Some time ago I was studying goshawk in my field guide - African Goshawk, that is, in preparation for a coming trip. The field guide said it’s “The most common large Accipiter in the region.” Useful information, except I didn’t exactly know what “large Accipiter” means in African terms. Size, we try to teach, is the first and most useful bird field mark.
The African Goshawk’s length was listed as 15-18,” with a 27” wingspread, but how big is that? We’ve been trained to always assess size based on familiar birds - robin-sized, crow-sized, etc. To an American, large Accipiter means Northern Goshawk, 21” long with a 41” wingspread, or maybe a very big female Cooper’s Hawk. African Goshawk actually falls more in the small Cooper’s range, but I had to look at the actual measurements of Coop up to figure that out.
Listing measurements of common birds, in categories of similar species, provides a ready size reference when an unfamiliar bird appears.
I decided that what I needed was a way to quickly translate my size assessments in the field to inches, since that is how they are listed in the foreign field guides. So I got out my pencil (I’m always marking up field guides), and on the inside cover wrote down the names of familiar American birds, with their size in inches (see photo). Since some foreign field guides only have size in centimeters, which many Americans have trouble relating to, a metric-based cheat-sheet like this is especially helpful.
Now, if I’m in Africa and see a cuckoo that is definitely smaller than robin, I know that means smaller than 10” and therefore too small for 7 of the 10 species of African cuckoos I might encounter. If I see a Tringa-type shorebird (meaning a shorebird in the same genus as a yellowlegs ) and it’s Greater Yellowlegs-sized, I know I’ve got something around 14” and just by checking the size listed in the field guide I discover that’s too big for anything but Common Greenshank or Spotted Redshank.