iSqi.] Lucas, Bird Skeletons from Guadalupe Inland. 22 1 



There seems to be an increase in the size of the sknll indica- 

 ted by these specimens, tor in this particnlar yiinco insulat'is ex- 

 ceeds y. hycDialis and Polyboriis lutosiis^ P. tliariis. 



The last bird to be considered is Salphictcs guadalupe7isis ^ 

 and this species is remarkable from the fact that it has gained and 

 not lost in power of flight, for its wing decidedly exceeds that 

 of S. obsoletus^ while the sternum of the island bird is a little 

 more than one half longer than that of the continental form. 

 Why this little Guadalupe Wren should have developed such pow- 

 erful wings, comparativeh' speaking, is not perhaps quite clear, 

 but it ma}- be possible that in these Guadalupe birds we have a case 

 paralleling that of the insects of the Azores, which either fly well, 

 or do not fly at all, the inference being that all insects of but 

 moderate powers of fliglit have been swept out to sea and lost. 

 Be that as it may, Salpuictcs^ and to some extent Carpodacus 

 amplus^ indicates that insulation is not of necessit}' degeneration 

 so far as the power of flight is concerned. 



There are two interesting facts that Mr. Bryant has recorded 

 in regard to Salpinctes guadahipeJisis^ the first being that meas- 

 urements show a slight increase in the length of bill during an 

 interval of ten 3'ears, while in the same space of time the species 

 had become the most abundant on the island, Junco insulai'is 

 having previously taken the lead in that respect. 



Now there may be no correlation between the power of flight 

 and increase in numbers, but is it not probable that superior wing 

 power would give superior abilitj'to obtain food, to elude the pur- 

 suit of enemies and to escape being blown out to sea while su- 

 periority in these points would not unnaturally lead to an increase 

 in the number of individuals.'' 



There are certain facts well illustrated by the proportionate 

 measurements for these birds, and although these facts are doubt- 

 less well known I do not remember to have seen them formally 

 stated. They are as follows : 



The first symptom of weakening flight appears in a decrease in 

 the length of the sternum, diminution in the depth of the keel not 

 taking place until later on. 



This is followed by reduction in the length of the wing, begin- 

 ning with the manus and fore arm, the humerus apparenth^iot 

 being aflected until the rest of the wing is perceptibly lessened. 

 Then the outer wing bones disappear, leaving only the humerus 



