Swainson's Hawks will start to fledge soon so I thought I would share a little tip on one aspect of ageing them in flight. Of course there are other ways to age Swainson's Hawks, but this is just a note to share. Check out the contrast between the dark flight feathers and the pale body on the adult (left) versus the juvenile (right). Light adults have a much higher contrast to the underside (due in part to their darker flight feathers) than juveniles and this is a good mark to look for on distant birds. Also, adults have a dark tail tip and full "bib." Beware of one thing...although uncommon, some juveniles look bibbed similar to adults. Note the juvenile's fresh buffy plumage they show when recently out of the nest.

I'm not a big quizzer, but does anyone want to ID this bird…and if you've seen the pic before, give it a few days before responding. I won't say when and where it was taken since it is a quiz and not a sighting report.

Thanks for any replies..."click" on image to enlarge

A bunch of people have sent me photos asking about "sub-adult" accipiters. The term "sub-adult" can be a confusing term because it is used in various ways depending on what you read or hear, and can have more than one meaning. So I thought I would discuss the term in regards to accipiters (and certain buteos). Also, some references have conflicting definitions or usages of certain terms, so my posts are my opinions/thoughts (although some things are plain fact). And, my goal is to try and keep things simple and easy to understand.

To state bluntly, there is no such thing as a sub-adult accipiter. Accipiters show either a ”juvenile” (1st-year) plumage or “adult” (2nd-year and older) plumage (this is also true for most raptors, i.e. Red-tailed Hawk). The adult plumage is acquired after their first molt, which starts at about one year old and takes several months to complete. Some birds retain a few juvenile feathers after their first molt, but these birds are not “sub-adults”. They are adults, since they are in adult plumage. Besides, there are many birds that don’t retain any (or any obvious) juvenile feathers in their first adult plumage. A juvenile in summer going through its' first molt that has a mix of adult and juvenile feathers is still not a sub-adult. They are birds in "transition" or "molting juveniles". A true sub-adult raptor shows real and certain plumage differences from juvenile and adult. They may not appear completely different, but have basic differences that are diagnostic. For instance, Swainson’s Hawk has a sub-adult plumage that always differs from juvenile and adult (albeit, not greatly).

Be very careful of telling retained juvenile from retained (old and faded) adult feathers, I would be wary of distinguishing these without practice! Knowing molt patterns and sequences helps greatly in confirming ages based on the presence of retained feathers. Eye color can be an indicator of age but not a criteria when used alone for ageing raptors. Eye color usually changes quicker in males than females or between individuals. And eye color tone and rate of change varies between buteo species. For instance, Swainson's, Broad-winged, Red-shouldered, and Rough-legged Hawks tend to turn from pale to dark brown quicker than Red-tailed Hawks...and Ferruginous Hawks take quite a bit longer than all of them.

This "sub-adult" issue has come up more recently due to all the close-up photos on the internet, but seeing this stuff in the field or in flight is much more difficult, and sometimes impossible. Take a look at the birds below, some have a few retained juvenile feathers, some have none, some have 2 generations of adult feathers, some have pale eyes, and others have darker eyes. Would you be able to age these? How about in flight? The particular age of each bird below is less important than the fact that they are all in adult plumage.

And, one question: Why does the term "sub-adult" seems to be used frequently on the internet for accipiters, but no one seems to call a Red-tail with a few retained juvenile feathers a "sub-adult?" I know why...

 Adult Cooper's Hawk

  Adult Cooper's Hawk

  Adult Cooper's Hawk

  Adult Cooper's Hawk

  Adult Cooper's Hawk

  Adult Sharp-shinned Hawk

   Adult Sharp-shinned Hawk

   Adult Red-tailed Hawk

   Adult Red-tailed Hawk

My friend Shyloh sent me a photo today that reminded me of a post I was meaning to get to (too many to get to and not enough time). Check out the Cooper's Hawk sitting on its nest…it is in juvenile plumage, which means it was born last year. Many (but not all) raptors are sexually mature at this age and breed successfully. The first time I noticed something like this was about 22 years ago when surveying Bald Eagle pairs on the East Coast…although, I'm sure it had been documented before that. I witnessed a few eagle pairs where one of the pair was not quite in full adult plumage, having a dark tail tip and some dark on the head. Each time this occurred, it was the female that was the "non-adult." And this makes perfect sense since it is the female that chooses the mate. And would a female choose a young male or an adult male? It's a no-brainer, an adult is going to be chosen every time. In fact, I haven't seen a breeding pair of raptors where the male was in juvenile plumage, but if anyone knows of this occurring, let me know, because its bound to happen. It has been reported that immature male Harriers have helped adult males tend to a female with nestlings, but I can't verify that at the moment (not sure where it was cited).
Anyway, check out the male in the second photo, he's in adult plumage, but still has a pale eye, which indicates that he likely acquired his adult plumage last year. Eye color is not always accurate to tell specific ages, however, males change eye color quickly, and a pale-eyed adult male is almost always one in its first adult plumage. This is definitely not the case with females though who can take years and years to get a red eye (and sometimes never do). Also note the gray cheek of the male, females can have grayish cheeks but it takes them several to many years to show that. So, this is an interesting pair;.a female in juvenile plumage and a male who isn't much older (most breeding males have dark red eyes). By the way, some of this pertains to my next post….

If anyone is interested, below is a link to an article regarding a Harlan's x Rough-legged Hawk hybrid (photo below, "click" to enlarge). The article has a detailed write-up and many photos.
http://ebird.org/content/ebird/news/hybrid_HALHxRLHA