This post is the first of what will be a multi-part series about determining the age and color-type of the Swainson’s Hawk. The Swainson’s Hawk is a very common summer resident of many western states and I hope these posts will assist in helping birders to not only enjoy Swainson’s Hawks more, but also help to add more details to sightings that you enter into eBird. Like most other Buteos, the Swainson’s Hawk can occur in many different color-types ranging from what is called a ‘light type’ to what is called a ‘dark type’. Color types used to be referred to as color morphs or phases, but the general consensus now is that the word ‘morph’ or ‘phase’ does not make much sense since these birds are stuck with their plumage color for their entire lives and never actually morph or phase out of it.
There are three distinct ages of Swainson’s Hawk that can easily be recognized in the field, with little effort. They are the juvenile, subadult (also known as ‘immature’ or ‘basic 1’), and adult stages. Each of these ages can come in a variety of color-types. There are about 20 different possible combinations of age and color-type for the Swainson’s Hawk, making it one of the most diverse raptors as far as plumage goes. However this also makes it one of the most confusing.
This first post will focus on determining the age of a Swainson’s Hawk, and subsequent posts will go into more detail about determining what color-type the particular raptor is. So lets start with adult birds. Swainson’s Hawks acquire their adult plumage in their third year of life, when they are two years old. At this age males can typically be separated from females by plumage characteristics. Adults can come in a variety of color-types, but they all share some similar traits that identify them as adults and not a younger bird. Adult birds always show a dark band along the trailing edge of the underwing, as well as a dark band on the end of the tail feathers (known as the subterminal band). The tail is also marked with many narrow tail bands throughout the length of the tail. Most adult Swainson’s Hawks show a ‘bib’ on the neck of the bird. Below is a typical adult Swainson’s Hawk showing these characteristics.
Next, lets discuss juvenile birds. The juvenile plumage is retained on an individual hawk for much of its first year of life. Juveniles lack the ‘bib’ and usually show a dark malar mark that runs onto the sides of the neck and breasts instead, creating a rather clear, unmarked throat region. Juveniles also have a darker trailing edge to the wings, but it is not nearly as obvious as on an adult and is sometimes absent. Juveniles also lack an obvious subterminal band on their tail feathers. Juveniles cannot be sexed based on plumage traits. Below is typical juvenile Swainson’s Hawk displaying these characteristics.
Finally, their is the subadult. This plumage is acquired when the bird is one year old, and is kept throughout its second year of life. The subadult Swainson’s Hawk shares plumage characteristics of both juvenile and adult birds, as would be expected, however it is much more similar to the juvenile plumage in many instances. The subadult Swainson’s has a wide dark subterminal band on the trailing edge of both the wings AND tail. The subadult has many retained juvenile feathers in its wings and tail, typically giving it a ratty-looking appearance because the leftover juvenile feathers are shorter than the newer subadult feathers. The combination of juvenile and adult feathers also creates a blend of feathers, some showing dark subterminal bands and others not. The subadult also lacks a dense ‘bib’ on the throat. The tail and wings are much more adult-like than juvenile-like whereas the patterning on the throat and body is much more juvenile-like. Below is a typical subadult Swainson’s Hawk.
Hopefully, as I put up more posts focusing more specifically on each age and figuring out their color-type, it will be easier to instantly look at a bird, and ignoring color, realize what age it is. If you have any questions about what I have written in this post, feel free to contact me (firstname.lastname@example.org). The most helpful guide for learning more about age and color-types of western raptors is Brian K. Wheeler’s ‘Raptors of Western North America‘ from Princeton University Press. All of the photos in this post were taken by myself and cannot be used or borrowed without my permission.