Strange noise from my pond.
My pond is being visited by something that is making a strange sound every night. It's only strange because I've not heard it before, but the sound is starting to become annoying. I hope it's a mating call that will end soon. It's a noise resembling the sound of a whistle. It last for about 15 to 20 seconds and repeats from dusk until well into the night. It's very loud and can be heard from a distance. I think the sound is annoying the green frogs as well. They try to compete with their "banjo" calls, but give up relatively quickly. I'm familiar with the sounds of crickets and some tree frogs, but I have no idea what is making this weird noise.