Wednesday, October 04, 2006

Migrating Birds Nap Frequently

During migration, birds must travel long distances between their breeding and wintering grounds. The journeys frequently are thousands of miles from start to finish, and some birds may travel over 1,000 miles in nonstop flights. Some species travel during the day. Hawks, for example, glide from one thermal or updraft to another as they make their journey; these flying conditions are strongest during the day. Most birds, including songbirds and shorebirds, use more direct, powered flight. For such flights, the best conditions are at night, when heat is less intense and winds are weaker.

For this reason, many birds need to reverse their sleeping patterns during spring and fall. Instead of sleeping through the night and staying active during the day, they need to fly all night and then rest for the next flight during the day. Unfortunately migrating birds also need to eat, so the entire day cannot be spent sleeping.

It appears the solution is to take a series of cat naps during the course of a day. A study of caged Swainson's thrushes showed that sleeping patterns change during spring and autumn.

To find out how the birds get through these tiresome periods, scientists observed caged thrushes for an entire year, recording when and how long they slept. They found that during autumn and spring, when the birds are normally migrating, they reverse their typical sleep patterns, staying awake at night and resting during day.

But instead of sleeping for long stretches at a time, the birds took several naps a day, each one lasting only 9 seconds on average.

The thrushes also mixed up their shut-eye sessions with two other forms of sleep. In one, called unilateral eye closure, or UEC, the birds rested one eye and one half of their brains while their other eye and brain hemisphere remained open and active, keeping them semi-alert to danger.

The birds also occasionally slipped into another state, one that any college student who has ever been stuck in a boring lecture can relate to. Called drowsiness, this state is characterized by a partial shutting of both eyes that still allows for some visual processing.
(Thanks to squeakysoul for the tip.)

Tuesday, October 03, 2006

More Bad News for Wilson Bridge Eagles

A pair of bald eagles, nicknamed Martha and George, have nested near the Maryland side of the Wilson Bridge for several years. Despite the noise from heavy traffic and construction of a new bridge for the Beltway, they have maintained their nest and raised several chicks. Earlier in the year, Martha was severely injured in a fight with another female. As a result, she was taken to Delaware for rehabilitation, and her chicks died despite George's efforts to keep them alive. (See background here, here, here, here, and here.)

Martha is injured again, and this time her outlook is not as good.

Baker said it was unknown whether the beloved Martha, whose story captured the nation's attention in the spring, will survive her latest setback. She suffered a dislocated elbow, a grave injury for an eagle.

"The wing injury is pretty serious stuff," said Glenn Therres, eagle biologist for Maryland's Department of Natural Resources. "It's not like a broken leg, like you can put it in a cast and it will heal up." Therres guessed that she flew into a power line or tree branch during a recent storm.

She has been taken back to the Tri-State Bird Rescue and Research center in Delaware, where she recuperated from her other injuries this year. Specialists are deciding whether to send her to a special facility in Minnesota for surgery or to wrap the wing and hope it heals, Baker said.

It sounds like she may be spending the rest of her life in a wildlife rehab center. Such centers provide care and a safe home for the birds, and educational opportunities for the rest of us. Still it is sad to see wild birds unable to fly again, especially birds with the fierce wildness of raptors.

Update: Martha was euthanized due to her injuries.

Friday, September 29, 2006

Week in Review

This week's posts.

Sunday: A Dark and Birdy Afternoon

Monday: Birds of the Mid-Atlantic #24: Swainson's Thrush

Monday: Ivory-billed Woodpeckers in Florida

Tuesday: More Ivorybill Links

Wednesday: Editorial on the Ivorybill Paper

Thursday: I and the Bird #33

Thursday: Review: Birds of Shenandoah National Park, Blue Ridge Parkway, and Great Smoky Mountains National Park: A Field Guide

Friday: Loose Feathers #68

Loose Feathers #68

News and links about birds, birding, and the environment.

  • Some pollution regulators are starting to look at wildlife as significant sources of bacteria in the Potomac and Anacostia Rivers. Overpopulation by certain groups of mammals and birds leaves behind a tremendous amount of waste, just like human overpopulation leaves waste. This has been one justification given for Canada goose control in the District.
  • Smog has been reduced in the Washington area during the past 3 years; the number of Code Orange, Red, or Purple days fell from 114 in 1999-2002 to 63 in 2003-2006. That is the good news. Unfortunately for Washington residents, this is still well above what federal regulations mandate. Continued violation of clean air regulations could lead to sanctions and a loss of federal transportation funding. (If public transportation is included among the cuts, the sanctions could be counterproductive.)
  • Building a massive security fence across the southern U.S. border could disrupt the migrations of birds and mammals, especially ones whose northern range limit is in the U.S. Southwest. Birds that migrate at night could be disoriented by the bright floodlights planned for the fence.
  • More crowded nests lead to higher nestling mortality rates. When a nest is overcrowded, nestlings tend to fight for space and some end up falling out.
  • The Jamaica Environment Trust is looking to save Jamaica's remaining endemic species through the creation of 47 Important Bird Areas on the island.
  • Like it or not, wind power is probably here to stay. Demand for wind power as an alternative to coal has been growing in India and China.
  • A state judge in Connecticut ruled that monk parakeets are protected by law from capture and killing by power companies unless they have already tried nonlethal means of control. Monk parakeets cause problems for power companies by nesting on utility poles.
  • Here are some tips for distinguishing downy and hairy woodpeckers. I would add that the downy's trill goes down while the hairy's stays relatively level in pitch. Also check for spots on the tail; downies have them, but hairies do not.
  • Some teens in Montana are in trouble for smashing bluebird boxes.
  • Grace's Poppies, another DC blogger, has a post on the beauty of the National Arboretum.
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Thursday, September 28, 2006

