I saw another Red Bellied Hawk recently. First, I should admit that no ornithologist would call it that. Too bad! Second, there are other types of hawks than the one I have in mindthat have red bellies - the Red-Shouldered Hawk, the Kestrel (technically a falcon) and the Asian rufous bellied hawk/eagle (ornithologists do not agree as to what this bird is). What I have in mind is properly called the rufous morph of the Red-Tailed Hawk. I first became aware of the morph when my friend Willard Berkebile showed me a picture of one that hunted the area around his home. My research at the time indicated the morph was rare outside the American north-west. Since I have seen two more - both in central Indiana (Morgan and Putnam Counties). It turns out there are fourteen recognized sub-species of the Red-Tailed Hawk - more or less. One has to allow for a lot of argument about the difference between "morphs" and "sub-species" and the darkest Red Tail morph as recognized by some seek out other dark morphs for breeding and establish independent populations. The rufous morphs aren't at that point - at least yet.
Some ornithologists speculate that the Ruphous morphs enjoy a selective advantage in that they are rare enough and just different enough from the majority population to be mistaken by prey animals for something less dangerous. Really big Robins perhaps? There is no research to support this theory yet. In fact, the one detailed study of Red-Tailed Hawk morphs I could find seems to suggest the opposite. The study is titled - Differential Perch Site Selection by Morphs of the Red-Tailed Hawk. A large number of Red-Tailed Hawks winter in Benton County, Arkansas - including lots of morphs. Two seasons of observation produced this major conclusion - the darker the morph, (the rufous morph is considered darker than the standard model) the more likely it would perch lower and among more covering branches. The study author speculated that darker morphs stand out to prey and thus sacrifice broader and clearer field of vision over the hunting grounds in favor of concealment. The author also made the same conclusion as every other author of every study of any sort I have ever read - more study is needed!
Nevertheless, the "need for concealment theory" makes more sense to me than the 'really big robin theory'. Against the open sky- darker birds create a bolder profile than lighter birds. Or, maybe the lighter birds are just working on their tans. We'll go with the bolder profile thing. Unlike pack predators preying on herd animals, solo ambush predators have a need not to be recognized prior to the moment the claws make contact. Concealment, cover, disguise - these are the tools of the ambush predator.
"But what I do, I will also continue to do, that I may cut off the opportunity to be regarded just as we are in the things of which they boast. For such are false apostles, deceitful workers, transforming themselves into apostles of Christ. And no wonder! For Satan himself transforms himself into an angel of light. Therefore it is no great thing if his ministers also transform themselves into ministers of righteousness, whose end will be according to their works." II Corinthians 11:12-15.