LSC-CyFair

Bird Migration Tim Sebesta Dept. Chair of Exercise and Military Sciences Professor of Kinesiology LSC-CyFair

Golden-Crowned Kinglet

American Goldfinch

Yellow-Rumped Warbler

Ruby-Crowned Kinglet Eastern Phoebe

Orange-Crowned Warbler Cedar Waxwing Dark-Eyed Junco

Common Winter Birds in Houston Backyard

Migration Fun Facts •  The arctic tern flies a round trip that can be as long as 20,000 miles per

year, from the Arctic to the Antarctic and back. The sandhill and whooping cranes are both capable of migrating as far as 2,500 miles per year, and the barn swallow more than 6,000 miles.

•  How do they keep going? Some birds store a special, high-energy fat before the trip. Soaring raptors, for example, may not eat for several weeks as they migrate. Other species eat along their migration routes.

•  How high can they fly? Higher than Mt. Everest. Bar-headed geese have been recorded flying across the Himalayas at 29,000 feet. Other species seen above 20,000 feet include the whooper swan, the bar-tailed godwit, and the mallard duck. (Note: birds fly this high to reach their destinations efficiently. From radar studies, scientists know that birds can change altitudes to find the best wind conditions. To fight a headwind, most birds stay low, where ridges, trees and buildings slow the wind. To ride a tailwind, they get up high where the wind is as fast as possible.)

Migration Facts

•  778 are migratory •  300 species migrate to Latin America •  19 species of shorebirds migrate 8,000 miles

1 way •  34 species of wood warblers and 22 of the 29

species of waterfowl are shared between U.S., Canada, Mexico

Of the 852 bird species in the United States:

Migration Flyways •  The major wintering areas for North

American migrating birds are the southern United States and Central America.

•  Four major flyways south: the Atlantic flyway, the Mississippi flyway, the Central flyway, and the Pacific flyway.

How Did Bird Migration Routes Become Established?

•  Migration is affected not only by food supply, but also by wind and oceans currents. These make some routes and locations easier to reach. While many birds migrate from northern breeding areas in the summer, to southern wintering grounds (mainly because there is more land near the northern pole than the southern), there are many other migration patterns. Some birds breed in the far south of South America, Australasia and Africa, and migrate to northern wintering grounds. Some birds migrate horizontally, to enjoy the milder coastal climates in winter. Other birds migrate in terms of altitude; moving higher up a mountain in summer, and wintering on the lowlands.

Bird Migration Terminology •  Altitudinal migrant: a bird that migrates vertically, spending different seasons at different

elevations, but in the same geographical location. •  Breeding grounds: the habitat where a species nests and raises young. •  Circadian rhythm: an internal clock that governs a bird’s daily cycle •  Circannual rhythm: an internal clock that governs a bird’s yearly life cycle, triggering migration,

breeding etc. •  Diurnal migration: migration during the hours of daylight. •  Dynamic soaring: a fight pattern where a bird glides with the wind until it drops too low, then

climbs into the wing, turns and glides again. •  Fall: when weather forces large numbers of migratory birds off course and they come down to

rest somewhere that they do not normally occur. •  Flyway: a route that many migrating birds of various species use while migrating. A flyway may

be defined by a seacoast, a mountain range, a river system, an ocean current, or some other significant geographical feature that channels birds in flight.

•  Irruption: when large numbers of one or more species of birds move together to new territory in search of food. Irruption is not true migration.

•  Leading lines: physical features of the earth such as mountain passes, islands, and narrow necks of land that large numbers of birds must pass through or stop at.

•  Magnetic compass: the mechanism that allows a bird to navigate by locating magnetic north. •  Migrant: a migrating bird.

Bird Migration Terminology •  Nonstop migrant: a bird that completes its entire migration without stopping along the way.

Some nonstop migrations cover thousands of kilometers and span days. •  Nocturnal migration: migration during the hours of darkness. •  Partial migration: when part of a population of birds in a specific area migrate while the rest

remain resident year round. Sometimes, it is the juvenile birds that migrate. •  Pineal gland: a gland in the brain that controls the circadian rhythm of bird species. •  Staging post: stopovers where large numbers of migratory birds traditionally pause to feed

before moving on. The best known staging posts are those used by large birds such as cranes.

