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BIRD MIGRATION

Bird Habitats

Birds were the major survivors of the KT meteor, and have become the most populous and most varied of the major animal species. They hang around in huge "family" groups as flocks. There are relatively few direct peer predators. Mammals predate eggs in the nest and the  young.  Snapping turtles predate young waterfowl. 

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The evolution of birds can be tracked  through their structure differences that reflect  their adaptation to environment and diet. The ability to perch in trees ("Passarines") has led to a particularly prolific adaptation to life in temperate forests consisting of 60% of bird species. Non-perchers have evolved with features adapted for life on the river, ice, oceans, grasslands, and all types of trees. 

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Their number and variety of birds mean that they have filled every available niche. 

There are few omnivores in the bird world. The big predator Birds of Prey will dine on pretty much anything that moves. Others that thrive in the urban world include; grackles, pigeons, crows. 

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Presumably as a result of the competitive pressure, the rest resort to being  specialized in housing, migration, and  eaters - eat what no one else is eating. Darwin's insight from the finches in the Galapagos was focused on the evolution of beak design  that he could link to their diet. 

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The available habitats and some of the iconic species are; 

  • Ice                                  Penguins

  • Temperate forest        Passerines, Birds Of Prey, Woodpeckers.

  • Tropical Rain Forest    Tropic birds, finches,  parrots (macaw, parakeet),  hoatzin, toucan.

  • Grassland                     Ostrich, emu

  • Divers                            kingfishers, cormorants

  • Waters edge                 Oystercatchers, curlew

  • Waders                         Herons etc.

  • Waterfowl,                    Ducks

  • Seabirds                        Pelicans, Albatross, Boobies, gulls.

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The temperate forest and riverine are the most prolific environments.

 

Birds are also very selective breeders, mostly with females selecting their mates based on specific artistic features (blue feet in boobies), dancing skills (grebes),  song quality (songbirds), nest building skills (weaver birds) or even design of romancing spaces (bower birds). Some birds are monogamous, others change every season. 

 

There are 25 different  perchers or  Passarines that are seen routinely in the Austin area. There are  5 members of the same "Piranga" family ; northern cardinal, dicksissel, blue grosbeak, painted bunting,  and indigo bunting who are often seen in the same location and have a common diet of seeds. Their favorite  habitats and migration patterns overlap. Family members can produce fertile cross breeds. However there is no evidence of cross breeding, supporting the idea that for birds the  females choice of mate is based on "looks" and skills, rather than the males who will bonk anyone who is around ! 

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The tropical rain forest is home to the most spectacular examples of colorful birds presumably because of the challenges getting attention in dense foliage. 

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Migration

Picky eaters have to live somewhere that food is available all year round such as the tropics, or they have to migrate to follow their food choice over the seasons. There are 2 migration choices, within the same hemisphere, or all the way between similar latitudes in the northern and southern hemisphere.  In all around 1,800 out of about 10,000 bird species or 20% migrate.

 

Within the same hemisphere, 50% of N American species breed over the summer in the northern Boreal Forest or Canadian conifer belt, and fly south for the summer.  These include warblers, thrushes, flycatcher, sparrows, hawks.  Specific examples include; Pacific Loon, Barrows Goldeneye, Wooping Crane, Several Warblers, Snow geese. Landbirds have a flight range of around 2,500 km (1,600 mi) and shorebirds can fly up to 4,000 km (2,500 mi).

 

Trans-hemisphere migrants are rarer. The bar-tailed godwit is capable of non-stop flights of up to 10,200 km (6,300 mi).[171] Seabirds also undertake long migrations, the longest annual migration being those of sooty shearwaters, which nest in New Zealand and Chile and spend the northern summer feeding in the North Pacific off Japan, Alaska and California, an annual round trip of 64,000 km (39,800 mi).

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East Asia Flyway

Arctic through Asia Coast to Antarctica - Short Tailed Shearwater, American Golden Plover,

Arctic through Indonesia to Australia -  Spine Tailed Swift, Japanese Snipe, Eastern Curlew

Arctic through Borneo to Australia - Eastern Curlew

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US  Flyway

Arctic through Nova Scotia to Argentina  - American Golden Plover

Arctic through NY to N. Brazil - Blackpool warbler, warblers galore

Arctic through Caribbean to Argentina - Bobolink

Canada through Corpus to Belize - Ruby throated hummingbird

Dakotas through Corpus/AZ to Amazon - Swainsons Hawk.

