In retrospect, the question still remained a big "why?" inasmuch as we didn't go inside the Ecopark to look for the Thrushes anyway and the terrain next to the spillway was as even as can be. But all that is water under the bridge, or in this case, over the rocks.
What is important is that we got what we came for. For the five of us (my wife, Cynthia, myself, Jun Osano, Mark Jason Argallon and his brother, Paul Kevin) our singular purpose of being there was to look for (and hopefully take some pictures of) the White Wagtails that birding friend, Ruth Francisco, saw two days ago.
After waiting for about an hour, we saw all three wagtails at around 8:15 am. It was interesting that these birds visited the area with almost clockwork regularity. They would stay for a few minutes, fly off, then return to the same place in just about an hour. Learning from this behavior, we positioned ourselves to the spot closest to where they would always land. At about 10:05, one of the wagtails flew in and for the next ten minutes we took its photograph to our hearts content.
However, as I was saying earlier, because I was using my 300mm lens with a 1.4X extender, my subjects were merely dots in the resulting photographs. To be able to make a presentable image, I had to do an almost 100% crop.
Thankfully, during the in-between times when we were waiting for the reappearance of the White Wagtails, there were other interesting birds that kept us busy. Once again, because of their distance, I had to do some major cropping in order to fully show the beauty of these feathered creatures.