Migratory Birds in Texas: Types, Timing, and Importance, Exams of Animal Biology

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By Clifford E. Shackelford, Edward R. Rozenburg,

W. Chuck Hunter and Mark W. Lockwood

The Migratory Birds

Who They Are And

Where They Are Going

Migration and

of Texas:

FOURTH EDITION

Cover art of migrating warblers by Rob Fleming.

Suggested Citation: Shackelford, C. E., E. R. Rozenburg, W. C. Hunter and M. W. Lockwood. 2005. Migration and the Migratory Birds of Texas: Who They Are and Where They Are Going. Texas Parks and Wildlife PWD BK W7000-511 (11/05). Booklet, 34pp.

This booklet is intended to be used by the general public as an introduction to bird migration in Texas. Common names follow the 7th edition of the AOU Check-list. Added modifiers in parentheses represent distinct subspecies. All lists are in phylogenetic order.

By Clifford E. Shackelford, Edward R. Rozenburg,

W. Chuck Hunter and Mark W. Lockwood

The Migratory Birds

Who They Are And

Where They Are Going

Migration and

of Texas:

FOURTH EDITION

TABLE OF CONTENTS

SECTION 1 Questions and Answers on Migration 2

SECTION 2 The Migratory Flyways of North America

SECTION 3 Timing of Selected Spring Migrants

SECTION 4 Further Reading on Bird Migration

SECTION 5 Migratory Routes of Selected Species

SECTION 6 Grouping North American Birds by Migratory Status

SECTION 7 The Migratory Birds of Texas

SECTION 8 Lists of Trans-Gulf and Circum-Gulf Migrants

ii

What is migration?

Do all birds migrate?

Why do birds migrate?

Where do migrating birds go?

Migration is the cyclic or periodic travel of an animal as it returns eventually to its original place of departure. Migration is often annual and is closely linked with the cyclic pattern of the seasons. It is most evident among birds, which have a highly efficient means for traveling swiftly over long distances. The migration of most birds is a yearly cycle.

Not all birds migrate. The more severe the climate of an area, the greater percentage of nesting birds migrate. Two-thirds of bird species found in the United States migrate, some only short distances to more southern states. Those that do migrate have adaptations not seen in their non-migratory relatives. Migratory birds can build fat stores as an energy source for long flights. Migratory birds usually have longer, more pointed wings and weigh less than related non-migratory birds.

There are a number of explanations for migration: (1) Birds migrate to areas where food is more abundant, (2) there is less competition for nesting space, (3) the climate is milder, or (4) the daylight hours are longer. These enhance the chances of survival of a bird and its brood. Most birds require a rich, abundant supply of food at frequent intervals because of their high metabolic rate. Adequate food is not available throughout the year in most regions. North American birds must endure the hazards of winter or migrate to more friendly climates. In winter they migrate to the warmer, southern regions of the United States, Caribbean, Mexico, Central America and South America where food is abundant. In the spring, these birds fly north to habitats where spring and summer provide more food production and less competition for food and nesting sites than in their winter habitat. Summertime at northern latitudes also means more daylight hours to seek food for themselves and their nestlings.

Many nesting birds in Canada and the northern United States fly south to the tier of states along the Gulf of Mexico where the winter climate is more favorable and food is abundant. More than 330 species of birds that nest in the United States and Canada migrate to the West Indies or Central and South America. The principal wintering area for Neotropical Migrants extends through Mexico and Central America to Panama; it has the highest density of winter bird residents in the world.

Questions and Answers on Migration

How fast do migrating birds fly?

How high do migrating birds fly?

What birds migrate during the day?

What birds migrate at night?

Do birds usually migrate in groups?

The speed of flight depends largely on the species and the type of terrain covered. Birds fly faster when migrating than otherwise. Birds seem to fly faster in spring migration than in the fall. Migrants fly faster over water than over land. The American Golden-Plover may fly over 2400 miles south over the Atlantic Ocean at nearly 60 mph. Common Loons are among the fastest flyers at nearly 70 mph. Woodcocks on the other hand, fly at just over 10 miles per hour. Birds migrating over land may make stops for food and rest.

Most migrants fly at low altitudes, usually below 7400 feet. Small birds migrating at night fly between 800-1600 feet. In the daytime they fly much lower, often below 200 feet. Some fly much higher, the record is held by the Bar-headed Goose: 29,500 feet above sea level, over the Himalayas in India.

Swift, strong fliers and hunters are often daytime, or diurnal migrants. These include pelicans, herons, birds of prey, hummingbirds, swifts, swallows and finches. Some of these birds can feed on the wing.

