Content & Photos © Bill Schmoker unless noted otherwise. Thanks for visiting- drop me a comment!

Saturday, November 24, 2007

A light Harlan's Hawk

I made a run to the feed store in Hygiene, Colorado yesterday (yeah- that's its real name and yeah, it's a pretty clean place...) I was after corn to keep my Blue Jays happy, but brought along my camera in case I saw anything interesting on the short trip. I'm glad I did.

You see, I'm a bit of a raptor aficionado- I like them all, but one that always interests me in particular is the Red-tailed Hawk. For starters, there are plenty around here, with their numbers growing in the winter as birds arrive from points north to spend the season. Then there's the wide range of individual variation shown within the species, from birds that are extremely pale (actually, if you count albinistic individuals, completely white) to coal-black stunners.

Among the winter Red-tailed Hawks along the Front Range of Colorado, a small percentage are Harlan's Hawks- the harlani subspecies of Red-tailed Hawk. Once considered a separate species, these birds have a fairly restricted breeding range (mostly Alaska and Yukon) and they move into the lower 48 states, primarily in the southern central plains, to winter. Other habitat pockets throughout the western states provide wintering grounds for Harlan's Hawks as well, and once you are east of the Mississippi Valley you would be lucky to find one (for detailed maps on these and other raptor distributions, get Brian Wheeler's comprehensive Raptors of Western North America and Raptors of Eastern North America.)

Harlan's Hawks, like western Red-tails (calurus), are polymorphic, meaning they come in various color morphs (not phases- they are born and live their whole life as one color type- phase implies the color will later change.) Reversing the trend found in their calurus counterparts, dark birds are the most common type found within the harlani subspecies. Light-morph Harlan's Hawks are quite rare, and easy to overlook as just another Red-tail. In the Sibley Guide to Birds, David indicates that light-morph Harlan's Hawks may only comprise 1% of the population. So finding one is cool- a rare form of a rare species.

I saw this bird drop on prey along a road while I was stopped at an intersections and when it didn't immediately fly back up I guessed it had made a catch. When I diverted over to see if I could photograph it on the ground, it flew back up onto a roadside power pole to eat the vole (or whatever it is- anyone venture a guess?) I love that scenario, because raptors with prey are a lot less likely to fly off. The bird let me coast up on it and get a series of pics as it ate lunch- I'll spare you some of the more gory shots (for now, at least.) Once during its meal, it flew to the next pole to finish eating, and then flew off, but I only managed two receding flight shots.

Obviously one striking feature is all of the white on various parts of the head. Its overall color tone was pretty cold- the belly band was fairly heavy, almost black "droplets". With the tail folded it looks nice and red with dark bands, but I think the red is only in the outer two feathers, with the rest of the deck (upper surface of the tail) gray with dark speckling and a dark subterminal band... good for Harlan's. You can see this on the second shot below where the bird is pulling on the rodent, exposing more of the tail. Also, it might just be the light head, but the bird looks a bit big-eyed compared to other Red-tails (like I think Harlan's do.)

And here's the oddest part- the bird called several times, and it didn't sound like a Red-tail. I hear them frequently, and I honestly don't think I would have identified it as anything but some unknown raptor if I had only heard it. The call wasn't as high and shrill as a typical RT- I'm not great at describing sounds but I thought it was more of a croaky sound, lower-pitched and without as much of a whistled quality compared to our "normal" 'tails.

I wasn't sure if I really had a light Harlan's, but after looking at Hawks From Every Angle by Jerry Liguori and Brian Wheeler's books mentioned above I was feeling like it was a real possibility. Now I've heard back from a few experts who have much more experience with these birds who agree with me that the bird is an adult light-morph Harlan's Hawk. Both also commented that they sound a bit different than other Red-tails. Wicked.

Friday, November 23, 2007

Comparing Common & Pacific Loons

We finally got some seasonal weather around Colorado's Front Range, with snow last Tuesday night into Wednesday morning and cold temps since then. On Wednesday, my sidekick Garrett & I saddled up and headed out to have a look at a couple of loons that had been lingering around Longmont, a Common and a Pacific.
The first order of birding in snowy, cold weather is to bundle up- think layers. Since it is hard for me to take a pic of myself, here's the G-man in his winter birding outfit, ready to roll:

Finding both birds was pretty straightforward- but both were being lazy, sleeping & preening near the middle of their respective lakes, putting them well away from any shoreline and associated predators. Plus the light was flat, light snow flurries came and went, and it was a bit breezy. Not great photographic conditions, but quite realistic for late fall loon watching. So I decided to video both birds and put together a little comparison video.

