The better binoculars you have the easier it is to see and appreciate birds, and the more you'll enjoy (and learn from) the field trips. However, if you don't want to spend money on binoculars, the department does have some binoculars that we can use. Their quality ranges from okay to rather poor. If you are still interested in purchasing binoculars, I've provided a brief introduction to binoculars and recommendations for purchase below.
Binoculars are described by two numbers, for example 8x40. It is important to understand these two numbers before choosing a binocular to purchase (yes, technically, "binocular" is singular). In the example, 8 is the power, which is the amount of magnification. A higher number means more magnification. The 40 in 8x40 refers to the diameter (in millimeters) of the objective lenses (objectives are the lenses that face away from you (i.e., toward the object you are viewing)). A larger number means a larger lens, which implies more light being let in (a brighter image) and a larger field-of-view (the total area you can see).
Eye relief: this can be important if you wear glasses. It refers to how far away your eyes can be from the ocular lens (the lenses facing your eyes) and still be able to see through the binoculars. I wear glasses and have deep-set eyes, so I usually need eye relief of at least 16 mm. If you wear glasses, I would make sure you get at least 14 mm of eye relief.
If you are just starting to look at birds and use a binocular for the first time, I recommend buying 7 or 8 power. It is easiest to hold these steady (9 or 10 power (or higher) are shaky unless you have very steady hands and/or a lot of experience), and they provide a larger field-of-view than higher powers. A larger field-of-view is nice, because it makes it easier to find what you are looking for in the binocular, something that is very difficult when you are first starting out. Lower power isn't recommended, just because you won't have enough magnification to see details; 6 power would probably be okay, but it is at the very low end.
I recommend an objective lens diameter of 35 to 45 mm. While it seems like larger is better, past 45 mm binoculars become cumbersome and heavy. 50 mm is about the largest usable diameter in the field. On the low end, 30 mm would probably be okay, but I'd recommend larger. Remember, if the lenses are small, you'll have a darker image and not as large of a field-of-view, making it harder to find things.
You can spend as little or as much as you want on a binocular. If you spend less than $50, you'll probably not get a very good view. I've been looking at a few websites and found some decent binoculars for $60 to $70. If you are interested in birds in general and think you'll continue to use binoculars for a while, you may want to spend more than that. I would recommend shopping around; take a look at the options at Eagle Optics. They have a good selection. I'm not necessarily suggesting that you buy from them, just recommending it as a good starting point. They also have a series of informative articles here.
In case you're curious, the binocular that I use is an 8x42 roof prism. The best way to find out if you'll like a binocular and whether it will fit your face is to actually try it out.
Feel free to email me if you have any specific questions about binoculars, I'll be glad to help.