Gulf Crossings

Movin' On

I have accepted a job at the Houston Arboretum and Nature Center, starting Oct. 8, 2007.  I'm not sure if this blog will be maintained, but I plan to start one at the Arboretum, and continue bird posts.  You can reach me at beley8 AT comcast.net.  Thanks for reading.

Grebes in Flight?

John Arvin, our Research Coordinator, casually asked yesterday if any of us had ever seen a grebe in flight.  Honestly, I'd never thought about it.  And, no I haven't.  And he doesn't know anyone who has (in 55 years of birding).  Grebes are obviously nocturnal migrants, and they have great difficulty taking flight.  The process involves a long run across the water, much like an airplane taxiing down the runway.  There are instances of migrating birds coming down on land, and being unable to take off again.  When disturbed, grebes dive under water.

As always, when confronted with this sort of question, I immediately went online to look for answers, in this case, photos of flying grebes.  I found two in an hour of searching, and one was barely large enough to identify.  The other was a Little Grebe from the Phillipines.  You can see that here.  It might be fun next spring to set up a camera near a pond with grebes, wait, and see if I can get lucky.

If you know of anyone who has a photo of a grebe in flight, I'd love to see it.  Please email me.

Bill

Photo by Greg Lavaty

What's Up With This Bird?

No, not the House Sparrow.  Perhaps you'll recognize the Common Redpoll on the right.  This bird showed up last week on the Bolivar Penninsula, just northeast of Galveston, TX.  Last week, as in "the middle of the summer."  This is the eighth documented record of C. Redpoll for Texas, and the second (or third) for the TX coast (both in the summer).  One of the first things we're tempted to do when an accidental shows up is to speculate on why it's there.  Usually one can speculate that the bird overshot migration, or is just a wanderer (whatever that means).  But what could cause a Redpoll to wander to the Texas coast in the middle of summer, while others are breeding in northern Canada?  Redpolls are known to experience irruptive cycles in response to food availability (but not this far south!). I'm not sure if a cycle happened this past winter.  Other northern finches show up in Texas, but rarely on the coast, and never in the summer.  At any rate, this bird should have flown the opposite direction last spring.  One might wonder if this bird (and the other summer record(s)) might have had some sort of illness or injury that messed up its compass.  Any other ideas out there?

Bill

How to do Bad Science

Recently, I was included (with a group of ex-grad school cohorts and colleagues) in an email thread begun by a prominent ornithologist at my alma mater.  In it, he refers to (and includes a PDF of) a recent paper published in the journal BioScience entitled "Changes in Bird Abundance in Eastern North America: Urban Sprawl and Global Footprint".  The authors and reviewers will remain nameless - you can look it up if you're curious.  However, let it be known that I wouldn't let a dermatologist do brain surgery on me, if you know what I mean.... The major conclusions of the paper are:

Overall, breeding bird species numbers in North America have declined 19% since 1965.  In addition:

Forest bird numbers are increasing.

Neotropical migrant bird numbers are increasing.

Birds that breed and winter in North America are decreasing.

Rock Doves and House Sparrows are declining significantly.

Hmm.  There seems to be something counter-intuitive about this.  Most of us have learned or studied the effects of forest fragmentation and the loss of forest habitat over the last 300 years in North America.  Fragmentation of forest exposes nesting birds to increased nest parasitism by Cowbirds, and increased predation by crows, jays, domestic cats, and raccoons, all of whom favor open habitats.  Evidence is mounting that neotropical migrant numbers are decreasing due to deforestation in the tropics, which is rampant and increasing.  Studies are currently being done which may point to the loss of stopover habitat in the southern U.S. as another cause of the decrease in populations of a number of migrant species.

To reach the conclusions listed above, Breeding Bird Survey data was analyzed from 1965 to 2005.  The entire basis for the analysis done was a table listing bird species from the Atlantic and Mississippi flyway.  Each species was catagorized by where it bred, and where it spent the boreal winter.  Fully resident in North America, migrate south to southern U.S., Mexico, northern South America and the Amazon basin, or migrate to southern South America.  Unfortunately, the table contained a significant amount of data that was just plain wrong.  Chestnut-backed Chickadee winters in Mexico?  The bird is a N. American resident, and occurs nowhere near the Atlantic or Mississippi flyway.  Canada Warbler a N. American resident?  The species winters in north and central South America.  Cape May Warbler winters in Amazonia?  Nope - the West Indies - no records for South America.  And so on.  Probably more than 20% of the table is wrong.  In addition, on BBS counts it is widely understood that common species will be recorded in large numbers, and this must be accounted for in any population trend study.

