Hi David,
A number of issues could be going on with your silver maple -- and you're right in that they could be birds or insects.  I am sending you links to some fact sheets with descriptions and photos from extension agencies.  You can take a look at the photos and read the descriptions (complete with measurements) and see if any describe what you're seeing.
From the University of Minnesota, two types of insects:  
What's wrong with my plant? : Garden : University of Minnesota Extension (umn.edu)

Asian Long-Horned Beetle is an invasive pest making its way westward from New York City.  Ohio State University Extension's fact sheet is thorough in its description and its photos.  The recommended action if ALB is infesting a tree is to have the tree removed to prevent further spread of the insect.  
Asian Longhorned Beetle | Ohioline (osu.edu)

If you feel that you cannot make a determination, it may be best to call in a certified arborist.  You can find one near you at https://www.treesaregood.org/findanarborist

Finally, this is a paragraph from Iowa State University Extension describing holes left by sapsuckers.  Those are more uniform and usually in a band around the tree, which does not look like what you have from the photo:  

There are several bands of holes around the trunk of my pine tree. Is the tree infested with borers?

The holes were likely created by sapsuckers. Members of the woodpecker family, sapsuckers damage trees by drilling holes in the trunk or large branches. Sapsucker damage is very distinctive. They drill uniform, 1/4 inch holes in distinct rows (in contrast, the holes created by insects are random). Sap that flows from these wounds is eaten by the sapsuckers. They also feed on insects, such as ants, beetles and wasps that are attracted to the sap. The damage caused by sapsuckers is usually not serious. However, sapsuckers can destroy trees if they drill several rows of holes around the trunk within a small area. The bands of holes effectively girdle the tree trunk. To discourage additional damage to trees, home gardeners can wrap a piece of burlap around the damaged areas. Another option would be to spread a sticky substance, such as Tanglefoot, around the affected area. Trees most commonly attacked by sapsuckers include apple, crabapple, sugar maple, mountain ash, birch and pine.

If you feel that you cannot make a determination, it may be best to call in a certified arborist. You can find one near you at https://www.treesaregood.org/findanarborist

Best of luck.

You are most welcome.  Please feel free to write again with any of your gardening questions.