Sunday, February 15, 2009

Mexico - moist forest

In central Mexico, at the right elevation on the continental divide, one enters into lush bands of cloud forest, where the moisture provided by the fog creates a rich diversity of vegetation and animal life. If you have climbed up from the dry lowland areas to the west, this feels like another world altogether. This forest only starts at a certain elevation but if you keep climbing, the higher elevations pose many challenges and the cloud forest trees start to drop out whilst hardy conifers become increasingly dominant (in the same way as if you travel north in the temperate zones). This is the reason for the word “band” of cloud forest, i.e. an altitudinal band.

The south of Mexico also has lowland rainforest. In fact, the northernmost extension of lowland Neotropical rainforest is in Veracruz and before fragmentation of this forest occurred it was the northernmost realm of area-sensitive species like the Scarlet Macaw. This post is a combination of some of these moister forest types to contrast them with the dry forest type of the previous post.

Let’s start on the ground! On the slopes of the two Volcanes de Colima with their evocative names, Volcan de Nieve and Volcan de Fuego, lies some of the lushest forest I have seen in western Mexico. This is probably the best place in the world to see the secretive Long-tailed Wood-Partridge, endemic to 4 mountainous areas of central Mexico, including the high elevations around Mexico City. This was our best sighting of this beautiful bird as it walked out across the jeep track in front of us.

Also on the ground is the much smaller Singing Quail of humid evergreen and semi-deciduous forests. This bird was photographed in the eastern part of the range. Singing Quail have superb camouflage – their brown and white plumage matching dappled light on leaf litter – making finding and photographing them a challenge.

Much easier to see than the two previous species is the Plain Chachalaca. This calling bird reveals the red gular patch that would otherwise be hidden. Chachalacas are cracids of course and more arboreal than New World Quails.

The Common Pauraque will be a familiar species to many. In parts of Mexico they are VERY common and on some night we found many sitting on the roads.

The Squirrel Cuckoo seems to be a favourite of many, with their beautiful long “full” tails. This is one of the most widespread Neotropical Cuckoos and occurs in a variety of habitat types from scrub to moist forest on both the Pacific and Caribbean slopes.

There is something special about the colour of trogons. Whether red or yellow bellied, their soft plumage seems to emphasise their rich colour. Of course, the most colourful part is the belly, but their greenish blue backs are also magnificent. Note the highlights in this Black-headed Trogon.

And here a Violaceous Trogon strikes a pose that shows their colour to good effect.

Speaking of colour… what can i say about the Keel-billed Toucan except - WOW what a creature!! There is hardly a more quintessential symbol of the Neotropical forests than the toucans! Veracruz is as far north as this family gets. Look how that huge bill can be used to delicately pluck even tiny fruit. The bill looks heavy but it actually quite light.

Also the northernmost representative of a uniquely Neotropical family, the Red-capped Manakin light up the forest with their superbly contrasting colours. The stocky little manakins pack quite a punch, delighting observers with not just their colour but also they peculiar dancing displays when on leks.

The becards are a peculiar group that no-one seems to agree on – at least when it comes to their taxonomy (other than the fact that they are Neotropical suboscine passerines). This is a male Rose-throated Becard showing off the feature that gives them their name. Also note the flycatcher-like bill shape – they are related to tyrant flycatchers at least to some extent (Sibley and Monroe actually put them in the same family though others disagree).

The woodcreepers are another Neotropical family that reach their northern limit in Mexico. No woodcreeper has yet been recorded north of the U.S border, although this may happen in future. This photo shows a Streak-headed Woodcreeper climbing along under a thick tree limb. As you may have guessed they gleam and probe for insects with those long decurved bills. Woodcreepers are NOT related to treecreepers (the family to which the American Treecreeper, better known as the Brown Creeper, belongs) but, since both spend their time climbing up tree trunks, they have converged in some features such as cryptic brown or reddish brown plumages, pointed rectrices to aid climbing and (usually) slightly decurved bills suited to probing.

Also clad in browns and white are the wrens. Unlike woodcreepers though, wrens are true songbirds (oscine versus suboscine passerines). Whereas the woodcreepers are a South American radiation that drifted north (probably during the Great American Exchange when North and South America came into contact about 3.5 million years ago), the wrens are a North American family that radiated southward to conquer South America. These handsome Band-backed Wrens were often high in the canopy and hard to photo but they came out onto this snag after a torrential downpour offering me a great photo op.

The “silkies” are also known as silky-flycatchers but they are not flycatchers at all. They are a small family of their own (Ptilogonatidae), most closely related to waxwings. The Phainopepla is also a member of this family. They share some features in common with waxwings such as their soft plumage texture, crests, small bills, plumage patterns dominated by grey or black with splashes of colour and flocking behaviour. Like waxwings they eat fruit and insects but probably more insects than waxwings do. Here is a Grey Silky in a feeding tree (the short shaggy crest doesn’t show well from this angle).

Next, I’ve combined two unrelated “sparrows” in one photo: the Collared Towhee (genus Pipilo) and the Green-striped Brushfinch (genus Atlapetes). The idea behind putting these photos together is to show how unrelated birds sometimes look very similar. In addition to sharing structural features driven by ecological conditions and ecological niches like the woodcreepers and the treecreepers, species can also “converge” in plumage patterns. Sometimes a particular pattern just works well in a particular environment. I guess for ground-dwelling sparrows in western and central Mexico at reasonably high elevations (>1500m) where these species are found, something about that environment makes the combination of dark forecrown, supercilium, black face-mask, white throat and black breast band work to sends a clear signal… to your kind and others too apparently!

Why not finish with a tanager – the beautiful Yellow-winged Tanager, even though that yellow spot is not always so visible.

You can view some of these photos in larger size on my web page:

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