumble of chips, trills, and whistles, I listened until the brazen squawks of the introduced Nanday Parakeets

(Aratinga nenday), a hundred strong, override this little songster’s melody. Yesterday I had just as many of the local Monk Parakeets (Myopsitta monachus) cruise by and they were just as loud!

Heading back from the direction I came there is a short boardwalk that reaches out into the lagoon. If there is any water underneath, it is obscured by dense vegetation. I hear the siskin again and find it flitting about in a willow tree.




A Great Egret sallies past.


"Too much sun!" so it is time to head back into the shade, but not until I attempt a shot of a passing White-rumped Swallow (Tachycineta leucorrhoa),


and zipping over the canopy were some Brown-chested Martins, too.

And every so often another caracara or pigeon will skirt overhead.



The cheery song of a House Wren (Troglodytes aedon) reveals the little brown gnome rummaging along the forest floor. I must note that this area does not actually denote a forest as much as a thick congregation of trees.

I favor any shaded portion of the road by crossing from one side to the other. {The name of this dirt road is Tegu Lizard Path but has ample space to accommodate service vehicles.}. Often, I startle something in the underbrush, I believe it to be a lizard. Sure enough, “What else?!” a large Argentine Black-and-white Tegu (Salvator merianae) swaggers its way across the path towards the sanctafying cover of the forest.


Just before I reach the junction of the Middle Path, that heads East to the coast, I come across a mixed flock, their songs sound like warblers. A somewhat familiar tune catches my ear until, “That’s right, a Tropical Parula!” (Setophaga pitiayumi). And as usual, it scrambles among the branches, barely giving you a second to see it from behind the leaves. But then it sallies to some bare branches and..."Gracias!"

I find a beautifully blue plumaged Masked Gnatcatcher (Polioptila dumicola) with the same attitude. Again a little patience...

A song rings out from the shadows. “Another warbler, perhaps?” “Pishing” (A birding term for imitating an alert ‘call’ that captures a bird’s curiosity so it will come out in the open.) reveals a Golden-crowned Warbler (Basileuterus culicivorus). It quickly dives back into its refuge where it boldly bursts out another tune.

Up to this point, I did not realize that Gull Pond (Laguna de las gaviotes) ran along the eastern side of the path; it was hidden by the trees, the Middle Path is a berm that separates its sister pond Laguna de los patos, or Duck Pond, on the other side. [All of the paths are landfill]. I notice the Middle Path is lined more with brush and grasses, so I decline to not be sautéed under the rising sun and continue my way South. Besides, I am curious to find out the latest vocalist belting out a tune just ahead. It is a short, cheery whistle that terminates with an upward slur. I cannot find the bird until I catch a shadow drop further down into the vegetation. I wait it out until this Golden-billed Saltator (Saltator aurantiirostris) boldly hops up onto an exposed log and delights me with its song.

The flights of swallows, martins and pigeons keeps me glancing between the leafy boughs. I am glad for the distractions as it made me keep one eye on the sky. Otherwise, I would have missed several Wood Storks (Mycteria americana) cruise past. I follow their course until they become one with the canopy,


only then do I focus on a sharp “Pik!” call coming from a large Paraiso or Chinaberry tree (Melia azedarach). I know it to be a woodpecker, but which one? Fortunately, it pops into view, rolling about on the underside of a limb as it searches for food. This little tyke’s body is splattered with




black-and-white spots, hence its name Checkered Woodpecker (Veniliornis mixtus); its red hind-crown marks it as a male.


As I continue under the cool canopy with shuffling lizards and birdsong, my senses are put on constant alert. The trail has a steep drop off in some places, and here I located a Gray-cowled Wood-rail (Aramides cojaneus) with a chick. They were barely discernible as silhouettes meandering along the water’s edge. I had better views when scoping out over the wall, from the opposite side of the pond, where an adult briefly appeared in this general location.


Another arboreal species catches my eye, not so much the individual but its nest. Tucked among the boughs is a cement gray mass, looking something like a half-sized rugby ball with spikes!


This is the home of the Camoati Wasp (Polybia scutellaris). I will allow the display in the nature center to fill you in on the details of this social wasp.







I come across an opening leading down to the Duck Pond. Accidentally bursting out into the clearing I flush a tiger-heron and a pair of kiskadees. I scan the periphery of this cove and find a Roadside Hawk (Rupornis magnirostris) near its end; the bird takes flight, its barred primary feathers highlighted in bright cinnamon. There does not seem to be much water, however, a small, pooled area harbors a sunning Hilaire’s Side-necked Turtle (Phrynops hilarii) on a partially submerged log.


Making my way back up the path a pleasant two note whistle followed with one downward inflection stops me in my tracks – “It is so close, but where!?” I see movement, pause, there is a deep rufous chest with a white belly between the leaves, I cannot see the head. It disappears. I wait. It flies down. And then graciously it hops up onto a bare limb to reveal all its beautiful lines: a satiny-black back and tail, the white supercilium terminates with a flash of cinnamon. A black bill and mask that is underscored with a white moustachial stripe. A deep rufous throat, chest, and flanks merge to an all-white underside. I take a deep breath, slowly exhale. Black-and-rufous Warbling-finch (Poospizanigrorufa) at its finest.

Back on top, a shaded bench is the perfect place to relax and have a bite to eat. A brief interlude from a Creamy-bellied Thrush (Turdus amaurochalinus) cools my spirit even more. I have seen quite a few and now I know its song.


