Saturday, December 11, 2010

Peru: Part 3 - Ascending the Western Andes

The ascent of the western slope of the Andes takes one through various dry forest and scrub types, although this is complicated by the numerous river valleys, each with their own effect on precipitation levels depending on their geography and, hence, some of which are very dry and others less so. The microclimates and barriers to dispersal associated with this complicated topography create many centers of endemism in different “pockets” of the Andes. When you view the Andes from the air you get a sense of why this is; for example, here is a photo of the Sacred Valley around Cusco as seen from the air. Notice how the mountains affect the cloud formation pattern and of course the many ridges and their intervening valleys. This north-south “spine” is what creates such diversity of habitats and life forms.

As you climb the western slope of the Andes you reach montane scrub habitats, particularly in rocky areas, which are often very dry and sometimes characterized by having many cacti.Above treeline you reach the dry, windswept Puna grasslands, characterized by bunch grasses and scattered shrubs. This photo shows the dry Apurimac Valley (notice how little vegetation there is) and in the foreground you can see where the montane scrub gives way to Puna grassland.

This photo gives a closer view of a small plateau with Puna grassland (notice the bunch grasses) in the foreground, while the Andes “make weather” in the background.

In these wind swept habitats, it is wise to watch the skies for raptors. Anywhere above approximately 1600 m ASL, one may encounter the large Black-chested Buzzard-Eagle.

The Mountain Caracara also like the dry open habitats of the western Andes but is typically found above 3000 m ASL, though sometimes lower. Caracaras are in the falcon family (Falconidae), not hawks as you might think...

In the montane scrub, this pair of Bare-faced Ground-Doves blend well against the brown rocks. Notice the cactus in this photo (common in this type of habitat).

With the increase in altitude one encounters a different set of hummingbirds. One of the common species in the western Andes is the aptly named Shining Sunbeam. Notice the unusual rufous overall plumage coloration of the sunbeams (genus Aglaeactis).

If the above photo seems out of place to you, then pat yourself on the back. I have to confess to cheating here because this photo was taken on the humid eastern slope of the Andes (the Shining Sunbeam is one of the species that manages to live on both sides). The moisture-depositing fog and moss-covered branches are the give away hint!

Another peculiar hummingbird of the dry montane scrub is the Bearded Mountaineer. This unique large hummer (only species in the genus Oreonympha) has a very attractive green and pink “beard” when seen from a certain angle but also you can see only see the shape and not the colour in this photo.

The largest hummer of all is the Giant Hummingbird, another occupant of the western Andes and also the only member of their genus (Patagona). At 20 - 22 cm in length (same size as a European Starling!) you could be forgiven for not believing that this is a hummingbird. They are so big that their wing beats are noticeably slower than most hummers. Notice the arid hillside in the first photo, typical of the arid habitats they prefer (and of course the bird is perched on a cactus). The second photo is a crop to show the details a little better.

Where there are river valleys that permit trees to grow a little taller in the dry western Andes, one encounters species like the Black-necked Woodpecker. This species is in the genus Colaptes (same as Northern Flicker) and is one a few “flickers” that have greenish plumage (we will meet another one when we get to the lowlands on the east side).

As in the dry western lowlands and foothills, there are also many small seed-eating birds up slope. One of the most common and widespread (in diverse habitat types) is the Hooded Siskin.

The Band-tailed Sierra-Finch is a seed-eating small passerine of montane scrub habitats of the western Andes. Their overall pattern of grey and white plumage is found in several Andean genera.

The male Ash-breasted Sierra-Finch is also grayish overall, whereas female and immatures are browner and streaked. They occur in the western Andes from about 2500m up to over 4500 m ASL. There are enough similar looking species in these habitats in this altitudinal range as to require care with identification.

Although different in colouration to Ash-breasted Sierra- Finch, the Peruvian Sierra-Finch is in the same genus and inhabits similar habitats and a similar altitudinal range. They are often found in small flocks.

Remember those suboscine passerines? There are several interesting examples in the western Andes. One such group is the cansteros (Lit. basket makers). Canasteros are long-tailed ovenbirds that prefer open habitats at high altitude. They derive their name from their nests, made of interwoven sticks. This is the Rusty-fronted Canastero.

And this is the Streak-throated Canastero. Compare these two birds and you will quickly realize that the identification of canasteros can be quite tricky at times!

At the altitudes, the Cream-winged Cinclodes (formerly Bar-winged Cinclodes), relative of the Surf Cinclodes of the coast and similar to that species in plumage, is common in a variety of open-habitat types. I was surprised to find this one in a leaky tunnel along a perilous Andean road.

This Cream-winged Cinclodes is in more typical open habitat and accompanied by a member of another suboscine family (Tyrannidae) the White-browed Ground-Tyrant.

The ground-tyrants are an interesting group of largely terrestrial flycatchers that prefer open habitats (where walking on the ground is easiest). There are several species in the high Andean grasslands and scrub, whilst some of the members of this group find their preferred open habitat closer to the water’s edge or in dry coastal areas. This photo of White-browed Ground-Tyrant shows them in their Puna habitat. Note how yellow (dry) rather than green this habitat is and the combination of short grass, tall tussocks and some scattered shrubs on the slope.

This crop of the same photo shows the bird in more detail. Note their long legs and upright stance, an artifact of their terrestrial habits.

The Spot-billed Ground-Tyrant seems to prefer arid rocky habitats as shown here.

Also in the Andean grasslands are members of a more cosmopolitan group of birds, the pipits. When I first learnt about pipits it was the many Palearctic migratory species, but on every continent, where grassland occurs (i.e. not Antarctica) you will find a pipit or two. This is the Paramo Pipit, revealing their cryptic plumage that keeps them so well camouflaged in the straw-coloured Puna grasslands.

Next, we learn that not all is dry in the high Andes...


  1. Interesting how similar the color pattern on the Ash-breasted Sierra-Finch is to a Dark-eyed (Slate-colored) Junco. At a quick glance it would be quite easy to confuse them. Sometimes these sorts of things co-occur because the species have a very similar habitat, but clearly does not apply here.

    Am enjoying your commentary & photo tour of your trip very much.

  2. Interesting you should say that - I had thought that the Black-hooded Sierra-Finch and the male Peruvian Sierra-Finch looked a lot like Oregon Junco. The photo in this post of a Peruvian Sierra-Finch is of a female and she looks less "hooded" than the male(these two species and Ash-breasted Sierra-Finch are all in the genus Phrygilus)


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