How the frog found water nine inches up in the air and why it chose that in preference to a ground-level pond comes down to amphibian sensory biology, microclimates, and behavioural ecology. Frogs do not map elevation, navigating instead by moisture, smell, and line-of-sight. Their keen sense of smell detects humidity gradients as well as the scent of stagnant water or moist organic matter from some distance. During a heatwave, the air above an elevated pool creates a localized microclimate of higher humidity, enabling the frog to follow humidity gradients, effectively sniffing and feeling its way toward dampness.

Because the birdbath sits beside a bush, the frog probably hopped into the foliage seeking shade before stumbling upon the birdbath. Amphibians display strong site fidelity; when exploration yields a life-saving resource such as water, they remember it and will return repeatedly. Knowledge of its whereabouts could be a life-saver.

If I was a thirsty fly, I would be worried. Very worried!

Choosing the birdbath over a ground-level pond makes some sense. Ground-level water sources attract predators like cats, birds, and grass snakes, all seeking water, whereas a raised birdbath offers an elevated sanctuary somewhat out of reach of many ground-dwellers. Also, having introduced frogs over the last few years, the resident adult population makes the larger ponds centres of territorial or breeding competition. The quiet birdbath may serve as a peaceful, uncontested private spa away from the hustle and bustle.

Permitting me to top up the water until the frog is submerged to its neck suggests behaviour driven by a desire or need for cutaneous absorption and thermal regulation rather than selecting a hunting stance. Amphibians do not drink through their mouths; they absorb water and salts through a specialised drinking patch of skin on their pelvis and belly. Submerging to its neck efficiently rehydrates its entire body. Allowing me to add water while it stays put suggests a degree of habituation. Seeing it regularly has perhaps taught it that I am not a threat, but rather the bringer of gifts in the form of a welcome influx of cool water, overriding its initial instinct to flee in favour of immediate comfort.

Ultimately, the frog is using the birdbath to beat the heat. Frogs are quintessential sit-and-wait predators, so when they find themselves in a micro-habitat that happens also to attract potential prey they will rarely resist the chance of a free lunch. In a drought, small bodies of water such as the birdbath act as magnets for all kinds of flying insects, (such as mosquitoes, midges, and various flies as well as wasps and bees), all looking for moisture or a place to lay eggs. Frogs exploit the 'Oasis Effect' to set up shop and await dinner on the wing - self-propelled pizza, no drone required.

With good vision attuned to movement and hardwired predatory responses, a dark shape moving within a frog's visual field triggers an automatic tongue-snapping reflex with no need of complex, forward planning. Even submerged to its neck, the birdbath is an ideal hunting ground for an opportunist hunter. Insects land to drink or lay eggs, putting them right at eye level of a semi-submerged frog. The frog has turned the birdbath into a climate-controlled spa to soak up moisture and snap up passing meals without expending energy or risking exposure to predators looking for their own free lunch.