If the loons were together one of the most obvious features to compare would be the size differences, but they weren't even on the same lake, and other good size reference species like Western Grebes weren't present, either. But even with distant lone loons, much can be inferred from structure and field marks that are visible at long range.

I suspect that the Common Loon is a juvenile, but it could be a basic adult. Even at 200 meters or so, you can see the somewhat flat-topped & blocky head, white above the eye, fairly large & slightly upswept bill (underside curved upward a bit more than the topside is curved downward.) Also note the whitish partial collar intruding into the dark nape, creating an uneven border between the white throat and the nape. In contrast, the Pacific Loon (a juvenile) has a rounded head profile, curving smoothly back to the nape. The bill is relatively smaller and more symmetrical, and the nape line is straight, contrasting sharply with the white neck.
Somehow the even curve of the head and neck combined with the clean dark nape reminds me of a cobra with its hood puffed up. When the bird turns its head away, the silvery-gray coloration on the nape is more visible. The forecrown of the bird and the foremost part of the nape are darker gray, almost black.

To get the shots I videoscoped the birds with my Leica 77mm APO-Televid scope with a 32X wide angle eyepice, connecting a Leica C-Lux 2 camera with their Digital Adapter 2 (plus my homemade cable release bracket.) Anyway, check out the video I put together to compare the two:

Thursday, November 22, 2007

Happy Thanksgiving!

Happy Thanksgiving to everyone out in the blogisphere- hope turkey day was good to you all. Bill

Wednesday, November 21, 2007

IFO- Take a Course!

The latest issue of Birding arrived the other day, bundled with a brochure outlining the 2008 Institute for Field Ornithology (IFO) offerings. I contributed the cover shot of a hen White-tailed Ptarmigan that I took on the slopes of Mount Audubon, west of Boulder, Colorado (and I've got some other shots sprinkled throughout the brochure.) I'm also excited to be assisting Ted Floyd on one of the workshops- Colorado Bird Community Biology: The San Luis Valley. The course will be 6-10 June, headquartered at The Nature Conservancy's Medano-Zapata Ranch . This little bison ranch (100,000 acres or so) sits on the high valley floor around 7500 feet above sea level near the Great Sand Dunes National Park, between the Sangre de Cristo and San Juan Mountains. To say that the natural setting is spectacular is an understatement, and the creature comforts at the ranch facility are top-notch, too.

Extremely varied habitat is found within and nearby the ranch, including two wetland-dominated national wildlife refuges (Monte Visa NWR and Alamosa NWR) the sage-shrubland valley floor, piñon-juniper foothills, montane forest mountain slopes, and alpine tundra (not to mention the continent's tallest sand dunes.) Among the diverse ecological settings of the San Luis Valley and its surrounding mountains we will address the following questions:
What causes communities to have the avian constituents that they do?
What factors limit membership in bird communities?
How do member species partition the resources in their communities?
How is bird community ecology affected by humans?
Of course, we won't be sitting around a classroom with the windows closed talking all day- our class will be field-based and you can count on lots of great birding in a remote, under-visited (thank goodness!) part of the state. If you'd like more information, email me and I'll send you an itinerary or try to answer whatever questions you may have.

Check out the other 2008 IFO offerings, too- lots of great topics in great places with great instructors!

Friday, November 16, 2007

Banish Bird Bonks?

Bounce on over to David Sibley's blog to read about a potentially simple but effective way to reduce bird strikes on windows using fluorescent yellow highlighter pens. Basically, you can make a nearly invisible (to us) grid on the inside of your window with the highlighter (marking the outside works, too, but the highlighter will wash off when it rains.) The idea is that birds, with their visual acuity extending into near-UV wavelengths, can see the grid pattern and will veer off instead of colliding.

He & his kids have quantified some promising data from their experiments and have identified some other ideas to test- sounds like a great science fair project! Anyway, if this pans out it would be great to spread the word- windows kill on the order of nearly a billion birds in North America each year!

Great idea, David (& David's kids)! So if you have a bonk-prone window and haven't installed or don't want to install a Bird Screen , give the Sibley bird-repelling method a try & let David know how it works.

Sunday, November 04, 2007

Spark Birds

Jeff Gordon (aka Jeff Gyr) took advantage of a recent rainy day at the Cape May Hawk Watch platform to interview prominent birders gathered for the Cape May Autumn Weekend, asking them what their "spark bird" was. It is a great topic for conversation, and he got some great responses. Jeff featured a bunch of my photos in his podcast to illustrate the stories- thanks, Jeff! Click below to check it out.