Thursday, June 25, 2009

Kwando River reaches all-time high

As with other rivers in the region, the Kwando River has been rising steadily as the 2009 flood season progresses. It recently exceeded the previous highest level on record (from 1969), but with last week's unseasonal rains has risen even higher.

The Kwando River flows in a south-easterly direction forming the boundary between Botswana and the Caprivi Strip in Namibia, but is diverted in a north-easterly direction when it encounters a slightly elevated faultline - and here it changes its name to the Linyanti. However, a small channel breaches the faultline at the point where the Kwando first meets it, and - unusually - flows out of the parent river to die in the arid Kalahari some 50 kilometres to the south-east. This of course, is the famous Savuti Channel, which dried up during the mid-1980s, and this is the reason why we are so excited about the high water levels in the Kwando River - the Savuti is flowing quite steadily once again, and has almost reached the western boundary of the Chobe National Park. If, or when, the water reaches the Savuti Marsh, it will re-create a wildlife paradise second to none in the region. Birdwatchers are advised to keep track of the progress of the water in the Savuti Channel, since the arrival of the water at the Marsh will undoubtedly bring with it good birding, and possibly a few surprises too.

The top end of the Savuti Channel where it leaves the Linyanti Swamp (Photo: P Hancock)

Peterhouse Expedition to Makgadikgadi revisited

If you were born in Botswana in the past 20 years, you would find it difficult to believe that the lower Boteti River, from Khumaga down to Sokwane and beyond, was virtually perennial prior to 1990, with water year-round, substantial reedbeds and flourishing riparian woodland. All that remains today is an insignificant, dry channel terminating in a parched dustbowl in the south-western part of the Makgadikgadi Pans.

In order to appreciate how the area looked prior to its desiccation, you need to journey back in time. This is well worth doing, since the water flow in the Okavango system, which feeds into the Boteti, is returning to higher levels, and it is entirely conceivable that the river will once again reach this area, restoring it to a rich biodiverse wetland.

With this in mind, I managed to track down copies of the Peterhouse Natural History Society journals in the Peter Smith collection in the library at the Okavango Research Centre. For a month every year between 1966 and 1971, a group of schoolchildren from Peterhouse School in Zimbabwe visited the Makgadikgadi Pans to research and document the fauna of this – then little-known – area. These were no ordinary school jollies, although I have little doubt that the participants enjoyed themselves immensely – the children collected valuable scientific information including mammal and bird specimens, compiled checklists and found and documented many bird nests. Their reports make fascinating reading, and are a valuable contribution to our understanding of the avifauna here at the time of Botswana’s Independence.

Here are a few interesting highlights:

· Goliath Heron – a number seen along the river at Khumaga
· African Fish-Eagle – very common along river at Sokwane (also breeding here)
· Black Crake – very common along river
· Wattled Crane – seen along river
· African Mourning Dove – common in riverine woodland
· Coppery-tailed Coucal – common near river, in reedbeds
· Giant Kingfisher – quite common along river at Sokwane
· White-rumped (Hartlaub’s) Babbler – common all along river

Standing in the dry riverbed at Sokwane today, it is very difficult to visualize these birds here! We look forward to the return of the river, and to see to what extent they recolonise the area.

Friday, June 5, 2009

Freckled Nightjar reported from Central Kalahari

During the last week of May, Map Ives and Grant Woodrow of Okavango Wilderness Safaris heard a Freckled Nightjar calling in the northern part of the Central Kalahari Game Reserve (CKGR), well outside its known range.

The Freckled Nightjar is a bird of rocky areas and is abundant in the eastern Hardveld of Botswana - there are also records from the Aha and Tsodilo Hills in north-western Ngamiland. However there is certainly no typical Freckled Nightjar habitat in the CKGR!

Other birders visiting the CKGR should please look out for, and report observations of the Freckled Nightjar from this area.

Perhaps the bottom line here is 'Birds do fly' !!

Okavango floodwaters reach Toteng

Today, the Okavango floodwaters reached Toteng, flowing strongly down the hitherto dry Kunyere Channel towards Lake Ngami.

It is anticipated that the water will reach the Lake within ten days, filling it rapidly since there is an extensive waterbody remaining from last year's floods. This is great news for birders, as the Lake is likely to expand to over 50 square kilometres in extent, and provide rich habitat for waterbirds. Best time to visit would be late September or October this year when smaller waterbodies in surrounding areas have dried, and migratory ducks and waders would be arriving in numbers.

Tuesday, June 2, 2009

A Little Piece of the Okavango Restored

There have been some interesting attempts to manage the Okavango Delta in the past, to ‘improve’ the provision of the ecosystem’s goods and services, but it is doubtful whether many of these were successful. The system is very dynamic and fluctuates hugely within natural bounds, moving to its own rhythm.

During the 1970s and 80s, the flood levels in the Okavango were higher than average, but by the end of this period they declined and the outflow down the Thamalakane and Boteti Rivers no longer reached Rakops and the Mopipi reservoir at the distal end. Since large quantities of water were needed at the Orapa diamond mine, the Nhabe Channel was blocked, thereby diverting water down the Boteti River towards the Mopipi reservoir from whence it was pumped to Orapa. Of course, this deprived people living along the Nhabe from their water supply, but by the mid-nineties this did not make any difference since the Okavango waters ended in Maun, some 25 kilometres short.

The position of the bund at the start of the Nhabe channel

Now with the return of higher floods imminent, Debswana has removed the bund at the mouth of the Nhabe Channel. This is in line with the Okavango Delta Management Plan, and is a highly commendable action aimed at restoring the Nhabe Channel. This watercourse flows westwards to Lake Ngami, some 80 kilometres distant. If it flows this year, it will recreate valuable waterfowl habitat, as well as improving the quality of life for people living along its length, illustrating once again that what is good for birds is generally good for people too. Despite the Nhabe being blocked, Lake Ngami has actually filled to varying extent over the past five years, being fed by the Kunyere Channel, and this is likely to continue, with any water reaching the Lake from the Nhabe being an added bonus.

Work in progress - the pipes have been removed and the bund is being levelled (Photo: P Hancock)

The Nhabe Channel is likely to support significant numbers of ducks and geese once flows are restored, particularly Red-billed and Hottentot teal, White-faced Duck, Comb Ducks and Southern Pochard. For some reason, channels that have been dormant for a number of years (whether due to natural or man-made changes) attract vast numbers of waterfowl when they flow again, possibly due to a build-up of nutrients in the form of dung from the herbivores that graze along the channels when they are dry. It is expected that African Fish-Eagles and other piscivores such as Reed Cormorant and African Darter will soon recolonise the area.

It is likely that the Nhabe Channel will once again support large numbers of waterfowl (Photos: W Tarboton)
Once the Nhabe Channel becomes more permanent, aquatic vegetation in the form of reeds, sedges and waterlilies will become re-established, and provide suitable habitat for African and Lesser jacanas, African Pygmy-Geese and Whiskered Terns. The riparian woodland that has degenerated over the past two decades will also recover and boost numbers of frugivores such as Meyer’s Parrot, Burchell’s and Meves’s starling, Black-collared Barbet and Grey Go-away-bird.

African Fish-Eagles will quickly colonise the Nhabe