•  Star compass: the mechanism that allows a bird to find its way by the location of the stars. •  Stopover: a place where migrating birds stop to rest, shelter and feed. These are typically

places with abundant food supplies. •  Sun compass: the mechanism that allows a bird to find its way by the location of the sun. •  Thermal current: warm air rising into the atmosphere from the ground. Thermals are usually

strongest in the morning. •  Thermal soaring: when a bird uses the rising air of a thermal to lift it high in the air. The bird

can then glide down to the bottom of the next thermal and rise again. •  Wintering grounds: the territory where a bird species spends the winter months. •  Zugunruhe: a restlessness observed in birds as the time to migrate approaches.

Why Do Birds Migrate? •  The reasons are complex and not fully understood.

But a simple explanation is food and a safe place to breed. Birds which breed in the summer in the extreme north such as the Arctic benefit from an abundance of food as plants and insect life flourish in the long daylight hours; and because few large permanent predators can survive the harsh winter. Many birds that breed in the Arctic simply lay their eggs on the ground. Being able to fly, they can avoid the harsh winter conditions, and be the first to arrive to enjoy the summer benefits.

Western Sandpiper

Why Do Birds Migrate? •  Behavior is inherited; however, birds will not migrate in the

absence of certain physiological and environmental cues. In the late summer, the decrease in sunlight stimulates a migrating bird's pituitary gland to produce the hormone prolactin and its adrenal gland to produce the hormone corticosterone. These hormones, in turn, cause the birds to accumulate large amounts of fat just under the skin, providing them with enough energy for the long migratory flights. The hormones also cause the birds to become restless just prior to migration. The exact time of departure, however, is dictated not only by the decreasing sunlight and hormonal changes, but also by such conditions as the availability of food and the onset of cold weather.

When And How And Do Birds Migrate? Environment and Physiology Trigger Bird Migration •  Millions of migratory birds move from a warm winter range to a summer breeding range each

year. Some are so predictable that their arrival in the summer range can be forecast almost to the day. We know when to expect them from long experience, but how do birds know when it's time to migrate?

Circannual Rhythm and Daylight Trigger Migration •  Before a bird can migrate, it must be physically ready. In both spring and fall, birds put on

weight, storing fat in the body cavity and beneath the skin. Many molt, replacing flight feathers so that their feathers are in peak condition for extended flight. And they build flight muscles for strength and endurance.

•  These changes are brought on by a combination of the bird's circannual rhythm (a natural annual cycle), and the shift in the hours of daylight that signals a change of season. In general, shortening days affect hormone levels and induce birds to eat more, store more fat, increase muscle mass, and molt. Later, when these physical changes have taken place, hormones also cause restlessness immediately prior to departure.

•  The relationship between light and the circannual rhythm is complex: birds in captivity can be induced to go through their annual changes more quickly if light levels are manipulated, yet the rhythm still proceeds if light levels in captivity never change. Birds migrate north from the Southern Hemisphere, where days are getting shorter, from equatorial regions where the hours of daylight and darkness change very little, and from Central America and the southern United States, where days are growing longer. Similarly, birds that migrate south to breed may begin their journeys in places where the days are getting shorter or longer, depending on where they spend the winter.

When And How And Do Birds Migrate? Weather Influences Bird Migration •  Birds respond to weather conditions as well as light when deciding when to depart a

summer or winter range. An early spring with unusually warm temperatures can trigger early departure and early breeding. Likewise, extended bad weather or a cool spring can delay things.

•  Birds generally wait for good weather with favorable winds - they avoid rain, overcast conditions, and winds that might blow them off course. As a result, good weather triggers a wave of departures, with large groups of birds leaving at the same time and arriving at a stopover or destination together. Most will stop to feed or wait out bad weather before moving on with another wave of migrants.

•  Climate and location also heavily influence fall migration for birds in the higher latitudes. These birds arrive later, breed later, molt later, and leave later than the rest of the population.

Males Go First •  For some species, it's important for males to get a head start in spring in order to claim

good territory in the breeding range and be ready to attract good mates when females arrive. Departing males can either delay migration of the rest if they encounter bad conditions and return, or trigger an exodus if they leave and don't come back.

