1890.] Probable Causes of Polygamy Among Birds. 1035 
accordance with the law which guided it toward specialization of 
color, finding its action at the outset nullified by the law of pro- 
tective resemblance, made truce therewith, developing characters 
conformatory to both, first by modification of the form of plumes 
and addition of appendages of periodic color-brilliancy, and sec- 
ondly by enabling the possessor of these characters to exhibit 
them at discretion, for in times of danger the wing-like neck tufts, 
previously employed to attract attention, in turn conceal the 
shrunken air-sacs from observation when depressed. Similar 
cases have produced other combinations of protective resemblance 
with high coloration, those parts of the body being most ornate 
which are screened from observation of other birds of prey, yet 
capable of voluntary display to an appreciative admirer, as many 
have witnessed in the sudden transformation of a passive, incon- 
spicuous gobbler or peacock by mere erection and distension of 
certain parts. 
If we premise that the original gallinaceous type from which 
the existing forms have sprung was an inhabitant of treeless plains 
of vast extent, the causes which have induced some to betake them- 
Selves to forests, while others clung to their original habitat, are 
difficult to surmise. Owing to well-recognized natural agencies, 
forest limits may have widely extended and at last invaded their 
haunts ; or we may conjecture that migration, induced by climatic 
changes, was the cause of their first woodland experience. In 
either event the proximity of forests would result in the discovery 
by the birds of their value as a resort in times of danger, or for 
roosting purposes, or in the search of mast, when from any cause 
there was a scarcity of food stuffs in their accustomed feeding 
grounds. This would eventually remove the counter effects of 
the law of protective resemblance to sexual selection, and favor 
higher ornamentation, and thus, by slow degrees, the evolution 
change of habits to accord with altered environment. The fact 
of the more gorgeously ornamented polygamists being forest- 
hunting species (witness the Menurida and Phasianidz) is in full 
accord with our supposition. We may, on the other hand, attrib- 
ute the continuance of Cupidonia and Cutrocercus in their orgi- 
