Thursday, November 17, 2011

Raptors in the Valley

Every trip to the Rio Grande Valley of Texas produces wonderful memories and many specialty bird species but being a bit of a raptor fanatic I was especially excited by the great variety of raptors I spotted last Saturday AM before boarding a plane and flying home on my brief visit to the Rio Grande Valley Bird Festival.

Osprey feeding on fish in field near Lagun Atascosa NWR, TX 11-12-11

In all, I saw 15 species of raptors including "honorary raptors" Turkey & Black Vultures. The Osprey above was feeding on a fish carcass when a Turkey Vulture winged in below looking for scraps. The Osprey wasn't about to give up and after a wicked stare down returned to eating its prize.

Turkey Vulture looking for scraps 11-12-11 near Laguna Atascosa NWR, TX

The day started both dim and a bit dismal, so digiscoping was rough at first. At distance and without any direct lighting the birds above & below lack much detail and appear a bit soft.

female American Kestrel finishes off a mouse carcass near Harlingen, TX 11-12-11

As here in Florida, the wintering American Kestrels (smallest member of the falcon family in the US) had arrived in the lower valley in force. The female above fed on a mouse carcass on the dismal AM of the 12th. Note the difference a blue sky and a bit of direct lighting can make though on the male below.

male American Kestrel, digiscoped near Weslaco, TX 11-11-11

This adult male American Kestrel was digiscoped using the exact same equipment (Leica V-Lux 30 camera handheld behind an APO Televid 65 mm spotting scope) on the preceding AM, 11-11-11 and shows what a wonderful addition blue skies and direct lighting can be!

adult Red-tailed Hawk digiscoped with Leica APO Televid spotting scope & Leica V-Lux 30

Some of the Red-tailed Hawks like the adult above, resembled Eastern race birds (Buteo jamaicensis borealis) with lighter breast markings.

immature Red-tailed Hawk digiscoped near Weslaco, TX 11-11-11

Others like the heavily marked immature above were more typical of Western Red-taileds (B.j. calarus) though. This is one of the things that make birding here so fantastic, in migration and for breeding this area sits at the interface where East meets West so you have large numbers of representative species and races, and generally trip lists average higher than many other areas in the country.

adult Red-shouldered Hawk digiscoped near Harlingen, TX 11-12-11

The adult Red-shouldered Hawk above I would have expected to have been a member of the "Texas" subspecies (Buteo lineatus texanus) here between Harlingen & Brownsville, but it looks a whole lot like the femalem"Alleni" race (B.l. alleni), I see near my home in Florida with the lighter brownish-gray head and face. I'll have to ask raptor expert and valley resident, Bill Clark, about plumage variation and distribution of texanus v. alleni!

adult Harris' Hawk, digiscoped near Laguna Vista, TX 11-12-11

The sun finally shown near mid morning and vieiwng & subsequent picture quality rose with it. The Harlan's Hawk, adult above was one of many seen out in the south Texas coastal prairie habitat that is so good for so many specialty raptors found in the region.

adult pair of Harris' Hawks digiscoped near Laguna Vista, TX 11-12-11

The pair of adults above offers a nice example of the reversed sexual size dimorphism shown by this and most other species of raptors. The larger female at right is showing a full crop (the distended bulge on her breast). Both are banded which is almost certainly some of Bill Clark's handiwork. He's doing a lot of research on these birds in this area.

adult White-tailed Hawk in poor light 11-12-11 digiscoped near Laguna Vista, TX

Another of the specialty raptors found in this habitat is the White-tailed Hawk, I think I saw 8 individuals this AM. This bird was in poor light earlier in the AM when intermittent sprinkles and dark gray clouds were present. Like many buteos and other raptors it seems that White-tailed Hawk males are slightly lighter in plumage than females. It's subtle but this is likely a female with the darker slaty-gray head and darker chin.

adult male White-tailed Hawk, digiscoped at distance 11-12-11 AM

The bird above is an adult male - note the more "pearl-gray" head (distinctly lighter than the mantle/back color), and clean white throat. His mate was nearby with a very dark "hood".

immature White-tailed Hawk digiscoped early AM 11-12-11 near Los Fresnoa, TX

Immature White-taileds are wholly different with almost completely dark bodies except for the white oval on the breast. This youngster was one pole away from the pair above and was still begging for food! Kids today anyway... :)

White-tailed Kite, adult digiscoped near Harlingen, TX 11-11-11

I saw many White-tailed Kites on the 12th as well but didn't try to photograph these birds as I'd gotten great images of these in the days before closer to town. The images above and below were from the gloriously sunny morning of the 11th. These were formally called "Black-shouldered Kite" which is certainly appropriate.