When And How And Do Birds Migrate? •  Birds tend to commence migration in large numbers only when they have a

favourable tail wind. In North America the winds north in spring and south in autumn are ideal to assist seasonal migrations. Once started however only very bad weather will stop them. Many birds fly high when migrating because of prevailing winds at higher altitudes and also because the cold at these altitudes helps them disperse all the heat being generated by their flight muscles.

•  Not all birds from a summer breeding site overwinter at the same area. What happens, come autumn, if a male bird meets a female bird in the breeding grounds who has a different overwintering site? Whose site do they go to now they are a pair? In many species the pair bond breaks up at the end of the breeding season, but some like swans mate for life. In the case of the Bewick's Swan the male decides where to fly to for the winter and the female follows him. However, the female decides when it is time to travel back to the tundra for another year's breeding.

•  The reverse scenario is when birds with different breeding sites overwinter in the same area; if pairing commences on the overwintering ground, whose breeding ground to they return to. The answer may be different for different species.

Bewick’s Swan

When And How And Do Birds Migrate? •  Timing of migration is a mix of internal stimulus which results in a

feeding binge to put on fat to survive the journey and then the tendency to aggregate into flocks. Once the pre-migration flock is gathered, the feeding continues while the birds wait for suitable weather conditions. Thus while the birds' internal clock probably releases the hormonal triggers at a fairly accurate date each year, the availability of food and the presiding weather conditions decide when the migration starts and hence when we see the first spring migrants arrive and the last autumn ones leave.

•  A 12-year study of Common Terns at Cape Cod showed that an average 75% of birds, and as much as 83%, returned to the same area to nest in successive years. Eighty percent nested within 25 feet of the original nest site. Another study of Layson Albatrosses showed that in the following year a nest was on average only 13 inches away from the previous nest.

When And How And Do Birds Migrate? •  Migratory routes are not fixed eternally and in some species part of the

population follows one route and part another. Also, some birds travel south by a different route to that which they use to travel north, e.g. Golden Plover.

•  Some migrants fly very long distances. Some arctic terns fly 11,000 miles each way. Other birds fly lesser distances. Blackpolls from Hudson Bay overwinter in Venezuela, 5,000 miles each way and Golden Plovers fly 2400 miles each way in the USA.

•  Speed - birds often fly faster when on a migratory flight then they do during ordinary flight. Thus distances of 200 to 400 miles a day are commonplace among long distance migrants. Some birds, however, migrate more slowly, e.g. Robins coming up the Gulf coast average 13 miles a day.

•  Most flights occur at between 600 and 5,000 ft above sea level with an average height of 1525 ft a.s.l. However, mountains may mean greater heights are needed and heights over 10,000 ft a.s.l. are not uncommon.

Golden Plover

How Do Birds Migrate Such Long Distances?

•  Birds exploit the winds to their favour so they can go the distance by burning minimal fuel. They may shift altitude to find the best wind "conveyor belt". Winds at high altitude may blow in the opposite direction from wind on the ground, and usually are blowing strongly. Larger birds rely on thermals (hot air) rising from the ground in the mornings to gain altitude by simply soaring. These birds usually migrate during the day. They may also follow strong updrafts along ridges.

•  A few birds fly non-stop, some for several days, covering enormous distances. But most birds break journey at staging posts. A vital aspect of being able to make such long trips is to lay down enough fat reserves.

•  Preparing for the journey: Besides laying down fat reserves, migrating birds also need to eat a lot to fuel their regular feather molts. Their feathers must be in tip-top condition for their long trips. Different species molt at different times; for most shorebirds it is just after breeding and before the migration to wintering grounds.

How Do Migrating Birds Find Their Way?

•  Studies suggest birds orientate themselves to the compass points using the position of the sun during the day, and the stars at night. They can also sense magnetic north. In addition they use other clues such as visual layout of the land, smell (of the sea), sound (waves on shores, winds through mountain passes).

•  The most amazing aspect of bird migration is that the location, route and perhaps even the techniques are hard-wired into their brains. Many migrating birds abandon their young as soon as they fledge, and a short time later, the young make the migration on their own.

