The Peregrine Falcon is one of the most well-known birds on Earth. The general public knows this species because of its widespread population decrease followed by decades worth of reintroduction efforts that have brought this species back from the brink. They also know this species as the fastest bird on Earth. But until you actually get to see a Peregrine in the wild, you can never really understand how regal, sleek, and truly amazing this species really is. Fortunately, as birders, we are lucky.
There are three subspecies of the Peregrine Falcon found in the United States. They are the ‘American’ Peregrine (Falco peregrinus anatum), the ‘Peale’s’ Peregrine (F. p. pealei), and the ‘Arctic’ Peregrine (F. p. tundrius). Of these, the ‘American’ Peregrine is the most widespread and most commonly encountered. The Peregrines that were reintroduced into the western United States were true ‘American’ Peregrines; captive-raised and released. However, in the eastern United States, the birds that were released came from a mix of lineage of subspecies from all over the world. This has broken the species into two main groups, the ‘American’ Peregrine (an official subspecies found mostly west of the Great Plains) and the ‘Eastern’ Peregrine (not a subspecies, just a mix of lineages, found primarily east of the Great Plains).
For this post, I would like to explain how to tell the age of a Peregrine in the field based on some simple field marks. Luckily, the two main groups; ‘American’ and ‘Eastern’ are quite similar in appearance, and so all of the following information on ageing applies to both. In the cases of the ‘Arctic’ and ‘Peale’s’ Peregrine, these subspecies are rare and live in very small and restricted ranges so I have left them out of this post.
Peregrine Falcon’s have three distinct age classes that can easily be classified in the field; juvenile, subadult, and adult. The most well-known plumage age is the adult, so lets start with that. The adult Peregrine has dark slate-colored upperparts. The breast and belly are white or pale tawny-rufous with distinct, black barring. The adult Peregrine has a broad black malar mark, creating a ‘helmet’ over its head. Sexes are somewhat different in plumage, with the female typically having more markings on the breast than the male, which usually have a clean breast. In addition, females area typically a bit more of a grayish-black on their uppersides rather than the bluish-gray of males. Peregrines have typically molted into ‘adult’ plumage at around 13 months of age.
Juvenile Peregrines are quite different in coloration. This plumage is held for about the first 10 months of a young Peregrine’s life. Juveniles can have ‘helmets’ that are quite variable in width. Their upperparts are a dark brown rather than bluish-gray but easily fade to light gray, which sometimes can make them look almost as pale as a Prairie Falcon. The breast and belly are a tawny coloration with vertical, blotchy streaks throughout. The color difference between an adult and a juvenile on both their upperside and underside is quite noticeable, even at a considerable distance (assuming the lighting is decent).
The third and final age is the subadult. This plumage is seen on a bird as it transitions from juvenile to adult plumage between its 10th and 12th month of life. This plumage shows a blending of both juvenile and adult feathers, creating a beautiful pattern. Young, migrating Peregrines wait to molt until they have reached the wintering grounds, so you should only expect to see this plumage on the wintering grounds, unless you are in an area with non-migrating falcons. The feathers on the head are molted first, followed by the upperside and underside. Look at the following photos closely to see the blend of juvenile and adult feathers.
There are some birds that can trip you up, however. Once into adult plumage, Peregrines conduct a complete molt annually. As their older feathers become worn and faded, they will begin to replace them with new, fresh-looking feathers. This can make a bird appear like it is a subadult, but looking closely you can tell that the older feathers are old adult feathers, not juvenile feathers by the markings on the feathers. This becomes easier as you are able to see and study more and more Peregrines. An example of a molting adult bird can be see below.
Hopefully this was a helpful post that will assist in encouraging you take look closely at each Peregrine you see! Remember to try to enter as detailed observations into eBird as possible. Knowing how many adult and juveniles are around can help with future conservation of this vulnerable species. If you have any questions, feel free to contact me!
Wheeler, Brian K. Raptors of Western North America. Princeton, NJ: Princeton UP, 2003. Print.