Being the height of spring migration, we’re spending as much time as possible in the field. Weather conditions have determined that it will not be a great year for sighting Neotropical migrant songbirds along the Texas Gulf Coast (except for the fallout of 4/23!), but we have been seeing a few things of interest—notably Blackpoll Warblers, a Black-whiskered Vireo (Elisa only), and a Prairie Warbler at Lafitte’s Cove.
We’ve also been seeing a variety of interesting predator-prey interactions we’ve not seen before. Catching songbirds in the act of grabbing prey in the dense thickets of a place like Lafitte’s Cove is the supreme challenge of bird photography. The split-second timing of the action, coupled with contrasty lighting conditions and a myriad of obstructions really test your resolve.
Slightly less formidable, though still not easy, is documenting waders and divers grabbing and eating prey. I truly love watching these birds going about making a living.
Finally, we witnessed some survival of the fittest action in stark, brutal terms at the Smith Oaks Rookery, High Island.
Great Egret nestlings put on a show of pure Id as they attempted to jostle, push, or toss each other from their nests. One nasty little bird had its sibling by the scruff of the neck and attempted to toss it from the nest for a solid fifteen minutes. When it accepted that its nemesis was just as strong and heavy as it was, the aggressor cuddled up for warmth. Charming.
In less than two hours, I witnessed three displaced Great Egret nestlings being eaten by alligators. The Cain and Abel stuff probably tapers off for the night as the warming rays of the sun disappear.
Sometimes siblings can get in each other’s space. –Gisele Bundchen
Many great actions are committed in small struggles. –Victor Hugo
As I write this, we stand on the cusp of the best month of birding on the calendar! But for the past few weeks we’ve been (mostly) photographing our more typical species (year-’rounds, wintering or summering species) going about their business, not transients flying through from somewhere to somewhere else.
One of the more pleasant surprises of the past few weeks is the recognition that Brazos Bend State Park (BBSP) is starting to rebound a bit from the catastrophic floods of the recent past. It is still nowhere near the mecca for observing wader action that it was before, but day by day things are improving. It will be interesting to see if songbirds return for nesting in a big way. Elisa spotted a female Northern Cardinal building a nest just above water-line on Pilant Slough, and the trilling songs of Northern Parulas are everywhere. Can Prothonotary Warblers be far behind?
As noted, wader action at BBSP is still a bit down from the best of times, but the patient observer can still see a few things occasionally. Especially prominent now are the American Bitterns. Bitterns can be seen hunting all over BBSP. On our last visit, we observed one confrontation between two birds on Pilant Slough. Soon calling and confrontations should be common, only to die away by May.
In any case, starting today, we’ll shy away from BBSP for a few weeks and visit Galveston more. Hundreds of millions of songbirds have started streaming across the Gulf of Mexico, and we’re not going to miss it! With luck, we’ll capture some of these birds in action . . . Sipping from a flower, here, or grabbing a dragonfly, there. Can’t wait!
What we achieve inwardly will change outer reality. –Plutarch
This week on Galveston, Common Loons could be seen in many stages of transitional plumage. Every bird looked slightly different. All the birds I saw had some degree of spotting on the wings, and so lacked the brown, scalloped pattern of nonbreeding wing plumage. I saw one bird with a shaggy mane of pin feathers (Thanks to S.M. for pointing out this bird!) and one bird in almost complete breeding colors—only a stray feather here or there needed to be pigmented.
Many birds were engaged in hunting behavior much of the time. I saw fish, crabs, and a single mantis shrimp (Squilla empusa) being taken. This is clearly the time of year to be gorging and fattening up. It’s a long way back to Canada and environs for the breeding season! A good deal of preening was also going on, likely related to molting and keeping feathers in shape for the big trip ahead. Two birds had already pair-bonded and spent a significant amount of time together–another reminder that breeding in birds is often a process that unfolds in many stages over much of the year.
Feet, what do I need you for when I have wings to fly?—Frida Kahlo
Among extant birds, grebes have a unique method of foot propulsion. There are other foot-propelled divers, loons, for example, but these birds have significant webbing between the toes. The birds with webbed toes push themselves forward against the drag force of water. Grebes, on the other hand, have separate toes with stiff, collapsible asymmetrical lobes on each side. The lobes on the inside are larger than those on the outside. Grebes are also unusual in that their relatively short femora (thigh bones) are oriented perpendicular to the long axis of the body, and the toes beat along a complex dorso-lateral to ventro-medial path, rather than parallel to the direction of the body’s forward motion.
The traditional interpretation of how grebes paddled through the water, and the one I was taught, is that the lobes of the toes would unfold during then power stroke to provide maximum drag to push against, and fold up to reduce drag on the the recovery stroke. A more recent interpretation is that the grebe foot acts like a (slotted) hydrofoil and provides a lift force that propels the bird forward from behind (Johansson and Norberg, 2001)–physically similar to the way in which a wing allows a bird or airplane to fly. The lift hypothesis has an immediate visceral appeal to me given the asymmetrical lobes of the toes—like the vanes of a flight feather. Lift is usually explained by elementary physics textbooks as the result of the Bernoulli principle, essentially the conservation of energy for a moving fluid. This explanation is not correct quantitatively. The true explanation likely involves the most terrifying of all physics concepts . . . turbulence . . . .
As a photographer on the surface, I haven’t been able to document the strange way in which grebes move through the water. Once and a while, when conditions were right, I have been treated to a glimpse of the legs in motion as in the image below. Swimming with grebes is one more activity to add to an already lengthy bucket list.
