Black-throated Blue Warbler Dendroica caerulescens
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
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 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.
Many species, such as this osprey nesting in an abandoned granite quarry, are quite adaptable and readily use man-made structures for nest substrates.
Artificial platform constructed for Common Loons White stork nest in Central Europe
This help? Can you name this bird, nestingon a man-made platform?
Can you name this bird, nestingon a man-made platform in the Eastern Deciduous Forest? Does this help?
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.
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
Statant Cupped – crotch of tree Dusky FlycatcherNest
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
Bell’s Vireo Nest Nest of unknown vireo species(post fledging)
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
3. Platform Cupped nest Anna’s Hummingbird
Cupped nest of sticksand mud Barn Swallow Nest Cliff Swallow Nests Domed mud nest
Why Build Nests? • help keep eggs and hatchlings warm • provide protection from predators and the elements
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
Forest Fragmentation increases nest predation Many experiments have shown that nests in small woodlots receive more predation than those in large contiguous woodlots
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
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
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)
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)
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
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
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 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
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 • 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 • 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