A classic case of using statistics on bad data and coming up with stupid conclusions.  Obviously the authors did not know much about the ranges of N. American birds (not sure what happened with the reviewers).  Unfortunately, the conclusions of this paper are now in the literature, and may influence conservation decisions.  Expect to see a retraction or major revision to this paper - none of the ornithologists I know are going to let it pass.

Bill

Another aspect to the "border fence"

There is a fine line between conservation work and environmental advocacy.  The mission of the Gulf Coast Bird Observatory has always been the study of birds and the conservation of their habitats around the Gulf of Mexico.  Our mission does not include taking positions on political issues.  The Audubon Society and many other organizations do a wonderful job fighting the battles to help save our environment through legislation.  However, a big part of our mission is to educate the public and raise awareness of issues that might affect wildlife.  I have posted in the past about the threat that coastal wind farms pose to migratory birds.  There is a new threat - more direct, more insidious, and fast-tracked to destroy a lot of irreplaceable habitat along the Rio Grande in south Texas.

Most everyone has heard of the new border fence that is supposed to stop illegal immigration from Mexico. So far, only a portion of the fence has been built in desolate areas with little valuable habitat.  A map was recently leaked by someone in Homeland Security that shows the proposed fence in the lower Rio Grande Valley. This map and the sources quoted there are from this article in the Daily Kos.  The proposed fence will plow through some of the most unique and valuable habitat in North America.

From the Kos article: "The first name given by Spanish explorers to the Rio Grande was the Rio de las Palmas, after the extensive forests of sabal palm trees there. Those forests are mostly gone now, replaced by grapefruit orchards, etc.  Only small patches of it remain, in sanctuaries and wildlife refuges, such as Sabal Palms run by the Audubon Society east of Brownsville, Texas.  The bird life at this southernmost point of the lower 48 has a Central American feel."

Many bird species from Mexico reach their northern limits here.  Plain Chachalaca, Green Jay, Hook-billed Kite, Brown Jay, Clay-colored Robin, Altamira Oriole, Great Kiskadee, and others.  The Valley, and its remaining habitat, is a meca for birders from around the world.  The string of wildlife refuges and preserves here, including Sabal Palm, Audubon Frontera Thicket, Santa Ana, and the World Birding Center at Bentson Rio Gande Park are the last refuges of these tropical birds in the U.S.  From the US Fish and Wildlife service website:  "Life tends to be richest at its borders. Here, on the international border between U.S. and Mexico, a host of nature's borders converge climate, community, land form and geography. Only 5% of the native landscape remains on the lower river and its nearby reaches, yet the diversity within these fragments adds up to an astonishing 1,200 types of plants, 700 species of vertebrates (including nearly 500 bird species) and 300 kinds of butterflies. You'll find 11 different biological communities, from the Chihuahuan thorn forest to tidal wetlands.  Numbers alone cannot depict the true value. A rare ocelot merges with the shadowy brush. A pair of crested caracaras glides above the river. A Mexican bluewing butterfly flutters into view, while great kiskadees cry an insistent "kis-ka-dee, kis-ka-dee". "

Unfortunately, anti-immigration zealots, as well as elements of Homeland Security don't seem to care about that.  Here is a description of this portion of the $49 billion fence:  "The Wall will be a double barrier with the first located 100' back from the Rio.  Though in some cases, local conditions will require a setback as far as 1000'.  There will be an "alley", 150 ft. wide, between the two fences.  All vegetation will be removed from the riverbank all the way back to a buffer zone inside the second fence, to enable better surveillance - 500+ feet minimum in all locations (from Kos)" 

Also from the Kos article: "The BP agent I  spoke to said the only way to make the fence "work" would be to completely remove all vegetation from the river shore, the space between the fences, and a buffer zone on the U.S. side of the innermost fence.  The current heavy vegetation found along the shore is the only way to prevent the river from eroding its banks.  There is a spot at the Butterfly Park where the heaviest vegetation has failed and in the last two years I have seen almost  10 feet of river bank slide into the water.  The fence, by its very location along the Rio Grande, would be situated on a flood plain and be subject to washing out in those areas, especially near the Gulf of Mexico, which are prone to hurricanes."  These statements are especially ironic, since the Fish and Wildlife Service, in concert with other groups, has spent millions of dollars of taxpayer money to protect this very habitat.