A silhouette under the canopy resembles the thrush, but it seems thicker billed and the head flat. “Yep!” It turns out to be a Streaked Flycatcher (Myiodynastes maculatus).


Another mixed flock sweeps in, many birds are of what I have seen earlier.


I see a similar sized rufous-brown bird dive beyond my view, at the same time a song I have not heard until now rings out. I am torn as to which one I should focus on first. I go for the obscure and search below at the base of the trees. The crackling of dead leaves redirects me a few meters to my right. There it is, a woodcreeper. It is difficult to get a good look, let alone a picture. I find a small window in the direction it is heading, and prefocus with hopes of getting a shot. The flash goes off, in a flurry it is gone. Thankfully it turned out and allowed for an identification, Narrow-billed Woodcreeper (Lepidocolaptes angustirostris).


Several high pitched “tsee” notes have me looking back up to find a Glittering-bellied Emerald (Chlorostilbon lucidus). Finally, my first hummer!


I pause, then I realized, “The song, it stopped!” The flock has moved further ahead. The numbers have thinned out a bit – some warblers, several blackbirds, a gnatcatcher, I find a Sayaca Tanager (Thraupis sayaca),

and then hear a song, but it is more finch-like. "Ahh," a Saffron Finch

(Sicalis flaveola), and it appears to have attracted a mate. “Nice!” I notice this southerly range of birds is not as intensely yellow as their northern counterparts.

Sharp “Spit!” calls lead me off in another direction. I do not know this bird, but it allows me to take some decent pix for identification. ***A look on the Avibase checklist for the region and it has it classified under Thraupidae, the Tanagers, which is the second largest family of birds. Specifically, it is a Black-crowned Warbling-finch (Microspingus melanoleucus).

A red beacon grabs my attention from behind a low-lying tree. Just beyond a windbreak has cleared a small area. My curiosity is rewarded with a Crimson-headed Cardinal (Paroaria coronata). The last time I saw this bird was on the island of Maui; the location was at a resort and these birds seemed to be everywhere, even though it is not native to that part of the world – that will be another story on ‘Invasive’ species.


Getting closer to the southerly end of the reserve, the Coypu Pond has a landfill that juts out like a small spit. Here, many birds relax, preen, and soak up the sun as do many of the local turtles.


I find a trio of two different species: two more Hilaire’s side-necked turtles and a higher domed, D'Orbigny Coot (Trachymys dorbigni).


Coypu is the title given to the Nutria (Myocastor coypus), and the name of this body of water. Earlier I saw this oversized muskrat swimming in the open water at the end of the pond. Then upon my return, it was comfortably munching away just under the trees.


Today, a Great egret gracefully cruises towards me.


The aquatic weed removers are parked here, one machine is just being put into service. I hope this will not interfere with any photo ops on my way out. These things look like a miniature version of an old paddle steamer or river boat, except that the collecting wheel is




housed on the nose of the boat with a ramp that directs the aquatic plants into a holding crate. Of course, the steam engine is a thing of the past – some of these machines can be operated by remote control!


I am approaching the southeastern end of Duck Pond, where there is a small but informative natural history center. Right now, my interest is in the drinking fountain and a much-needed baño break. The cool shade of the

Tipu tree sentinels is relinquished as I exit through the Ingreso Brasil (Brazil Entry) gate and merge with the throngs of people; music blares from the parrillas. My camera gear receives a bit of attention but mostly one of curiosity. Often, I will point out a bird in the distance, snap an image, magnify it a bit and then show them the screen. It is so much fun to see how amazed they are because of how close it appears, especially among the children.

The weed remover is busy thrashing about as it consumes thick mats of water lettuce. Jacanas, egrets, and flycatchers use the opportunity to snatch up an easy snack. I find a couple of Cattle Tyrants (Machetornis rixosa) among the ubiquitous kiskadees.


“Oh wow!” I see a Southern Screamer (Chauna torquata) tucked in on a tiny island, it is relatively close but the weed eating machine is heading in its direction. I race ahead with hopes of getting there before contact is made. Yesterday was my first encounter with this robust, gray titan that stands on legs that are long, thick, and pink! It has been described as an oversized goose wearing two collars, one thick and black, the other thin and white. A slight crest, a bare red face, and a call that can be heard from quite a distance, hence its name.

The noise and churning of the blades are quite a commotion but this pájaro stands its ground. From behind, it passes within ten feet before the bird leans forward, raises its wings and off it goes.

I am happy with this encounter as when I returned home, another cropped image reveals the two carpal spurs that the bird possesses on each wing, they can measure up to 5cm in length. So, with the strength behind that five-foot wingspan it can deliver a potentially deadly blow.




This anatomical feature can be found on the lapwings, (Vanellus chilensis). It is the yellow extension midway down the front of the wing.





jacanas, and some species of ducks, too, however these birds only have one spur per wing.


A spectacular way to end the day! My next visits will be to experience the southern hemisphere's winter and to see what different encounters ensue. Time to relax with a glass of Malbec and some of the best beef to be had, anywhere! Take care!


*Porteños - the name for citizens of Buenos Aires

**xeno-canto.org - website for bird songs from all over the world


Location: Costanera Sur Ecological Reserve, Buenos Aires, Argentina

Date: December of 2022

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