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Just this morning, I received an e-mail from The Cornell Lab of Ornithology announcing a new Great Blue Heron nest cam (they also have a Red-tailed Hawk nest cam this season). The nest is on the property at the Lab's "Sapsucker Woods" campus. In addition to point-blank nest views, the nest cam provides an audio feed so you can hear various other birds calling and singing in the background. It should be fun trying to pick out warbler songs over the next few weeks.
The best feature of the nest cam site is a live chat stream, which allows for a fun exchange among the many folks who are watching. Questions come fast and furious as some of those watching admit to knowing very little about birds. During the 4-5 minutes that I followed the chat stream there were questions/discussions about plumes, incubation, sexing the adults, and a resident Canada Goose named "Sweetie."
The questions and answers about plumes included mention of plume hunting and how that was in part responsible for the formation of the The National Audubon Society. Some chat participants were unaware of the impacts of plume-hunting and how it inspired early bird conservation efforts.
On this day, it's cold and blustery in Ithaca, New York, so the moment-to-moment video and audio provided by the camera are a far cry from scintillating. One of the adults has been standing essentially motionless over a single egg (looks like an over-sized American Robin egg) as the wind ruffles its feathers. During the time that it took me to write this short article, the adult heron has moved just twice. First it turned to face the opposite direction, stepping on the egg briefly as it did so and then, finally, it sat down on the egg.
Despite the general lack of activity in the nest, the chat remains lively. In addition to feeding our voyeuristic nature, this nest cam fosters a wonderful opportunity for birders and non-birders to share and learn together in real time. Over the next several weeks I will likely be one of many who pop in occasionally to see what the birds are doing and sample what everyone is talking about. I can't wait to see the baby herons and hear their incessant "walla walla walla" vocalizations.
Editors Note: This is the first in a series of short articles that will explore the various flight styles employed by different groups of birds.
Albatrosses, petrels, and shearwaters (the tubenoses) are highly adapted to lives spent mostly on the wing over vast windy expanses of water. For centuries humans have been awed by their capacity to cover great distances without exerting much apparent effort and yet, a clear understanding of the aerodynamics that make this possible is comparatively recent.
In simple terms, tubenoses take advantage of the differences in wind speed (wind gradient) at various heights over the ocean's surface as well as the wind speed differences on the windward and leeward sides of each swell. Though we perceive wind speeds to be fairly constant, the ground speed of air masses vary with altitude. Friction near the ground or water surface translates to a loss of wind speed. Conversely, the wind speed increases with altitude as surface friction is reduced. Dynamic soaring is possible because seabirds are able to extract energy as they move between air masses with different wind speeds. Radio controlled glider enthusiastic Joe Wurts, who is widely credited with being the first to understand and demonstrate how dynamic soaring works, offered this description.(http://illumin.usc.edu/189/dynamic-soaring)
Let's say the bird is flying at about 40 mph, and the wind is 10 mph. When the bird is going downwind, the airspeed 'of the Bird' is 40 mph, but the ground speed is 50 due to the 10 mph tailwind. Now the bird gets close to the ocean surface where the wind is less, let's say 5 mph. It keeps its groundspeed of 50 mph but since the tailwind is only 5 mph, it has 45 mph airspeed. It turns around, keeping the 45 mph airspeed, and now is heading upwind at 45 mph, with 40 mph groundspeed. It then climbs into the stronger headwind, and keeps the groundspeed of 40 mph, but with the wind of 10 mph, it is now at 50 mph airspeed. It then turns around and repeats the process.
Click on the link below to see Joe Wurts doing a demonstration of dynamic soaring with one of his radio-controlled gliders.
Click on the link below to see Joe Wurts doing a demonstration of dynamic soaring with one of his radio-controlled gliders.
As seabirds bank in and out of air masses with different ground speeds there is a net speed gain, which allows them keep moving along an invisible axis running down the middle of their arcing flight path with no additional input of propulsion (wingbeats). As birds bank up out of the calmer leeward side of the swell they use the added wind speed coming off the windward face of the wave to launch upwards and repeat this cycle using gravity and tailwind to pick up speed on the downward arc. When winds are heaviest, albatrosses and smaller tubenoses may go for long periods without a single wingbeat, while the smaller short-winged shearwaters, petrels, and storm-petrels often make a few quick flaps in between glides. Other birds, like White-throated Swifts (long arcing glides along rimrocks) and pelicans and gulls (gliding along nearshore waves), may be seen using their own versions of dynamic soaring, particularly during periods of heavy wind.
Definition of terms:
Ground Speed -- The speed of an airborne object in relation to the ground. In the case of the birds and planes it is the combination of airspeed and windspeed.
Air Speed -- The speed of an airborne object relative to the air it is moving through.
Wind Shear -- A change in wind speed or direction along a straight line.
