Identification is something that all birders struggle with at some point. Whether you are new to the hobby or have been at it for years, proper identification can be a challenge. This is an aspect of birding I am always trying to improve on, especially when it comes to warblers, sparrows, and shorebirds. Fortunately there are a few things to focus on when trying to properly identify a bird by sight.
A few subtle differences within every species will leads to proper identification. In the front of your field guide there is a section devoted to bird identification which describes the various field marks, also referred to as topography of a bird. Many of these distinguishing field marks can be found on the bird’s head. Eye lines, eye rings, and eye brows, are markings to pay attention to when unsure what you have observed. Other areas of the head to pay attention to are the crown, throat, and beak colour. As you move down the bird, markings on the breast, belly, wings, and tail all become important in identification.
I recommend studying the front of your field guide and familiarizing yourself with the field marks of a bird. Not always is the entire bird visible when birding, so focussing on the part of the bird you can see, and running through a check list in your head will help. Make a mental note of all the distinguishing field marks to reference with your guide later. If you carry a camera with you when you bird, snap a photo. Regardless of the quality of the photo you get, most times they can be used for identification.
As you become more familiar with the various field marks on a bird and what to look for, identification will become easier. As with anything, practice makes perfect, so the more you bird the better you will become.