And of two thorougly "ducking" into their food:
I was very intrigued by those algae bubbles, which added quite a surreal touch to the photograph. So I googled, and ofkose, there was quite a lot of info...
I realized that algae bubbles seem to be classified as "pests" for reef tank enthusiasts.
"When we hear of 'bubble algae', one reflex is to think of the infamous "Valonia ventricosa", without even considering the many other algae that form bubble-like structures. Premature judgment can be regrettable, but there is this added twist: the much-cited 'Valonia' of our nightmares is no longer Valonia, but, thanks to Olsen & West (1988) now has its own Genus, Ventricaria. "
Suggestions were given for controlling the algae:
"e can try to manually reduce said presence to provide relief, and include in the affected tank a set of agencies that exert pressure against the problem alga. Since availability of usable nutrients fuels the alga's aggressive growth and reproduction, we attempt to restrict such availability. That is pretty much the standard threefold approach to most algal outbreaks:
1. Manual removal of the problem alga
2. Suppression via appropriate herbivores
3. Denial of resources
Normally, there would be a fourth aspect, of fiddling with temperature, pH, or some other physical-environmental parameter to suppress the problem alga. However, the environmental tolerances of most bubble algae exceed those of most ornamentals put into reef tanks."
I can't find much about naturally-occurring bubble algae, though, I get only reefkeeping fora!
Therefore, I decided that for this particular (public) pond, near the Campushallen (University) where I photographed the ducks, algae bubbles, far from being a "problem", actually food for the birds.
So...I don't care about the unhappy reef tank lovers, I am very happy indeed that the Northern Shovellers were happily feeding on these bubbles and enjoying themselves!
Ducklings, water and green bubbles...is there anything else required for sheer enjoyment of the childish kind?