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Black-throated Blue Warbler. Dendroica caerulescens . Nesting Ecology. Not all bird species build nests. Egg laid by a Fairy Tern. Adult Fairy Tern and egg. What is a Nest?. A nest is a structure made by birds to hold eggs.

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Black-throated Blue Warbler

Dendroica caerulescens 

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Not all bird species build nests

Egg laid by a Fairy Tern

Adult Fairy Tern and egg

what is a nest
What is a Nest?

A nest is a structure made by birds to hold eggs

types of nests

They are usually "scrapes" in a depression in the ground. The bird shapes the scrape with her abdomen by rotating in the same place many times.

Ground nests were likely the first nests made by birds

Types of Nests
types of nests1
Types of Nests
  • Platform nests – probably the first elevated nests
  • Platforms eliminate risk from most ground predators
  • Platform nests built by herons, cormorants, eagles and osprey (left) are very simple in structure.

Osprey Nest

-Essentially they are flat areas with a slight depression to hold the eggs.

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Many species, such as this osprey nesting in an abandoned granite quarry, are quite adaptable and readily use man-made structures for nest substrates.

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Artificial platform constructed for Common Loons

White stork nest in Central Europe

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This help?

Can you name this bird, nestingon a man-made platform?

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Can you name this bird, nestingon a man-made platform in the Eastern Deciduous Forest?

Does this help?

types of nests2

Saw-whet Owl peering out of a nest cavity

Types of Nests
  • Insulated cavity nests shelter eggs from cooling winds and allow the parent's body heat to warm the eggs efficiently
  • Examples: woodpeckers excavate holes in trees, kingfishers excavate holes in sandy cliffs.
types of nests3

Wood Thrush nest with cowbird eggs

Types of Nests
  • Cupped nests are the most solid, the warmest and the most complex of the nests
  • Most songbirds build cup nests, using various materials
types of cupped nests

Pensile - suspended from their walls and have very stiffly woven rims

Warbling Vireo Nest

Types of Cupped Nests

Suspended Cupped

2.

Black-capped Vireo Nest

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Bell’s Vireo Nest

Nest of unknown vireo species(post fledging)

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Pendulous - suspended by their rims and have flexible woven sides. The deeply cupped part of the nest swings freely

Baltimore Oriole Nest

Crested OropendolaTrinidad and Tobago

Montezuma’s OropendolaCosta Rica

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3. Platform Cupped nest

Anna’s Hummingbird

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Cupped nest of sticksand mud

Barn Swallow Nest

Cliff Swallow Nests

Domed mud nest

why build nests
Why Build Nests?
  • help keep eggs and hatchlings warm
  • provide protection from predators and the elements
nest predation
Nest Predation

Gopher Snake Raids Swallows' Nests

  • “More chicks may leave the nest via a predator’s stomach than their own volition”
  • Predation has been reported to be as high as 88% in deciduous vegetation
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Forest Fragmentation increases nest predation

Many experiments have shown that nests in small woodlots receive more predation than those in large contiguous woodlots

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Two primary types
  • Nesting together
    • breeding colonies
    • 13 % of bird species nest colonially
  • Roosting together
    • colonial roosts

Some do both

  • breeding colony during nesting season
  • colonial roosts other times of year
  • Some do one or the other
  • solitary breeders, colonial roosters (snail kites)
  • colonial breeders, solitary other times of year
ecological correlates of coloniality
Resources are either

widely scattered and hard to defend

unpredictable in space andtime

Nesting sitesare inaccessible

cliffs, islands, etc.

Adele Penguin colony near Anver’s Island, Antarctica

Ecological correlates of Coloniality
an example with weaver birds passeriformes ploceidae
Native to Africa

Similar, but not closely related to North American finches

Most species are colonial nesters and flocking foragers

Some species are territorial, nesting in pairs and foraging singly

Food seems to be the reason for differences

An example with Weaver Birds (Passeriformes; Ploceidae)
an example with atlantic puffins charadriiformes alcidae
Found primarily in coastal areas of the North Atlantic

Feed on fish and crustaceans by diving in open water

hard to protect feeding territory

Nest in burrows at tops of cliffs or on islands

inaccessible to mammalian predators, but are preyed upon by Black-backed Gulls

An example with Atlantic Puffins (Charadriiformes; Alcidae)
an example with great egrets ciconiiformes ardeidae in the everglades
Common breeder in the everglades

Sit-and-wait predator

Feeds primarily on fish, but will take insects and other arthropods

An example with Great Egrets (Ciconiiformes; Ardeidae) in the Everglades
an example with great egrets ciconiiformes ardeidae in the everglades1
Breeds in mixed species colonies