Threats To Migrating Birds •  Sadly, in addition to surviving storms and bad weather,

exhaustion and other natural obstacles, migrating birds are increasingly face human threats. Habitat destruction that affects staging posts handicap their ability to re-fuel. These include draining wetlands, cutting down forests. Pollution of the sea, water and air also affects them. Migrating birds are also distracted and killed by lit-up skyscrapers, lighthouses and other unnatural man-made formations that mislead them. Sadly, many migrating birds are also hunted, for food and for sport.

Help Migratory Birds In Your Community

•  Because many birds use constellations for guidance, well-lit skyscrapers and communication towers provide misleading cues and lure birds away from the correct path. These man-made structures can sometimes cause them to circle for hours until they become disoriented, exhausted or stunned, leading to predation and death. You can help prevent this tragedy by encouraging cleaning crews, building management and security guards to turn off the lights in offices, especially during peak migration seasons, and by working with others in your community to address the proliferation of communications towers.

Help Migratory Birds – Be A Caring Consumer •  Much of the coffee we drink comes from Central and South America.

Traditional plantations grow coffee under a canopy of trees, which provides habitat needed by over-wintering birds. Increasingly, however, land is being cleared to grow coffee in full sun; this habitat loss, coupled with the alarming rate of summer habitat loss in the United States, is the most significant factor contributing to the decline in Neotropical migratory birds. You can help preserve critical winter habitats for birds such as the ruby-throated hummingbird, Baltimore oriole, Kentucky warbler, and swallow-tailed kite by purchasing only shade-grown coffee and cacao.

•  http://nationalzoo.si.edu/ConservationAndScience/MigratoryBirds/Coffee/Bird_Friendly/birdlist.cfm

Eliminate The Poisons In Your Yard •  Yet, we assume that the lawn and garden chemicals found on the shelves at hardware

stores are safe to use around birds (and people.) Take a close look at the labels. Too many popular pesticides are lethal to birds. And while many pesticides may not kill birds on contact, they can contaminate bird food (insects) and water.

•  What are the alternatives? Mechanical and biological techniques for pest control provide less hazardous options.

•  Website http://www.audubon.org/bird/pesticides/#Insecticides ACEPHATE (An organophosphate insecticide used in Orthene and other Products.) BENDIOCARB (A carbamate insecticide used in Ficam and other products.) CHLORPYRIFOS (Organophosphate used in Dursban, Dragon, Ortho-Klor, and other

products.) DIAZINON (Organophosphate used in Bonide Diazinon Soil Granules, Knox-Out, and other

products.) DIMETHOATE (Organophosphate used in Cygon and a variety of other products.) BRODIFACOUM (An anticoagulant rodenticide used in d-CON, Talon-G, and other products.) GLYPHOSATE (An alphatic herbicide used in Roundup and other products.)

Cat Predation •  Americans keep an estimated 60 million cats as pets. •  Scientific studies actually show that each year, cats kill hundreds of millions of migratory

songbirds. In 1990, researchers estimated that "outdoor" house cats and feral cats were responsible for killing nearly 78 million small mammals and birds annually.

•  University of Wisconsin ornithologist, Dr. Santley Temple estimates that 20-150 million songbirds are killed each year by rural cats in Wisconsin alone.

•  Cats are a serious threat to fledglings, birds roosting at night and birds on a nest. Research shows that de-clawing cats and bell collars do not prevent them from killing birds and other small animals. For healthy cats and wild birds, cats should not be allowed to roam free.

•  Work with your local humane society, veterinarians and state wildlife agency to enact and enforce free-roaming cat regulations.

Cat Collar with Bell To Reduce

Risk

Bird-Window Collisions •  Contemporary homes and modern office buildings often use insulated and reflective glass

to replace walls. These windows may be aesthetically pleasing to humans, but often they are lethal to birds. Unfortunately, many birds cannot distinguish the difference between real sky and a reflection of the sky in a window.

•  In the United States alone, Dr. Dan Klem of Muhlenberg College estimates that each year during migration 98 to 976 million birds fly full tilt into windows and are fatally injured.

•  Dr. Klem says we can minimize these collisions by breaking up the reflection on the outside of the window with a non-reflective window coating, window screens, flash tape and bird netting.