Nighttime or nocturnal migrants usually are birds that live in thick vegetation and rarely venture out of it. They include waterbirds, cuckoos, flycatchers, thrushes, warblers, orioles and buntings. Nighttime movement gives them protection from their diurnal predators. They feed and rest by day to build up energy stores for their long-distance flights at night.

Most birds are gregarious during migration, even those that are usually solitary at other times such as insectivores and birds of prey. Birds, such as shorebirds and waterfowl, with similar habits often migrate together. Migrating flocks will often show remarkable cohesion. Traveling in large groups provides safety for individual birds by confusing predators and making it difficult to pick out a specific victim. A characteristic migratory formation is the ‘V’ of geese, ducks, pelicans, and cranes with the point turned in the direction of flight.

How well can birds navigate?

What do birds use for orientation and navigation?

How do birds navigate at night?

Do birds use landmarks to navigate?

Migrants often return to breed in the same locality where they were hatched. This journey may cover thousands of miles over many types of terrain and through extremes of weather. Birds show an amazing ability to orient themselves and home in on their destination. Migrating birds have many potential cues for orientation and navigation between summer and winter habitats. They do not depend on any single navigational cue.

It has been demonstrated that birds use various guiding factors. These include topographic landmarks (mountains, valleys, rivers, coastlines), ecological factors (vegetation zones), and climatic changes (air masses differing in temperature and humidity). Birds have also demonstrated a compass sense. They are able to fly in a particular constant direction regardless of their starting point with respect to their destination. Birds have shown that they can relate a release point to their home area, determine which direction to take (orientation), then maintain that direction of flight (navigation). We presume this to be, in part, due to sensitivity to the intensity and direction of the earth’s magnetic field. Experiments have shown that the orientation of birds is also based on celestial bearings. They can use the sun as a point of orientation during the day and the stars at night. Birds can compensate for the movement of the sun throughout the day with an internal clock mechanism that seems to give them the ability to gauge the angle of the sun above the horizon.

Migrant birds that travel at night use the stars to determine their bearings. In clear weather, captive migrants head immediately in the proper direction using only the stars. They can orient themselves correctly to the arrangement of night skies projected on the dome of a planetarium. Birds apparently can determine their longitude and latitude by the position of the stars. Evidence also indicates that the glare of the moon can interfere with this orientation.

Many birds, especially diurnal migrants, can recognize the topography beneath them and can navigate using familiar landmarks. Some birds follow coastlines to avoid flying over large bodies of water. At times, many follow river valleys. River valleys are like highways offering direction and shelter and food when the birds land to rest. Some birds, such as hawks, that migrate by day concentrate along mountain ranges where they ride updrafts along the mountains.

How does the weather affect migration?

How did migration originate?

Why do birds fly to specific locations in the spring and

fall?

Weather is one of the chief external influences on migration. Cool air masses moving south in the fall can trigger migratory flight. Cool air brings high pressure, low or falling temperatures and winds moving in the direction of flight and clear skies. If the cool air meets warmer air, clouds, precipitation and fog may result. Fog, especially, causes birds to descend to the ground and cease migration. Sudden changes in the weather can be disastrous for birds. In the spring, a warm, moist mass of air (low pressure with higher or rising temperatures) moving north over the Gulf of Mexico can start a wave of migrating birds to move northward from the American Tropics or southern United States. A southward moving cold front meeting such a warm air mass can result in heavy rains and high winds. This can stop migration immediately or within 24 hours. These spring “fallouts” or “groundings” of migrants may occur when the migrating birds literally fall into sheltered areas seeking food and refuge. This can be disastrous if the migrants are forced down into the ocean drowning thousands of birds. Resumption of southerly winds and rising temperatures starts migration northward again.

The roots of the migratory habits of modern birds are believed to date back millions of years, and were tempered by environmental changes caused by the Ice Ages of the Quaternary period over the last 2,500,000 years. Migration, as is known among modern birds, probably developed gradually by stages. As the environment changed, some animals changed their habitat slightly, hardly leaving their home region. The movements of others were more erratic, moving toward more favorable places. These first stages of migration were stabilized by natural selection. As winters grew more severe, much of a given bird population probably perished rather than attempting to flee any unfavorable conditions. A fraction of this population probably sought more favorable conditions elsewhere. Natural selection favored the ‘migrants’ and migratory tendencies were retained.

