Ecology of the Atlantic Forest

Avian Ecology of the Misiones Atlantic Forest

     Before looking at individual localities within the Misiones Atlantic Forest mosaic, it is worth considering how the birds are distributed in this bioregion as a whole. The forest in Misiones is not uniform and consequently, while perhaps a majority of birds can be found throughout the area, certain bird species are more typical of different zones.
 
Misiones_Zones
 
The broad divisions in the makeup of Misiones Atlantic forest are:
  • Northern Misiones Humid Subtropical Forest
  • Northern Misiones Transitional Forest
  • Araucaria Upland Forest
  • Southern Misiones Mixed Forest
In the extreme southwestern portion of the province, natural habitat changes to:
  • Subtropical Grasslands

Northern Misiones Humid Subtropical Forest

    The area immediately around Iguazú National Park is dominated by species of Laurel (Nectandra and Ocotea spp.) and Rosewood (Aspidosperma polyneuron), with Guatambu (Balfourdendron riedelianum), Timbo (Enterolobium contortisiliquum) and Incense (Boswellia sacra) among the more dominant trees present in the canopy.  Reaching to 35m, this formation typically has a thick bamboo undestorey and, in areas where they have not been overharvested, stands of the edible palmito palm (Euterpe edulis) still survive.  Soils are often thin and rocky outcrops may be present on steeper slopes and in stream beds.

Northern Misiones Transitional Forest

South of Iguazú National Park the forest and its avifauna changes and may be considered to form a separate zone, the main difference being the absence of emergent Rosewood and palmito stands, with thicker soils and more undulating terrain.  Much deforestation has occured up the western side of the province, along the Ruta 12 and around the main centres of population, and remaining forest cover is present mainly in the Urugua-i Provincial Park (80 000ha) and the reserves of the Corredor Verde.

Birds to look out for in the two northern zone forests are:

Brazilian Merganser (may be extinct in Argentina)
White-fronted Piping-guan
White-mantled Hawk
Purple-winged Ground-Dove (may be extinct in Argentina)
Amethyst Woodstar
Spot-billed Toucanet
Plain-brown (Thrush-like) Woodcreeper
Black-capped Foliage-Gleaner
Stripe-headed Antwren
Speckle-breasted Antpitta
Ocellated Bamboowren
Grey-hooded Flycatcher
Large-headed Flatbill
Russet-winged Spadebill ?
Southern Bristle-Tyrant
Bay-ringed Tyrannulet
Band-tailed Manakin
White-bearded Manakin
Cream-bellied Gnatcatcher
Green-chinned Euphonia

Range Expansions and vagrants in Iguazú

     In addition to the species listed above, a number of birds not particularly related to Atlantic Forest have recently been expanding their range southward into Argentina.  This may be happening because of climatic changes brought about by Global Warming.  After crossing the Iguazú – Paraná River divide, small populations have established and can be seen in the region of the town of Puerto Iguazu and the Corredor Verde.  Others, usually known as vagrants (marked “V” in the list below), have turned up once or at most a few times in Northern Misiones and then disappear.  We owe quite a few of both types of these new records to the feeders in the Hummingbird Garden in Puerto Iguazu!

Look out for:

Thrush-like Wren
Swallow-tailed Hummingbird
Sombre Hummingbird (V)
Ruby-Topaz Hummingbird
Scaled Dove
Barred Antshrike
Common Tody Flycatcher
Masked Water-Tyrant (V?)
Silver-beaked Tanager
Brazilian Tanager (V?)
Cinnamon Tanager (V?)
Lined Seedeater


Araucaria Upland Forest

    Further south the land rises to form the Misiones Cordillera Central, a low chain of hills running roughly southwest-northeast from Cerro Azul in southwestern Misiones to the Brazilian border at Irigoyen.araucaria1_kr

About two-thirds of the way along this range,  from around San Pedro eastwards, the elevation is sufficient to support extensive stands of the gymnosperm Araucaria angustifolia.  Known locally as Pino Parana or Monkey-puzzle tree, this genus appeared geologically before the dinosaurs ruled the earth and it was the dominant tree all over the world for millions of years through the Jurassic and Cretaceous periods.  Succeeded by the flowering plants, Araucarias are still found in small pockets around the world, in places like South America, where there are two species and New Caldonia, where about twenty species survive.

