House sparrow

1
House sparrow
2
House sparrow

• Cool facts are provided by Cornell University
• The House Sparrow was introduced into Brooklyn,
  New York, in 1851. By 1900 it had spread to the
  Rocky Mountains. Its spread throughout the West
  was aided by additional introductions in San
  Francisco, California, and Salt Lake City, Utah.
• The House Sparrow has been present in North
  America long enough for evolution to have
  influenced their morphology. Populations in the
  north are larger than those in the south, as is
  generally true for native species (a relationship
  known as Bergman's Rule).
• Although not a water bird, the House Sparrow can
  swim if it needs to, such as to escape a
  predator. Sparrows caught in a trap over a water
  dish tried to escape by diving into the water and
  swimming underwater from one part of the trap to
  another.
• The House Sparrow is a frequent dust bather. It
  throws soil and dust over its body feathers, just
  as if it were bathing with water.

3
Rock Pigeon
4
Rock Pigeon

• Because of their domestic roots, and because
  people have bred pigeons for many different
  colors and adornments, feral Rock Pigeons can
  have a variety of plumages. For a description of
  the most common varieties, as described for
  PigeonWatch, go here.
• The Rock Pigeon makes a flimsy nest, but it often
  reuses the location repeatedly, building a new
  nest on top of the first. Because the pigeons do
  not try to remove the feces of their nestlings,
  the nest turns into a sturdy, potlike mound that
  gets larger month by month. Unhatched eggs and
  mummies of dead nestlings may also get cemented
  into the nest.
• The Rock Pigeon has such a long history of
  association with humans, having been used for
  food and entertainment for over 5,000 years, that
  the original range of the species is impossible
  to determine. Escaped (feral) pigeons from pigeon
  breeders readily form flocks, and wild birds may
  join them.
• Homing pigeons, domestic Rock Pigeons, are well
  known for their ability to find their way home
  from long distances. Despite these demonstrated
  abilities, wild Rock Pigeons are rather sedentary
  and rarely leave their local areas.
• You can help discover new information about Rock
  Pigeons by joining the Cornell Lab of
  Ornithology's PigeonWatch.

5

• European Starling

6
European Starling

• All the European Starlings in North America
  descended from 100 birds released in New York's
  Central Park in the early 1890s. A group
  dedicated to introducing America to all the birds
  mentioned in Shakespeare's works set the birds
  free. Today, European Starlings range from Alaska
  to Florida and northern Mexico, and their
  population is estimated at over 200 million
  birds.
• Although the sexes look very similar, they do
  show some subtle differences. The male tends to
  be larger, more iridescent, and have longer
  throat feathers, but some females can be larger,
  more glossy, and have longer feathers than some
  males. During breeding when they have yellow
  bills, the base of a male's lower mandible is
  blue-gray, while the female's is pinkish. The
  male's eyes are a uniform deep brown, but the
  female has a narrow, lighter colored ring around
  the outer edge. In confusing cases, some males
  four years old or older can develop a faint ring
  in the eye, and some older females can lose it.
• A female European Starling may try to lay an egg
  in the nest of another female. A female that
  tries this parasitic tactic often is one that
  could not get a mate early in the breeding
  season. The best females find mates and start
  laying early. The longer it takes to get started,
  the lower the probability of a nest's success.
  Those parasitic females may be trying to enhance
  their own breeding efforts during the time that
  they cannot breed on their own.

7
American Robin
8
American Robin

• Hundreds of thousands of American Robins can
  gather in a single winter roost. In summer,
  females sleep on the nests and males congregate
  in roosts. As young robins become independent,
  they join the males in the roost. Female adults
  go to the roosts only after they have finished
  nesting.
• The American Robin eats both fruit and
  invertebrates. Earthworms are important during
  the breeding season, but fruit is the main diet
  during winter. Robins eat different types of food
  depending on the time of day they eat earthworms
  early in the day and more fruit later in the day.
  Because the robin forages largely on lawns, it is
  vulnerable to pesticide poisoning and can be an
  important indicator of chemical pollution.
• An American Robin can produce three successful
  broods in one year. On average, though, only 40
  percent of nests successfully produce young. Only
  25 percent of those fledged young survive to
  November. From that point on, about half of the
  robins alive in any year will make it to the
  next. Despite the fact that a lucky robin can
  live to be 14 years old, the entire population
  turns over on average every six years.
• Although the appearance of a robin is considered
  a harbinger of spring, the American Robin
  actually spends the winter in much of its
  breeding range. However, because they spend less
  time in yards and congregate in large flocks
  during winter, you're much less likely to see
  them. The number of robins present in the
  northern parts of the range varies each year with
  the local conditions. For a discussion of how
  snow cover affects wintering robins, based on
  Great Backyard Bird Count data, click here and
  here.

