Sunday, 1 November 2009
PERU 2009: Life on an oxbow lake.
If you've ever seen an Amazonian river system from the air (or from an aerial photograph) you've maybe noticed the snaking of the river with tight curves. You may also have noticed some pale moon-shaped gaps in the forest too. Well, these will be choked-up oxbow lakes. Oxbows are remnant tight river curvatures; the river simply having redirected and cut off the "loop". The "loop" is full of standing water and forms an oxbow lake, the vegetation eventually covering the lake.
The strange and almost prehistoric-looking Hoatzin loves these areas. It feeds on the vegetable matter of the margins of the lake and has a huge gut to process this. The festering contents of this gut makes this species unpalatable and the Hoatzin goes unmolested by man; known locally as "Stinkbird". Hoatzins nest over open water on the oxbow lakes. The young are vulnerable to other predators though but have developed their own escape process. Approach the nest of this species and the adult will flee. The young will eventually hurl themselves into the water, spread their wings and float. As a juvenile the Hoatzin has a vestigial claw on the bend of the wing that it uses to climb back out of the water to the nest once danger has passed.
Another much desired species frequenting these oxbows is the Sungrebe. This Neotropical finfoot appears to be more numerous in the area as the wet season approaches in Manu. We quite easily saw 10 - 15 individuals in a morning this year.
And this is how it's done. Drifting around quietly on the lake using a catamaran allows us to approach the banks in search of antbirds, pass floating vegetation for crakes and watch Giant Otters at a safe range.
Giant Otters are not the only mammalian interest though (we saw a family party of 7 this year by the way). Long-nosed Bats are always found near water in these parts; usually roosting under partly submerged logs, but this group (50+) found refuge in the thatched roof of the boat shed.
Horned Screamers are common around the lakes and also present on the river banks. Related to geese they are noisy inhabitants (they honk rather than scream) and for such a large cumbersome bird they take to the air with great ease.
But it's not all waterbirds. Checking the edges of the lakes can reveal Amazonian Streaked Antwren, Band-tailed Antbird and Silvered Antbird; a trio always found near water. Careful scrutiny of any bamboo patches may lead to the discovery of a roosting Ladder-tailed Nightjar, like this female pictured below.
A complete wildlife experience with Red Howler Monkeys, Ospreys, Yellow-billed Terns, Muscovy Ducks and this year we found a Pied-billed Grebe. The latter is a vagrant to Amazonian Peru, normally reaching the marshes of the coast only.