White-tailed Kite, adult digiscoped near Harlingen, TX 11-11-11

The white tail is easily visible when the birds fly, but generally they are covered by the folded wings when perched. On the image above the wings are drooped enough to expose the pure white tail. I love how the red eyes are set in dark, smoky black feathering to reduce the glare from the highly reflective white body - just like football players use under their eyes.

adult Crested Caracara digiscoped through Leica Televid spotting scope

Crested Caracara are also commonly found in the coastal prairie habitat and I saw at least 6-7 individuals Saturday AM. Adults (as above) show darker black wings, bellies, backs & caps and brighter "soft parts" on the legs and base of the bill. Note the also the dark horizontal barring at the lower portion of the white back and breast.

immature & adult Crested Caracara in flight Rio Grande Valley -2008

Immature birds show browner back, wings, and belly; duller "soft parts", and show brown vertical streaks on the lower breast. Plus, immatures show a dusky undertail, the adult is neat white with a distinct black terminal band. The image above was from an earlier visit to the valley in 2008 but shows an adult (upper left) and immature (lower right) Crested Caracara in flight together. Perhaps you can note the differences in coloration. Note also the distinctive 4 points of white on both birds just inside the end of each extremity - just inside each wing tip, the face, throat, breast and upper back, and then the base of the tail. Caracara's are a unique bird that are technically classified as a falcon even though they lack most typical family characteristics.

adult male Aplomado Falcon digiscoped at great distance >250 yards 11-12-11

The crowned jewel of this area though has to be the lovely & elegant Aplomado Falcon after searching long & hard I was finally able to stumble across a distant pair teed up on a nesting platform in the last minutes before heading for the airport and my flight home. The male is in view & the female was just out of sight to the left here. The distance made this barely even worthy of description as a records shot - that is one to document I at least saw the bird. I was still pleased as punch to see this bird at all and have seen them much better in the past. I ran into 3 others looking for this bird puzzling over a distant adult Peregrine Falcon when I spotted this bird. It was there first time seeing this amazing critter, which is being reintroduced to this area at present. They are still a rare treat and their markings are stunning. This male was unbanded so it was not a bird released in this area, but as to whether it's progeny of introduced birds or a wandering individual who found his way here from Mexico one can only guess.

adult male Aplomado Falcon, digiscoped @ Laguna Atascosa NWR, TX 2004

This is an image of the first Aplomado Falcon I saw well near this same area in Laguna Atascosa NWR during the amazing Rio Grande Bird Festival back in 2004. It was fun to relive the excitement I felt at this moment with these three folks with binoculars I'd run into on this dirt road... Birding is so cool!

Sunday, May 15, 2011

the troubles with Red-shouldereds...

I digiscoped all of the images of the Red-shouldered Hawks in this post, within one mile of my house in the state of Florida, USA between November 2010 and May 2011. Looking at these you can conclude that, "the guy must live in pretty good Red-shouldered Hawk habitat." Probably true, but particularly when you look at the three images in the collage above, you also likely noted how very different these birds can look! To some degree this great range of plumage variation can be merely dismissed by understanding the distribution of the varying races or subspecies of Red-shouldered Hawk that can occur in Florida.

At far left above we see the "Florida" Red-shouldered Hawk (Buteo lineatus extimus). It is the palest race and is seen at the left on the image above. It is resident in the lower 1/3rd of the Florida peninsula from near Lake Okechobee south. The darkest eastern subspecies, the "nominate" (B. l. lineatus) is at far right above. They breed from Maine and very southern Ontario south to northern South Carolina and Oklahoma respectively. These birds migrate south in the winter though and at least some of the birds reach the Northern edge of the "Florida" Red-shouldered's range. As you can see I saw at least one of these birds in my neighborhood between Fort Myers & Sarasota this winter.

The light extreme of the extimus race (above) is easily separable from the dark nominate form (lineatus) below. Note the darker head and richer orange on the breast markings of the nominate vs. the extreme pale head and seemingly bleached out breast markings of the south Florida bird. I liken these two to a full-on redhead vs. a strawberry blonde, respectively.

Unfortunately, the simplicity of separation isn't quite so straight forward as there is another recognized subspecies (B. l. alleni) that sits right between these two in both plumage characters and range. Alleni is believed to resident from the southern half of South Carolina south throughout much of Florida and west across all of Mississippi, Alabama, and Louisiana and then reaching the extreme northern gulf coast of Texas (being replaced by the resident Texas race B. l. texanus). Confused?!? - you should be as it's not that easy.

The popular & primary (scientific) literature describe these three Eastern subspecies pretty much as I have. To over simplify, '...lineatus the darkest, ...extimus the lightest, ...alleni in between...' Unfortunately, it seems all of the tomes, specialty guides, and papers all fail to mention an obvious "fly in the ointment" here. From personal observation and few discussions with other raptor junkies it seems that plumages of males and females within each race show consistent and predictable differences in coloration (dimorphism). As seen in the shot above, males (left with smaller feet) are always lighter headed and paler through the breast than females (right, larger). This seems to be consistent on pairs I've seen and I believe this is probably the rule rather than the exception.

With all of this variation in race and given the apparently consistent sexual dimorphism shown, it seems near impossible to assign a sub-specific name to all of the birds I see, but it doesn't stop me from guessing. The bird above is clearly a local breeder. It is on the same pole as the bird at top center (and I believe it is the same individual), but the bottom image was taken just last week and the top last winter. Given the size of the legs and toes, I believe this is a smaller male. Given that it is intermediate in plumage (not extremely light as male extimus), I'd guess it is a member of the intermediate alleni race. Of course, this can't be proven yet. Stay tuned if you're inquisitive though, as I will be offering more on this subject soon!