Food consumption rate, rectrix asymmetry, tarsus length, body mass and plumage colors for individual male house sparrows P. domesticus and brown-headed cowbirds M. ater
| . | Passer domesticus . | . | Molothrus ater . | . | ||
|---|---|---|---|---|---|---|
| . | Food-stressed . | Food-unstressed . | Food-stressed . | Food-unstressed . | ||
| Food intake (g bird-1day-1)a | 2.40±0.13 | 3.13±0.25 | - | - | ||
| Rectrix asymmetryb | 1.31±1.03 | 0.78±0.49 | - | - | ||
| Tarsus length (mm) | 17.24±0.70 | 16.85±1.09 | 22.36±1.16 | 21.49±2.15 | ||
| Pre-molt body mass (g) | 26.74±1.62 | 26.13±1.83 | - | - | ||
| Post-molt body mass (g) | 27.67±2.45 | 26.57±2.86 | 44.88±3.32 | 44.72±3.74 | ||
| % change in body mass (g) | 1.73±1.49 | 0.84±2.28 | - | - | ||
| Pre-molt melanin patch sizec,d | 6.47±0.85 | 6.62±0.96 | 24.29±1.74 | 23.13±0.56 | ||
| Pre-molt melanin darkness(%)d,e | -3.29±4.09 | -3.70±2.30 | 16.57±1.08 | 16.87±2.15 | ||
| Pre-molt structural hue(degrees)d | - | - | 201.3±2.50 | 207.0±7.75 | ||
| Pre-molt structural saturation(%)d | - | - | 26.12±8.21 | 26.86±8.94 | ||
| Pre-molt structural darkness(%)d | - | - | 15.49±3.37 | 15.59±3.75 | ||
| . | Passer domesticus . | . | Molothrus ater . | . | ||
|---|---|---|---|---|---|---|
| . | Food-stressed . | Food-unstressed . | Food-stressed . | Food-unstressed . | ||
| Food intake (g bird-1day-1)a | 2.40±0.13 | 3.13±0.25 | - | - | ||
| Rectrix asymmetryb | 1.31±1.03 | 0.78±0.49 | - | - | ||
| Tarsus length (mm) | 17.24±0.70 | 16.85±1.09 | 22.36±1.16 | 21.49±2.15 | ||
| Pre-molt body mass (g) | 26.74±1.62 | 26.13±1.83 | - | - | ||
| Post-molt body mass (g) | 27.67±2.45 | 26.57±2.86 | 44.88±3.32 | 44.72±3.74 | ||
| % change in body mass (g) | 1.73±1.49 | 0.84±2.28 | - | - | ||
| Pre-molt melanin patch sizec,d | 6.47±0.85 | 6.62±0.96 | 24.29±1.74 | 23.13±0.56 | ||
| Pre-molt melanin darkness(%)d,e | -3.29±4.09 | -3.70±2.30 | 16.57±1.08 | 16.87±2.15 | ||
| Pre-molt structural hue(degrees)d | - | - | 201.3±2.50 | 207.0±7.75 | ||
| Pre-molt structural saturation(%)d | - | - | 26.12±8.21 | 26.86±8.94 | ||
| Pre-molt structural darkness(%)d | - | - | 15.49±3.37 | 15.59±3.75 | ||
Values are means ± 1 S.D. For P. domesticus, N=21; for M. ater, N=5 (food-stressed), N=10 (unstressed).
Represents the average amount of food consumed over five 24-h periods by all birds within the treatment group.
Percentage length difference (mm) in six pairs of rectrices; measured with calipers to the nearest 0.1 mm.
Measured from digital photographs in cm2 for sparrows (relative to an area standard); measured with calipers to the nearest 0.1 mm for cowbirds.
Only four birds per treatment group were used in these comparisons for cowbirds because juveniles did not display ornamental plumage prior to molt.
For sparrows, calculated as a percentage relative to a black standard included in each photograph. More negative values correspond to blacker plumage.