An inconsistency in photo-shooting with phone camera

Hello — I bought my wife a Samsung Galaxy S7 about a year ago. She took it to London, England, on a holiday, and with it, took a photo of Trafalgar Square, from the edge of the Square and looking right across it to Nelson's Column. In the far distance was a clock-tower. The whole tower was hardly visible, so far off was it (perhaps the distance would be about a mile, but I don't know for certain. However, it certainly must have been several hundred yards). Yet, when she showed me the shot, she was able to zoom in on it enough to see, not only the distant clock-tower, but also the clock-face, and could easily read the time that was showing on it. (She always uses HD setting for her pictures.)

Today, she wanted to take a photo of some goldfinches, feeding at the bottom of our small garden, which would have been only about 23 feet away from where she stood. Yet, though she magnified the shot as much as she could, afterwards, the birds showed up "woolly" on the photo, when she zoomed in. (The foreground of the picture was sharp — her hand had not trembled, or anything like that.) She has remarked that there is no zoom facility on her phone camera, so she just shot the picture as she would have taken a picture of our living-room. We are two innocents where technical matters are concerned, so my questions are:

Why did the clock-face magnify so very well, when the birds, at such a closer range, were blurred? Also, is there some function (zoom shot?) that she does not know about, and ought to use? If so, I cannot find it.

I should be most grateful if someone out there can help me, or clear the matter up, at least. Thanks in hopeful anticipation!
smasheroO16