It appears that the Refuges are being targeted first since private landowners are ready to put up a determined fight against the eminent domain threats.  It is hard to relay the magnitude of this threat.  Regardless of your political leanings or feelings about immigration, if you care about wildlife habitat, and respect the years of work that conservationists have put into protecting this area, please oppose this fence.  It's an environmental disaster.

Bill

Altamira Oriole photo by Greg Lavaty
Fence photo from the website of Congressman Duncan Hunter (R-CA)

New Research on How Birds Orient Themselves During Migration

Researchers have long known that birds figure out where to go during migration by using a combination of the earth's magnetic fields, the stars, the sun, the moon, and polarized light pattern cues at the horizon at sunrise and sunset.  The exact nature of how each compass system integrates with the others, and how these systems are calibrated and recalibrated has been a mystery.  The magnetic compass changes with latitude, and others systems may be altered by weather or time of day.  To be effective despite these alterations, it would be necessary for all compasses to be calibrated to a common reference.

A paper published in Science magazine in August, 2006, "Polarized Light Cues Underlie Compass Calibration in Migratory Songbirds", by Muheim, Phillips, and Akesson provides experimental evidence that the polorized light cues at sunrise and sunset are the common reference that other systems calibrate to.  The actual reference value is an average of both sunrise and sunset cues.  These researchers were able to re-orient the magnetic compass of Savannah Sparrows by presenting a false polarized light cue.  Earlier orientation experiments often did not provide the birds a view of the horizon.  In these cases, the magnetic compass became the reference, and other systems were calibrated with respect to the magnetic field.  It is unknown if all species of birds use this same sequence of cues to orient in migration.  Future work will no doubt discover if this system is universal in birds, or if other combinations have evolved in different bird groups.

Bill

Photo of Colima Warbler by Greg Lavaty

Wind Farms in Spain

Here is a post from GCBO's Research Coordinator John Arvin:

I spent the previous two weeks in southern Spain and Gibraltar. This area is one of the most important bird migration corridors in the world because birds migrating between tropical Africa and western Europe are essentially squeezed into a narrow stream to cross the Mediterranean at its narrowest point. An outstanding feature of the migration in this area is that of raptors, storks, and other large bodied species that migrate using rising air currents to move by soaring to conserve energy. It is also an area of extensive wind energy production.

I was struck by how closely the situation there mirrors our own situation on the Gulf coast. We are also located in a globally important migration corridor with a strong component of migrating raptors. The latter is especially concentrated along the western Gulf coast where the flight path is narrow by virtue of being squeezed between the ocean and the north-south mountain chains in northern Mexico. It occurred to me that students of Gulf coast migration and conservationists could learn much about the interaction of large numbers of migrating birds and the wind energy schemes that are planned or actually under development along the Gulf coast, particularly the western Gulf coast of southern Texas.

I tried to meet with a local ornithologist who is a life-long student of the migration in the region of the Straits to talk about their experience but he was away. I will be establishing contact with him and probably other ornithologists in Spain to learn what I can from their experience since most of the published research on the subject of bird – wind turbine interaction has not been carried out in a major migration corridor.

Follow the Radar...

Here are five radial velocity radar images from the Gulf Coast today at around 12:30 pm.  With a south wind, this is about the time most birds arrive after crossing the Gulf.  Don't forget, however, that a lot of birds are circum-Gulf migrants - they fly northward around the east coast of Mexico instead of crossing water.  A sixth image show percipitation at Oklahoma City for comparison. 