9
Black-capped Chickadee
10
Black-capped chickadee

• The Black-Capped Chickadee hides seeds and other
  food items for later recovery. Each item is
  placed in a different spot and a bird can
  remember thousands of hiding places.
• The chickadee's simple-sounding calls have been
  found to be extremely complex and language-like.
  They code information on identity and recognition
  of other flocks as well as predator alarms and
  contact calls.
• Breeding pairs and nonbreeders join up into
  flocks outside of the breeding season.
  Nonbreeders may be members of several flocks,
  with a different position in the dominance
  hierarchy of each flock.

11

• Barn Swallow

12
Barn Swallow

• The Barn Swallow is the most abundant and widely
  distributed swallow species in the world. It
  breeds throughout the northern hemisphere and
  winters in much of the southern hemisphere.
• The long tail of a Barn Swallow may indicate the
  quality of the individual bird. Females prefer to
  mate with males that have the longest and most
  symmetrical tails.
• An unmated male Barn Swallow may kill the
  nestlings of a nesting pair. His actions often
  succeed in breaking up the pair and afford him
  the opportunity to mate with the female.

13

• American Crow

14
American Crow

• American Crows congregate in large numbers in
  winter to sleep in communal roosts. These roosts
  can be of a few hundred, several thousand, or
  even up to two million crows. Some roosts have
  been forming in the same general area for well
  over 100 years. In the last few decades some of
  these roosts have moved into urban areas where
  the noise and mess cause conflicts with people.
• Young American Crows do not breed until they are
  at least two years old, and most do not breed
  until they are four or more. In most, but not
  all, populations the young stay with their
  parents and help them raise young in subsequent
  years. Families may include up to 15 individuals
  and contain young from five different years.
• The American Crow appears to be the biggest
  victim of West Nile virus, a disease recently
  introduced to North America. Crows die within one
  week of infection, and few seem able to survive
  exposure. No other North American bird is dying
  at the same rate from the disease, and the loss
  of crows in some areas has been severe.
• In some areas, the American Crow has a double
  life. It maintains a territory year-round in
  which all members of its extended family live and
  forage together. But during much of the year,
  individual crows leave the home territory
  periodically. They join large flocks foraging at
  dumps and agricultural fields, and sleep in large
  roosts in winter. Family members go together to
  the flocks, but do not stay together in the
  crowd. A crow may spend part of the day at home
  with its family in town and the rest with a flock
  feeding on waste grain out in the country.
• Despite being a common exploiter of roadkill, the
  American Crow is not specialized to be a
  scavenger, and carrion is only a very small part
  of its diet. Its stout bill is not strong enough
  to break through the skin of even a gray
  squirrel. It must wait for something else to open
  a carcass or for the carcass to decompose and
  become tender enough to eat.

15
House finch
16
House Finch

• The House Finch was originally a bird of the
  southwestern United States and Mexico. In 1940 a
  small number of finches were turned loose on Long
  Island, New York, and they quickly started
  breeding. They spread across the entire eastern
  United States and southern Canada within the next
  50 years.
• The red or yellow color of a male House Finch
  comes from pigments that it gets in its food
  during molt. The more pigment in the food, the
  redder the male. Females prefer to mate with the
  reddest male they can find, perhaps assuring that
  they get a capable male who can find enough food
  to feed the nestlings.
• When nestling House Finches defecate, the feces
  are contained in a membranous sac, as in most
  birds. The parents eat the fecal sacs of the
  nestlings for about the first five days. In most
  songbird species, when the parents stop eating
  the sacs, they carry the sacs away and dispose of
  them. But House Finch parents do not remove them,
  and the sacs accumulate around the rim of the
  nest.