Arctic through Colorado, Central America to Brazil - Tennessee Warbler

Arctic  through CA and Central America  to Brazil - Cliff Swallow

Arctic along CA coast to Antarctica - Arctic Tern 

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Key spots

New York in Mid May  - Warblers galore

Brownsville TX Late May  - Warblers, Tanagers, Orioles

Corpus TX Late Sept - Hawk watch 

SF Headland CA Late Sept - Hawks

San Diego CA Mid May and Sept - assorted warblers, flycatcher, orioles

Malaga SW Spain in April - eagles, warblers.

Ethiopia  in Feb - large range 

Aqaba, in April - warblers, wheatears, eagles

Crocodile island Luxor i n late March to early April - warblers pipits, eagles.

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Austin area Passarines 

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Structurally distinct non-Passarines (non-perching toes)

  • Ostriches, emus, cassowaries,  

  • Chickens  

  • Ducks, geese, swans, and similar waterfowl

  • Flamingos & Grebes 

  • Pidgeon, grouse, quail, turkeys, and pheasants

  • Rails, moorhens, coots, and similar pond-swimmers

  • Cranes, herons, ibises, egrets, other wading birds

  • Gulls, terns

  • Nighthawks and nightjars

  • Hummingbirds 

  • Tropicbirds  

  • Loons, albatrosses, shearwaters, skuas, petrels, and other seabirds

  • Penguins, auks, and puffins

  • Storks

  • Cormorants & Boobies

  • Pelicans  

  • Hawks, eagles, owls, falcons -  "Birds Of Prey"  

  • Kingfishers and rollers   

  • Woodpeckers, toucans & hornbills, and barbets

  • Parrots, macaws, parakeets, and budgerigars

Passarines  (perching toes)

  • Flycatchers

  • Shrikes

  • Vireos

  • Crows, Jays

  • Larks

  • Swallows

  • Chickadees, Titmice

  • Verdin

  • Bushtit

  • Nuthatches

  • Creepers

  • Wrens

  • Dippers

  • Kinglets

  • Wren-tit

  • Gnatcatchers

  • Leaf Warblers

  • Grassbirds

  • Thrushes

  • Mockingbirds, Thrashers

  • Bulbuls

  • Starlings

  • Accentors

  • Wagtails, Pipits

  • Waxwings

  • Phenopepia

  • Longspurs, Snow Buntings

  • Warblers

  • Bananaquit

  • Tanagers

  • Towhees, Sparrows

  • Cardinals, Grosbeaks, Buntings, Dicksissel

  • Boblink, Blackbirds, Grackles, Meadowlarks, Orioles

  • Finches, 

  • Weavers

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England matrix

BOP - Kestrel

Local -  European Robin (insects)  - Bearded tit, Firecrest 

Perchers -  Thrush 

Divers - Common kingfisher

Waders - Herons

Edge - godwit

Waterfowl - Swan 

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Food - Apples -  Cardinals, Tanagers, Thrush

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Magnetic sensitivity of cryptochrome 4 from a migratory songbird

Nature volume 594, pages535–540 (2021) 

Abstract : Night-migratory songbirds are remarkably proficient navigators1. Flying alone and often over great distances, they use various directional cues including, crucially, a light-dependent magnetic compass2,3. The mechanism of this compass has been suggested to rely on the quantum spin dynamics of photoinduced radical pairs in cryptochrome flavoproteins located in the retinas of the birds4,5,6,7. Here we show that the photochemistry of cryptochrome 4 (CRY4) from the night-migratory European robin (Erithacus rubecula) is magnetically sensitive in vitro, and more so than CRY4 from two non-migratory bird species, chicken (Gallus gallus) and pigeon (Columba livia). Site-specific mutations of ErCRY4 reveal the roles of four successive flavin–tryptophan radical pairs in generating magnetic field effects and in stabilizing potential signalling states in a way that could enable sensing and signalling functions to be independently optimized in night-migratory birds.

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​Robins have a protein in their eyes called cryptochrome 4 that reacts to blue light and Earth's magnetic field. When light hits the protein, it creates a pair of electrons whose chemistry shifts based on which direction the bird is facing—essentially giving the robin a built-in compass.

Klaus Schulten first proposed this idea in 1978, but the scientific community rejected it. Decades later, when researchers finally proved cryptochrome exists in animal eyes, Schulten said he "just fell off his chair."

In 2021, Jingjing Xu and Henrik Mouritsen's team in Oldenburg, working with Peter Hore's group at Oxford, confirmed the robin's version of the protein is magnetically sensitive. According to Mouritsen, the sensation might feel like "seeing where north is as kind of a shading on whatever else you would be seeing."

The weirdest part? The robins' compass stopped working inside wooden lab huts, scrambled by radio signals and nearby electronics. A grounded aluminum screen fixed it instantly. If researchers can prove the protein is truly the sensor, they'll have shown that birds navigate home using a fundamentally quantum mechanism.

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