According to Wiki, pigeons are one of several bird families that lack a
uropygial gland, “informally known as the preen gland or the oil gland, is a bilobed sebaceous
gland possessed by the majority of birds”
https://en.wikipedia.org/wiki/Uropygial_gland
However, when (unwelcome) feral pigeons use our bird bath, they leave the water surface covered with a whitish, I assume, oily substance, as shown here:
In contrast, the water remains clear after use by all other species (Red Wattle Birds, Magpies, Magpie Larks, ravens, Crimson Rosellas, starlings , etc etc).
Any suggestions about the source of this substance?
Robin Hide
With the current heat , even the rarely visiting choughs wanted water:
