One of the things that I used to think was that maybe Azure
Kingfishers could not survive in the ACT in winter because there are
no small fish near the surface in winter. (OTOH, maybe the AKs are
just sensible...) But I don't know how deep AKs can dive...
Anyway, the shallow water species I see most often in the ACT is the
introduced Mosquitofish Gambusia sp. Redfin predate them
voraciously (I have seen Mosquito fish jump out of the water onto
the shore in their desperate attempts to get away from Redfin). So
Mosquitofish are not found in open water but near water vegetation,
in the shallows and/or near the banks.
When the water is warm Mosquitofish are to be found in large schools
very close to the surface. When the water is cold, they tend to
stay near the lake/stream bed. Typically, I do not see them at all
in Winter.
I should say that I did see the Azure Kingfisher yesterday, and the
day before, thanks be to Steven and Lyndon who good naturedly
ignored the fact that when they first spotted me I was lurking in
the vicinity of some Angus cows.
One of the snaps I took shows the Azure Kingfisher with a fish that
it had caught. While the details of the fish are a bit patchy, one
detail does stand out, as it were: it has an gonopodium. As far as I
am aware, the only species of fish with a gonopodium in the ACT is
the Mosquito fish, Gambusia sp. The female is much larger
than the male and has a bluish spot near the vent, perhaps to assist
the male line up his gonopodium.
On the day on which I took the snap there had been ice riming the
edges of Our ACT Kingfisher's Molongolo Backwater. So the water was
cold. The water in which the Kingfisher was fishing looked to be
less than about a metre deep.
Quite by coincidence, I saw Mosquito fish at or near the surface
today for the first time this year, so the rime, and the ACT's run
of morning minuses, did not keep that particular school from moving
about. Perhaps they were motivated by some Redfin.
There is some speculation to be had here... how deep can AKs dive?
Was this AK able to survive off Mosquito fish by diving to near the
bed, rather than fishing from the surface? And, if AKs can survive
off Mosquito fish by catching near the bed of shallows in winter, as
well as from the surface in summer, and since there are many, many
mosquito fish in the ACT, why aren't AKs here all year in copious
numbers?
PS
Mosquitofish must be the kissing cousins of Cane Toads. They were
introduced to control mosquitoes, which they don't do very well, and
they are themselves voracious predators on smaller native fish
being, IMHO, a significant threatening process.
|
|
