32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 72 



Other group, but is not comparable, as this family is represented by only 

 one species, the horned lark (Otocorls alpestris). A number of 

 Species included in other families have a higher average temperature 

 than this so that this must be discarded. Among the others the 

 Bombycillidae, Mimidae, and Turdidae each show an average of 108.9° 

 while the three families remaining in the category under discussion 

 vary only two- or three-tenths of a degree below this. From 108.6° to 

 108.9° would seem therefore to be the maximum for families of 

 perching birds where records are available for a number of species. 

 A comparative examination of some of the species of perching birds 

 brings out still other facts of interest. It has already been stated that 

 the swallows as a group possess the lowest average body temperature. 

 In the seven species examined in this family only one, the rough- 

 winged swallow {Stelgidopteryx serripennis) , showed an average body 

 heat above 107.5°. Turning to the higher temperatures it is found 

 that in the Tyrannidae there are five species in which the mean tem- 

 perature for the male or female is 110° or more. The Fringillidae 

 include three species in this category and the Corvidae, Icteridae, 

 Mniotiltidae and Turdidae each possess one. In other words there 

 are records for twelve species in all in which this is true. The highest 

 average temperature for both sexes is that of the western wood pewee 

 (Myiochanes richardsoni) with a mean of 110.2°. The highest single 

 reading believed to be valid was found in this species in an indi- 

 vidual killed in the Graham Mountains, Arizona, at two o'clock in the 

 afternoon on June 25, 1919. This bird, shot dead as it rested quietly 

 in the shade of a cottonwood fell to the ground without a struggle. 

 When the temperature was taken the extraordinary reading of 112.7° 

 was secured. From the data at hand it is indicated that the hig^iest 

 average body temperatures for a number of related species may be 

 found in the Tyrannidae. This statement is made only tentatively as 

 further observation may show that other groups are equal in this 

 respect. It is not unusual for individual birds in several other groups 

 of perching birds to register 110° or more as shown by the column 

 of maximum temperatures in table 3, and accident of association of 

 such high records might give a high average. Only by recording many 

 extended observations can error from this cause be reduced to a mini- 

 mum. 



EXPLANATION OF TABLES 



The data secured during this investigation into the body tempera- 

 ture of birds are summarized in two tables that are given in the 

 pages that follow. The table giving in detail the individual records, 