17
Dark-eyed Junco
18
Dark-eyed junco

• Juncos are the "snowbirds" of the middle
  latitudes. In the eastern United States, they
  appear in all but the most northern states only
  in the winter, and then retreat each spring. Some
  juncos in the Appalachian Mountains remain there
  all year round, breeding at the higher
  elevations. These residents have shorter wings
  than the migrants that join them each winter.
  Longer wings help the migrants fly long
  distances.
• The Dark-eyed Junco includes five forms that were
  once considered separate species. The
  "slate-colored junco" is the grayest, found from
  Alaska to Texas and eastward. The "Oregon junco"
  is boldly marked blackish and brown, with a
  distinct dark hood, and is found in the western
  half of the continent. The "gray-headed junco"
  has a brown back and gray sides and lives in the
  central Rocky Mountains. The "white-winged junco"
  is all gray with white wingbars, and breeds only
  near the Black Hills of South Dakota. The
  "Guadalupe junco" of Baja California is dull and
  brownish. Two other forms may be distinguishable
  the "pink-sided junco," a pale version of the
  Oregon junco, living in the northern Rocky
  Mountains, and the "red-backed junco," a
  gray-headed junco with a dark upper bill, found
  in mountains near the Mexican border.
• The Dark-eyed Junco is a common bird at winter
  bird feeders across North America. Data from
  Project FeederWatch show that it is often the
  most common feeder bird in an area, and it is on
  the top-ten lists of all regions except the
  Southeast and South-Central (where it is 11th and
  12th, respectively). To view the top-25 lists of
  feeder birds from across the continent, go to the
  Project FeederWatch Data Retrieval page.

19
Rufous hummingbird
20
Rufous Hummingbird

• The Rufous Hummingbird is a common visitor to
  hummingbird feeders. It is extremely territorial
  at all times of the year, and will aggressively
  attempt to drive away all other hummingbirds,
  including much larger species.
• The Rufous Hummingbird makes one of the longest
  migratory journeys of any bird in the world, as
  measured by body size. Its 3,900 mi (6,276 km)
  movement from Alaska to Mexico is equivalent to
  784,500 body lengths. In comparison, the 11,185
  mi (18,000 km) flight of the Arctic Tern is only
  514,286 body lengths.
• The Rufous Hummingbird has an excellent memory
  for location, no doubt assisting it to find
  flowers from day to day, or even from year to
  year. Some birds have been seen returning from
  migration and investigating where a feeder was
  the previous year, even though the feeder was
  currently absent.

21
White-crowned sparrow
22
White Crowned Sparrow

• Four of the five subspecies of White-crowned
  Sparrows are migratory. The sedentary race lives
  in a very narrow band along the California coast.
  The most widespread race, breeding across
  northern Canada and wintering in the eastern
  United States, is the least-studied and least
  well known of all the races.
• A young male White-crowned Sparrow learns the
  basics of the song it will sing as an adult
  during the first two or three months of its life.
  It does not learn directly from its father, but
  rather from the generalized song environment of
  its natal neighborhood.
• Because male White-crowned Sparrows learn the
  songs they grew up with and do not travel far
  from where they were raised, song dialects
  frequently form. Males on the edge of two
  dialects may be bilingual and able to sing both
  dialects.

23
Wilsons warbler
24
Wilsons Warbler

• The Wilson's Warbler is found in a large
  diversity of environments in the winter. It is
  the only migrant warbler regularly found in
  tropical high plains (paramo).
• The Wilson's Warbler trends toward brighter,
  richer coloration from the eastern part of the
  range to the west. The Pacific coast populations
  have the brightest yellow, even orangish,
  foreheads and faces. Western-central and Alaskan
  birds are slightly larger than the eastern and
  Pacific coast populations.

