HawkArtScience: Hawksaloft.com blog

(Archive: About Eagles)

30 October 2009, Friday
Golden Eagle aging, hasn't really changed

You can take that a number of ways! But seriously, in the Fall of 2009, observers still think that the amount of white at the base of the flight feathers is relevant, let alone key, to aging this species?! In 1987, the first edition of the Peterson Field Guide the Hawks of North America by Brian Wheeler and Bill Clark had a grainy black and white photo labeled,

variant with no white patch [arrow points into underwing on photo]

Wheeler and Clark's next book, A Photographic Guide to North American Raptors (1995) has a nice color image and accompanying text for juvenile Golden Eagle:

Amount of white in patches on underwings is variable from none to lots.

Brian Wheeler's two-voume series, Raptors of North America (2003) again reiterates this and fine tunes it with photographs, all on one page, showing this range in the amount of white ... "none to lots."

In 2004, Jerry Liguori had the definitive* article in Birding on aging Golden Eagles. Front and center — also to the right here — he made a composite image of three juvenile GEs. While it's a composite, it is not an illustration but a photo array of 3 actual juvenile Golden Eagles. Right here and now, you can view and download Jerry's piece at ABA.org: How to Age Golden Eagles, June 2004.
(*using "Liguori" and "definitive" in proximity is always redundant)

Final point on our timeline, in 2005, Lig's Hawks from Every Angle was published handling this issue again and providing his very unique and very detailed fieldnotes for flight ID of all the hawks of North America.

We'll be right back, and continue this discussion after you purchase these handy reference guides...

Welcome back. As you may recall I was beating you about the head and shoulders with a long brown juvenile Golden Eagle feather as a metaphor for the fact that little or no visible white along the base of the flight feathers does not an adult Golden Eagle make, or any age along the path to adulthood for that matter. With that said, it is still true that the amount of white diminishes over time with successive molts. Take another look at Jerry's composite, now, and project a year, or two years, hence for each of these same-aged birds. If you hear anyone in the field spinning out this bogus aging scenario using the amount of white primarily, well, run--run, I say. Maybe email them a Liguori PDF... if they even have a computer!

For the fine points, you should refresh using books and articles, as they are available (see above). But here are three points of reference one needs to see for comparison and conjecture on a GE in flight: the upper wing coverts, to tell juv from others; the trailing edge of the flight feathers, to look for variety or uniformity plus plain or the dark terminal band; a view of the spread tail, to see all the feathers. To do this aging responsibly, I think you can see that you need to have a bird fairly early in its approach and then in close and/or take a picture for later examination, it also works to follow the bird away and continue gathering data. This is how to improve your game!

Speaking of game, we are in the throes of the 2009 World Series of Poker right now, there are lessons from the pros in poker that the professional hawkwatchers know too (I've got a Law of Birding for this coming along). You need to take the odds into consideration. For example, in early September and through the Broadwing peak, the odds of a Golden Eagle, any age, is about as low as filling an inside straight. What are the odds that distant dark eagle is a Bald Eagle? I'd bet on it. And if you see a Golden Eagle well, and it has no white in the wings, go all in on it being one of those juveniles... focus in on the tail type and trailing edge of the wing for a clear tell. To get the best odds, bet on distant, badly lit, or just really and naturally dark juvenile Bald Eagle (see the Bald Eagle image in the set below).

No offense, but if you don't make a point of seeing at least 25 Golden Eagles a year, you have no business calling a September distant bird in the field a GE and/or asking online if a big, all dark eagle-like bird you saw at a bad angle is an adult GE. Hold your cellphone up to your binoculars and take a picture, then let's communicate, or better yet... bring some money to the hawkwatch and let's play poker.

To adapt the sage advice of Faber College's Dean Wormer, "Identifying your hawks and eagles ass-end going away is no way to go through life, son." Of course Faber — under Dr. Wormer's tenure — pioneered the academic policy known as double secret probation. And speaking of college, more precisely, for those with mathematical training:
Wb ≤ U
{Where Wb equals the amount and extent of white at the base of the flight feathers; and U represents the absolute integer of uselessness}

Here are a few of my recent eagle images:

Eagle1: image 1 0f 4 thumbEagle1: image 2 0f 4 thumbEagle1: image 3 0f 4 thumbEagle1: image 4 0f 4 thumb


15 December 2009, Tuesday
Bald Eagles, briefly

If you started hawkwatching in the 1960s, like I did, then seeing a Bald Eagle was a very big deal. I think it took me six years to get my first one. Now, both the northern and southern populations have increased to levels that only the very close birds get an oooo or ahhh... from those who put in the hours.

The Fall migration of the northern birds, is difficult to detect across much of the Northeast. In terms of September Bald Eagles, and certainly the adults seen during Broadwing season, these are essentially and nearly exclusively birds from the southern population — Florida and the Gulf Coast — headed back down after spending the Summer dispersed into eastern Canada and points just South. There appears to be another northerly dispersal from the Ohio River (over to the Delaware Bay) of Bald Eagles, all-juvs, that happens in July and August... who knows when these birds turn around and get counted at Fall sites in the Northeast?!

Wheeler (2003) summarizes the timing of Bald Eagle movements nicely... so check it out or recheck it. For a glimpse into the departure timing using satellite telemetry for a small, but interesting, set of juvenile BEs from Labrador, you can see the youngest birds from up there aren't around here until November. The youngest! Comparing movements at the biggest sites — Duluth and Iowa — we see adults push South in December, mostly. So this is the autumn timing for what is often referred to as "our birds."

