Differential effects of global versus local testosterone on singing behavior and its underlying neural substrate Beau A. Alward, Jacques Balthazart, and Gregory F. Ball (published ahead of print November 11, 2013)
1. Excerpt: “These results have broad implications for research concerning how steroids act at multiple brain loci to regulate distinct sociosexual behaviors and the associated neuroplasticity.”
3. Here we experimentally demonstrate opposing effects of frequency-dependent social environments on plasma hormone levels (testosterone and corticosterone) and immune function between red- and black-headed male morphs of the Gouldian finch (Erythrura gouldiae).
4. The increases in LH [luteinizing horomone] plasma concentrations are in all probability triggered by increases in GnRH secretion, and, as a consequence, it has long been assumed that the preoptic GnRH neurons represent the target where information about photoperiod and additional cues must converge to regulate reproduction.
5. See also Bird odour predicts reproductive success.
Clearly, science works best when alternative hypothesis can be experimentally tested. If experimental evidence supports a null hypothesis that is unknown to me, the birds are primarily visual or auditory creatures. If not, given what is known about amino acid change and plumage, they are primarily olfactory creatures like all other creatures on this planet.
I would like to examine any evidence that supports a bird-brained type of associated null hypothesis to determine its validity in the context of the facts represented in items 1-5 above, which obviously effect hormones, the brain, and behavior in birds. When that evidence becomes available to me, it can be compared in the context of what is currently known about plumage color: Difference in Plumage Color Used in Species Recognition between Incipient Species Is Linked to a Single Amino Acid Substitution in the Melanocortin-1 Receptor, reported as “Birds use plumage colour to recognize and select potential mates.”
The single amino acid substitution of plumage color links the biophysical constraints of thermodynamics and organism-level thermoregulation to protein folding in the human influenza A/H3N2 virus, and to its receptor-mediated antigenic effects. See for example: Substitutions Near the Receptor Binding Site Determine Major Antigenic Change During Influenza Virus Evolution.
As I noted in my blog post on Antigenic change due to a single amino acid and in my comment on the Science Magazine article linked above: “The idea of biophysical constraints seems antithetical to the idea of nature somehow selecting mutations that cause amino acid substitutions. ”