•  Life size animate "scares" (plastic falcons, owls and balloons) and falcon or owl silhouettes attached to windows with suction cups are not effective deterrents.

•  Planting trees and installing window awnings to block the sun from hitting the window may eliminate some reflection. Putting a bird feeder on or within a few feet of a window helps to slow birds down and lessen the effect of impact.

•  Migration isn't the only time homeowners have trouble with bird-window collisions. Birds may hit your windows during breeding season and in the winter too.

House Sparrows And Starlings •  Every Spring, birds that nest in cavities compete with each other for a

limited number of nest sites. The neotropical migrants that nest in cavities - purple martins, tree swallows and great-crested flycatchers - have adapted to competition from chickadees, titmice and woodpeckers.

•  The "rules of competition" changed around the turn of the century when we humans imported two European cavity nesting species: house sparrows and starlings.

•  House sparrows eliminate nest competitors by attacking the adults and killing the young when they are on the nest. Starlings eliminate nest competitors by taking over cavity nesting sites. Our native birds don't seem to be able to defend themselves from house sparrow and starling attacks. So, if you put up a nest box to help bluebirds, martins, chickadees, titmice, woodpecker, wrens or flycatchers, you must monitor the box and eliminate house sparrows and starlings.

Protect, Create and Restore Habitat •  Getting involved in migratory bird conservation here in the United States or in Latin America can

be as simple as writing a check, donating equipment or picking up a shovel. Many agencies and organizations that work to protect, create and restore breeding and wintering habitat for migratory birds are participating in Partners in Flight. You can get involved in this international effort by contacting any of the participants listed at the end of this booklet.

•  Then think about your lawn. How much lawn do you really need? •  Survey your yard for dead and dying trees. Top them so they don't fall on your house, but leave

the standing trunks and make a brush pile with the downed canopy. Dead trees and brush piles provide shelter, nest sites and food (insects) for migrating birds.

•  Providing water can be as simple as putting out a bird bath or as complicated as installing a pond with a creek and waterfall. Birds are attracted to water features that are shallow (less than 2" deep), clean (hosed out daily, sanitized with hot soapy water and bleach at least weekly) and noisy (the sound of dripping water is a magnet for songbirds). Water features are most effective when placed out in the open, where birds can see predators coming.

•  If you put out bird feeders, select a safe feeder and keep it clean. Polycarbonate plastic tube feeders are the easiest to clean. Use one kind of seed per feeder, don't use seed mixes. Wash seed, suet and fruit feeders in hot soapy water and chlorine bleach at least once a month. If you use a tray or bowl feeder, plan to sanitize it more often. To be sure your hummingbird feeders do not harm the birds.

•  You don't have to put out a bird feeder to provide food for our neotropical migrants. Landscape your yard with native evergreen and fruiting trees, shrubs, grasses and vines. Design your garden so that your plants flower and fruit throughout the spring, summer and fall.

Help Migratory Birds In Your Own Backyard

•  You can make your yard a stopover for migratory birds by providing them with some essentials: water (even just a shallow dish), cover (evergreens and brush piles), and berry-producing trees and shrubs (such as dogwoods, American holly, viburnums, American highbush cranberry, and serviceberry). To attract the insects that birds eat, mulch your leaves in a sheltered corner and don't deadhead flowers such as coneflowers, marigolds, cosmos, and sunflowers. Birds will feed on the seeds. You may also choose to put out a variety of seed feeders during migratory periods, along with cut or dried fruit.

•  Certification will require: –  At least 50% native plants –  Food for the wildlife year round,

preferably provided by plants. A feeder alone will not be considered.

–  Shelter for the wildlife, including: brushy plants, tall trees, shrubs, and wildflowers. Artificial shelter such as nest boxes, brush piles, rock piles, and bat houses may also be included.

–  Water in a useable, reliable form for the wildlife.

