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Falcon (Falco berigora), brown morph
Credit & Copyright: Dr. Bruce G.
Explanation: The Brown Falcon is a sharp-eyed, uncommon to rare nomad found in open woodlands, forest edges, farmlands, and roadsides, occasionally hovering and diving for small prey. They are found from New Guinea to Australia, including several major islands in the Bismark Archipelago, on Tasmania, King and Flinders Islands, and other offshore islands.
Brown Falcons may be an example of Gloger's Rule in ecology. This rule states that within a given species, those races, subspecies, or morphs (color forms) found in warmer and more humid areas can be more heavily pigmented than those in cooler, drier areas. The pattern is that animals in more tropical climates are likely to be darker or more richly colored. The reason may be that arid regions tend to have higher direct solar radiation ("insolation"), so animals there have evolved lighter coloration by which to shed sunlight because of the high heat load.
Many examples of Gloger's Rule can be found, including subspecies of Peregrine Falcon, in which the breeders along the humid Pacific Coast of North American tend to be darker and the breeders in the open tundra tend to be relatively pale.
Shown here is an old juvenile or young adult Brown Falcon of the intermediate form of the brown morph. Brown Falcons of the dark morph form are nearly all brown except for the primaries, and, in some birds, part of the face and the throat which are cream or white. Brown Falcons also occur as rufous morph and light morph forms which can be quite a bit paler.
A local common name for Brown Falcon in Australia is Cackling Falcon, a name that fits its raucous distress calls. At least one bird field guide describes it as "probably [the] noisiest Australian raptor" with "screeches, [and] demented hoarse cacklings, at times like [a] laying hen."
The bird I photographed here was kept captive and complained about it. I taped several variations of its distress or alarm calls (click on the following icons to play mp3 sound files):
Like other species of falcon, at times, when unduly disturbed, the Brown Falcon can be aggressive.
Next week's picture: Silky Molerat
Author & Webmaster: Dr.
Bruce G. Marcot, Tom Bruce
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