The bee hummingbird is the smallest extant bird species on the face of
the earth - extant being the opposite of extinct, that is to say, there
are no living species of birds in the world smaller than the bee
hummingbird. Exactly how small do you have to be to earn that
distinction? No larger than 2 and a half inches long at most, with many
birds no bigger than 2 inches total. With weight in a range between
0.056 and 0.067 ounces (1.6-1.9 g), these small birds are easily
mistaken for insects, and are in fact not much bigger than the
honey-making bugs for which they are named. They are also blessed with
bright iridescent coloring of red, blue and green.
Eagle is a common name for many large birds of prey of the family Accipitridae; it belongs to several groups of genera that are not necessarily closely related to each other.
Most of the 60 species of eagles are from Eurasia and Africa.
Outside this area, just 14 species can be found – two in North America,
nine in Central and South America, and three in Australia.
Eagles are large, powerfully built birds of prey, with a heavy head and beak. Even the smallest eagles, like the booted eagle (Aquila pennata) (which is comparable in size to a common buzzard (Buteo buteo) or red-tailed hawk (B. jamaicensis)),
have relatively longer and more evenly broad wings, and more direct,
faster flight – despite the reduced size of aerodynamic feathers. Most
eagles are larger than any other raptors apart from some vultures. The smallest species of eagle is the South Nicobar serpent eagle (Spilornis klossi),
at 450 g (0.99 lb) and 40 cm (16 in). The largest species are discussed
below. Like all birds of prey, eagles have very large hooked beaks for ripping flesh from their prey, strong muscular legs, and powerful talons.
The beak is typically heavier than that of most other birds of prey.
Eagles' eyes are extremely powerful, having up to 3.6 times human acuity
for the martial eagle, which enables them to spot potential prey from a very long distance.[2] This keen eyesight is primarily attributed to their extremely large pupils which ensure minimal diffraction (scattering) of the incoming light. The female of all known species of eagles is larger than the male.
Eagles normally build their nests, called eyries,
in tall trees or on high cliffs. Many species lay two eggs, but the
older, larger chick frequently kills its younger sibling once it has
hatched. The dominant chick tends to be a female, as they are bigger
than the male. The parents take no action to stop the killing.
Due to the size and power of many eagle species, they are ranked at the top of the food chain as apex predators in the avian world. The type of prey varies by genus. The Haliaeetus and Ichthyophaga eagles prefer to capture fish, though the species in the former often capture various animals, especially other water birds, and are powerful kleptoparasites of other birds. The snake and serpent eagles of the genera Circaetus, Terathopius, and Spilornis predominantly prey on the great diversity of snakes found in the tropics of Africa and Asia. The eagles of the genus Aquila are often the top birds of prey in open habitats, taking almost any medium-sized vertebrate they can catch. Where Aquila eagles are absent, other eagles, such as the buteonine black-chested buzzard-eagle of South America, may assume the position of top raptorial predator in open areas. Many other eagles, including the species-rich Spizaetus
genus, live predominantly in woodlands and forest. These eagles often
target various arboreal or ground-dwelling mammals and birds, which are
often unsuspectingly ambushed in such dense, knotty environments.
Hunting techniques differ among the species and genera, with some
individual eagles having engaged in quite varied techniques based their
environment and prey at any given time. Most eagles grab prey without
landing and take flight with it so the prey can be carried to a perch
and torn apart.
The bald eagle
is noted for having flown with the heaviest load verified to be carried
by any flying bird, since one eagle flew with a 6.8 kg (15 lb) mule deer fawn.
However, a few eagles may target prey considerably heavier than
themselves; such prey is too heavy to fly with, thus it is either eaten
at the site of the kill or taken in pieces back to a perch or nest. Golden and crowned eagles have killed ungulates weighing up to 30 kg (66 lb) and a martial eagle even killed a 37 kg (82 lb) duiker, 7–8 times heavier than the preying eagle.Authors on birds David Allen Sibley, Pete Dunne,
and Clay Sutton described the behavioral difference between hunting
eagles and other birds of prey thus (in this case the bald and golden
eagles as compared to other North American raptors):
They have at least one singular characteristic. It has been observed
that most birds of prey look back over their shoulders before striking
prey (or shortly thereafter); predation is after all a two-edged sword.
All hawks seem to have this habit, from the smallest kestrel to the
largest Ferruginous – but not the Eagles.
Among the eagles are some of the largest birds of prey: only the condors and some of the Old World vultures
are markedly larger. It is regularly debated which should be considered
the largest species of eagle. They could be measured variously in total
length, body mass, or wingspan. Different lifestyle needs among various
eagles result in variable measurements from species to species. For
example, many forest-dwelling eagles, including the very large harpy and Philippine eagles,
have relatively short wingspans, a feature necessary for being able to
maneuver in quick, short bursts through dense forested habitats. Eagles in the genus Aquila, though found almost strictly in open country, are superlative soarers, and have relatively long wings for their size.
These lists of the top five eagles are based on weight, length, and
wingspan, respectively. Unless otherwise noted by reference, the figures
listed are the median reported for each measurement in the guide Raptors of the World in which only measurements that could be personally verified by the authors were listed.
