That's a hawk he's compared it too. The shape of the B-2 has not been borrowed from the bird but the requirements of stealth. Hawk's don't have stealth!! So the shape is just coincidental.
Unless there is a very large flock they do not show up on radar mate . so in a way they do have stealth
Coincidental? Not quite...
First...Birds, insects, hydrometeors, and flora are usually classified as volumetric radar targets...
Clear air radar echoes
Actual radar echo is usually a sum of echoes for many targets, since echoes are coming to the receiver simultaneously from a volume that is some millions of cubic meters. Normally weather radar signal processing averages the echo power from many successive pulses, and the resulting radar reflectivity is used for estimating precipitation intensity etc. Using the same principle on echoes from many insects in the radar measurement volume is also possible.
What this mean is that some bodies are so weak in radar reflectivity, depending on the frequency in use, that the best way to detect and track them is
IF there are enough of them in a cluster/mass.
So if a single bird drop out of the flock, that bird will not be detected and the flock as a
SINGLE volumetric target have a slightly lowered return. Same for insects. Same for a tree. In the case of the tree, it will have a smaller radar return in the winter than for the rest of the year. Why? Because no leaves in the winter.
RADAR Overview
A RADAR image acquired from a system with a particular frequency, polarization, and incidence angle can therefore provide information related to canopy water content, vegetation type, biomass components (foliage, branches, stems), and canopy structure (leaf orientation, leaf area index, main stem geometry and spatial distribution) (Jensen 2000, Carver 1988).
http://www.nrcan.gc.ca/earth-sciences/geography-boundary/remote-sensing/fundamentals/1451
Volume scattering is the scattering of radar energy within a volume or medium, and usually consists of multiple bounces and reflections from different components within the volume. For example, in a forest, scattering may come from the leaf canopy at the tops of the trees, the leaves and branches further below, and the tree trunks and soil at the ground level. Volume scattering may serve to decrease or increase image brightness, depending on how much of the energy is scattered out of the volume and back to the radar.
Using certain frequency will allow the user to bypass leaves. Using another frequency will allow the user to measure vegetation canopy. In other words, leaves are very much volumetric bodies.
Hydrometeors is a fancy word for rain drops and snow flakes. Same principle applies to these bodies.
Getting back to birds...Their feather layers are just like layers of leaves on a tree. When a radar signal impact a bird, again depending on the freq in use, if the operating freq is sufficiently high like the centimetric (X-band), those layers of feathers are actually very absorbent. Or RAM, in a manner of speaking.
Radar
Absorbent
Material.
In shaping to control radar cross section (RCS)...
The ogive is the nest best (lowest) after the sphere in terms of all-around reflectivity.
Oh-ghee-vee.
It is no accident that the American 'stealth' bodies, B-2, F-22, F-35, are patterned/shaped after the bird. In penetration flight, the B-2 mission planner will, to the best of SIGINT reconnaissance, map out enemy radar locations and will create a flight profile that will present to any seeking radar the lowest frontal aspect to best exploit the naturally low reflectivity of the ogive.
whose profile, from that particular point of view, clearly reminds that of the Northrop Grumman B-2 Spirit stealth bomber.