In the year 1950 about a quarter of a million hectares of Araucaria forest grew in the Inland Atlantic Forests of Brazil and Misiones.  Today an estimated 2000 hectares of old-growth Araucaria forest survive in northeastern Argentina.  Undoubtedly the best place to see really big Araucaria trees with their attendant tree-fern understorey, and the birds that go with them, is Cruce Caballero Provincial Park, a relatively small but very diverse protected area 20km east of San Pedro.  The species can also be observed in the more accessible Araucarias Provincial Park in San Pedro.

Birds of this zone are:

Vinaceous-breasted Parrot
Red-spectacled Parrot (may be extinct in Argentina)
Helmeted Woodpecker
Yellow-browed Woodpecker
Araucaria Tit-Spinetail
Canebrake Groundcreeper
Azure Jay


Southern Misiones Mixed Forest

    Further south the land forms undulating slopes and, following mainly southern-draining tributary rivers, enters the Uruguay River drainage.  A large area of forest (227 000ha) is protected in the Yaboti Biosphere Reserve which borders Brazil and harbours birding hotspots like Kaá Yarí Provincial Park as well as the unique formation of the Moconá Waterfalls.  Although with a maximum drop of 11m the Moconá Falls are not high, and indeed are sometimes covered completely by heavy runoff, with a width of 1800m they are considered the longest continuous waterfall in the world.  The avifauna here is allied to the transitional forests south of Iguazú but is also home to some unusual birds not present further north, most of which have been recorded from Argentina on only a very few occasions.

Moconá and southern region specialities are:

Long-trained Nightjar
Chestnut-tailed Antthrush
Black-capped Manakin
Brown-breasted Bamboo-Tyrant
Thick-billed Saltator


Bamboo Birds

    Species of bamboo are important throughout the Atlantic Forest, and a number of birds are found either exclusively in one kind of bamboo, or are associated with collective bamboo seeding events.  The author thanks Alejandro Bodrati, Kristina Cockle and Nacho Areta for bamboo species information (Bodrati, A. and K. Cockle 2006. Orn Neo 17: 243 – 258; Bodrati, A. and J. I Areta 2006.  Orn Neo 17: 597 – 600)
Bird species Bamboo species / growth stage
Purple-winged Ground-Dove
White-bearded Antshrike
Bertoni’s Antbird
Dusky-tailed Antbird
Ocellated Bamboowren
Planalto Tapaculo
Canebrake Groundcreeper
Brown-breasted Bamboo-Tyrant
Plain-breasted Pygmy-Tyrant
Ochre-faced Pygmy-Tyrant
Plumbeous Seedeater
Temminck’s Seedeater
Blackish-blue Seedeater
Sooty Grassquit
Uniform Finch
Seeding
Guadua/Merostachys
Chusquea
Chusquea
Chusquea
Chusquea
Merostachys/Chusquea
Chusquea
Chusquea
Chusquea
Seeding
Seeding
Seeding
Seeding
Seeding

Longitudinal Migrants

    Apart from the generally well-known north-south movements of long-distance migrants, other bird species make shorter-distance seasonal movements which are in general east-west or rotational within the Atlantic Forest as a whole.  These movements were brought to our attention by the work of Juan Ignacio Areta and Alejandro Bodrati (birds marked LM)  Other species in the list below, often present in this region in Austral winter, may share similar movement patterns or may exhibit different and as yet unknown forms of migratory behaviour.
 

Long-trained Nightjar
Black Jacobin                                  LM
Bare-throated Bellbird
Sharpbill
Swallow-tailed Cotinga              LM
Shear-tailed Tyrant                       LM
Rufous-tailed Attila
Green-backed Becard
Yellow-legged Thrush                 LM?
Golden-naped Euphonia            LM
Chestnut-backed Tanager
Blue-and-yellow Tanager

Misiones Grasslands

     In southwestern Misiones towards the border with Corrientes the forests grade into open grasslands that once covered huge expanses all the way down the length of Argentina.

Today, due to extensive conversion of habitat to pasture and pine plantations, especially in the Corrientes-Misiones limits, original grasslands are very scarce and the birds that once lived here, even rarer.  Populations of most species can still be found around the Esteros del Iberá marshes in northern Corrientes but are now present, if at all in Misiones, in a few remaining patches.

Misiones’ grassland birds include:

Sharp-tailed Tyrant
Strange-tailed Tyrant
Cock-tailed Tyrant (may be extinct in Argentina)
Streamer-tailed Tyrant
Lesser Grass-Finch
Marsh Seedeater