25
American Goldfinch
26
American Goldfinch

• The American Goldfinch changes from winter
  plumage to breeding plumage by a complete molt of
  its body feathers. It is the only member of its
  family to have this second molt in the spring
  all the other species have just one molt each
  year in the fall.
• The American Goldfinch is one of the latest
  nesting birds. It usually does not start until
  late June or early July, when most other
  songbirds are finishing with breeding. The late
  timing may be related to the availability of
  suitable nesting materials and seeds for feeding
  young.
• The American Goldfinch is gregarious throughout
  the year. In winter it is found almost
  exclusively in flocks. In the breeding season it
  feeds in small groups. Whether it maintains
  breeding territories is debatable.
• The American Goldfinch is mostly monogamous, but
  a number of females switch mates after producing
  a first brood. The first male takes care of the
  fledglings while the female goes off to start
  another brood with a different male.

27
Bald
Eagle
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Bald Eagle

• Humans are the most important source of mortality
  for this threatened species.
• The Bald Eagle isn't bald. The use of "bald" in
  its name is actually a shortening of the word
  "piebald," which describes something that is
  spotted or patchy, especially in black and white.
  Because the Bald Eagle has a dark brown body and
  a white head and tail, piebald is an apt
  description.
• Bald Eagles occasionally hunt cooperatively, with
  one individual flushing prey towards another.
• The immature Bald Eagle has a prolonged period of
  exploration lasting for four years. Some young
  from Florida have wandered north to Michigan, and
  birds from California have reached Alaska.

29
Barn Owl
30
Barn Owl

• Watch what happens inside a Barn Owl nest,
  through the help of a Nest Box Cam provided by
  The Birdhouse Network at the Cornell Lab of
  Ornithology. Currently there are active Barn Owl
  nests in California and Texas. Go here for
  pictures of the complete nest cycle from a nest
  in California in 2004.
• The female Barn Owl tends to be more spotted on
  the breast than the male. These spots may act as
  a stimulus to the male, indicating the quality of
  the female. If a female's spots were
  experimentally removed, her mate fed their
  nestlings at a lower rate than if the spots were
  left alone.
• Up to 46 different races of the Barn Owl have
  been described worldwide. The North American form
  is the largest, weighing more than twice as much
  as the smallest race from the Galapagos Islands.
• The Barn Owl is one of the few bird species with
  the female showier than the male. The female has
  a more reddish chest that is more heavily
  spotted. The spots may signal to a potential mate
  the quality of the female. Heavily spotted
  females get fewer parasitic flies and may be more
  resistant to parasites and diseases.
• The Barn Owl has excellent low-light vision, and
  can easily find prey at night by sight. But its
  ability to locate prey by sound alone is the best
  of any animal that has ever been tested. It can
  catch mice in complete darkness in the lab, or
  hidden by vegetation or snow out in the real
  world.

31
BewicksWren
32
Bewicks Wren

• The severe declines of Bewick's Wren in the
  eastern United States coincided with range
  expansion in the House Wren. It is suspected that
  the House Wren, which frequently removes eggs
  from nests in cavities, was directly responsible
  for the decline. The increased availability of
  nest boxes may have helped the spread of the
  House Wren, and therefore the decline of the
  Bewick's Wren.
• The male Bewick's Wren learns its song while
  still on the parents' territory. It learns the
  song not from its father, but rather from the
  neighboring territorial males. The song
  repertoire developed before the first winter is
  retained for life.

33
Brewers Blackbird
34
Brewers Blackbird

• The Brewer's Blackbird spread its range eastward
  from western Minnesota in the 20th century,
  taking advantage of human-produced changes in
  landscape. Where it overlaps with the Common
  Grackle, the blackbird takes over the open grassy
  areas, while the grackle dominates in urban and
  suburban areas.
• The Brewer's Blackbird nests in compact colonies,
  numbering from a few pairs to more than one
  hundred. Occasionally a pair will nest solitarily
  away from a colony. In the colony a female
  (sometimes aided by a male) defends a small area
  directly around her nest site.
• Within a colony most females choose the same kind
  of nest site, indicating that females follow the
  lead of the first nest builders. A colony may
  change its nest preference from year to year,
  building all nests in small bushes one year, and
  in tall trees the next.