In some cases, the original habitats were in present-day southern wintering areas. The birds developed a tendency to leave in spring to breed in territories to the north that were less crowded. Fall brought seasonal changes in weather and declining food supply in these newly settled regions. This forced the birds to migrate back to their former range for the winter. North American birds that originated in the tropics include hummingbirds, tyrant flycatchers, tanagers, wood warblers, orioles, and swifts. In recent

geological times these birds gradually spread northward as glacial ice receded and the continent became warmer. Other birds, such as plovers, ducks and geese, originally lived in what are now their northern breeding areas. Gradual climatic changes forced them to spend winters far to the south. Migrations appear to be the consequences of invasions or emigrations during which animals settle in new regions during part of the annual cycle, then return to the original region to complete the cycle. Migration patterns are not fixed. As climates change, migration routes change as well, causing birds to lengthen or shorten the routes, or to abandon them altogether.

There are many ecological implications of migration. The sequence of migratory movement is closely integrated with the annual cycle of ecosystems that are characterized by productivity fluctuations. The food resources of some regions could not be adequately exploited without bird populations moving. Migratory behavior occurs in species located at specific trophic levels where maximum fluctuation in food production occurs in both breeding and wintering regions. Many migrant birds avoid primary equatorial forests where productivity is usually constant throughout the year and food surpluses do not occur. They do, however, congregate in savannas where productivity varies with the seasons.

A coordinated sequence is apparent in the case of birds migrating from the northern Arctic regions to tropical winter regions; both life zones show broad fluctuations in productivity. In the Arctic, vegetation and animal production are very high during the summer. Ducks and shorebirds nest there in great numbers, exploiting the food resources. As winter comes, days shorten and food becomes scarce. The waterbirds migrate to southern climates where the rainy season has caused food production to increase to optimal levels. In winter, ducks and shorebirds concentrate in the most favorable areas and remain until spring when productivity there is lowest. By then, conditions at the breeding areas are again favorable for the birds. The life cycle of these birds is closely attuned with the productivity cycles in their breeding and winter habitats. The size of populations is controlled by the capacity of both habitats to sustain them.

The winter habitat of the “Lesser” Snow Goose is in the southeastern quarter of Texas. Combinations of mild weather, ample winter food supply and protection on numerous wildlife refuges in its wintering range, as well as the

Are there any ecological implications with migration?

How is migration coordinated with the seasons?

How do human activities affect migratory birds?

Do most migrants return after the winter?

Many birds perish during migration and the winter season. It is believed that less than half the birds that leave the nesting grounds in fall migration will return the following spring. Migration over water is one of the most hazardous times for birds, especially small songbirds. Millions of migrating birds perish at sea. These are often young birds or birds that are blown off- shore or forced down by bad weather.

Wildlife experts study waterfowl populations intensively to set hunting seasons and limits. They have a good idea of how many waterfowl head south each fall, about 100 million. About 40 million return; hunters kill about 20 million and about 40 million fall victim to predation, accidents, environmental factors and disease.

How does migration benefit birds and the environment?

What are migratory bird treaties?

Migration has considerable ecological significance. It enables fast-moving animals to exploit fluctuating resources and to settle in areas where they could not live if incapable of rapid travel. On the other hand, peaks of food production would be unexploited without the periodic presence of migratory populations.

In 1918, the United States and Great Britain (for Canada) ratified the Migratory Bird Treaty that closed hunting for certain groups of birds that migrated across their mutual borders. Hunting was permanently closed on insectivorous birds and other non-game birds. Game birds (including ducks, geese and cranes) were given protection except for an annual hunting season that could not exceed three and a half months. Additional treaties were signed with Mexico (1936), Japan (1972), and the USSR (1976) protecting migrants between the United States and those countries. These treaties protect most naturally-occuring species, while most introduced species are not protected in the U.S. (e.g.,House Sparrow, European Starling and Rock Dove [feral pigeon]).

How does migration affect the bird life of Texas?

How are migratory birds important to man?

The upper coast of Texas is in a truly unique position to observe migration. The state occurs directly in the center of the Central Flyway. Most birds that move along this route travel through Texas and eventually through the Upper Coast of Texas. Birds traveling the Atlantic Flyway during the fall reach the Florida panhandle, then may turn west and follow the Gulf Coast to Texas. Birds of the Mississippi Flyway follow that great river system to the Gulf then either cross it or turn west as well. The Pacific Flyway funnels birds between the Rocky Mountains and the Pacific Ocean. The Rockies end at Big Bend in Texas. Birds may be funneled to Big Bend where they can cross over the state and follow the Rio Grande or other watercourses to the Coast. Texas has recorded over 615 species of birds, more than any other state. These are mostly migrant birds that have followed one or more of these flyways into our state.