On 9 March 2012 a Black-throated Gray Warbler was reported from Bandon State Natural Area on Oregon's south coast. There was modest debate on the local listserv over whether this bird was overwintering or, perhaps, an early northbound migrant. I was in the overwintering camp.
Just a week earlier, I was melding together the Oregon and Washington sections of the Fall 2011 report for North American Birds when I noted that my co-editor, Brad Waggoner, had characterized a November 1st Black-throated Gray at Vancouver, Washington as being "a month tardy."
It's important to note that Brad lives on Puget Sound about 180 miles north of where this bird was seen. Vancouver is just across the Columbia River from Portland, where I live. Since low numbers of Black-throated Grays are still passing through Oregon during the first two weeks of October, I would have described this bird as being about two weeks late.
These discussions, which involved highly experienced birders, demonstrate that each of us has unique notions about the migratory timing of Black-throated Gray Warblers. These perceptions are shaped by where we live and our own set of experiences with this species.
My experiences with migrant Black-throated Gray Warblers have come primarily from the Willamette Valley in western Oregon. In the southern end of the valley–where I lived from 1984-86 and from 1998-2010–the first northbound Black-throated Grays would appear in during the first few days of April. Skinner Butte in downtown Eugene would almost always yield the earliest sightings for the valley and often for the entire state, in part because it gets daily coverage from late March through May. The first reports Portland (110 miles to the north) would come several days later, usually not until about the 10th of April or later. The fall migration of warblers through Oregon is diffuse and there are rarely weather systems that create noticeable fallouts. Along the outer, coast the southbound "passage" of warblers borders on undetectable. In the interior lowlands, focused efforts along riparian corridors, especially those bordering north-south running waterways will produced small mixed flocks of migrants that usually include a few Black-throated Grays until about 15 October.
Since my ideas about the migratory timing of this species were not the same as other equally experienced observers, I decided to compare my perceptions about Black-throated Grays with the data that one can easily mine from the eBird database. Here's what I found.
At a glance, the three maps above, which show the distribution Black-throated Gray Warbler reports for January, February, and March are remarkably similar. Compare these to the April map at the top of the article, which shows a major influx of Black-throated Grays all along the Pacific Coast during that month.
We can also look at the year-long bar graphs, which offer better resolution of what happens within each month. The bar and line graphs below provide a closer look at the migration timing in Northern California, Oregon, and Washington.
One of things that is exposed in looking at these graphic representations is that the spring migration of Black-throated Gray Warbler is incremental in nature. When we think about migration, we are captivated by those species that make long trans-oceanic crossings and non-stop flights that extend for multiple days. By contrast, the migrations of many passerines involve a more protracted series of short hops. In looking at the bar graphs above, it is apparent that the first influx of northbound Black-throated Gray Warblers Northern California about two weeks or more before they reach Washington. The southern end of the area represented by this set of graphs is approximately 500 miles to the south of the southern border of Washington. If we break down this distance as it relates to the number of days (about 15) between arrival dates at each end of this 500-mile divide, it translates to about 30-40 miles of northbound flight per day. Surely, this is an over-simplification, but the data does suggest that Black-throated Grays are either coming north in a series of short flights or making longer hops and then stopping to rest and feed for multiple days along the way.
In the end, this exploration confirmed my thoughts about what constitutes "early" and "late" in Oregon. More importantly, it demonstrated that the perceptions of my colleagues are equally valid given the experiences one would have living where they live.
Several months ago, this journal published an article entitled Creating a "Social Field Guide." Our mission is to make the BirdFellow Social Field the best place on the web to learn about birds and for our Social Field Guide to be the centerpiece of our online content. Believe it or not, you can contribute.
The first step is to create your BirdFellow account, which is free! Once you've created your private online workspace you'll have a place where you can store bird photos, keep lists, and write field report narratives about the birding trips you take. While we encourage folks to engage with the community, we offer customized privacy settings that allow you select how "public" you want your activities to be. Most folks want to share photos and potentially see their images included in our curated galleries of "Identification Photos."
We constantly "mine" our "Community Photo" galleries–the photos that BirdFellow users share publicly–for images that fill needs in our curated galleries. Our aim is to offer a comprehensive set of photos for each species that features all the varied plumages and subspecies for that particular bird. If you happen to add a photo to our community gallery that shows a plumage or subspecies that we don't have, we will ask your permission to add it to our curated gallery. Just this morning, I was reviewing our Community Photos for White-crowned Sparrow and found four images that I added to our Identification Photos gallery for that species.
Finally, you can add a "Field Note" to any species page (see example above). If you think that you've learned or discovered a behavioral or plumage clue that might help others more easily identify a particular species, we invite you to share it with the community. Printed field guides are great, but they are no match for the knowledge acquired through our collective birding experiences. If enough folks think that your Field Note is helpful and useful, we will incorporate it into our species account.
We invite you to create an account and start contributing to the BirdFellow Social Field Guide today.