35
California
Quail
36
California Quail

• The topknot looks like a single feather, but it
  is actually a cluster of six overlapping plumes.
• The California Quail digests vegetation with the
  help of protozoans in its intestine. Chicks
  acquire the protozoans by pecking at the feces of
  adults.
• Several California Quail broods may mix after
  hatching and are attended by all of the parents
  of those broods. Adults that engage in communal
  brooding live longer than adults that do not.
• Mated pairs call antiphonally they alternate
  calls and fit them into a specific pattern.
• Despite living in arid environments, the
  California Quail needs drinking water during
  periods of sustained heat. During cooler weather,
  it can get enough moisture from eating insects
  and succulent vegetation.

37

• Northern Flicker

38
Northern Flicker

• Although it can climb up the trunks of trees and
  hammer on wood like other woodpeckers, the
  Northern Flicker prefers to find food on the
  ground. Ants are its favorite food, and the
  flicker digs in the dirt to find them. It uses
  its long barbed tongue to lap up the ants.
• The red-shafted and yellow-shafted forms of the
  Northern Flicker formerly were considered
  different species. The two forms hybridize
  extensively in a wide zone from Alaska to the
  panhandle of Texas. A hybrid often has some
  traits from each of the two forms and some traits
  that are intermediate between them. The
  Red-shafted Flicker also hybridizes with the
  Gilded Flicker, but less frequently, and the
  Gilded Flicker is considered a separate species.
• The Northern Flicker is one of the few North
  American woodpeckers that is strongly migratory.
  Flickers in the northern parts of the range move
  south for the winter, although a few individuals
  often stay rather far north.

39
Red Breasted Nuthatch
40
Red-Breasted Nuthatch

• The Red-breasted Nuthatch applies sticky conifer
  resin globules to the entrance of its nest hole.
  It may carry the resin in its bill or on pieces
  of bark that it uses as an applicator. The male
  puts the resin primarily around the outside of
  the hole while the female puts it around the
  inside. The resin may help to keep out predators
  or competitors. The nuthatch avoids the resin by
  diving directly through the hole.
• During nest-building, the Red-breasted Nuthatch
  is aggressive towards many other bird species. It
  will chase away nest hole competitors such as the
  House Wren, White-breasted Nuthatch, and Downy
  Woodpecker. A particularly feisty nuthatch will
  also go after Yellow-rumped Warblers and House
  Finches. The nuthatch's aggressive tendencies
  subside after the nest is finished, although it
  remains aggressive towards potential predators
  and competitors.
• Red-breasted Nuthatches migrate southward earlier
  than many irruptive species. They may begin in
  early July and may reach their southernmost point
  by September or October.

41

• Red-tailed Hawk

42
Red-Tailed Hawk

• The "Harlan's Hawk" was once considered a
  separate species. It breeds in Alaska and
  northwestern Canada, and winters on the southern
  Great Plains. This very dark form has a marbled
  white, brown, and gray tail instead of a red one.
  Many individuals intermediate between Harlan's
  and more typical Red-tailed Hawks can be found.
• The raspy cry of the Red-tailed Hawk is used in
  movies to represent any eagle or hawk anywhere in
  the world.
• In the courtship display a pair of Red-tailed
  Hawks soars in wide circles at a great height.
  The male dives down in a steep drop, then shoots
  up again at nearly as steep an angle. He repeats
  this maneuver several times, then approaches the
  female from above. He extends his legs and
  touches or grasps her briefly. The pair may grab
  onto one other and may interlock their talons and
  spiral toward the ground.

43

• Spotted
• Towhee

44
Spotted Towhee

• Watch a Spotted Towhee feeding on the ground
  you'll probably observe its two-footed,
  backwards-scratching hop. This "double-scratching"
  is used by a number of towhee and sparrow
  species to unearth the seeds and small
  invertebrates they feed on. One Spotted Towhee
  with an unusable, injured foot was observed
  hopping and scratching with one foot.
• The Spotted Towhee hybridizes with the Eastern
  Towhee where their ranges meet in the Great
  Plains. It also hybridizes with the Collared
  Towhee where their ranges meet in Mexico.
• Twenty-one different subspecies of Spotted Towhee
  are recognized, three on islands off the Pacific
  Coast. The race from Isla Guadalupe off Baja
  California is extinct. The small race on the
  island of Socorro off Baja California and the
  larger race on Santa Catalina Island off southern
  California are vulnerable to extinction because
  of their restricted ranges. The Santa Catalina
  form formerly was found on San Clemente Island,
  but disappeared from there by 1976.

