The zoom range is 10X as indicated by the 6 to 60 mm range. An important figure is the lens opening: f/2.8 to f/4.3. These are great numbers. This means at the widest angle (6.0mm) the f-stop is 2.8 and racked all the way out to maximun zoom, the f-stop is 4.8. Many zoom lenses would fall to smaller openings such as f/5.8 at maximum zoom.

However, check out the wide angle. You may find it not wide enough for other uses such as group shots in confined spaces, or including eveything in a wide shot. Canon in designing this lens apparently favored the long side of the zoom range.

A tripod will be needed for zooms greater than 2X although a very steady hand in good lighting can get shots up to 4X zoom. Beyond that, it is very difficult to prevent blurring without a stablization aid.

You mentioned taking shots of birds approximately 45 ft away. Getting a sharp focus will be the challange. I suspect that you intend to shoot from indoors through glass. It would be best if you could shoot from a blind without any glass in front of the camera. However, if this is not practical for you, there are some things you can do to minimize the extra pane of glass in front of the camera. If you house is like others with installed storm windows, raise the lower storm and acreen to remove this impediment, and shot through only one pane of glass. That piece of glass msut be flat and free of defects. If you have thermal pane windows with a double pane of glass, the internal reflections will degrade the image. Seek another location.

There may be times when you will be tempted to turn on the flash. It won't work behind a pane of glass. The reflection off the glass will wash out the exposure and will not illuminate the scene very well.