Nests densely packed in vegetation 0.5 m or higher above ground/water

Single historic colonies may have contained as many as 750,000 breeding pairs

Usually 20,000 or fewer pairs breed in entire Everglades system at present

An example with Great Egrets (Ciconiiformes; Ardeidae) in the Everglades

L-67 breeding colony in the

central Everglades

an example with great egrets ciconiiformes ardeidae in the everglades2
Colonies generally located on tree islands or willow heads surrounded by sawgrass or cattail marsh

Inaccessible for most mammalian predators, although some colonies may support small raccoon populations

Black-crowned Night Herons take nestlings

Boat-tailed Grackles, Crows take eggs

An example with Great Egrets (Ciconiiformes; Ardeidae) in the Everglades
disadvantages of coloniality competition
Disadvantages of Coloniality: Competition

Feeding competition

  • lots of animals living in the same area means lots of demand for food
  • must forage over a wider area

Nesting material

Nesting site

  • some sites better than others
  • advantageous sites may be highly contested
disadvantages of coloniality cannibalism

Herring Gull

Disadvantages of Coloniality: Cannibalism

Neighbors of birds prey on young

  • therefore, one parent often must remain at nest to guard
  • less time available to forage
  • may raise fewer young
disadvantages of coloniality disease and parasites
Disadvantages of Coloniality: Disease and Parasites
  • Close proximity to conspecifics facilitates transmission of diseases and/or high parasite density
  • Many ectoparasites are species-specific, so the only way to become infested is through close association with other conspecifics
  • Cliff swallows
    • weight of chicks from nests with ticks was inversely related to number of ticks
    • experiment: fumigate a portion of nests
      • chicks at fumigated nests had a 50 % better chance of fledging than chicks at non-fumigated nests
advantages of coloniality detection and defense
Advantages of Coloniality: Detection and Defense
  • Predator detection
    • lots of eyes watching for predators, so more likely to be detected
    • alarm calls - one individual can alert entire colony
  • Group defense
    • mobbing
advantages of coloniality dilution effects
Advantages of Coloniality: Dilution Effects

Selfish Herd Concept

  • stay in group because your individual chances of getting eaten are smaller as part of group than living alone
  • not all positions in the herd (or nesting colony) are equal
  • only true if
    • predators only take a few individuals at a time
    • attack rate is independent of group size
    • for example, if you joined a group with 100 individuals but attackscame 100x more often there would be no dilution effect
advantages of coloniality predator satiation
Advantages of Coloniality: Predator Satiation
  • Food supply for predators is low or moderate for most of the year
  • Predator populations low to moderate
  • Sudden flush of superabundant prey
  • More available prey than predator can eat
advantages of coloniality food resources
Advantages of Coloniality: Food Resources

Information Center Hypothesis

  • obtain food
  • increase foraging efficiency: many sets of eyes can find food quicker than one set
      • remember that coloniality is associated with patchy food resources
  • unlike bees or ants (dances, chemical trails), information transfer is indirect
      • unsuccessful birds simply followsuccessful ones
an example with black vultures
An example with Black Vultures
  • Carrion is patchy resource
  • Black vultures specialize in large carcasses, so when food is found, it is often superabundant
  • Roost together
  • Scientist marked all vultures at roost
  • Sat out road kills and observed
an example with black vultures1
An example with Black Vultures
  • Day one
    • some vultures found
  • Day two
    • “finders” return first to carcass
    • followed by others
  • Why “give away” your information by roosting communally?
    • benefits of colonial roosting (lower predation risk, etc.)
proving the information center hypothesis
Proving the Information Center Hypothesis
  • Site Fidelity
    • Birds that find food must return to the same site
  • Differential foraging success
    • some find plenty of food, some don’t
  • Successful birds must be identifiable
    • hungry birds must be able to “know” who is eating well
  • Synchronous departure from colony by leaders and followers
  • Following must take place
  • Followers must be tolerated
    • allowed at least some access to food source

Must satisfy all six conditions to support ICH; Most studies only demonstrate a couple

advantages of coloniality mixed benefits
Advantages of Coloniality: Mixed Benefits
  • Unlikely that any single advantage discussed drives colony formation
  • Mixed Benefits
    • successful foragers get choice (i.e., central) positions at roost
    • less successful foragers gain feeding information while occupying more vulnerable roost positions
  • Hard to prove!
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Black-throated Blue Warbler

Dendroica caerulescens