Let's follow the radar around the Gulf:

Below is radar at Brownsville, TX on the Mexico border.  Note the northward movement of "stuff" parallel to the coast.  The scale on the right indicates the speed of any objects moving.  This should be compared to the wind speed.  The radar displays from ground level at the station, to around 10,000 ft. at its limit - 130 miles.  Most migrants under these conditions would be flying at about 4,000 ft.  The winds at Brownsville and Corpus at this altitude were about 30 kts, which explains the dark colors.  Birds flying would be measured at 30 kts, plus the speed of the bird.

Further up the coast at Corpus Christi, still paralleling the coast:

At Houston, showing the typical pattern of direct flight from the Gulf.  The wind speed was 7 kts - notice how much faster the "objects" here are moving.

Notice as we go eastward, the number of birds diminishes greatly. At New Orleans:

And, finally, Jacksonville, FL. Nothing much:

One last velocity image for comparison from Oklahoma City showing thunderstorms moving north northeast.

There you have it. If you'd like to check the images yourself anytime, they can be found Here .

Bill

Spring on the Upper Texas Coast

As spring migration draws to a close on the Upper Texas Coast, we pause to reflect on the unusual and the interesting. A Green-breasted Mango made an appearance at Sabine Woods, on the coast near the Louisiana border. Good photos can be seen here. There are 12 previous records of this Mexican hummingbird in the U.S., all in the lower Rio Grande Valley of Texas (except for two slightly up the coast near Corpus Christi, and one in North Carolina!). This bird generated a lot of discussion – Some suggested Green Violet-ear, and others cautioned that Black-throated Mango could not be ruled out. Take a look at the pictures and come to your own conclusion.

A Yellow-green Vireo was also seen at Sabine Woods. The sightings of this Mexican vireo in Texas have increased since it was first found in 1992. All records are in late spring, and probably represent “overshoots” – birds that migrate northward in Mexico and travel too far. Just down the coast a mile or so from Sabine Woods is a small grove of willows, about 50 yds. from the beach. These willows are a primary landing zone for many birds coming off of the Gulf. Several Cape May Warblers, a Townsend’s, and a possible Greater Pewee (pictured) were seen this spring. It is interesting that Cape May and Black-throated Blue are routinely found here and in Sabine Woods in the spring, but are extremely rare 15 miles or so down the coast at High Island. Both species are primarily eastern migrants (through Florida), as a majority of the birds winter in the Caribbean. However, some individuals do winter in Mexico, and these may be the birds seen on the Texas coast (but why not at High Island?). Alternately, a lot of sightings are after east winds – perhaps some eastern migrants are directed to the west with the winds.

I haven’t gotten the impression from anyone that bird numbers were down appreciably. Lots of folks had 20+ warbler species days, although I don’t think there were any spectacular fallouts. We may be approaching the day when bird numbers are low enough that these massive fallouts of migrants at coastal “fire-escapes” are almost a thing of the past. They are certainly much rarer now than they were when I started birding in the 70’s.

Bill

Photo by Greg Lavaty

The BigSit!

This past Sunday, the opening day of the Great Texas Birding Classic featured the BigSit! competition.  A team selects a prime spot, and reports all birds seen from within a 17 foot circle in 24 hours. Competitors are allowed to come and go, but cannot count any birds while not in the circle.  Our GCBO team utilizes a spot along a levee road at San Bernard National Wildlife Refuge, due south of Houston on the coast.  The refuge provided us a marsh buggy to sit on (about six feet high), which helped see stuff at a distance.  The levee separates a brackish marsh from a small woodlot.  Open water can be seen a ways out with a scope.

Our team totaled 103 species.  I haven't seen the other results yet, but I think the teams from south Texas did better.  We missed a lot of expected things, and had very few shorebirds and very few migrant passerines.  Since a north wind had been blowing since Saturday morning, we suspect that most of the migrants left the night before, although spots east of us like High Island reported tons of birds on the coast.  Most of the Friday night arrivals apparently were directed slightly eastward, as the wind shifted from the south, then the west, and then the north that night.

Best birds?  A Golden-fronted Woodpecker was very unexpected - only the second record for the upper Texas coast.  Raptors were scarce - Caracara, Broad-winged, Red-tailed, and Swainson's.  There were thousands of soaring Anhingas.  Lots of snakes and alligators.  Not much else of note.  It was a beautiful day, and I have the sunburn to prove it.

Bill

Photo by Greg Lavaty