This is the second in a series of posts concerning how to age Swainson’s Hawks and how to determine what color type, and if possible, what sex the particular bird is. The first post can be found at this link, and goes into detail about how to tell a juvenile, subadult, and adult Swainson’s in the field. This post will go into detail about how to know color-type and sex of adult Swainson’s Hawks.
The adult Swainson’s Hawk is the only age of this species that can sexed based on plumage characteristics in the field. There are about 9 or 10 different color-types that the adult bird can come in, however, in general they can be narrowed down to four different types to make things easier. These are the light type, light-intermediate type, intermediate type, and dark type. Both adult males and females have their own versions of light, light-intermediate, and intermediate types; but both typically share similar plumage characteristics if they are dark types. Obviously, with different color-types breeding with each other, there is also a lot of individual variation between birds, and rarely will you find two birds that are identical. This sounds confusing, but I will break it all down by type and sex, below.
Light type Adults:
Only about 10% of the world Swainson’s Hawk population are dark types, the other 90% is made up of light and intermediate types. So, since most people will encounter lighter types, lets first compare light type adult males to light type adult females. For light types, determining the sex of the bird usually comes down to looking at the color of the head and breast. For the males, the bib is a rich rufous color and then as you move up towards the bird’s head, the color changes to gray. Adult males have white bellies and leg feathers. Typically, where the bib and belly meets is crisp, with a very clearly defined boundary. Carefully look at the following photos of an adult male light type, trying to pick out these identifying features.
Female adult light types are fairly similar to light type adult males, however the bib color is more chocolate brown and the head is also chocolate brown in color, not gray like in males. The bib is still very clearly defined and it is obvious where is ends, and the belly markings begin. In addition, the breast is not as white and unmarked as in males. Check out the photo below of an adult female light type.
Dark type Adults:
Now lets, jump to the most extreme color-type, the dark type. Knowing the light type and the dark type will help when I try to explain the intermediate types. The dark type Swainson’s Hawk cannot easily be sexed, although on rare occasions the male dark type may show a grayish tinge to the head. Dark types are just that, dark. There is no bib, the head, breast, and belly are all the same dark color. The underwing coverts are rufous and heavily marked, not at all like the clean and lightly marked underwings of light types. Also note, that this color type does not show the white throat patch that is shown ON ALL OTHER color types! This is by far my most favorite color type of this species. Below is a photo of a dark type adult.
Light-intermediate type Adults:
Next are light-intermediate types. This color type is the next step up from a light type. Both male and female birds look fairly similar to their respective light types although they have more markings on their breasts and underwing coverts. The male has a less-defined bib but rather has markings that run down the breast and into the belly. The gray head is still visible. The underwing coverts have more rufous markings.
The female light-intermediate type has a less-defined bib, that is chocolate brown in color, the head is brown, and there is heavy brown streaking in the belly. The underwing coverts have brown markings.
Intermediate type Adults:
The final color type of an adult Swainson’s Hawk that is worth mentioning is the intermediate type; also known as the rufous type. This color-type is (as it sounds) intermediate between a light type and a dark type, and therefore shares many of both type’s characteristics. Male and female can still be determined in this color type, mainly by looking at head and breast color. In this type, the belly, flanks, and leg feathers are always a rufous color, usually with darker streaking throughout. Male intermediate types have uniformly rufous bibs and bellies, whereas females usually have a more defined bib that contrasts with the belly coloration. The white throat patch is still visible in this color type. Unfortunately, I only have photos of a female intermediate type, but I think you can visualize what a male would look like.
So, to review, there are four main color types of the adult Swainson’s Hawk. In all types except for dark types, males and females can usually be separated by head and bib color; males typically showing a lighter, grayer head and a rufous bib whereas females usually show a uniform brown head and bib. As mentioned earlier, Swainson’s Hawks show a lot of individual variation, and so it is unlikely that you will ever see a bird that looks identical to any other bird, however all adult birds should fit into one of these four main categories. One other color type that is less common than the four above, is the dark-intermediate type, which is just a darker version of the intermediate type, but still not yet the truly dark type.
Hopefully this post was informative and not just extremely confusing. If you do have any questions, please contact me (firstname.lastname@example.org) or feel free to leave a comment. I will try to answer all questions in a future post. Also, keep checking back because I will soon be posting about how to tell color types on juvenile Swainson’s Hawks and subadult Swainson’s Hawks!
All photos on this post were taken by myself, unless otherwise noted, and cannot be used without my permission.