Avian Architects: Part 3

Golden Eagle [Aquila chrysaetos] nestlings resting, stretching wings on a ledge nest; Coaldale, Colorado

The largest nests on record are those of the Golden Eagle (Aquila chrysaetos) which tend to build new nests on top of the previous year’s nest. This can result in massive structures often containing more than a ton of material. Fortunately, Golden Eagles prefer rocky alpine crags as nest sites – which support these massive structures more easily than a tree. Golden Eagles as well as many hawks are known to bring fresh sprigs of green leaves, pine and evergreen boughs throughout the nesting season, well after the young have hatched. Many researchers believe that this is evidence of a rudimentary aesthetic sense, concealment from predators, a natural coolant, or as with other raptors may serve to fumigate a nest to repel parasites, fungal disease and insects.

Golden Eagle [Aquila chrysaetos] nestlings, growing up; Coaldale, Colorado

Golden Eagle [Aquila chrysaetos] nestlings, curiosity. What is that?? ; Coaldale, Colorado

Golden Eagle [Aquila chrysaetos] nestling, last of 2, almost ready to leave the ledge; Coaldale, Colorado

Golden Eagle [Aquila chrysaetos] nestling, last of 2, soon to fledge; Coaldale, Colorado

Colonies of birds, such as murres (Uria) and guillemots (Alcidae) will nest on rocky coastal cliffs and ledges, laying elliptical or pear-shaped eggs. This egg shape prevents the eggs from rolling easily, keeping them protected from falls. Instead of using branches, the bird will place small rocks or feces to hold or cement the eggs in place.

Peregrine Falcon [Falco peregrinus] adult guarding nestlings in nest on rocky canyon ledge; Yellowstone NP., WY

Other species of birds will use crevices in cliffs, stuffing branches into them to hold their eggs in place. This includes birds such as peregrine falcons (Falco), condors (Vultur gryphus), and ravens (Corvus corax). Gyrfalcons can use their nests for generations, using rock ledges or old raven nests — one having been discovered to be over 2,500 years old.

Common Raven [Corvus vorax] nestling, meal time; Yellowstone NP., WY

Common Raven [Corvus corax] nestlings anxiously waiting on the incoming meal; Fremont County, CO

Common Raven [Corvus corax] nest with 2 nestlings crowding a 3rd on their narrow ledge; Granite, CO

Common Raven [Corvus corax] 3 nestlings on a ledge; Granite, CO

Common Raven [Corvus corax] 4 nestlings waiting for a meal from their cliff face nest; along Sante Fe Trail site near Del Norte, Colorado

Red-tailed Hawk [Buteo jamaicensis] nestlings on a nest tucked into an alcove in a red rock wall; Escalante Canyon, Colorado

Leaving a high ledge to the ground we have what many birds prefer, a basic scrape or a shallow depression on the ground without much nesting material, though it may have a light lining of down, grass, pebbles, weeds, or other debris. Scrapes are popular nest types for terrestrial birds or birds that prefer open habitats that lack abundant trees, such as shorebirds or tundra species. These nests are typically found in open habitats without trees in areas with terrestrial tundra or shores (sandy beaches).

Killdeer (Charadrius vociferus) lay their eggs out in the open on the ground in gravel or dirt depressions. They make several imitation scraped nests as well to confuse any predators. Their eggs are speckled in color, allowing them to blend in. If a predator comes near, the mother bird will act as if it is injured to lure it away from the nest. Although we have yet to spot a nest or eggs, almost as soon as the precocious young ones can walk they are exploring their surroundings and the adults are ready for the next brood.

Here’s what the precocious cuties look like:

Killdeer [Charadrius vociferus] fledgling exploration; Bosque del Apache NWR, NM

Killdeer [Charadrius vociferus] fledgling taking a sip; Bosque del Apache NWR, NM

Time to wade the waters; Bosque del Apache NWR, NM

Killdeer [Charadrius vociferus] pair mating while year’s first fledglings roam nearby; Bosque del Apache National Wildlife Refuge, NM

Birds That Build Scrape Nests: American avocet (Recurvirostra americana), Arctic tern (Sterna paradisaea), Common ostrich (Struthio camelus), Killdeer and many other shorebirds. Piping plovers (Charadriidae) make shallow depressions on the beach with a few twigs. Despite the lack of coverage, their nests can still be hard to spot because they are so well-camouflaged.

Soon to follow …. Cup-shaped nests

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