45

• The Song Sparrow

46
The Song Sparrow

• The Song Sparrow is found throughout most of
  North America, but different populations in
  different areas can look surprisingly different.
  Those found in the arid Southwest are lightly
  marked and pale while those in the Pacific
  Northwest are dark and heavily streaked. The
  sparrows found on the Aleutian Islands of Alaska
  are even darker, and are huge one-third longer
  than the eastern birds, and weighing twice as
  much.
• The range of the Song Sparrow is nearly
  continuous from the Aleutians to the eastern
  United States. However, the species is also found
  on the plateau of central Mexico, about 1500 km
  (930 mi) from the next closest population. The
  Song Sparrows of central Mexico have white
  throats and chests with black streaks.
• Despite the large morphological differences
  between populations of Song Sparrows, genetic
  divergence is rather low. High rates of dispersal
  and gene flow may keep the populations
  genetically similar, but local selective
  conditions maintain the physical differences.
• Like many other songbirds, the male Song Sparrow
  uses its song to attract mates as well as defend
  its territory. Laboratory studies have shown that
  the female Song Sparrow is attracted not just to
  the song itself, but to how well it reflects the
  ability of the male to learn. Males that used
  more learned components in their songs and that
  better matched their song tutors (the adult bird
  they learned their songs from) were preferred.
• The Song Sparrow, like most other North American
  breeding birds, uses increasing day length as a
  cue for when to come into breeding condition.
  But, other cues can be important too, such as
  local temperature and food abundance. A study
  found that male Song Sparrows from the coast of
  Washington state came into breeding condition two
  months earlier than Song Sparrows in the nearby
  mountains, where the daylight changes were the
  same, but temperatures were cooler and trees
  budded out two months later.

47
Stellers Jay
48
Stellars Jay

• The Steller's Jay and the Blue Jay are the only
  New World jays that use mud in the construction
  of their nests.
• The Steller's Jay shows a great deal of variation
  in appearance throughout its range, with some
  populations featuring black crests and backs, and
  others blue. One black-crested form in southern
  Mexico is surrounded by eight other blue-crested
  forms.
• The Steller's Jay periodically irrupts away from
  its normal range. Most of these far-ranging
  individuals appear to be young birds. For an
  example of such an irruption as detected by
  FeederWatch data, click here.
• Steller's and Blue jays are the only North
  American jays with crests. The Blue Jay is
  expanding its range westward. Where they meet,
  the two species occasionally interbreed and
  produce hybrids.

49
Varied Thrush
50
Varied Thrush

• Males, but only rarely females, defend and
  maintain small feeding territories around bird
  feeders. They are aggressive and dominate many
  other feeder bird species.
• To defend a territory a male may first give a
  Tail-Up display where the bird faces away from
  the intruder and holds its tail up to show off
  the gray-and-white patterned undertail coverts.
  If the intruder keeps coming the male may turn
  around and give the Head-Forward display with the
  wings fanned to show off the orange wing stripe
  and the tail cocked up over the head showing the
  white corners.
• Data from Project Feeder Watch show that
  populations go up and down every other year. Go
  here for a discussion.

51

• Belted King Fisher

52
Belted King Fisher

• The breeding distribution of the Belted
  Kingfisher is limited in some areas by the
  availability of suitable nesting sites. Human
  activity, such as road building and digging
  gravel pits, has created banks where kingfishers
  can nest and allowed the expansion of the
  breeding range.
• The Belted Kingfisher is one of the few bird
  species in which the female is more brightly
  colored than the male. Among the 93 species of
  kingfishers, the sexes often look alike. In some
  species the male is more colorful, and in others
  the female is.
• During breeding season the Belted Kingfisher pair
  defends a territory against other kingfishers. A
  territory along a stream includes just the
  streambed and the vegetation along it, and
  averages 1 km (0.6 mi) long.The nest burrow is
  usually in a dirt bank near water. The tunnel
  slopes upward from the entrance, perhaps to keep
  water from entering the nest. Tunnel length
  ranges from 30 to 250 cm (1 to 8 ft).

