Save the Blue Swallow
2002-04-11 12:54
Pietermaritzburg - The relentless destruction of Mistbelt grassland in the KwaZulu-Natal midlands over the last 20 years has contributed to a drastic decline in the population of Blue Swallows, South Africa's most critically endangered bird.
There are now less than 40 known breeding pairs of Blue Swallow in KZN. The main reason seems to be that suitable habitat and nesting sites are being lost through changing land-use patterns, of which exotic afforestation is the most severe, followed by increased intensive agriculture and rural human population growth.
A recent study on the effect of habitat transformation on Blue Swallows in the midlands found that in a 360 square kilometre area over the last two decades, nearly half the remaining primary grassland has been destroyed, commercial afforestation has increased by 54% and the number of active Blue Swallow nesting sites has decreased by 55%.
According to researcher, KZN Wildlife's James Wakelin, the birds have very specific nesting and habitat requirements and simply disappear when these are not available.
Although in Zimbabwe Blue Swallows breed in man-made structures such as road culverts, those in KZN only nest in underground sinkholes or aardvark burrows where they build half-cup-shaped nests of mud mixed with fine grass and roots.
They line the nests with white feathers which possibly act as "landing lights" as the birds fly from the light outside into the dark hole and might also play a part in pre-breeding courting.
Sinkholes are the Blue Swallows' "five-star accommodation" but they will settle for aardvark burrows as the "motel option" if there are no sinkholes available, Wakelin said. Both types of accommodation are in decline.
"Groundwater flow is reduced by afforestation and other forms of land use practice, like crop irrigation, and this reduces the formation of natural sinkholes. Aardvark numbers are also falling drastically, mainly through loss of habitat and poaching, so there are fewer suitable burrows to nest in," he said.
Desperate times
Along with Helena Matterson of the Blue Swallow Working Group and KZN Wildlife's Doug van Zyl, Wakelin decided to start reversing the trend. At a test site at Impendle Nature Reserve, they have dug artificial burrows and plastered them with cement so that they are durable and can be used almost immediately.
Freshly dug aardvark burrows need to mature so that the walls of the burrow harden and stabilise, which takes two or three years.
"Some people say it's not right to create artificial nest sites but the birds' natural sites are being destroyed rapidly, so I see nothing wrong with creating some for them. Desperate times call for desperate measures," he said.
Blue swallows are already nesting in artificial sites in the Ixopo region and Wakelin hopes that some will move into the Impendle nests during next summer's breeding season.
It is conventionally thought that all Blue Swallows spend winter congregated thousands of kilometres to the north in central Africa, but Wakelin has his doubts that KZN Blue Swallows actually go there, because they haven't picked up behavioural habits, like nesting in culverts or roofs, from birds from other areas.
He is planning further research into the movement of swallows during the breeding season and during migration. But wherever they spend winter, breeding pairs return to the same areas year after year for the summer period, although it's not known for certain if the same birds return to exactly the same nests.
Blue swallows feed on the wing, mainly on small insects like beetles and flies, so they need open grassland uncluttered by vegetation. Fragmentation of grassland is a threat because the birds can only fly a limited distance from their nests in order to collect food for their chicks.
Above a certain distance, the adult birds must eat the food they have collected in order to replace the energy they have expended getting there. When that happens, the site becomes unsuitable and the adults birds desert the nest.
Maintaining the grassland
More than 90% of the original Mistbelt grasslands of the KZN midlands has been permanently transformed. Only one percent of the component remains in a near pristine state and of that only a small percentage (0,3%) is formally protected.
"The future of Blue Swallow conservation seems to lie in the hands of private landowners," Wakelin said.
"Blue swallows only occur in one formally protected area in KZN -the Impendle Nature Reserve. The majority of the active nests are on privately owned land. This means that the Blue Swallow is far from secure, especially considering economics is the greatest cause of land-use change.
"There are private landowners who are trying to protect the Blue Swallow but some form of compensation needs to be investigated to ensure continued maintenance of the grassland habitat."
The KZN population is the southern-most breeding area for Blue Swallows and has the largest breeding population in South Africa.
Although often confused with the black saw-wing swallow, Blue Swallows are recognisable by their lustrous dark metallic blue colouring and long tail streamers in the male.
They also have white feathers on the rump and flanks, which are only visible from close up when they are preening or courting.
Their call is a metallic wheezy chittering, which they utter in flight.