FOOD SOURCES: Natural or Supplemental

•  Identify the types of plants that provide fruits, nuts, berries, seeds, nectar and other materials that wildlife might eat. –  Acorns from oak trees –  Fruits attract numerous birds and small mammals –  Sunflower (Helianthus) provides seeds for many kinds

of birds –  Tubular flowers attract hummingbird species

FOOD SOURCES: Natural or Supplemental

•  Identify the types of plants that provide fruits, nuts, berries, seeds, nectar and other materials that wildlife might eat. –  Acorns from oak trees –  Fruits attract numerous birds and small mammals –  Sunflower (Helianthus) provides seeds for many kinds

of birds –  Tubular flowers attract hummingbird species

FOOD SOURCES: Natural •  Tall Trees

– Live Oak – Red Mulberry – Pecan

•  Small Trees – Yaupon – Mexican Plum – Shining Sumac

•  Shrubs – American

Beautyberry – Texas Wax Myrtle – Dewberry

•  Perennials – Turks’s Cap – Cardinal Flower – Shrimp Plant – Firecracker plant

FOOD SOURCES: Supplemental

WATER SOURCES: The Key Ingredient

SHELTER: Natural

SHELTER: Artificial

Wildscaping Tips: ■ Use native plants adapted to your local conditions that

provide the kind of food and cover wildlife require. ■ Recycle leaves, plant clippings and kitchen scraps into

compost and don’t bag grass clippings. ■ Conserve water. Irrigate in the early mornings or evenings to

reduce water waste. ■ Closely follow all label instructions when applying pesticides

and fertilizers, and try to minimize their use. For more information on creating your Habitat visit: www.tpwd.state.tx.us/wildscapes

How To Watch Spring Migratory Birds Along The Texas Coast

•  Plan to arrive after April 15 and before May 15 for the best birding. Make reservations at a central spot that will give you access to several birding areas along the coast.

•  Make High Island one of your main stops. Smith Oaks, a 122.2-acre sanctuary here, is one of the best-known migratory stopovers on the coast. Boy Scout Woods and Eubanks Woods are other excellent birding sites on High Island.

•  Consider Anahuac National Wildlife Refuge. Although this is better known as a wintering ground for thousands of ducks and geese, there are good numbers of birds here year-round. In spring, areas such as The Willows may serve as migrant traps for a variety of warblers and other birds.

•  Spend some time at the Bolivar Flats Shorebird Sanctuary on the Bolivar Peninsula. This is a great spot for regularly occurring shore birds, as well as migrants, and has been recognized as an internationally important site by the Western Hemisphere Shorebird Reserve Network. Bring a scope for the best views.

•  Stop at Aransas National Wildlife Refuge, best known as the wintering place of endangered whooping cranes. The cranes start to leave the refuge in early April to go north to nesting grounds in Canada, but there is still much to see here in migration.

•  Visit Laguna Atascosa National Wildlife Refuge. This area has plenty of varied habitats and can be a good migrant trap in spring, especially when the weather is bad.

•  Check your bird guides and maps for other birding locations on the upper Texas coast. Those mentioned are the most visited, but there are many more birding opportunities in the region.

Where To Go To View Migratory Birds

Texas Ornithological Society - http://www.texasbirds.org/ National Audubon Society - http://www.audubon.org/ American Birding Association - http://www.americanbirding.org/ American Bird Conservancy http://www.abcbirds.org/ World Birding Center - http://www.tpwd.state.tx.us/worldbirdingcenter/ Bird Links to the World (Texas)

http://www.bsc-eoc.org/links/links.jsp?page=l_usa_tx Houston Audubon Society - http://www.houstonaudubon.org/ Outdoor Nature Club - http://www.texasbirding.net/hog/ USGS - http://www.mbr-pwrc.usgs.gov/id/framlst/infocenter.html Enature - http://enature.com/birding/birding_home.asp Saturday Edition of the Houston Chronicle, Star Section, “Wonders of Nature” TEXBIRDS listserv - http://listserv.uh.edu/archives/texbirds.html http://www.texasbirding.net/maps/wharris.htm    

Sources Of Information About Migratory Birds

To keep current with efforts in migratory bird conservation, get on the mailing list for the free

Partners in Flight Newsletter http://www.partnersinflight.org/ (National Fish and Wildlife Foundation, 1120 Connecticut Ave. NW, Suite 900, Washington, DC 20036.) TEXAS Parks & Wildlife, 4200 Smith School Rd., Austin 78744