Effects of Variable Food Supply on the Body Condition of Breeding Tawny Owls Strix aluco in Southern Finland
Table 1
Linear regression models explaining the relationships between the condition (body mass, g) of breeding tawny owls of different sex and age and the Julian Day of the bird catching (indicating the seasonal status of prey availability). The age classes are young (<3 yr) and old (≥3 yr) individuals, or (in the last two models) 1, 2, or 3 (or more) years. Formulas, coefficients of determination (), test statistics (, or in last two models), degrees of freedom (df), and values are given.
Formula
/
df
Female body mass = 7144.248 − (17.363 * Julian Day)
0.180
−8.748
1, 244
<.001
Male body mass = 4979.046 − (8.612 * Julian Day)
0.150
−6.290
1, 218
<.001
Young female body mass = 689.104 − (1.727 * Julian Day)
0.198
−4.012
1, 60
<.001
Old female body mass = 731.642 − (1.885 * Julian Day)
0.238
−6.623
1, 136
<.001
Young male body mass = 481.609 − (0.884 * Julian Day)
0.081
−2.338
1, 50
.023
Old male body mass = 480.426 − (0.589 * Julian Day)
0.108
−4.334
1, 146
<.001
Female body mass = 677.704 − (1.861 * Julian Day) + (17.039 * Female age)
0.299
43.501
2, 197
<.001
Male body mass = 430.333 − (0.616 * Julian Day) + (17.554 * Male age)