I mentioned at the opening that grebes were unique among extant birds. Hesperornithiformes, a group of toothed Cretaceous foot-propelled diving birds, are thought to have had a method of propulsion similar to grebes and to have possessed asymmetrically lobed individual toes. On a recent visit to the New Mexico Museum of Natural History in Albuquerque, I had the opportunity to study the feet of a life-sized model of Hesperornis regalis, the largest of these Cretaceous divers from the Kansas Chalk Sea. Reading the label . . . sure enough, reconstruction supervised by Dr. L. D. Martin, my late (paleo)ornithology professor, a gifted teacher with so many fascinating stories to tell about the lives of birds. . . .
While grebe-watching, I am always interested in seeing these birds return to the surface with prey. In my experience along the Gulf Coast, Eared Grebes rarely return to the surface with prey. After dozens of dives, I have seen only one small fish clamped in a beak. This means that grebes are either remarkably unsuccessful hunters (unlikely), or that they can swallow small prey underwater (likely). Pied-billed and Least Grebes can be seen with large prey on the surface like fish, crawfish, frogs, and dragonflies. Perhaps small prey may be easily swallowed in the submarine realm, whereas large prey items may need to be manipulated into an ideal orientation in the air. In any case, grebes are certainly among the most interesting subjects for study and observation. Elisa doesn’t have to ask me twice to go grebe-watching!
Reference
Johansson, L.C., and Norberg, U. M. L. Norberg. 2001. Lift-based Paddling in Diving Grebe. The Journal of Experimental Biology204: 1687-1696.
Anhingas may spread their wings when underwater to lure fish into the shade their wings create, a hunting technique known as “canopy-feeding” that is also used by herons standing over the water.—Brinkley and Humann (2013)
Like cormorants, Anhingas can sometimes be seen, wings spread, drying their feathers on live trees and dead logs in or near water. Also like cormorants, Anhingas are skilled underwater fishers, and lucky observers can sometimes see these birds paddling past with fish. Anhingas, though, have sharp, dagger-like bills that they use as spears rather than meat hooks to snag.
Many a time I have waited patiently for an Anhinga to re-emerge after a dive—but they are only slightly more predictable than Pied-billed Grebes, and with or without prey, they are difficult to photograph while swimming past with their jerky, bobbing head motions.
While seeming like resident birds at places like Brazos Bend State Park, Texas Anhingas actually do migrate along the coast in the U.S., and to an extent, inland during summer.
Internet sources are riddled with “facts” about Anhingas that can be refuted by simple observation. These birds, for example, are said to lack preen glands, which is plainly not the case. They are also said to be unable to fly (or at best are poor flyers) with wet plumage, which is nonsense as they can often be seen taking off from the surface of water.
Anhingas are said to have feathers that saturate with water because of a lack of oils in the feathers. Brinkley and Humann (2013) indicated that this is not the case, however. Rather than lacking oils, the feathers have a fine structure that permits the penetration of water, resulting in low buoyancy and permitting a low swimming and fishing profile.
There is also much speculation about what Anhingas are up to when they are sunning themselves. Personally, I think it has to do with thermal physiology and grooming. After a big meal meal, Anhingas will climb from the water and sun themselves. Perhaps the warmth of the sun will speed the chemistry of digestion. Often they will also preen themselves by dipping their beaks into their preen glands and comb through their feathers with their oiled, finely crenulated beaks to keep plumage in fine aerodynamic and hydrodynamic condition.
The northeast corner of 40-acre Lake is a good spot to observe Anhingas spearfishing. Sometimes, if you look down into the water from the levee between 40-acre and Pliant Lakes, you can see them silently submarine past. This summer, from time to time, I plan to park myself here, perhaps seated on the bench, and try to improve my collection of Anhinga images.
Reference
Brinkley, Edward S., and Humann, Alec. 2013. Darters (Anhinga) in Elphick, C., Dunning, John B., Jr., Sibley, D. A. The Sibley Guide to Bird Life and Behavior. Alfred A. Knopf, New York. 588 p.
Sunny days (especially sunny weekend days) seem to be in short supply along the Texas Gulf Coast this winter. Happily, this weekend should be among those rare sunny occasions—so we’re headed to Brazos Bend State Park (BBSP) to see if we can spot the Least Grebes we saw just after the new year. Allow me take you back in time a few weeks . . . . New Year’s Day had come in with a grudge—weeks of damp and dreary days latched on like leeches and drained the life right out of us. So, when the first Sunday of 2015 rotated into place with a bright, sunny sky, we geared up and headed out, giddy with optimism.
We weren’t the only ones venturing out to take advantage of the weather. This Least Grebe with it’s powder-puff posterior aimed sunward was practicing “high-sterned sunbathing,” according to the literature (Well, that’s a polite way of putting it!). The skin exposed by raising the feathers on its back-side is black and thought to absorb solar radiation. It seems reasonable enough. While in this position, I observed the bird paddle its feet back and forth to produce a stationary “waggle,” which could be interpreted as at the bird’s way of distributing the heat more evenly. You can see faint ripple-marks produced by our rump-warming friend in the photo above.
The Least Grebe drew quite a crowd of onlookers along Pilant Slough at BBSP. Aside from being downright adorable, Least Grebes are infrequently seen in our neck of the woods. We usually see Pied-billed Grebes at BBSP. Although Pied-billed Grebes can be seen all over the US, Least Grebes are a tropical to sub-tropical species, and the Texas Gulf Coast populations are at the northern extremity of their typical permanent range. Even our mild Texas freezes can be fatal. As we left the park, I was excited to see two Least Grebes together. We’re hoping that they’re a mated pair and make it through our winter to raise a few broods!
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Do you see that out there? The strange unfamiliar light? It’s called the Sun. Let’s go and get us a little.” – Nora Roberts, The Hollow