There is a semi-recent article (not online: Wilson Journal of Ornithology 2008, 120(2): 304-310) showing the northbound dispersal of Florida via GPS, but you can start with this one on band recoveries. The article link is only an abstract, but your local university library should be able to get the full article. The adults hit the Northeast, either Derby Hill or MA coastal sites around May 1st annually, with the fresh, brown unworn-of-the-year trailing and continuing way into June.

Enjoy the new and higher than ever Bald Eagle records, just be aware, we're recording a lot of U-turn birds.


21 December 2009, Monday
Bald Eagles, remix

For the northern population, committed pairs along with other adults are on the move in mid-February. At a hawkwatch along the Great Lakes, you can observe this on pre-frontal conditions, but it's not always the ideal conditions, at your usual observation point as Bald Eagles can act like rain birds — hawks that don't seem to need the same set of posh circumstances to get going.

Elsewhere, where northern Bald Eagles are wintering: on lakes, rivers, along the coast, their northbound movement can be detected if you think in terms of an overlay... ye olde independent clear acrylic sheets on maps in the days before computers; think layers for a graphics app, if you know that. In other words, two things happening kind of in two different dimensions, for different reasons, yet over the same landscape. The wintering number are still there, but additional adults, and some will be in pairs, are "playing through."

Committed pairs in eagles, buteos and other raptors remain together all year. This is not all the adults of a species, or even all the breeding adults, but it's happening and you can detect it, with or without a hawkwatch!

A recent study used DNA to confirm pair (high) fidelity in Eastern Imperial Eagles.

By performing DNA analysis on the feathers left behind at nesting sites, the researchers were able to identify individual Eastern imperial eagles in a nature reserve in Kazakhstan. Their analysis showed that not one adult strayed from its mate - a degree of fidelity highly unusual among birds, the vast majority of which mate with and raise offspring from multiple partners.

With the current cold snap, we are just starting to see wintering Bald Eagles in the Northeast. As you enjoy them, count on the February overlay, and add it to things to look for over the next couple of months, because, by March, you've missed it.

Test09: image 1 0f 4 thumbTest09: image 2 0f 4 thumbTest09: image 3 0f 4 thumbTest09: image 4 0f 4 thumb


20 January 2010, Wednesday
Wayback Machine: Bald Eagles

On or about the first Earth Day, Syracuse's Onondaga Lake was not only ecologically dead, but a toxic danger to the community. Between the raw, then slightly strained sewage discharged by the City directly, to... I don't know exactly... but, tons of mercury, etc. from factories on the shore, this was one dead lake.

Onondaga Lake is a curiosity, as its an inland salt water body with a rich oral history. Later, white settlers conducted their commerce here, and into the early 20th century, we used to actually recreate in it... you can find the old-timey brownish photos of those activities, and when I was a kid in the fifties, you could still see a hint of this and imagine the rest. The lake is kind of famous for collegiate regattas too. While you still don't want to fall in there if you can help it, people canoe, kayak, sail a little, and fish in it nowadays.

In fact, Onondaga Lake is on the international professional fishing circuit — two seasons of the year! In summer, it's the professionals with boats and sponsors... looks like a NASCAR event but with boats and fish and sponsors. I'm sure there's a cable channel for that.

In Winter, a different professional fishing tour comes to town: Bald Eagles. And just about a year ago, I got an email from Syracuse Post-Standard columnist, Sean Kirst, because when he Goggled "Bald Eagles and Onondaga Lake," my web site came up. He included his phone number, and we talked for nearly an hour about this new local phenomenon, on background (as we say in the media sourcing biz). Since his column can be about anything local, 99.5% human though, a natural addition to the community was nice. Sean also brought in the view from the Onondaga Nation, who of course, have lived along Onondaga Lake nearly forever.

And all this was very well received both in print and online. Online, Syracuse.com can be updated from both ends, and it was — with comments from readers and additional images from a staff photographer. Spilling over to the sports section, where hunting and fishing has its own beat writer, readers submitted their own picts of the Bald Eagles on Onondaga Lake.

Yesterday, under the category, "great minds think alike," as I was rooting around collecting links for this blast from the past piece, I noticed that Sean had just done an update for this Winter at Syracuse.com!

Speaking of wintering Bald Eagles in eastern North America, where would you go to see a gathering of eagles? The most birds, I mean. Would it be the Delaware Water Gap or along the Hudson? How about the Connecticut River just above New Haven, the Quabbin or Newburyport by the new/old chain bridge? Local is always a good idea and right now is the best time. But I'm asking about the most wintering Balds. Add up all these numbers from these fine sites and you'd fall short of the greatest gathering: Wolfville... that's in the Annapolis Valley (no, not that Annapolis). Still don't know?


They've got the urge for going, and
they've got the wings so they can go.

— Joni Mitchell

Hawk•art•science blog
Truth and beauty. Art and science. Entries here will be on that flightline, although I will stray from the hawk-part on occasion, or will I? I aiming this beast at hawkheads and/or the young seasonal revolutionary biologists. It's for the flexible and young-at-heart too.
Comments, questions, excited utterances, and/or exasperated afterthoughts from you, dear reader, are welcome and will receive a reply. — Tom Carrolan
(Image above: "Recent self-portrait No.3, 2009")

Original recipe Hawksaloft.com
The Hawksaloft.com website was launched in 1997, following three years of printed handbills, plus numerous emails, all voicing my alt.hawkwatching ideas in New England. If you've been here before, the original site is archived in all its old-timey graphic glory. To navigate the old way, just click on Psychedelia the Hawk Owl and be transported back in time... trippy. Any bookmarks or links found anywhere online still work.

Not everything that counts can be counted and
not everything that can be counted counts.

— Albert Einstein