Yellowbilled stork and crocodile river guards

The yellowbilled stork and Nile crocodiles seen here may be contemplating the water hyacinth invader plants floating by; or not. Such plants were unknown to their distant ancestors living in these parts. The world changes, also in nature and even when people are not messing things up. The forensics do, however, link human activity to the spread of the water hyacinth from South America.

There are usually winners who become threats and losers who become threatened everywhere in nature. Species distributions increase for too strong invaders, decrease for threatened species too weak for fighting back; ecologies are rarely static, or not for long.

Even utopian fantasies were designed in the human mind to last for up to a thousand years or so, a negligible interval in the history of life on earth. People care about their children, but what happens to the generations of their offspring after a thousand years is an academic question for non-academics, i.e. irrelevant.

Neither stork nor crocodile is known for deep contemplation on such matters, or any matters for that matter. Shallow forms of mental activity more noted in mammals than birds and reptiles are confined to edible items, mating and aggression as may be required. Some humans are known for still favouring the same categories, even though deeper versions of contemplation are theoretically possible.

The yellowbilled stork, in Afrikaans called the nimmersat (never sated), one of eight South African stork species, does not live in South Africa on a permanent basis but visits here in summer as a nonbreeding tourist only. A multi-entry visa does not translate to a passport easily in a xenophobic society.

The Nile crocodile, one of 23 crocodile species on earth, no longer frequents all of its old haunts. In the north it has been exterminated by people from the northerly parts of the Nile in Egypt and even Israel and Syria where it was known to have lived very long ago. The same has happened around many densely populated rivers and lakes of central Africa and southern Africa. These days this crocodile (still) lies about next to some Nile tributaries and lakes of southern Egypt and the Sudan, spreading southwards through the tropics, mainly along easterly parts of Sub-Saharan Africa to northeast South Africa, where it may be seen almost exclusively in a few game reserves.

Yellow-billed storks lay two or three dull white eggs in platform stick-nests in trees, hatching the eggs in 30 days, both parents participating.

Nile crocodiles also lay eggs, from 20 to 95 of them per annual clutch, the eggs white, the size of chicken eggs. These eggs are buried in moist sand above the water level, the female lying on top of the buried eggs for long periods, only to protect them from egg eaters. She usually mates with several males, none of them having any part in egg or child protection duties. Nile crocodile eggs hatch on average after three months.

Water hyacinths multiply exceedingly more effectively than either yellowbilled storks or Nile crocodiles (Maclean, 1993; Riëtte, 2016).