53
American Coot
54
American Coot

• Although it swims like a duck, the American Coot
  does not have webbed feet like a duck. Instead of
  having all the toes connected by webs, each coot
  toe has lobes on the sides of each segment.

55
Great Blue Heron
Male
Female
56
Great Blue Heron

• The white form of the Great Blue Heron, known as
  the "great white heron," is found nearly
  exclusively in shallow marine waters along the
  coast of very southern Florida, the Yucatan
  Peninsula, and in the Caribbean. Where the dark
  and white forms overlap in Florida, intermediate
  birds known as "Wurdemann's herons" can be found.
  They have the bodies of a Great Blue Heron, but
  the white head and neck of the great white heron.
  
• Although the Great Blue Heron eats primarily
  fish, it is adaptable and willing to eat other
  animals as well. Several studies have found that
  voles (mice) were a very important part of the
  diet, making up nearly half of what was fed to
  nestlings in Idaho. Occasionally a heron will
  choke to death trying to eat a fish that is too
  large to swallow.
• Great Blue Herons congregate at fish hatcheries,
  creating potential problems for the fish farmers.
  A study found that herons ate mostly diseased
  fish that would have died shortly anyway. Sick
  fish spent more time near the surface of the
  water where they were more vulnerable to the
  herons.

57
Mallard
58
Mallard

• The Mallard is the ancestor of nearly all
  domestic duck breeds (everything except the
  Muscovy Duck). Many of the domestic breeds look
  like the wild birds, but usually are larger. They
  are variable in plumage, often lacking the white
  neck ring or having white on the chest. Feral
  domestic ducks breed with wild Mallards and
  produce a variety of forms that often show up
  with wild ducks, especially in city parks.
• The widespread Mallard has given rise to a number
  of populations around the world that have changed
  enough that they could be considered separate
  species. The "Mexican Duck" of central Mexico and
  the extreme southwestern United States and the
  Hawaiian Duck both are closely related to the
  Mallard, and in both forms the male is dull like
  the female. The Mexican Duck currently is
  considered a subspecies of the Mallard, while the
  Hawaiian Duck is still given full species status.
  
• Mallard pairs are generally monogamous, but
  paired males actively pursue forced extra-pair
  copulations. Copulation between members of a pair
  usually takes place in the water after a long
  bout of elaborate displays. Forced copulations
  are not preceded by displays, and several males
  may chase a single female and mate with her.
• Mallard pairs form long before the spring
  breeding season. Pairing takes place in the fall,
  but courtship can be seen all winter. Only the
  female incubates the eggs and takes care of the
  ducklings.

59
Red-Winged Blackbird
60
Red-Winged Blackbird

• Different populations and subspecies of
  Red-winged Blackbirds vary markedly in size and
  proportions. An experiment was conducted that
  moved nestlings between populations and found
  that the chicks grew up to resemble their foster
  parents. This study indicated that much of the
  difference seen between populations is the result
  of the different environments.
• The Red-winged Blackbird is a highly polygynous
  species, with one male having up to 15 different
  females making nests in his territory. In some
  populations 90 of territorial males have more
  than one female. But, from one quarter to up to
  half of the young in "his" nests do not belong to
  the territorial male. Instead they have been
  sired by neighboring males.
• The male Red-winged Blackbird fiercely defends
  his territory during the breeding season. He may
  spend more than a quarter of all the daylight
  hours in territory defense. He vigorously keeps
  all other males out of the territory and defends
  the nests from predators. He will attack much
  larger animals, including horses and people.
• The Red-winged Blackbird forms roosting
  congregations in all months of the year. In the
  summer it will roost in small numbers at night in
  the wetlands where it forages and breeds. In
  winter, it can form huge congregations of several
  million birds, which congregate in the evening
  and spread out each morning. Some may travel as
  far as 80 km (50 mi) between the roosting and
  feeding sites. It commonly shares its winter
  roost with other blackbird species and European
  Starlings.