Why so many hadedas?

2012-02-20 00:00

MOST of us know that there are more hadedas around now than there used to be. Scientists are now looking into the reasons for the high numbers and we have seen letters to the news- papers­ with comments from interested folk. I must confess that I am a little bemused as I thought the reasons for the high numbers were pretty obvious. However, let’s talk about these interesting birds.

Most people know that hadedas are ibises, and as KwaZulu-Natal residents we are fortunate in being able to see all four South African species — the Hadeda Ibis, Southern Bald Ibis, Glossy Ibis and African Sacred Ibis — on a regular basis. There are actually five southern Africa species in the ibis family (Plataleidae), the fifth being the African Spoonbill, which is just an ibis with a beak designed to find food in water.

So, what do hadedas eat? Not fruit as one member of the public recently suggested, but invertebrate animals, such as crickets, worms and beetle grubs. Hadedas, like all ibises, have incredible beaks with highly sensitive tips that can actually feel their prey when the beak is pushed into the ground.

Essentially, all animals have three basic needs for survival — suitable food, water and shelter. Where all three of these things are found, healthy populations normally thrive. So where there are lots of invertebrate animals, especially those that live in burrows in the soil, hadedas get all the food they need.

In the wild, hadedas frequent open, moist grassland and savannas, especially along well-vegetated river courses, but also marshes, flooded grasslands and the edges of large wetlands. They are also at home on irrigated agricultural lands, and lawns in gardens and so are never far from water­. As far as shelter goes, they require large trees.

So although they feed on the ground in relatively open places they need large trees in which to roost and to build nests.

So, hadedas can be expected to thrive where there are forests and wetlands — two biomes that we know have come under great threat in recent times. Indeed, if hadedas relied on natural forests and wetlands they might well be facing extinction. So the short answer to the question “why so many hadedas?” is that they are adaptable.

With all the talk about climate change, and the impacts that growing human populations are having on our biodiversity, we tend to think that all animals respond negatively to growing human numbers — this is not true.

While many animals do respond negatively, and there is a great need to implement strategies designed to conserve our biodiversity, some animals­ actually take advantage of human activity and as a consequence can become almost as problematic as humans themselves. Yes, we have chopped down much of our indigenous forests, but we have replaced them with suburban gardens and vast plantations of exotic trees. We have eliminated many of our wetlands, but we spray water all over our gardens and agricultural lands. Clearly, invertebrate populations, especially those that thrive in gardens and agricultural lands, have exploded, providing hadedas with the means to fill their bellies.

In the same way that we manage depleted populations by conservation strategies designed to increase numbers, we have to manage burgeoning numbers by culling. While many people understand the damage that can be caused by excessive elephant numbers and accept that culling is necessary, few people ever think of the damaging effects that huge numbers of hadedas must be having on our environment. Hopefully studies being conducted on hadedas will come up with some answers to this problem. Till then – we will have to get used to their tuneful voices every morning and evening.

As a parting shot you may like to know that the French naturalist Adulphe Delagorgue, who undertook various expeditions in KZN during the mid 1800’s, considered hadedas as quite uncommon and largely confined to natural forests. He also records preparing them for the pot, saying that they were quite tasty. Could one of the solutions to the problem of large numbers be that we should be harvesting them as food?

 

• Dr Jason Londt is a natural scientist with a special interest in entomology.

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