Review: Birds of Shenandoah National Park, Blue Ridge Parkway, and Great Smoky Mountains National Park: A Field Guide

Birders today have a wealth of bird guides and other identification material to use on their trips into the field and for home study. Even as North American guides have continued to expand their coverage and have become more sophisticated, there has continued to be interest in guides with a narrower, more regional focus. A newly-published field guide profiles the bird species of a region close to me: Birds of Shenandoah National Park, Blue Ridge Parkway, and Great Smoky Mountains National Park. The book was written and organized by Ernest Preston Edwards.

As Edwards explains in his introduction, the Blue Ridge is an interesting area ecologically due to its rapid changes in elevation. Variations in the landscape encourage avian diversity. While southern bird species inhabit the lower elevations, a few miles away one may find some northern species at the tops of the ridges. Several species can be found breeding in the Mid-Atlantic at such higher elevations. There have been 336 species recorded in the area covered by this book.

Aside from a brief introduction that includes maps of the book's coverage and a diagram of bird topography, the bulk of the book consists of species accounts and plates. The descriptions and plates accompany each other on facing pages. Species accounts include the English and scientific names, a brief description of characteristic plumages, and notes on habitat and locations to find the species. Specific locations are rarely given; the note simply states whether to look along Skyline Drive, the Blue Ridge Parkway, or the Great Smoky Mountains National Park. Rare species and vagrants are placed at the very end of the book, for reference and to signal that these are relatively unlikely. There are no range maps. In a continental guide, the lack of maps would be a major drawback, but in a small regional guide, they are probably unnecessary.

The illustrations are mostly reprinted from a work by the same principal author and illustrator: A Field Guide to the Birds of Mexico and Adjacent Areas. A small number were contributed by Ramiel Papish and F.P. Bennett. The authors chose to use painted illustrations rather than photographs. While photographic guides have been improving lately, especially with the publication of highly-detailed guides to specific familes, illustrations are still largely the best choice for general field guides that cover all species in a given area. The illustrations are competently done and show the salient markings. Male and female forms are shown for sexually dimorphic species, and immature forms are shown for species where there is a major difference from adult plumages. While most illustrations are in color, some - particularly among the loons, grebes, some raptors, gulls, and terns - appear in black-and-white. For these species shape and pattern are generally more important than color.

This guide's illustrations do not quite measure up artistically to those in the Sibley guides, which have set the standard for illustrated field guides. The colors in the illustrations tend to be duller than Sibley's. They are more in line with those in the National Geographic guide. Some birds also seem slightly misshapen. This is especially noticeable among the thrushes. Other family groups, such as the woodpeckers, are much better.

With all of the field guides to North American birds that already exist, one might reasonably ask if another one is really necessary. Someone who does a lot of travelling or demands a high level of detail for the tricky species and subspecies may be better off looking elsewhere. However, this guide will be of use to at least three groups of birders. Beginning and some intermediate birders who watch birds primarily in the southern Appalachians will find this guide useful because it narrows identifications down to the most likely species. One of the challenges of starting out birding is making such distinctions between common and rare birds. Since the guide is very small and lightweight, it can easily be carried into the field. For that reason, it may be good for backpackers who need to reduce weight as much as possible. While the guide is marketed for birders in the Appalachian Mountains of Virginia, North Carolina, Tennessee, and West Virginia, birders in the Mid-Atlantic region outside of the Appalachians may use this book profitably. Most species found in the Blue Ridge are present in other areas at one time or another during the year, and vice-versa. Unless you do a lot of birding along the shore, the regional focus should not be an obstacle.


Full citation:

Ernest Preston Edwards, Birds of Shenandoah National Park, Blue Ridge Parkway, and Great Smoky Mountains National Park: A Field Guide. Illustrations by Edward Murrell Butler, Ramiel Papish, and F.P. Bennett. Blacksburg, Virginia: McDonald and Woodward Publishing Company, 2006. Pp. x, 142; maps, illustrations, checklist, and index. $19.95 paper. ISBN: 0939923963.

To purchase:

Amazon

Crossposted at Blue Ridge Gazette.

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