NO. 12 BODY TEMPERATURE OF BIRDS WETMORE 3 1 



When ranged by families the highest temperatures noted are to be 

 found in pigeons, cuckoos, woodpeckers and in the great passerine 

 order beginning (in table 4) with the Tyrannidae and ending with the 

 Turdidae. It must be noted too that the range of body temperature 

 among ducks is in general comparatively high. Gulls and sliorebirds 

 show a general agreement, compatible with their close relationship 

 as now commonly accepted. The quails (Odontophoridae) seem to 

 have a temperature high for birds that have been considered compara- 

 tively low in development. The observations recorded for the owls 

 probably do not represent a true average as many of the readings upon 

 which the mean is based were taken during the day when temperature 

 in these birds normally is at low ebb. The low average given for the 

 kingfishers is based upon a small number of observations and may be 

 incorrect. Humming-birds, with their tiny bodies seem to have a con- 

 siderable range in temperature, but as a whole fall low in body warmth. 

 This apparent lack of heat may be due in part to the small bulk of 

 their bodies in comparison with the size of the thermometers used. 

 Part of their heat may have been absorbed and dissipated by the glass 

 of the inserted instrument. 



Observations upon the greater part of the species of woodpeckers 

 found in the United States reveal an almost uniform high level of 

 body temperature. The general range and the limits of variation 

 from high to low are similar to those of passerine families. As in 

 other families individuals large in body show a general lower tem- 

 perature and a smaller limit of variation than do some others of 

 smaller bulk. The records on the whole are -so uniform that further 

 comment regarding them is superfluous. 



An examination of the species and families of passerine birds 

 reveals much of interest. Of the twenty-two families for which 

 records are given eleven or exactly one-half, have a mean temperature 

 averaging below 108°. It will be noticed that most of these families 

 are those having only a small number of species represented in the 

 records. In several instances observations were available on one 

 species alone and only in the crows, swallows, vireos, wrens and 

 nuthatches is the number of species available comparatively large. 

 The Hirundinidae (seven species) with an average temperature of 

 106.7° is the only family in the order falling below 107°. Seven 

 families, the Tyrannidae, Alaudidae, Fringillidae, Tangaridae, Bomby- 

 cillidae, Mimidae and Turdidae, have mean temperatures higher than 

 108.5°. These seven families include 86 of the 203 species of passeri- 

 form birds represented, or approximately 42 per cent. The Alau- 

 didae show a mean temperature of 109.4°, which is higher than for any 