Migratory birds have considerable economic impact in North America. Since European settlers first came to the New World, they hunted various birds, such as ducks and geese, rails, doves and shorebirds, for food and sport. During the late 19th century, many species were hunted to near extinction for the market as food and feathers for adornment on women’s hats. As their numbers dwindled, controls and seasons were instituted to stop their decline and stabilize the populations. Laws established to protect nongame birds and regulate hunting of game birds include the Migratory Bird Treaties mentioned above. Today, regulated hunting is a major industry in many areas of the United States. Most non-game birds were recognized to be welcome allies against insect pests. Most of the migratory birds of North America are insect eaters. Healthy, stable populations of these “songbirds” help to keep insect pests within tolerable limits. There are numerous instances where flocks of birds have descended on areas threatened with disastrous insect infestations and virtually eliminated the threat. All birds have increasing recreational value as birdwatching and other forms of nature related activities become more popular. Ecotourism, including birdwatching, camping, hiking, nature study and photography have become part of a multi-billion dollar industry. Throughout the United States, more people are engaged in nature tourism than either hunting or fishing. Together, hunting, fishing, and ecotourism are part of an industry that is worth over $100 billion annually in the United Sates alone. It pays in many ways to protect and maintain our natural assets.

Mississippi Flyway

Trans-Gulf Ci rc um

- G u l f

Atlantic Flyway

Island Route

Timing of Selected Spring Migrants

Early-season Examples

Mid-season Examples

Late-season Examples

American Golden-Plover early March to late April Chimney Swift late March to late April Ruby-throated Hummingbird late March to mid May Purple Martin mid February to early March

Northern Parula early March to mid April Black-throated Green Warbler late March to early May Yellow-throated Warbler early March to mid April Black-and-white Warbler early March to late April

Hudsonian Godwit mid April to the beginning of May Buff-breasted Sandpiper mid April to the beginning of May

Olive-sided Flycatcher early to late May Eastern Wood-Pewee late April to mid May “Traill’s” Flycatcher (Alder/Willow) early to late May Magnolia Warbler late April to mid May Blackburnian Warbler late April to mid May

Barn Swallow early March to early April

Yellow-billed Cuckoo mid April to mid May Golden-winged Warbler mid April to the beginning of May Cerulean Warbler mid April to the beginning of May

Bay-breasted Warbler late April to mid May

SPECIES APPROX. MIGRATION TIMING

These are selected examples and is in no way an

inclusive list; involves most of Texas

Further Reading on Bird Migration

This is in no way considered an inclusive list

Able, K. P. and S. A. Gauthreaux, Jr. 1975. Quantification of nocturnal passerine migration with a portable ceilometer. Condor 77:92-96. Able, Kenneth P. 1999. Gathering of Angels: Migrating Birds and Their Ecology. Cornell Univ. Press. 193 pp. DeGraaf, Richard M. and John H. Rappole. 1995. Neotropical Migratory Birds: Natural History, Distribution, and Population Change. Cornell Univ. Press. 676 pp. Ehrlich, P. R., D. S. Dobkin and D. Wheye. 1988. The birder’s handbook. Fireside books, New York, NY. 785 pp. Elphick, Jonathan (editor). 1995. The Atlas of Bird Migration: Tracing the Journeys of the World’s Birds. Random House Publ. 180 pp. Finch, D. M. and P. W. Stangel. 1992. Status and management of Neotropical migratory birds. USDA Forest Service, General Technical Report RM-229. 422 pp. Fisher, A. C. 1979. Mysteries of bird migration. National Geographic Magazine, August, pp. 154-193. Gauthreaux, Jr., S. A. 1996. Historical perspectives in bird migration: methodologies and major research trajectories (1945-1995). Condor 98:442-453. Gauthreaux, Jr., S. A. 1979. Priorities in bird migration studies. Auk 96:813-815. Gauthreaux, Jr., S. A. 1972. Behavioral responses of migrating birds to daylight and darkness: a radar and direct visual study. Wilson Bulletin 84:136-148. Gill, F. B. 1990. Ornithology. W.H. Freeman, New York, NY. 660 pp. Greenberg, Russell and Jamie Reaser. 1995. Bring Back the Birds: What you can do to save threatened species. Stackpole Books. 312 pp. Hagan, J. M. and D. W. Johnston. 1992. Ecology and conservation of Neotropical migrant landbirds. Smithsonian Press, Washington, DC. 609 pp.