Things You'll Need
Instructions
Measure the egg size. Study its color, markings and shape. Take a picture of the eggs with a coin for size comparison. If the egg is small and has a mix of colors such as gray, cream and white with brown speckles, it is most likely to be from a sparrow species. Research types of wild bird eggs common to the area of California you will be visiting. Take out books on bird eggs from your local library to compare your findings.
Examine the nest's location. Determine where the nest is placed. Not all nests are found in trees or openings to houses and buildings. Some types of birds are ground nesters. Figure out what the nest is made of -- for example, chickadees use soft materials such as rotten wood chips or lichen, moss or grass to create their nests. Fur is also used to cover the loose eggs.
Watch for parent birds returning to the nest. This is the most effective way to tell what type of eggs are in the nest. Observe the birds in the nest area. Parent birds will regularly tend to the nest if the female recently laid the eggs.