Biodiversity of the Rewa Head B Zoological Society of London ...

Chapter 2. Bird Species Diversity and Relative Abundance
Avian diversity and relative abundance was measured by conducting a series of spot
counts drifting downstream along 60 miles of the Rewa Head, and through mist netting
at camps set roughly 12 miles apart along from the East-West Split to Powis Falls.
For reference we used Steven Hilty’s Birds of Venezuela in conjunction with Robin Restall’s
Birds of Northern South America and the Smithsonian Institution’s A Field Checklist of
the Birds of Guyana. In English names we have chosen to follow Hilty’s nomenclature.
Principal Findings
• 187 species recorded through drift spot counts and mist netting. This rises to
251 with the inclusion of the Smithsonian Institution’s 2006 data.
• 10 Guianan Shield Endemics.
• Confirmed presence of threatened harpy and crested eagle.
• High diversity of raptors with 12 species recorded.
Mist Netting Survey
We conducted mist net surveys at 5 points along the 60 miles of river on which we
were focussing our research. We used three 40ft standard BTO NR nets with a mesh
size of 3cm. These proved fine enough to capture small birds such as antbirds and
hummingbirds, and strong enough to capture species up to the size of a pigeon.
Figure 23. Ash and Rob identifying a plain-brown woodcreeper (Dendrocincla fuliginosa).
Method
The nets were erected 50-200m from camp in a variety of habitats such as near vine
tangles, tree falls and along the river edge in order to catch unobtrusive species which
would not have been recorded during a drift transect. The nets were erected at 6am
and taken down at 5:30pm during surveys and were checked every hour. Five netting
sites were used from the East-West Rewa split down to Powis Falls covering a variety
of habitats from open, scrubby bush, to palm thickets and dense forest. Ashley Holland
has been identifying birds in the Rewa for several years and he, Ryol Merriman and
Kevin Alvin had worked previously with the Smithsonian Institution during their
collecting expedition in 2006 and were adept at removing and identifying birds in the
nets, being familiar with the majority of species caught.
20 Biodiversity of the Rewa Head